**Modeling and Detecting**

preparation of the chapters. It is hoped that the contents of this book lead to improvements in our knowledge and thoughts on the comprehensive management of climate change and

Kurdistan Agricultural and Natural Resources Research and Education Center

**Dr. Ata Amini** Associate Prof.

AREEO Sanandaj, Iran

global warming.

VIII Preface

**Chapter 1**

**Provisional chapter**

**Introductory Chapter: Lake Urmia - A Witness to the**

**Introductory Chapter: Lake Urmia - A Witness to the** 

In spite of the irregular behavior on a daily basis, observations show that, in the atmospheric character of some geographic area, there is some long-time regularity. However, in the twentieth century, the world temperature increased which influenced the world climate. Climate scientists reported that humankind's growing emission of greenhouse gases will make the long-term change in the climate and global temperature. As organizations, governments, and people have moved onward with strategies and actions to decrease greenhouse gas (GHG) emissions, to adapt to the impacts of climate change, the need for information to support climate-related decisions has grown rapidly in recent years. There is a lack of credible infor-

Greenhouse gases enter the atmosphere through burning coal, natural gas, oil, solid waste, wood products, and trees. The greenhouse gases are emitted during the production and transport of fossil fuels or as a result of livestock and other agricultural practices. Changes in greenhouse gas emissions are influenced by many long- and short-term factors. Larger releases of greenhouse gases result in higher concentrations in the atmosphere. However, as a part of the biological carbon cycle via a certain chemical reactions, carbon dioxide, as a main greenhouse gas, is removed from the atmosphere when it is absorbed by plants. The removal and emissions of greenhouse gases by natural processes tend to balance. Human activities, since the industrial revolution, by adding heat-trapping gases to the atmosphere, have contributed substantively to climate change. It seems that there are enough scientific evidences to prove that the greenhouse gases caused the climate alteration and global warming [11]. In addition, we realized that global temperature was increased over the last decades. However

mation system to inform climate adoptions and estimate their efficiency.

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

DOI: 10.5772/intechopen.83605

**Simultaneous Effects of Human Activities, Climate**

**Simultaneous Effects of Human Activities, Climate** 

**Change, and Global Warming**

**Change, and Global Warming**

Additional information is available at the end of the chapter

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.83605

**1. Climate change and global warming**

Ata Amini

Ata Amini

#### **Introductory Chapter: Lake Urmia - A Witness to the Simultaneous Effects of Human Activities, Climate Change, and Global Warming Introductory Chapter: Lake Urmia - A Witness to the Simultaneous Effects of Human Activities, Climate Change, and Global Warming**

DOI: 10.5772/intechopen.83605

Ata Amini Ata Amini

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.83605

### **1. Climate change and global warming**

In spite of the irregular behavior on a daily basis, observations show that, in the atmospheric character of some geographic area, there is some long-time regularity. However, in the twentieth century, the world temperature increased which influenced the world climate. Climate scientists reported that humankind's growing emission of greenhouse gases will make the long-term change in the climate and global temperature. As organizations, governments, and people have moved onward with strategies and actions to decrease greenhouse gas (GHG) emissions, to adapt to the impacts of climate change, the need for information to support climate-related decisions has grown rapidly in recent years. There is a lack of credible information system to inform climate adoptions and estimate their efficiency.

Greenhouse gases enter the atmosphere through burning coal, natural gas, oil, solid waste, wood products, and trees. The greenhouse gases are emitted during the production and transport of fossil fuels or as a result of livestock and other agricultural practices. Changes in greenhouse gas emissions are influenced by many long- and short-term factors. Larger releases of greenhouse gases result in higher concentrations in the atmosphere. However, as a part of the biological carbon cycle via a certain chemical reactions, carbon dioxide, as a main greenhouse gas, is removed from the atmosphere when it is absorbed by plants. The removal and emissions of greenhouse gases by natural processes tend to balance. Human activities, since the industrial revolution, by adding heat-trapping gases to the atmosphere, have contributed substantively to climate change. It seems that there are enough scientific evidences to prove that the greenhouse gases caused the climate alteration and global warming [11]. In addition, we realized that global temperature was increased over the last decades. However

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

as stated by [6], the climate change holds significant risks to the natural resources, environments, and societies on which they depend. Climate change and global warming affect human life, meanwhile human activities are also influencing climate.

the considerable spatial and temporal changes in the precipitation total series of regions during the last 10 years. The human activities such as dam construction and interbasin water transfer intensify such changes [1]. The most well-known evidence to demonstrate the effects of climate change and human activities is shrinking and drying up of Lake Urmia in Iran.

Introductory Chapter: Lake Urmia - A Witness to the Simultaneous Effects of Human Activities…

http://dx.doi.org/10.5772/intechopen.83605

5

So far managing renewable resources and infrastructure in much of the nation's experience is based on the historic record of stable climate. The Lake Urmia basin in northwest Iran is a closed drainage

the world. In addition, Lake Urmia is the second largest saltwater lake in the world. As a result of arid to semiarid climate of the Lake Urmia basins, the agriculture is mainly dependent on irrigation. The sprinkler irrigation was developed, and large numbers of wells were excavated to supply the required water in the agricultural sector. The reduction in rainfall along with decreasing groundwater tables and a rising population in the basin will likely exert growing pressure to continue diverting stream flow before it reaches Lake Urmia. Over the last two decades, it was sharply dried and its surface reduced about 80% from 2003 [5]. The water table of Lake Urmia was decreased severely in recent years which caused serious socio-environmental consequences [4]. The dried lake bed is with a cover of salt, mainly sodium chloride, making a vast salty desert. The examinations for estimating the relative contributions of human activities as water resources development including agricultural development and dam constructions and climate change have been conducted by [9]. The results showed that the variability in inflow as a result of human activities is more prominent than the variability in precipitation. In addition, the flow origin from the Lake Urmia was decrease up to 40% due to the development of irrigated area which increased pressure on the water availability in the watershed. Shadkam showed that over 30 years annual inflow to Lake Urmia has thrown down by 48% which 3/5 and 2/5 of this change was caused by climate change and water resource development, respectively, as misconduct in human activities [9]. **Figure 1** shows the changes in

water level and water surface in Lake Urmia within the last two decades.

**Figure 1.** The changes in surface and water level of Lake Urmia [4].

and maximum depth of 16 m, making it one of the largest lakes in

**5. The Lake Urmia**

basin with an area of 51,876 km<sup>2</sup>

### **2. The climate effects on human life**

Humans for food, livelihood, commerce, natural resources, and security rely on earth which is a complex and dynamic system. Climate always influences the humans. In recent decades, regardless of the wealth and technology of modern industrial societies, in many ways, climate still affects human life. The impacts of climate change and consequently the rising greenhouse gas levels including warming temperatures lead to extreme weather events, altered weather patterns, crop failure, rising sea levels, ocean acidification, marine ecosystem shift, and homelessness. These impacts directly or indirectly threaten our health by affecting the weather we experience, the water we drink, the food we eat, the energy we use, the air we breathe, and other aspects of human health and well-being.

### **3. The human contribution to climate change and global warming**

Although there are scientists who suspect that the human activities could have emotional impact on recent changes in climate and global temperature, the Intergovernmental Panel on Climate Change, IPCC, approved that the warming detected over last 50 years is attributable to man-made activities [7]. It seems that there is no doubt that human activity has changed the composition of world's atmosphere and environment. The noticeable problem is that human activities' influences will continue to alter atmospheric composition through the current century and hydrologic cycle and temperature are expected to be change inconsistently. Climate change and global warming, in complex ways, interact with other ongoing changes in human and environmental systems. For example, humanity's choices about land use, energy, and food makings affect and are affected by climate change and global warming. Although the details of how the upcoming influences of climate alteration will unfold are not as well understood as the basic reasons and mechanisms of climate alteration, we can rationally assume that the consequences of climate alteration will be more severe if actions are not taken to limit its magnitude and adapt to its impacts.

### **4. Climate change in Euphrates-Tigris Basin**

The increase of the frequency and intensity of droughts in Asia and Africa is reported as an evidence of climate change in recent years [8]. Most regions in the Middle East including Iran are in the midst of a water crisis and their worst drought in decades. As a result, the water resources declined considerably. At the current rate of decline, the basin's water supply will not be enough to avert a widespread humanitarian crisis [2]. [10] used Gravity Recovery and Climate Experiment (GRACE) satellite mission and concluded an alarming rate of decrease in total water storage equal to 143.6 km3 from January 2003 to December 2009. Amini analyzed the climate data from Iran and its riparian countries [1]. The results revealed the considerable spatial and temporal changes in the precipitation total series of regions during the last 10 years. The human activities such as dam construction and interbasin water transfer intensify such changes [1]. The most well-known evidence to demonstrate the effects of climate change and human activities is shrinking and drying up of Lake Urmia in Iran.

### **5. The Lake Urmia**

as stated by [6], the climate change holds significant risks to the natural resources, environments, and societies on which they depend. Climate change and global warming affect human

Humans for food, livelihood, commerce, natural resources, and security rely on earth which is a complex and dynamic system. Climate always influences the humans. In recent decades, regardless of the wealth and technology of modern industrial societies, in many ways, climate still affects human life. The impacts of climate change and consequently the rising greenhouse gas levels including warming temperatures lead to extreme weather events, altered weather patterns, crop failure, rising sea levels, ocean acidification, marine ecosystem shift, and homelessness. These impacts directly or indirectly threaten our health by affecting the weather we experience, the water we drink, the food we eat, the energy we use, the air we breathe, and

**3. The human contribution to climate change and global warming**

more severe if actions are not taken to limit its magnitude and adapt to its impacts.

The increase of the frequency and intensity of droughts in Asia and Africa is reported as an evidence of climate change in recent years [8]. Most regions in the Middle East including Iran are in the midst of a water crisis and their worst drought in decades. As a result, the water resources declined considerably. At the current rate of decline, the basin's water supply will not be enough to avert a widespread humanitarian crisis [2]. [10] used Gravity Recovery and Climate Experiment (GRACE) satellite mission and concluded an alarming rate

Amini analyzed the climate data from Iran and its riparian countries [1]. The results revealed

from January 2003 to December 2009.

**4. Climate change in Euphrates-Tigris Basin**

of decrease in total water storage equal to 143.6 km3

Although there are scientists who suspect that the human activities could have emotional impact on recent changes in climate and global temperature, the Intergovernmental Panel on Climate Change, IPCC, approved that the warming detected over last 50 years is attributable to man-made activities [7]. It seems that there is no doubt that human activity has changed the composition of world's atmosphere and environment. The noticeable problem is that human activities' influences will continue to alter atmospheric composition through the current century and hydrologic cycle and temperature are expected to be change inconsistently. Climate change and global warming, in complex ways, interact with other ongoing changes in human and environmental systems. For example, humanity's choices about land use, energy, and food makings affect and are affected by climate change and global warming. Although the details of how the upcoming influences of climate alteration will unfold are not as well understood as the basic reasons and mechanisms of climate alteration, we can rationally assume that the consequences of climate alteration will be

life, meanwhile human activities are also influencing climate.

**2. The climate effects on human life**

4 Climate Change and Global Warming

other aspects of human health and well-being.

So far managing renewable resources and infrastructure in much of the nation's experience is based on the historic record of stable climate. The Lake Urmia basin in northwest Iran is a closed drainage basin with an area of 51,876 km<sup>2</sup> and maximum depth of 16 m, making it one of the largest lakes in the world. In addition, Lake Urmia is the second largest saltwater lake in the world. As a result of arid to semiarid climate of the Lake Urmia basins, the agriculture is mainly dependent on irrigation. The sprinkler irrigation was developed, and large numbers of wells were excavated to supply the required water in the agricultural sector. The reduction in rainfall along with decreasing groundwater tables and a rising population in the basin will likely exert growing pressure to continue diverting stream flow before it reaches Lake Urmia. Over the last two decades, it was sharply dried and its surface reduced about 80% from 2003 [5]. The water table of Lake Urmia was decreased severely in recent years which caused serious socio-environmental consequences [4]. The dried lake bed is with a cover of salt, mainly sodium chloride, making a vast salty desert. The examinations for estimating the relative contributions of human activities as water resources development including agricultural development and dam constructions and climate change have been conducted by [9]. The results showed that the variability in inflow as a result of human activities is more prominent than the variability in precipitation. In addition, the flow origin from the Lake Urmia was decrease up to 40% due to the development of irrigated area which increased pressure on the water availability in the watershed. Shadkam showed that over 30 years annual inflow to Lake Urmia has thrown down by 48% which 3/5 and 2/5 of this change was caused by climate change and water resource development, respectively, as misconduct in human activities [9]. **Figure 1** shows the changes in water level and water surface in Lake Urmia within the last two decades.

**Figure 1.** The changes in surface and water level of Lake Urmia [4].

Amini and Hesami got the same results for two main subwatersheds of Urmia basin. They reported that the total irrigated area increased by ~20% between 1989 and 2000 and the net irrigation water requirement, NIWR, for a crop grown in the region in 2000 was slightly higher than that in 1989 as a result of global warming [4].

warming [3]. The lake restoration was taken placed by local, national, and international organizations. However, the decision-makers inappropriately put the man-made infrastructures such as dams and interbasin water transfer, which are unsustainable projects in water sector, to increase the flow toward the lake. In fact, construction of numerous dams in the watershed has choked off water source from the mountains towering on either side of the Lake Urmia. **Figure 2** shows the existing, under construction, and under study dams in the basin of Lake Urmia. **Figure 2** shows intensification in diversion of surface water and water utilization fur-

Introductory Chapter: Lake Urmia - A Witness to the Simultaneous Effects of Human Activities…

http://dx.doi.org/10.5772/intechopen.83605

7

Reducing the basin's water consumption and demand-side plans must be considered immediately by the official organization. Moreover, the current projects for water transfer need drastic revision. Such projects have had harmful socioeconomic and environmental side effects in other parts of the basin. To maximize the welfares of the water resources, an integrated management of the water resources and agricultural development based on ecological potential of the basin including changing the rules of water pricing and recognition of cost

The IPCC clearly confirmed in its Fifth Assessment Report that the climate change is existent and its primary cause is human-made especially through burning fossil fuels and other activities that release heat-trapping greenhouse gases into the atmosphere. There is no debate that the human needs to take actions to adapt and lessen the impact of climate change. In fact, there is a hierarchy of governor plans that can assist to protect population healthiness and welfare. The predictions of future climate change and global warming and defined scenarios by IPCC indicate that unless substantial and continued activities are taken to decline emissions of GHGs, world will continue to warm. Thus, we can reasonably expect that such changes are driving several related and interacting deviations in the environmental system and consequently the human life. In the case of Lake Urmia, a national committee in order to lake restoration was formed in 2013 called Lake Urmia Restoration National Committee (ULRNC). The ULRNC presented a road map and action plan based on integrated water resources/watershed management in cooperation with the universities in Iran and international organizations. The ULRNC reviewed 19 proposed programs and approved a 10-year program in three phases such as stabilizing the present status, restoration, and sustainable restoration. Although the provincial office claims that the restoration continues as scheduled, due to drying up the found and misconducting of management in water and agricultural sectors in the region, it seems that Lake Urmia will most likely fail to attain an ecological balance within a 10-year program by 2023. Although the specifics of how the upcoming impacts of Lake Urmia decline will unfold are not as well recognized as the main causes and mechanisms of lake shrinking, it is rationally expected that the avoidable consequences of lake drying will be more severe if activities are not taken to limit its

ther than current levels which at present appear to be unsustainable.

allocation outlines as a prospect is required.

**6. Need for adaptive management**

level and adapt to its influences.

Hosseini-Moghari using spatial and hydrology and in situ data assessed the contribution of human acts to the decline of inflow water for the lake, the groundwater table reduction, and water storage in the lake reservoir [5]. They found that 50% of the total basin water loss is due to sectorial management of water resources in the region. The human interaction with the lake environment in Lake Urmia basin caused about 8 BCM of groundwater losses within 11 years. However, the climate change and drought are the causes for 40% of lake shrinking in the last two decades. Such findings may be used to support decision-maker in water sector to restore the Lake Urmia. It seems that there is no debate that the Lake Urmia diminishing was caused by a combination of water withdrawals for irrigation and climate change and global

**Figure 2.** The spreading of dams in Urmia watersheds.

warming [3]. The lake restoration was taken placed by local, national, and international organizations. However, the decision-makers inappropriately put the man-made infrastructures such as dams and interbasin water transfer, which are unsustainable projects in water sector, to increase the flow toward the lake. In fact, construction of numerous dams in the watershed has choked off water source from the mountains towering on either side of the Lake Urmia. **Figure 2** shows the existing, under construction, and under study dams in the basin of Lake Urmia. **Figure 2** shows intensification in diversion of surface water and water utilization further than current levels which at present appear to be unsustainable.

Reducing the basin's water consumption and demand-side plans must be considered immediately by the official organization. Moreover, the current projects for water transfer need drastic revision. Such projects have had harmful socioeconomic and environmental side effects in other parts of the basin. To maximize the welfares of the water resources, an integrated management of the water resources and agricultural development based on ecological potential of the basin including changing the rules of water pricing and recognition of cost allocation outlines as a prospect is required.

### **6. Need for adaptive management**

Amini and Hesami got the same results for two main subwatersheds of Urmia basin. They reported that the total irrigated area increased by ~20% between 1989 and 2000 and the net irrigation water requirement, NIWR, for a crop grown in the region in 2000 was slightly

Hosseini-Moghari using spatial and hydrology and in situ data assessed the contribution of human acts to the decline of inflow water for the lake, the groundwater table reduction, and water storage in the lake reservoir [5]. They found that 50% of the total basin water loss is due to sectorial management of water resources in the region. The human interaction with the lake environment in Lake Urmia basin caused about 8 BCM of groundwater losses within 11 years. However, the climate change and drought are the causes for 40% of lake shrinking in the last two decades. Such findings may be used to support decision-maker in water sector to restore the Lake Urmia. It seems that there is no debate that the Lake Urmia diminishing was caused by a combination of water withdrawals for irrigation and climate change and global

higher than that in 1989 as a result of global warming [4].

6 Climate Change and Global Warming

**Figure 2.** The spreading of dams in Urmia watersheds.

The IPCC clearly confirmed in its Fifth Assessment Report that the climate change is existent and its primary cause is human-made especially through burning fossil fuels and other activities that release heat-trapping greenhouse gases into the atmosphere. There is no debate that the human needs to take actions to adapt and lessen the impact of climate change. In fact, there is a hierarchy of governor plans that can assist to protect population healthiness and welfare. The predictions of future climate change and global warming and defined scenarios by IPCC indicate that unless substantial and continued activities are taken to decline emissions of GHGs, world will continue to warm. Thus, we can reasonably expect that such changes are driving several related and interacting deviations in the environmental system and consequently the human life. In the case of Lake Urmia, a national committee in order to lake restoration was formed in 2013 called Lake Urmia Restoration National Committee (ULRNC). The ULRNC presented a road map and action plan based on integrated water resources/watershed management in cooperation with the universities in Iran and international organizations. The ULRNC reviewed 19 proposed programs and approved a 10-year program in three phases such as stabilizing the present status, restoration, and sustainable restoration. Although the provincial office claims that the restoration continues as scheduled, due to drying up the found and misconducting of management in water and agricultural sectors in the region, it seems that Lake Urmia will most likely fail to attain an ecological balance within a 10-year program by 2023. Although the specifics of how the upcoming impacts of Lake Urmia decline will unfold are not as well recognized as the main causes and mechanisms of lake shrinking, it is rationally expected that the avoidable consequences of lake drying will be more severe if activities are not taken to limit its level and adapt to its influences.

### **Author details**

#### Ata Amini

Address all correspondence to: ata\_amini@yahoo.com

Kurdistan Agricultural and Natural Resources Research and Education Center, AREEO, Iran

[10] Voss KA, Famiglietti JS, Lo MH, Linage C d, Rodell M, Swenson SC.Groundwater depletion in the Middle East from GRACE with implications for transboundary water management in the Tigris-Euphrates-Western Iran region. Water Resources Research. 2013;**49**:904-914 [11] Wilson G, Fairén V, García-Sanz J, Zúñiga I, Otto D, Breitmeir H et al. Module 1: Introduction to climate change in the context of sustainable development, Climate Change: From science

Introductory Chapter: Lake Urmia - A Witness to the Simultaneous Effects of Human Activities…

http://dx.doi.org/10.5772/intechopen.83605

9

to lived experience, lifelong learning program. 2011. p. 180

### **References**


[10] Voss KA, Famiglietti JS, Lo MH, Linage C d, Rodell M, Swenson SC.Groundwater depletion in the Middle East from GRACE with implications for transboundary water management in the Tigris-Euphrates-Western Iran region. Water Resources Research. 2013;**49**:904-914

**Author details**

8 Climate Change and Global Warming

Address all correspondence to: ata\_amini@yahoo.com

Research. 2011;**47**:W06506

Available from: http://www.ipcc.ch

Organization; 2003. p. 322

Lakes Research. 2016;**42**(5):942-952

Change. NY, US: Cambridge Press; 2001

Kurdistan Agricultural and Natural Resources Research and Education Center, AREEO, Iran

[1] Amini A, Zareie S, Taheri P, Wan KBY, Mustafa MR. In: Bucur D, editor. Drought Analysis and Water Resources Management Inspection in Euphrates—Tigris Basin,

[2] Chenoweth J, Hadjinicolaou P, Bruggeman A, Lelieveld J, Levin Z, Lange MA, et al. Impact of climate change on the water resources of the Eastern Mediterranean and Middle East region: Modeled 21st century changes and implications. Water Resources

[3] Hassanzadeh E, Zarghami M, Hassanzadeh Y. Determining the main factors in declining the Lake Urmia level by using system dynamics modeling. Water Resources

[4] Hesami A, Amini A. Changes in irrigated land and agricultural water use in the Lake

[5] Hosseini-Moghari SM, Araghinejad S, Tourian MJ, Ebrahimi K, Döll P. Quantifying the impacts of human water use and climate variations on recent drying of Lake Urmia basin: The value of different sets of spaceborne and in-situ data for calibrating a hydrological model. Hydrology and Earth System Sciences. 2018. DOI: 10.5194/hess-2018-318 [6] IPCC. Climate Change—The Physical Science Basis—Chapter 8. WGI Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. 2007.

[7] IPCC. Climate Change: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Third Assessment Report of the Intergovernmental Panel on Climate

[8] McMichael AJ, Campbell-Lendrum DH, Corvalán CF, Ebi KL, Githeko A, Scheraga JD, et al. Climate Change and Human Health: Risks and Responses. Geneva: World Health

[9] Shadkam S, Ludwig F, Oel P, Kirmit Ç, Kabat P. Impacts of climate change and water resources development on the declining inflow into Iran's Lake Urmia. Journal of Great

River Basin Management. Romania: InTech Publication; 2016

Management. 2011;**26**(1):129-145. DOI: 10.1007/s11269-011-9909-8

Urmia basin. Lake and Reservoir Management. 2016;**32**(3):288-296

Ata Amini

**References**

[11] Wilson G, Fairén V, García-Sanz J, Zúñiga I, Otto D, Breitmeir H et al. Module 1: Introduction to climate change in the context of sustainable development, Climate Change: From science to lived experience, lifelong learning program. 2011. p. 180

**Chapter 2**

**Provisional chapter**

concentration) on

concen-

**Assessing the Expected Impact of Climate Change on**

Climate change is likely to have profound impacts on quality of water resources, by altering the magnitude and timing of nutrient delivery to stream network. However, water quality responses to climate change are difficult to predict, especially for nutrient loads because of combined uncertainties in water quality and quantity projections. In this study, the potential medium (2031–2060) and long-term (2069–2098) impacts of

nitrate load in an Atlantic agro-forested catchment (NW Spain) were assessed using the soil and water assessment tool (SWAT) model. Climate change scenarios are based on

tration scenarios. The results showed that nitrate load will increase in the future horizons (2031–2060, 6%; 2069–2098, 7%) in relation to current values (1981–2010), possibly due to the decline in grassland biomass, as well as an increase in the rate of mineralisation linked to the increase in temperature. Consequently, lower rates of fertilisers will be needed in these areas in future horizons, which should be taken into consideration when planning management strategies in order to mitigate the impacts of potential

data projected by regional models from the ENSEMBLES project and two CO2

**Keywords:** nitrate, climate change, SWAT model, agro-forested catchment

project changes in climate variables (temperature, rainfall and CO2

**Assessing the Expected Impact of Climate Change** 

**on Nitrate Load in a Small Atlantic Agro-Forested** 

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

DOI: 10.5772/intechopen.80709

**Nitrate Load in a Small Atlantic Agro-Forested**

María Mercedes Taboada-Castro, Ricardo Arias and

María Mercedes Taboada-Castro, Ricardo Arias and

Additional information is available at the end of the chapter

Additional information is available at the end of the chapter

**Catchment**

**Abstract**

climate change.

**Catchment**

María Luz Rodríguez-Blanco,

María Luz Rodríguez-Blanco,

María Teresa Taboada-Castro

María Teresa Taboada-Castro

http://dx.doi.org/10.5772/intechopen.80709

#### **Assessing the Expected Impact of Climate Change on Nitrate Load in a Small Atlantic Agro-Forested Catchment Assessing the Expected Impact of Climate Change on Nitrate Load in a Small Atlantic Agro-Forested Catchment**

DOI: 10.5772/intechopen.80709

María Luz Rodríguez-Blanco, María Mercedes Taboada-Castro, Ricardo Arias and María Teresa Taboada-Castro María Luz Rodríguez-Blanco, María Mercedes Taboada-Castro, Ricardo Arias and María Teresa Taboada-Castro

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.80709

#### **Abstract**

Climate change is likely to have profound impacts on quality of water resources, by altering the magnitude and timing of nutrient delivery to stream network. However, water quality responses to climate change are difficult to predict, especially for nutrient loads because of combined uncertainties in water quality and quantity projections. In this study, the potential medium (2031–2060) and long-term (2069–2098) impacts of project changes in climate variables (temperature, rainfall and CO2 concentration) on nitrate load in an Atlantic agro-forested catchment (NW Spain) were assessed using the soil and water assessment tool (SWAT) model. Climate change scenarios are based on data projected by regional models from the ENSEMBLES project and two CO2 concentration scenarios. The results showed that nitrate load will increase in the future horizons (2031–2060, 6%; 2069–2098, 7%) in relation to current values (1981–2010), possibly due to the decline in grassland biomass, as well as an increase in the rate of mineralisation linked to the increase in temperature. Consequently, lower rates of fertilisers will be needed in these areas in future horizons, which should be taken into consideration when planning management strategies in order to mitigate the impacts of potential climate change.

**Keywords:** nitrate, climate change, SWAT model, agro-forested catchment

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

### **1. Introduction**

Nitrogen (N) is a key nutrient in river systems. Its concentration and form in the aquatic environment generally reflect the integration of a number of sources within the catchment including point and/or nonpoint sources. In addition to these anthropogenic contributions, there are "natural" contributions from the mineralisation and nitrification of organic nitrogen in soils [1]. Within aquatic environments, nitrate (NO3 ) is generally the dominant N fraction due to high NO3 mobility in the environment [2], as a result of its persistence, high solubility and low reactivity. The N problem, due to the excessive application of fertilisers for crop production, has been of growing concern in recent decades as it affects the water quality for consumption, promotes the development of eutrophication and reduces biodiversity [3, 4].

Peninsula, western France, the Netherlands, Belgium, northern part of Germany, western Denmark and the United Kingdom. Uncertainties involved in climate predictions are larger in this transition zone of the Atlantic region than in other areas, e.g. the northern and the southern parts of the continent. Therefore, this transition zone should be an in-depth studied area. This paper provides an overview of the effects of changes in climate on nitrate loads in NW Spain. Specifically, the main objective of this study was to assess the impacts of the potential

Assessing the Expected Impact of Climate Change on Nitrate Load in a Small Atlantic…

an Atlantic agro-forested headwater catchment located in NW Spain using the SWAT model (one of the most widely used catchment models throughout the world) in order to provide information to catchment management so that they can anticipate possibly the impact on water quality and design and implement the necessary mitigation actions within the catch-

The Corbeira catchment is located in the headwater of the Mero basin, at about 30 km from the city of A Coruña in NW SPain (**Figure 1**). The catchment covers an area of 16 km2

Elevations range from 65 to 470 m a.s.l., with a mean slope of 19%. The geological substrate is

**Figure 1.** Location of the study area, general view of the Corbeira catchment and land-use map.

concentration) on nitrate load in

http://dx.doi.org/10.5772/intechopen.80709

.

13

changes in climate variables (temperature, rainfall and CO2

ment management programs.

**2. Study area characterisation**

Changes in the climatic conditions and, particularly, increases in air temperature, shifts in rainfall patterns and an increase in the frequency of flood and droughts alter the processes controlling the mobilisation and transfer of N from agricultural land to aquatic ecosystems [5–7]. Rising water temperatures influence biological processes and chemical characteristics of water resources, e.g. increasing the mineralisation of organic matter, decreasing oxygen solubility, increasing the variability in pH values and increasing growth rates of aquatic organisms. A lower water availability might affect the quality of surface water resources adversely and even have a significant negative impact on human health and the economic development of the entire region [7, 8].

Since protecting and restoring the aquatic ecosystem is a policy priority in Europe [9], catchment management planning should focus on adaptively managing climate change impacts, although climate change is not explicitly included in the European Water Framework Directive (WFD), because climate change is expected to have profound effects on water resources and water quality [10]. The facts show that effects of climate change have not been properly addressed in policy formulation and water resource management strategies in many regions around the world, probably due to the lack of accurate and reliable data on the possible effects of climate change on water resources. Nitrogen pollution is already considered as a global problem [11], and it is expected that N loss will aggravate in vulnerable areas due to climate change [5, 8]. For this, it is of upmost importance to assess and quantify the impacts of climate change and vulnerability of water resources and evaluate the efficiency of possible adaptation and mitigation policies.

While many researches in different study areas assessed the climate change impacts on catchment hydrology and water supply, water quality has been studied much less [6, 12–14]. So, little is known about the potential effects of climate change on biogeochemical processes at catchment scale and its associated impacts on water quality. So far, very few studies have addressed the water resource on the Atlantic region of Europe, and, consequently, little is known about the effects of climate change in water quality in this area. This can constitute a challenge because hydrological processes in this region will change in response to climate change [15–17], as they are expected to undergo a Mediterranization process. In fact, in the northwest of Iberian Peninsula, an increase in temperatures (2–3°C) is expected, particularly during spring and summer, with marked uneven distribution of rainfall, i.e. more rain in autumn but drier spring and summer [18]. Likewise, according to the Intergovernmental Panel on Climate Change [19], climate change will cause an increase in the future winter storm and flooding for the Atlantic region of Europe, which encompasses northern Iberian Peninsula, western France, the Netherlands, Belgium, northern part of Germany, western Denmark and the United Kingdom. Uncertainties involved in climate predictions are larger in this transition zone of the Atlantic region than in other areas, e.g. the northern and the southern parts of the continent. Therefore, this transition zone should be an in-depth studied area.

This paper provides an overview of the effects of changes in climate on nitrate loads in NW Spain. Specifically, the main objective of this study was to assess the impacts of the potential changes in climate variables (temperature, rainfall and CO2 concentration) on nitrate load in an Atlantic agro-forested headwater catchment located in NW Spain using the SWAT model (one of the most widely used catchment models throughout the world) in order to provide information to catchment management so that they can anticipate possibly the impact on water quality and design and implement the necessary mitigation actions within the catchment management programs.

### **2. Study area characterisation**

**1. Introduction**

12 Climate Change and Global Warming

due to high NO3

in soils [1]. Within aquatic environments, nitrate (NO3

Nitrogen (N) is a key nutrient in river systems. Its concentration and form in the aquatic environment generally reflect the integration of a number of sources within the catchment including point and/or nonpoint sources. In addition to these anthropogenic contributions, there are "natural" contributions from the mineralisation and nitrification of organic nitrogen

and low reactivity. The N problem, due to the excessive application of fertilisers for crop production, has been of growing concern in recent decades as it affects the water quality for consumption, promotes the development of eutrophication and reduces biodiversity [3, 4].

Changes in the climatic conditions and, particularly, increases in air temperature, shifts in rainfall patterns and an increase in the frequency of flood and droughts alter the processes controlling the mobilisation and transfer of N from agricultural land to aquatic ecosystems [5–7]. Rising water temperatures influence biological processes and chemical characteristics of water resources, e.g. increasing the mineralisation of organic matter, decreasing oxygen solubility, increasing the variability in pH values and increasing growth rates of aquatic organisms. A lower water availability might affect the quality of surface water resources adversely and even have a significant negative

Since protecting and restoring the aquatic ecosystem is a policy priority in Europe [9], catchment management planning should focus on adaptively managing climate change impacts, although climate change is not explicitly included in the European Water Framework Directive (WFD), because climate change is expected to have profound effects on water resources and water quality [10]. The facts show that effects of climate change have not been properly addressed in policy formulation and water resource management strategies in many regions around the world, probably due to the lack of accurate and reliable data on the possible effects of climate change on water resources. Nitrogen pollution is already considered as a global problem [11], and it is expected that N loss will aggravate in vulnerable areas due to climate change [5, 8]. For this, it is of upmost importance to assess and quantify the impacts of climate change and vulnerability of water resources and evaluate the efficiency of possible adaptation and mitigation policies.

While many researches in different study areas assessed the climate change impacts on catchment hydrology and water supply, water quality has been studied much less [6, 12–14]. So, little is known about the potential effects of climate change on biogeochemical processes at catchment scale and its associated impacts on water quality. So far, very few studies have addressed the water resource on the Atlantic region of Europe, and, consequently, little is known about the effects of climate change in water quality in this area. This can constitute a challenge because hydrological processes in this region will change in response to climate change [15–17], as they are expected to undergo a Mediterranization process. In fact, in the northwest of Iberian Peninsula, an increase in temperatures (2–3°C) is expected, particularly during spring and summer, with marked uneven distribution of rainfall, i.e. more rain in autumn but drier spring and summer [18]. Likewise, according to the Intergovernmental Panel on Climate Change [19], climate change will cause an increase in the future winter storm and flooding for the Atlantic region of Europe, which encompasses northern Iberian

impact on human health and the economic development of the entire region [7, 8].

mobility in the environment [2], as a result of its persistence, high solubility

) is generally the dominant N fraction

The Corbeira catchment is located in the headwater of the Mero basin, at about 30 km from the city of A Coruña in NW SPain (**Figure 1**). The catchment covers an area of 16 km2 . Elevations range from 65 to 470 m a.s.l., with a mean slope of 19%. The geological substrate is

**Figure 1.** Location of the study area, general view of the Corbeira catchment and land-use map.

dominated by the basic schist of the Órdenes Complex [20], and the main soil types present in the catchment are umbrisol and cambisol [21], which represent 74 and 25%, respectively. Predominating land use is a forest covering 65% of the catchment area, followed by pasture (26%), impervious areas (5%) and cultivated land (4%). The population density in the catchment is low (35 inhabitants km−<sup>2</sup> ); there are no industries, and human activities are reduced to rural traditional agriculture and livestock (0.29 LU ha−<sup>1</sup> ).

The mean annual temperature is about 13°C, with mean annual minimum and maximum temperatures of 8.6 (February) and 18.4°C (July), respectively. The mean annual rainfall is about 1170 mm, more than 65% occurring between October and March. The annual mean flow rate is 0.18 m<sup>3</sup> s1 , and it is mainly supplied by groundwater. For more information of the study area, see Rodríguez-Blanco et al. [22–24].

### **3. Methodology**

### **3.1. Model description**

The SWAT model was developed by the Agricultural Research Service of the US Department of Agriculture (USDA) to quantify and predict the impact of agricultural management practices on water, sediment and agricultural chemical in large complex catchments [25, 26], although is has been satisfactorily applied in small catchments all over the world [10, 14–16]. It is a continuous, distributed model, although not completely distributed, since it does not use cells but divides the basin into sub-basins that are further divided into Hydrological Response Units (HRUs). For this reason, sometimes it is defined as semi-distributed. It is based on physical principles to describe the relationship between the input and output variables. It needs specific data from the catchment (climate, physical properties of the soil, topography, vegetation, soil management practice, etc.), which are used to model physical processes related to the movement of water and sediments, growth of crops and nutrient cycles. SWAT simulations can be separated into two components, the land phase for water and pollutants loadings to channels and the routing phase for in-stream water quantity and quality. Regarding nitrogen, the model simulates N transport and transformation at HRU scale; considering the processes of denitrification, volatilisation and organic N, stable organic N associated with humic substances and fresh organic N associated with the crop residues are distinguished. Nitrate can be transported from land to stream network via surface runoff, lateral flow and groundwater flow. A more detailed description of the SWAT model can be found in [25, 26]

#### **3.2. Climate change scenarios**

Reseach into the impact of climate in the future has focused on evaluating the effects that change in temperature, rainfall and CO2 concentration might cause on nitrate load, following the methodology used in [15, 27]. Two simulation sets were used: one evaluated the response of the catchment to changes in single-climate variables (temperature, rainfall or CO2 concentrations) and the other one assessed the impact caused by simultaneous changes in temperature, rainfall or CO2 concentrations. In total, 14 different climate change scenarios were used (**Table 1**).

**Scenario**

1 2 3 4 5 6 7 8 9 10 11

T (°C) P (mm) CO2 (ppm)

> 12

T (°C) P (mm) CO2 (ppm)

> 13

T (°C) P (mm) CO2 (ppm)

> 14

T (°C) P (mm) CO2 (ppm)

Notes: Scenario 1, T

11, Scenario 1 +

4 +

**Table 1.**

Climate change scenarios used in the simulations.

Scenario 8 +

Scenario 10.

Scenario 5 +

Scenario 9; Scenario 12, Scenario 2

 +

Scenario 6 +

 +

mean 2031–2060 C; Scenario 2, T

 +

max 2031–2060 C; Scenario 3, T

 + 2031–2060%; Scenario 6, P – max 2031–2060%; Scenario 7, P – mean 2069–2098%; Scenario 8, P – max 2069–2098%; Scenario 9, 1.5 × CO2; Scenario 10, 2 × CO2; Scenario

Scenario 10; Scenario 13, Scenario 3

 +

Scenario 7 +

Scenario 9; and Scenario 14, Scenario

15

mean 2069–2098 C; Scenario 4, T

 +

550 1.8 −3.5

660 2.7 36.6

660

660

660

660

660

660

660

660

660

660

660 max 2069–2098 C; Scenario 5, P – mean

660

http://dx.doi.org/10.5772/intechopen.80709

17.2

−22.4

−26.5

−37.5

−30.2

−20.6

−28.5

−28.0

−56.1

−56.8

−29.6

3.2

3.2

2.9

3.8

4.7

4.5

4.9

5.5

5.0

3.7

2.9

660

660

660

660

660

660

660

660

660

660

660

−1.0

−5.2

−17.6

−31.8

−21.0

−14.5

−16.4

−19.1

−27.4

−8.7

−8.9

1.6

1.6

1.7

2.2

2.5

2.6

3.0

2.7

2.5

2.2

2.2

Assessing the Expected Impact of Climate Change on Nitrate Load in a Small Atlantic…

550

550

550

550

550

550

550

550

550

550

550

550 1.6 −26.0

−28.3

−12.9

−30.4

−15.5

−24.1

−17.2

−23.9

−30.7

−46.4

−37.9

54.7

1.5

2

1.7

1.9

2.1

2.5

2.7

2.4

2.8

1.6

2.3

550

550

550

550

550

550

550

550

550

550

550

CO2 (ppm)

CO2 (ppm)

P (mm)

P (mm)

P (mm)

P (mm)

(°C)

T (°C)

T (°C)

T (°C)

**Modified parameter**

**Jan**

1.0 1.6 1.8 2.7 −1.2 −26.0

−3.5

36.6

550 660 1.0 −1.2

1.0

−5.2

−12.7

−10.6

−11.4

−9.8

−11.8

−6.8

−8.2

−8.7

17.8

0.9

0.7

0.9

1.1

1.0

1.3

1.5

1.4

1.2

1.0

1.4

660

660

660

660

660

660

660

660

660

660

660

550

550

550

550

550

550

550

550

550

550

550

17.2

−22.4

−26.5

−37.5

−30.2

−20.6

−28.5

−28.0

−56.1

−56.8

−29.6

−1.0

−5.2

−17.6

−31.8

−21.0

−14.5

−16.4

−19.1

−27.4

−8.7

−8.9

−28.3

−12.9

−30.4

−15.5

−24.1

−17.2

−23.9

−30.7

−46.4

−37.9

54.7

1.0

−5.2

−12.7

−10.6

−11.4

−9.8

−11.8

−6.8

−8.2

−8.7

17.8

3.2

3.2

2.9

3.8

4.7

4.5

4.9

5.5

5.0

3.7

2.9

1.6

1.6

1.7

2.2

2.5

2.6

3.0

2.7

2.5

2.2

2.2

1.5

2

1.7

1.9

2.1

2.5

2.7

2.4

2.8

1.6

2.3

0.9

0.7

0.9

1.1

1.0

1.3

1.5

1.4

1.2

1.0

1.4

**Feb**

**Mar**

**Apr**

**May**

**Jun**

**Jul**

**Aug**

**Sep**

**Oct**

**Nov**

**Dec**


dominated by the basic schist of the Órdenes Complex [20], and the main soil types present in the catchment are umbrisol and cambisol [21], which represent 74 and 25%, respectively. Predominating land use is a forest covering 65% of the catchment area, followed by pasture (26%), impervious areas (5%) and cultivated land (4%). The population density in the catch-

The mean annual temperature is about 13°C, with mean annual minimum and maximum temperatures of 8.6 (February) and 18.4°C (July), respectively. The mean annual rainfall is about 1170 mm, more than 65% occurring between October and March. The annual mean

The SWAT model was developed by the Agricultural Research Service of the US Department of Agriculture (USDA) to quantify and predict the impact of agricultural management practices on water, sediment and agricultural chemical in large complex catchments [25, 26], although is has been satisfactorily applied in small catchments all over the world [10, 14–16]. It is a continuous, distributed model, although not completely distributed, since it does not use cells but divides the basin into sub-basins that are further divided into Hydrological Response Units (HRUs). For this reason, sometimes it is defined as semi-distributed. It is based on physical principles to describe the relationship between the input and output variables. It needs specific data from the catchment (climate, physical properties of the soil, topography, vegetation, soil management practice, etc.), which are used to model physical processes related to the movement of water and sediments, growth of crops and nutrient cycles. SWAT simulations can be separated into two components, the land phase for water and pollutants loadings to channels and the routing phase for in-stream water quantity and quality. Regarding nitrogen, the model simulates N transport and transformation at HRU scale; considering the processes of denitrification, volatilisation and organic N, stable organic N associated with humic substances and fresh organic N associated with the crop residues are distinguished. Nitrate can be transported from land to stream network via surface runoff, lateral flow and groundwater flow. A more

Reseach into the impact of climate in the future has focused on evaluating the effects that change

odology used in [15, 27]. Two simulation sets were used: one evaluated the response of the

and the other one assessed the impact caused by simultaneous changes in temperature, rainfall

concentrations. In total, 14 different climate change scenarios were used (**Table 1**).

catchment to changes in single-climate variables (temperature, rainfall or CO2

concentration might cause on nitrate load, following the meth-

concentrations)

); there are no industries, and human activities are reduced to

).

, and it is mainly supplied by groundwater. For more information of the

ment is low (35 inhabitants km−<sup>2</sup>

14 Climate Change and Global Warming

flow rate is 0.18 m<sup>3</sup> s1

**3. Methodology**

**3.1. Model description**

**3.2. Climate change scenarios**

in temperature, rainfall and CO2

or CO2

rural traditional agriculture and livestock (0.29 LU ha−<sup>1</sup>

detailed description of the SWAT model can be found in [25, 26]

study area, see Rodríguez-Blanco et al. [22–24].

4 +

Scenario 8

11, Scenario 1+ Scenario 5 + Scenario 9; Scenario 12, Scenario 2 + Scenario 6 + Scenario 10; Scenario 13, Scenario 3 + Scenario 7 + Scenario 9; and Scenario 14, Scenario + Scenario 10.

**Table 1.** Climate change scenarios used in the simulations.

which reach the stream mainly in groundwater flow. The estimated yield (4.8 kg ha−<sup>1</sup>

study of the impact of climate change on nitrate load in the catchment study.

confidence reasonable to analyse climate change scenarios in the study area.

 **yield (kg ha−<sup>1</sup> y−<sup>1</sup>**

Reference period (1981–2010) 4.66 8.09 Scenario 1 4.89 5 9.71 Scenario 2 4.99 7 11.34 Scenario 3 5.01 8 12.28 Scenario 4 5.16 11 15.89 Scenario 5 4.67 0 9.18 Scenario 6 4.53 −3 10.70 Scenario 7 4.53 −3 10.71 Scenario 8 4.31 −7 15.06 Scenario 9 4.71 1 7.51 Scenario 10 4.75 2 7.18

An increase in the nitrate load is predicted, both increasing in temperature and CO2

trations, while a decrease was forecast for scenarios with reductions in rainfall (**Table 2**). The variation in the nitrate load in future scenarios is lower than that foreseen for streamflow and suspended sediment [15, 27], indicating thta it is less sensitive to changes in rainfall, tempera-

load is similar to that streamflow, except in scenarios with changes in rainfall, as frequently

concentration than to discharge and sediment. The forecast pattern of nitrate

**) Percentage of change**

**4.2. Impacts of changes in temperature, rainfall and CO2**

**NO3**

Temperature (Scenarios 1–4), rainfall (Scenarios 5–8) and CO2

**Table 2.** Response of nitrate yield and concentration to changes in climate variables.

**load**

ture and CO2

defined in **Table 1**.

bias <10% were obtained during the calibration and validation period, indicating that the model was able to simulate the nitrate yield in the research area [28]. So, it was considered suitable for

The utility of the WXGEN weather generator embedded in the SWAT model was tested with the objective of assessing its use in simulations of climate scenarios. For this, the model was run using the climate generator for current conditions (reference period 1981–2010) to simulate nitrate load. Then, these results were compared with simulated nitrate load estimated using observed meteorological data. The statistical indicators (R2 = 0.60 and NSE = 0.55), according to the criteria proposed by Refs. [29, 30], suggest a satisfactory model performance and indicate that the WXGEN weather generator can be used with a reasonable degree of

a close value to the measured values (5.1 kg ha−<sup>1</sup>

) showed

17

concen-

**)**

). Nash-Sutcliffe efficiency >0.50 and percent

http://dx.doi.org/10.5772/intechopen.80709

Assessing the Expected Impact of Climate Change on Nitrate Load in a Small Atlantic…

 **concentrations in nitrate** 

**NO3**

concentration (Scenarios 9 and 10) based on scenarios

 **concentration (mg L−<sup>1</sup>**

**Figure 2.** Variation range of forecast mean annual temperature and rainfall (ENSEMBLES project) for (a) period 2031– 2060 and (b) period 2069–2098. Symbols identify different global models.

The different climatic scenarios used in this study are based on predicted future alterations from regional models in the ENSEMBLES project (socio-economic A1B scenario) for the closest meteorological station of the study area, for the periods 2031–2060 and 2069–2098. Due to variability of projections of future temperature and rainfall among the different models (**Figure 2**), the data from the models were combined to obtain the mean and maximum monthly rainfall and temperature for two periods: 2031–2060 (intermediate future) and 2069–2098 (distant future). Differences between projected and current values for the reference period (1981–2010) were used to develop the climate scenarios.

The stochastic weather generator has proven to be a useful tool for generating climate data series of high spatial and temporal resolutions to be used in climate change impact studies. In this study, the WXGEN weather generator included in the SWAT model was used to produce 30 years of synthetic daily weather data series for each climate change scenario, following the methodology used in [15, 17]. These weather data were used to run the SWAT model to simulate nitrate load under different climate change scenarios.

The nitrate load yields under the selected scenarios were compared with the 30-year simulation of the reference period. T-tests were conducted to determine the significance of the difference in nitrate load between the reference scenario and the climate change scenarios. All of the statistical tests were performed in PASW Statistics 18 for the Windows program package (SPSS Inc.) at a significance level of 0.05.

### **4. Results and discussion**

#### **4.1. Use of WXGEN weather**

The SWAT model was previously calibrated and validated for streamflow, suspended sediment and nitrate yield in the study area [15, 27, 28]. Regarding the nitrate, it pointed out the importance of agricultural land (30% of catchment area) as the main contributor to N losses (77%), which reach the stream mainly in groundwater flow. The estimated yield (4.8 kg ha−<sup>1</sup> ) showed a close value to the measured values (5.1 kg ha−<sup>1</sup> ). Nash-Sutcliffe efficiency >0.50 and percent bias <10% were obtained during the calibration and validation period, indicating that the model was able to simulate the nitrate yield in the research area [28]. So, it was considered suitable for study of the impact of climate change on nitrate load in the catchment study.

The utility of the WXGEN weather generator embedded in the SWAT model was tested with the objective of assessing its use in simulations of climate scenarios. For this, the model was run using the climate generator for current conditions (reference period 1981–2010) to simulate nitrate load. Then, these results were compared with simulated nitrate load estimated using observed meteorological data. The statistical indicators (R2 = 0.60 and NSE = 0.55), according to the criteria proposed by Refs. [29, 30], suggest a satisfactory model performance and indicate that the WXGEN weather generator can be used with a reasonable degree of confidence reasonable to analyse climate change scenarios in the study area.

#### **4.2. Impacts of changes in temperature, rainfall and CO2 concentrations in nitrate load**

The different climatic scenarios used in this study are based on predicted future alterations from regional models in the ENSEMBLES project (socio-economic A1B scenario) for the closest meteorological station of the study area, for the periods 2031–2060 and 2069–2098. Due to variability of projections of future temperature and rainfall among the different models (**Figure 2**), the data from the models were combined to obtain the mean and maximum monthly rainfall and temperature for two periods: 2031–2060 (intermediate future) and 2069–2098 (distant future). Differences between projected and current values for the reference

**Figure 2.** Variation range of forecast mean annual temperature and rainfall (ENSEMBLES project) for (a) period 2031–

The stochastic weather generator has proven to be a useful tool for generating climate data series of high spatial and temporal resolutions to be used in climate change impact studies. In this study, the WXGEN weather generator included in the SWAT model was used to produce 30 years of synthetic daily weather data series for each climate change scenario, following the methodology used in [15, 17]. These weather data were used to run the SWAT model to

The nitrate load yields under the selected scenarios were compared with the 30-year simulation of the reference period. T-tests were conducted to determine the significance of the difference in nitrate load between the reference scenario and the climate change scenarios. All of the statistical tests were performed in PASW Statistics 18 for the Windows program package

The SWAT model was previously calibrated and validated for streamflow, suspended sediment and nitrate yield in the study area [15, 27, 28]. Regarding the nitrate, it pointed out the importance of agricultural land (30% of catchment area) as the main contributor to N losses (77%),

period (1981–2010) were used to develop the climate scenarios.

2060 and (b) period 2069–2098. Symbols identify different global models.

16 Climate Change and Global Warming

simulate nitrate load under different climate change scenarios.

(SPSS Inc.) at a significance level of 0.05.

**4. Results and discussion**

**4.1. Use of WXGEN weather**

An increase in the nitrate load is predicted, both increasing in temperature and CO2 concentrations, while a decrease was forecast for scenarios with reductions in rainfall (**Table 2**). The variation in the nitrate load in future scenarios is lower than that foreseen for streamflow and suspended sediment [15, 27], indicating thta it is less sensitive to changes in rainfall, temperature and CO2 concentration than to discharge and sediment. The forecast pattern of nitrate load is similar to that streamflow, except in scenarios with changes in rainfall, as frequently


Temperature (Scenarios 1–4), rainfall (Scenarios 5–8) and CO2 concentration (Scenarios 9 and 10) based on scenarios defined in **Table 1**.

**Table 2.** Response of nitrate yield and concentration to changes in climate variables.

reported in the literature [12–14, 31], although this does not always happen. For example, Ficklin et al. [6] when analysing the sensitivity of nitrate load to increased CO2 concentrations observed a decrease in nitrate yield linked to increased streamflow.

The results obtained at seasonal scale point out that the differences between seasons are attenuated for those scenarios that consider annual anomalies (e.g. Scenarios 3 and 4). This reveals that the scenarios that consider a certain exchange rate of temperature and/or rainfall, frequently used in the evaluation of impact of climate change on water resources and water quality, show the impacts on an annual scale but will hardly report processes that occur at smaller scales, because they do not take into account the distribution of temperatures and

Assessing the Expected Impact of Climate Change on Nitrate Load in a Small Atlantic…

http://dx.doi.org/10.5772/intechopen.80709

19

Climate change is expected to increase the nitrate load in the Corbeira catchment (**Table 3**). This fact has been frequently attributted to greater water discharge [13, 14, 30]; however, Corbeira behaves differently in that there is an increase in nitrate load and a reduction in river flows, which shows that the streamflow will not be the determining factor of the nitrate load in this catchment in future scenarios. This contrast with the results of other studies in the Iberian Peninsula [12, 37], which reported reductions in N exports due to the decrease of

The simulations performed with the average anomalies (Scenarios 11 and 13, **Table 1**) forecast an increase in the nitrate load in the order of 6% for the period 2031–2060 and 7% for the horizon 2069–2098, reflecting a great similarity for the entire twenty-first century, despite the notable differences expected in the streamflow, which will decrease by 16 and 35% at the mid and end of the twenty-first century [15]. An increase in the nitrate load during the spring and, especially, during the winter, which will be able to counteract the expected losses during the summer and autumn seasons (**Figure 4**), is observed. This behaviour could be related to an increased activity of the enzymes of the soil in the stations with greater water availability, as indicated by [38].

In general, nitrate losses depend on the hydrological balance, the quantities present in the soil (both from natural inputs and fertilisation) and the degree to which they are absorbed by vegetation [39]. It is known that rising temperatures and droughts exert a great influence on nutrient dynamics, since the warming increases mineralisation and drought prevents the absorption of nutrients from the plants and facilitates losses to the system when the rains arrive. The increase in the nitrate load with climate change, in this catchment, could be related to an increase in mineralisation and with the decreased nitrate absorption by

> **) Percentage of change**

**NO3**

**(mg L−<sup>1</sup> )**

 **concentration** 

concentrations based on the

**NO3**

 **yield (kg ha−<sup>1</sup> y−<sup>1</sup>**

Reference period (1981–2010) 4.66 8.09 Scenario 11 4.94 6 10.16 Scenario 12 4.97 7 9.52 Scenario 13 4.97 7 20.12 Scenario 14 5.02 8 23.15

**Table 3.** Response of nitrate load to combined changes in temperature, rainfall and CO2

rainfall throughout the year, being necessary studies at seasonal scales.

streamflow.

scenarios defined in **Table 1**.

**4.3. Impacts of simultaneous changes in climate variables on nitrate load**

Since the entry of fertilisers into the simulations remained constant in relation to reference conditions, the forecast increase in nitrate load with increasing temperature is probably due to a greater contribution of N from agricultural areas, because of the decrease in plant biomass of grasslands and crops [15] with increasing temperature, as well as to the increase in organic nitrogen mineralisation. The N mineralisation in the soil depends on the nature and abundance of organic matter and temperature, humidity and pH and microbial activity. It is well known that it increases with the content of organic matter and temperature [32], which leads to an accumulation of inorganic nitrogen in the soil and an increased risk of leaching [33], provided that the water content does not limit the microbial activity [34]. In the study area, the annual rainfall is 1141 mm (1983/1984–2016/2017) so the water content of the soil should not be limiting for microbial activity, and, therefore, the increase of temperature could accelerate the transformation of nitrogen from organic to inorganic forms. Other authors, such as Ref. [31] in the Yorkshire river basin (the United Kingdom) and Ref. [14] in the Assiniboine basin (Canada), also attributed the increase in nitrate load to the accelerated mineralisation of biomass, although in all these cases, the nitrate followed the same trend as the streamflow.

The effects of climate variables on nitrate load were more noticeable on a seasonal level (**Figure 3**), highlighting the role of seasonal climate variations in affecting future nitrate. When changes in temperature were included, nitrate yield was forecast to rise in all seasons except summer, with the largest load increases in winter. These differences could be due to the increase of mineralisation in summer, with the consequent retention of nitrates in the soils because of the lack of water to transport them, while in the rainy seasons, the transport will be favoured, so it is more likely that load increases. Ref. [35] in laboratory experiences, carried out, therefore, with an artificial heating (heating, greenhouses), reported an increase in net mineralisation rates of 46%, while Ref. [36] when analysing the impact of climate change on quality of water in the Seine River (France) found an increase of between 8% and 26% in the net rate of mineralization.

When rainfall is modified, an increase in the nitrate load is expected in winter and a decline in the other seasons, especially in autumn, although the increase in winter does not compensate the losses in the other stations.

**Figure 3.** Seasonal response of nitrate load to changes in temperature (Scenarios 1–4), rainfall (Scenarios 5–8) and CO2 concentrations (Scenarios 9 and 10) based on the scenarios defined in **Table 1**.

The results obtained at seasonal scale point out that the differences between seasons are attenuated for those scenarios that consider annual anomalies (e.g. Scenarios 3 and 4). This reveals that the scenarios that consider a certain exchange rate of temperature and/or rainfall, frequently used in the evaluation of impact of climate change on water resources and water quality, show the impacts on an annual scale but will hardly report processes that occur at smaller scales, because they do not take into account the distribution of temperatures and rainfall throughout the year, being necessary studies at seasonal scales.

#### **4.3. Impacts of simultaneous changes in climate variables on nitrate load**

reported in the literature [12–14, 31], although this does not always happen. For example,

Since the entry of fertilisers into the simulations remained constant in relation to reference conditions, the forecast increase in nitrate load with increasing temperature is probably due to a greater contribution of N from agricultural areas, because of the decrease in plant biomass of grasslands and crops [15] with increasing temperature, as well as to the increase in organic nitrogen mineralisation. The N mineralisation in the soil depends on the nature and abundance of organic matter and temperature, humidity and pH and microbial activity. It is well known that it increases with the content of organic matter and temperature [32], which leads to an accumulation of inorganic nitrogen in the soil and an increased risk of leaching [33], provided that the water content does not limit the microbial activity [34]. In the study area, the annual rainfall is 1141 mm (1983/1984–2016/2017) so the water content of the soil should not be limiting for microbial activity, and, therefore, the increase of temperature could accelerate the transformation of nitrogen from organic to inorganic forms. Other authors, such as Ref. [31] in the Yorkshire river basin (the United Kingdom) and Ref. [14] in the Assiniboine basin (Canada), also attributed the increase in nitrate load to the accelerated mineralisation of biomass, although in all these cases, the nitrate followed the same trend as the streamflow. The effects of climate variables on nitrate load were more noticeable on a seasonal level (**Figure 3**), highlighting the role of seasonal climate variations in affecting future nitrate. When changes in temperature were included, nitrate yield was forecast to rise in all seasons except summer, with the largest load increases in winter. These differences could be due to the increase of mineralisation in summer, with the consequent retention of nitrates in the soils because of the lack of water to transport them, while in the rainy seasons, the transport will be favoured, so it is more likely that load increases. Ref. [35] in laboratory experiences, carried out, therefore, with an artificial heating (heating, greenhouses), reported an increase in net mineralisation rates of 46%, while Ref. [36] when analysing the impact of climate change on quality of water in the Seine River (France) found an increase of between 8% and 26% in the net rate of mineralization. When rainfall is modified, an increase in the nitrate load is expected in winter and a decline in the other seasons, especially in autumn, although the increase in winter does not compensate

**Figure 3.** Seasonal response of nitrate load to changes in temperature (Scenarios 1–4), rainfall (Scenarios 5–8) and CO2

concentrations (Scenarios 9 and 10) based on the scenarios defined in **Table 1**.

concentrations

Ficklin et al. [6] when analysing the sensitivity of nitrate load to increased CO2

observed a decrease in nitrate yield linked to increased streamflow.

the losses in the other stations.

18 Climate Change and Global Warming

Climate change is expected to increase the nitrate load in the Corbeira catchment (**Table 3**). This fact has been frequently attributted to greater water discharge [13, 14, 30]; however, Corbeira behaves differently in that there is an increase in nitrate load and a reduction in river flows, which shows that the streamflow will not be the determining factor of the nitrate load in this catchment in future scenarios. This contrast with the results of other studies in the Iberian Peninsula [12, 37], which reported reductions in N exports due to the decrease of streamflow.

The simulations performed with the average anomalies (Scenarios 11 and 13, **Table 1**) forecast an increase in the nitrate load in the order of 6% for the period 2031–2060 and 7% for the horizon 2069–2098, reflecting a great similarity for the entire twenty-first century, despite the notable differences expected in the streamflow, which will decrease by 16 and 35% at the mid and end of the twenty-first century [15]. An increase in the nitrate load during the spring and, especially, during the winter, which will be able to counteract the expected losses during the summer and autumn seasons (**Figure 4**), is observed. This behaviour could be related to an increased activity of the enzymes of the soil in the stations with greater water availability, as indicated by [38].

In general, nitrate losses depend on the hydrological balance, the quantities present in the soil (both from natural inputs and fertilisation) and the degree to which they are absorbed by vegetation [39]. It is known that rising temperatures and droughts exert a great influence on nutrient dynamics, since the warming increases mineralisation and drought prevents the absorption of nutrients from the plants and facilitates losses to the system when the rains arrive. The increase in the nitrate load with climate change, in this catchment, could be related to an increase in mineralisation and with the decreased nitrate absorption by


**Table 3.** Response of nitrate load to combined changes in temperature, rainfall and CO2 concentrations based on the scenarios defined in **Table 1**.

linked to the increase in temperature. A higher rate of mineralisation of organic matter will result in the released nitrate being dragged by the water towards the fluvial course. Despite this, the concentrations of nitrates planned for the end of the twenty-first century would be well below the limits established by the current legislation in force for drinking water, so the supposed increase would not be a limitation for human consumption, although a deteriora-

Assessing the Expected Impact of Climate Change on Nitrate Load in a Small Atlantic…

http://dx.doi.org/10.5772/intechopen.80709

21

This paper is a contribution to the projects 10MDS103031 of the Xunta de Galicia and CGL2014- 56907-R of the Programa Estatal de Investigación, Desarrollo e Innovación Orientada a los Retos de la Sociedad, which was funded by the Spanish Ministry of Economy and Competitiveness. M.L. Rodríguez-Blanco has been awarded a postdoctoral research contract (Juan de la Cierva Programme), which was funded by the Spanish Ministry of Economy and Competitiveness.

María Luz Rodríguez-Blanco\*, María Mercedes Taboada-Castro, Ricardo Arias and

Faculty of Sciences, Centre for Advanced Scientific Research (CICA), University of

[1] Wade A, Soulsby C, Langan SJ, Whitehead PG, Edwards AG, Butterfield D, et al. Modelling in stream nitrogen variability in the Dee catchment, NE Scotland. The Science of the

[2] Kolenbrander GJ. Leaching of nitrogen in agriculture. In: Brogan JC, editor. Nitrogen Losses and Surface Runoff from Land Spreading of Manures. The Hague: Martinus

[3] Camargo JA, Alonso A, Salamanca A. Nitrate toxicity to aquatic animals: A review with new data for freshwater invertebrates. Chemosphere. 2005;**58**:1255-1267. DOI: 10.1016/j.

Total Environment. 2001;**265**:229-252. DOI: 10.1016/S0048-9697(00)00661-6

tion in the quality of water in the study area is expected.

**Acknowledgements**

**Conflict of interest**

**Author details**

María Teresa Taboada-Castro

A Coruna, Coruña, Spain

Nijhoff; 1982. pp. 199-216

chemosphere.2004.10.044

**References**

The authors declare no conflict of interest.

\*Address all correspondence to: mrodriguezbl@udc.es

**Figure 4.** Seasonal response of nitrate load to combined changes in temperature, rainfall and CO2 concentrations based on the scenarios defined in **Table 1**.

vegetation. A reduction in nitrate absorption is predicted for all land uses, especially significant in prairie areas (15% for the period 2031–2060 and 22% for 2069–2098). This points to less fertilizer being needed in these areas, which should be taken into consideration when planning management strategies in order to mitigate the impacts of potential climate change.

Despite the increase in nitrate concentration with climate change, the figures expected by the end of the twenty-first century would be well below the limits established by the current legislation for water for human consumption [40], so the supposed increase would be of concern for limitation for the human consumption, although it would result in degraded water quality.

The effects of land use have not been addressed in this study, since it was restricted to investigating the impacts of climate change on nitrate load because there is generally more uncertainty in climate projection than land use. So, more attention should be given to investigating the impacts due to climate change rather than land-use change. However, the effect of future land use on future nitrate load is controversial [10, 37, 39]. Some authors indicated that the effect of land cover is more visible than the climate change effect [37], while others found that stream nitrate concentrations were much more impacted by climate change than land-cover changes [10, 39]. This highlights the need to understand the combined effect of changes in land use and climate on catchment nitrogen discharge. This issue will be the aim of further research into modelling the water quality in the catchment study.

### **5. Summary and conclusions**

This study was carried out to determine the effects of climate change on nitrate load in an agro-forested catchment located in NW Spain using the WXGEN weather generator included in the SWAT model. The results suggested that the WXGEN generator was able to adequately estimate long-term nitrate load.

Overall, it is verified that the nitrate load will increase in the future horizons in relation to current values (about 6 and 7% for the periods 2031–2060 and 2069–2098, respectively), possibly due to the decline in grassland biomass, as well as an increase in the rate of mineralisation linked to the increase in temperature. A higher rate of mineralisation of organic matter will result in the released nitrate being dragged by the water towards the fluvial course. Despite this, the concentrations of nitrates planned for the end of the twenty-first century would be well below the limits established by the current legislation in force for drinking water, so the supposed increase would not be a limitation for human consumption, although a deterioration in the quality of water in the study area is expected.

### **Acknowledgements**

**Figure 4.** Seasonal response of nitrate load to combined changes in temperature, rainfall and CO2

research into modelling the water quality in the catchment study.

**5. Summary and conclusions**

estimate long-term nitrate load.

vegetation. A reduction in nitrate absorption is predicted for all land uses, especially significant in prairie areas (15% for the period 2031–2060 and 22% for 2069–2098). This points to less fertilizer being needed in these areas, which should be taken into consideration when planning management strategies in order to mitigate the impacts of potential climate change. Despite the increase in nitrate concentration with climate change, the figures expected by the end of the twenty-first century would be well below the limits established by the current legislation for water for human consumption [40], so the supposed increase would be of concern for limitation for the human consumption, although it would result in degraded

The effects of land use have not been addressed in this study, since it was restricted to investigating the impacts of climate change on nitrate load because there is generally more uncertainty in climate projection than land use. So, more attention should be given to investigating the impacts due to climate change rather than land-use change. However, the effect of future land use on future nitrate load is controversial [10, 37, 39]. Some authors indicated that the effect of land cover is more visible than the climate change effect [37], while others found that stream nitrate concentrations were much more impacted by climate change than land-cover changes [10, 39]. This highlights the need to understand the combined effect of changes in land use and climate on catchment nitrogen discharge. This issue will be the aim of further

This study was carried out to determine the effects of climate change on nitrate load in an agro-forested catchment located in NW Spain using the WXGEN weather generator included in the SWAT model. The results suggested that the WXGEN generator was able to adequately

Overall, it is verified that the nitrate load will increase in the future horizons in relation to current values (about 6 and 7% for the periods 2031–2060 and 2069–2098, respectively), possibly due to the decline in grassland biomass, as well as an increase in the rate of mineralisation

on the scenarios defined in **Table 1**.

20 Climate Change and Global Warming

water quality.

concentrations based

This paper is a contribution to the projects 10MDS103031 of the Xunta de Galicia and CGL2014- 56907-R of the Programa Estatal de Investigación, Desarrollo e Innovación Orientada a los Retos de la Sociedad, which was funded by the Spanish Ministry of Economy and Competitiveness. M.L. Rodríguez-Blanco has been awarded a postdoctoral research contract (Juan de la Cierva Programme), which was funded by the Spanish Ministry of Economy and Competitiveness.

### **Conflict of interest**

The authors declare no conflict of interest.
