**1. Introduction**

Water has a unique place on the planet as it supports life on the earth. Clean water is an important resource for drinking, irrigation, industry, transportation, recreation, fishing, hunting, the biodiversity support, and sheer aesthetic enjoyment.

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The main water stressors are human activities reflected by nutrients' inputs and climate change by increasing temperature and extreme weather phenomena. Nutrients, especially phospho‐ rus and nitrogen from various sources, and increasing temperature are the major causes of degradation of the aquatic ecosystems, namely eutrophication.

Eutrophication can be a natural process in surface waters occurring as they age through geological time, over hundreds or thousands of years or it can be very fast when the nutrients are present in high concentrations, due to anthropogenic activities and climate change [1, 2].

Degradation of these vital water resources (coastal areas, lakes, and reservoirs all over the world) can be measured by the loss of natural systems, followed by the modification of the trophic chains with their component species, and the increase in the number of individuals of a species in preference to others [3].

It is considered one of the major forms of water stress, which is extremely variable being influenced by the specific characteristics of sites such as nutrient stoichiometry, biodiversity, climate-related factors (temperature, precipitation, and storming), and the basin geomorphol‐ ogy [4, 5].

The main sources of nutrients (nitrogen and phosphorus), its effect on water quality associated with influence of climate change factors, are presented in this chapter. The stressors' effects, nutrients, and climate exchange were highlighted by the parameters: temperature, pH, Secchi disc (SD) transparency, chlorophyll *a* (CHL), dissolved oxygen (DO), total phosphorus (TP), total nitrogen (TN), and plankton populations. The trophic stage was assessed using temper‐ ature, limiting nutrients concentrations (N total, P total), and their ratio TN/TP, primary productivity (chlorophyll *a*), and transparency (Secchi disc) parameters, and also the Carlson's index that includes all of these. To illustrate how one can achieve a surface water quality evaluation was presented using the trophic status of Lake Snagov, Romania, assessment.

### **2. Water stressors**

Human activities accelerate the degradation rate of water, air, and soil. Continuous enrichment with nutrients and climate change are important stressors for water bodies. Increasing nutrients' concentrations associated with increasing temperature and extreme weather events involve important changes in the physical, chemical, and the biological configuration of the waters' characteristics [6].

#### **2.1. Nutrient inputs**

### *2.1.1. Sources of nutrients*

The mains stressors that influence the water quality and trophic chain reaction are macronu‐ trients, such as phosphorus (P), nitrogen (N), silicon (Si), and micronutrients such as potassium (K), sulfur (S), calcium (Ca), magnesium (Mg), iron (Fe), and molybdenum (Mo) are also needed. N, P, and K are considered primary nutrients, and N and P are the major limiting nutrients in most aquatic environments [6–8].

The nutrient inputs in natural water body by both point and disperse sources. The point sources may be wastewater effluents (domestic and industrial)—most importantly, runoff and leach flows from waste disposal systems, infiltrations from animal feedlots, unsewered industrial sites runoffs, sanitary sewers overflows, runoff from constructions sites, erosion into the lake. The most important dispersed (nonpoint) sources are leachate of synthetic and natural fertilizes from agriculture parcels and forest, runoff and infiltration from animal feedlots, runoffs from agriculture/irrigation, pasture and range, urban runoff from not-sewered areas, septic tank leachates, and atmospheric deposition on water surface [1, 10].

The results of enrichment of nutrient consist in the increase of aquatic primary production and lead to visible algal blooms causing high turbidity and increasing anoxia in the deeper parts, thus increasing the acidity and the modified aquatic ecosystems [9–11]. All these involve the water quality deterioration, drinking water treatment problems, and decrease in the perceived aesthetic value of the water body. The physical and chemical properties of the water influence the distribution and trophic dynamics in the water body. Depending on the content of nutrient and the production of organic materials, the water can have a trophic (degradation) level lower or higher.

### *2.1.2. Water trophic level classification*

The main water stressors are human activities reflected by nutrients' inputs and climate change by increasing temperature and extreme weather phenomena. Nutrients, especially phospho‐ rus and nitrogen from various sources, and increasing temperature are the major causes of

Eutrophication can be a natural process in surface waters occurring as they age through geological time, over hundreds or thousands of years or it can be very fast when the nutrients are present in high concentrations, due to anthropogenic activities and climate change [1, 2].

Degradation of these vital water resources (coastal areas, lakes, and reservoirs all over the world) can be measured by the loss of natural systems, followed by the modification of the trophic chains with their component species, and the increase in the number of individuals of

It is considered one of the major forms of water stress, which is extremely variable being influenced by the specific characteristics of sites such as nutrient stoichiometry, biodiversity, climate-related factors (temperature, precipitation, and storming), and the basin geomorphol‐

The main sources of nutrients (nitrogen and phosphorus), its effect on water quality associated with influence of climate change factors, are presented in this chapter. The stressors' effects, nutrients, and climate exchange were highlighted by the parameters: temperature, pH, Secchi disc (SD) transparency, chlorophyll *a* (CHL), dissolved oxygen (DO), total phosphorus (TP), total nitrogen (TN), and plankton populations. The trophic stage was assessed using temper‐ ature, limiting nutrients concentrations (N total, P total), and their ratio TN/TP, primary productivity (chlorophyll *a*), and transparency (Secchi disc) parameters, and also the Carlson's index that includes all of these. To illustrate how one can achieve a surface water quality evaluation was presented using the trophic status of Lake Snagov, Romania, assessment.

Human activities accelerate the degradation rate of water, air, and soil. Continuous enrichment with nutrients and climate change are important stressors for water bodies. Increasing nutrients' concentrations associated with increasing temperature and extreme weather events involve important changes in the physical, chemical, and the biological configuration of the

The mains stressors that influence the water quality and trophic chain reaction are macronu‐ trients, such as phosphorus (P), nitrogen (N), silicon (Si), and micronutrients such as potassium (K), sulfur (S), calcium (Ca), magnesium (Mg), iron (Fe), and molybdenum (Mo) are also

degradation of the aquatic ecosystems, namely eutrophication.

a species in preference to others [3].

ogy [4, 5].

16 Water Stress in Plants

**2. Water stressors**

waters' characteristics [6].

**2.1. Nutrient inputs**

*2.1.1. Sources of nutrients*

According to the content of mineral nutrients, and the effect of these on primary production, the trophic level classifications of water can be characterized using the terms as follows [12–14]:





### **2.2. Climate change**

### *2.2.1. Introduction*

Both natural and human factors change the earth's climate. The natural factors which cause the changes in climate are the modifications in the earth's orbit, alterations in the solar activity, or volcanic eruptions. Since the Industrial Revolution began around 1750, human activities have contributed substantially to climate change by adding greenhouse gas emissions including water vapors (H2O), carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and several others which have caused the earth's surface temperature to rise. Atmospheric CO2 concentrations have increased by more than 40% since preindustrial times, from approxi‐ mately 280 parts per million by volume (ppmv) in the eighteenth century to 396 ppmv in 2013. **Figure 1** shows the variations of the atmospheric CO2, CH4, N2O per year [7, 16].

**Figure 1.** Atmospheric CO2, CH4, N2O variations per year [7].

### *2.2.2. Effect of climate change*

Freshwater resources are vulnerable to climate change; warming of the climate system increases global average air and influences the hydrological cycle [17]. Climate change associated with the water cycle (**Figure 2**) includes water body and land temperature increase [18], accelerated glaciers melting, decreasing the surface of water and land occupied with snow, increased evaporation and level of lakes water reduction, increased level of coastal marine and ocean and inundation, wetland loss by sea level rise, changes in the seasonal distribution and amount of precipitation, increasing precipitation intensity sometimes as extreme weather—storms, changes in the balance between snow and rain, increasing nutrients' concentration by soil washing and soil erosion [19], increasing acidity in rivers, lakes, seas, and oceans [20]. **Figure 2** shows the conceptual diagram visualizing the main components of climate change and their major effects on freshwaters [21].

Waters with similar effect filters, however, should respond similar to climate variability. Hydrodynamic patterns are influenced largely by the depth and size of the lake affecting the annual heat budget, temperature stratification during summer and winter, the concentration of oxygen in the hypolimnion, salt solubility, and availability of nutrients. The retention time (a factor depending on morphometry and through-flow) determines if internal or external processes dominate.

Water Stress Induced by Enrichment of Nutrient and Climate Change Factors http://dx.doi.org/10.5772/64665 19

**Figure 2.** Conceptual diagram visualizing the main components of climate change and their major impacts on freshwa‐ ters [21].

Warming of the atmosphere will lead to warmer and wetter winters, and hotter and drier summers. Large quantities of precipitation are expected in winter and spring which will come down as rain rather than snow. The flow regime in stream and rivers changes reaching the maximum flow faster than usual. Larger runoffs combined with more frequent extreme rainfalls may result in floods, increased erosion, and wash out of nutrients, which ultimately lead to the eutrophication of rivers and lakes.

In subtropical and tropical regions, storms and floods occur during rainy seasons. In temperate zones, the summer temperatures increase, the stream and river flow decrease, and the period of thermal stratification extends. In the warmer lakes, the oxygen is less available because the solubility of this element declines with increasing temperature. Decreasing oxygen concen‐ tration with increasing temperature and increasing the decomposition rates of organic compounds will increase the consumption of oxygen, which may lead to deoxygenating in deeper parts of lakes. In glaciated regions, the discharge will first increase due to more melt water and later decrease when glaciers have disappeared [19, 22, 23].
