**1. Introduction**

Agriculture plays an important role in Iran's economy. It accounts for 18% of gross domestic product (GDP), 25% of employment, 85% of food requirements, 25% of non-oil exports, and 90% of input materials for the local industries [1].

The climate of Iran is very diverse, and great extremes are common features of it due to its geographic location and highly varied topography. The major area of the country (almost 90%) could be classified as arid to semiarid. Of the characteristic

of such a climate are hot summers with the temperatures reaching up to 55°C in the interior and southern parts. Evaporation demand is much higher than precipitation in most areas of the country. Consequently, water resource management under these conditions is an important issue and a great challenge especially in the agricultural sector.

Despite reliance of the country on agriculture, especially irrigated agriculture, water resources required for agricultural production are limited but provide a vital input to agricultural production in Iran. Currently more than 93% of water consumption (84 billion cubic meter; BCM) is used to irrigate 8.2 million hectares (Mha) of lands. Considering the growing demand for water in industrial and municipal sectors, combined with the environmental concerns, in the near future, there will be lesser freshwater resources available for agriculture in the country.

The latest agricultural statistics reveal that Iran produced 77 million tons of agricultural products from 84 BCM of water consumed. Therefore, currently the average water productivity (WP) in agriculture is almost 0.92 kg/m3 . This value is quite low and necessitates the use of appropriate approaches for its improvement [2].

Studies conducted on farmers' fields in five regions in the country (Kerman, Hamedan, Moghan, Golestan, and Khuzestan provinces) revealed that WP for the irrigated wheat varies in the range of 0.56–1.46, sugar beet (0.59–1.28), sugarcane (0.31), potato (1.45–3.0), silage corn (6.46), cotton (0.73), alfalfa (1.48), barley (0.56), and chickpea (0.18) kg/m3 [3, 4]. Based on the review of 84 references on values of WP during the past 25 years, it was found out that the average WPs of wheat are about 1.09 kg/m3 [5].

However, there is no information available or accessible that addresses assessment of WP in the Lower Karkheh River Basin (L-KRB). Preliminary estimates that are based on farmers' field visits and questionnaire on crop yield and applied water suggest WP of irrigated wheat to be about 0.6 kg/m3 in this region.

Soil and water salinity are major threats and barriers to the optimal crop production systems in most parts of the world, especially in arid and semiarid regions, including Iran [6, 7]. The salinization of land and water resources has been the main consequence of two factors including naturally occurring phenomena and anthropogenic activities. The first factor has caused primary fossil salinity and/or sodicity, while the second factor, which is more prominent, has caused human-induced or secondary salinity and/or sodicity [8].

Soil and water resource salinities are the major threats to the crop production and sustainability of natural resources, especially in irrigated agriculture based on groundwater resources in Iran. Salt-affected soils are the major features of many parts of the country, particularly in the Central Plateau, which is surrounded by two main ranges of high mountains along with the northwest to northeast (Alborz range) and northwest to southern parts and southeast (Zagros range).

Irrigated agriculture is the main cropping system in the country, while out of which at least 4.1 Mha of 8.2 Mha of total irrigated lands (nearly 50%) suffer from different levels of salinity and sodicity [9]. This is under conditions that irrigated agriculture is the main focus of government plans for increasing agricultural products and food security, especially in the recent decades.

Irrigated agriculture with low irrigation efficiencies has been one of the causes of human-induced salinization of land and water resources. This phenomenon has occurred mostly in unique topographic conditions of semi-closed or closed intermountain basins where irrigated agriculture has been practiced for many years. Distribution of land salinity in Iran is diverse. The extent and characteristics of salt-affected soils in Iran have been investigated and are reported by several

**177**

*Water Productivity Improvement Under Salinity Conditions: Case Study of the Saline Areas…*

researches [10–14]. Overall, the slight to moderate salt-affected soils are mostly formed on the piedmonts at the foot of the Elburz Mountains in the northern part of the country, while the lands with severe to extreme degrees of salinity are mostly located in the Central Plateau, Khuzestan province plains, Southern Coastal Plains, and some parts of the Caspian Coastal Plains (mainly in Golestan

Average yields of the common crops vary highly depending on the climatic and soil and water conditions. However, because of many limiting factors, mainly water and salinity stresses, the achieved yields are generally suboptimal. Average crop yield losses due to salinity stress are estimated to be up to 50% in areas where

Large areas of Iran suffer from salinity and sodicity hazards. Wide distribution of such areas in the country reflects the fact that many factors are contribution to this phenomenon. Indeed, the causes of soil salinity could be divided into natural or primary causes and secondary or man-made causes. The natural causes include geological and physiographic conditions, climatic conditions, and salt loads by water. The man-made causes are mainly because of improper irrigation management followed by waterlogging problems. Waterlogging is mostly occurring in the irrigation networks developed under regulated waters, e.g., dams. Because of water scarcity, especially in recent decades, the increased use of marginal brackish waters for irrigation without required management also has worsened this problem and is sparking the soil's secondary salinization. Overall, the man-made causes of soil salinity in Iran could be nominated as poor water management, use of saline groundwater, over exploitation of groundwater, poor land preparation, fallowing and overgrazing of lands, improper cropping pattern, and sea-water intrusion into

Because of the importance of facing with salinity in agriculture of Iran, many research projects are conducted specifically on salinity issues in the country till date. These research projects cover some provinces or regions in the country facing with soil and water salinity hazard, e.g., Yazd, Golestan, Fars, Khurasan, Khuzestan, Markazi, Hormozgan (Bushehr), Moghan, Azerbaijan, Esfahan, and Qom. Very roughly it could be stated that till now the majority of research projects conducted in the country cover mainly the following areas including the extent of salt-affected soils, characteristics of salt-affected soils, methods of reclamation of salt-affected soils, crop fertility and productivity potentials of salt-affected soils, productivity of saline water used in different parts of the country, amount and distribution of saline water resources (as drainage water and groundwater resources), and quality of saline waters in regard to the salts and other contaminants. However, very limited salinity research projects have been conducted on the aspects of evaluation and improvement of WP under salinity

Karkheh River Basin (KRB) is a typical and important basin in Iran regarding the supply of water resources for the fertile plains and favorite climatic conditions for productive agriculture in the downstream basin, mainly located in the Khuzestan province. The other important characteristic of the KRB is that both dryland and irrigated agricultural production systems exist in the basin. Water in KRB is becoming scarcer because of climate change together with the population growth. Therefore water demand, especially for the irrigated areas on the downstream basin which are under intensive development, is increasing. The productivity of rainfed agriculture is low, conventional irrigation management is poor, cropping systems are suboptimal, and policies and institutions are weak [16]. Considering these inefficiencies, improvement of water productivity in agricultural sector is a recent and

conditions in the country in general and in the L-KRB in specific.

important policy of the country especially in KRB.

*DOI: http://dx.doi.org/10.5772/intechopen.86891*

province in the northeast) [7].

salinity is present [15].

coastal areas.

### *Water Productivity Improvement Under Salinity Conditions: Case Study of the Saline Areas… DOI: http://dx.doi.org/10.5772/intechopen.86891*

researches [10–14]. Overall, the slight to moderate salt-affected soils are mostly formed on the piedmonts at the foot of the Elburz Mountains in the northern part of the country, while the lands with severe to extreme degrees of salinity are mostly located in the Central Plateau, Khuzestan province plains, Southern Coastal Plains, and some parts of the Caspian Coastal Plains (mainly in Golestan province in the northeast) [7].

Average yields of the common crops vary highly depending on the climatic and soil and water conditions. However, because of many limiting factors, mainly water and salinity stresses, the achieved yields are generally suboptimal. Average crop yield losses due to salinity stress are estimated to be up to 50% in areas where salinity is present [15].

Large areas of Iran suffer from salinity and sodicity hazards. Wide distribution of such areas in the country reflects the fact that many factors are contribution to this phenomenon. Indeed, the causes of soil salinity could be divided into natural or primary causes and secondary or man-made causes. The natural causes include geological and physiographic conditions, climatic conditions, and salt loads by water. The man-made causes are mainly because of improper irrigation management followed by waterlogging problems. Waterlogging is mostly occurring in the irrigation networks developed under regulated waters, e.g., dams. Because of water scarcity, especially in recent decades, the increased use of marginal brackish waters for irrigation without required management also has worsened this problem and is sparking the soil's secondary salinization. Overall, the man-made causes of soil salinity in Iran could be nominated as poor water management, use of saline groundwater, over exploitation of groundwater, poor land preparation, fallowing and overgrazing of lands, improper cropping pattern, and sea-water intrusion into coastal areas.

Because of the importance of facing with salinity in agriculture of Iran, many research projects are conducted specifically on salinity issues in the country till date. These research projects cover some provinces or regions in the country facing with soil and water salinity hazard, e.g., Yazd, Golestan, Fars, Khurasan, Khuzestan, Markazi, Hormozgan (Bushehr), Moghan, Azerbaijan, Esfahan, and Qom. Very roughly it could be stated that till now the majority of research projects conducted in the country cover mainly the following areas including the extent of salt-affected soils, characteristics of salt-affected soils, methods of reclamation of salt-affected soils, crop fertility and productivity potentials of salt-affected soils, productivity of saline water used in different parts of the country, amount and distribution of saline water resources (as drainage water and groundwater resources), and quality of saline waters in regard to the salts and other contaminants. However, very limited salinity research projects have been conducted on the aspects of evaluation and improvement of WP under salinity conditions in the country in general and in the L-KRB in specific.

Karkheh River Basin (KRB) is a typical and important basin in Iran regarding the supply of water resources for the fertile plains and favorite climatic conditions for productive agriculture in the downstream basin, mainly located in the Khuzestan province. The other important characteristic of the KRB is that both dryland and irrigated agricultural production systems exist in the basin. Water in KRB is becoming scarcer because of climate change together with the population growth. Therefore water demand, especially for the irrigated areas on the downstream basin which are under intensive development, is increasing. The productivity of rainfed agriculture is low, conventional irrigation management is poor, cropping systems are suboptimal, and policies and institutions are weak [16]. Considering these inefficiencies, improvement of water productivity in agricultural sector is a recent and important policy of the country especially in KRB.

*Multifunctionality and Impacts of Organic and Conventional Agriculture*

tural sector.

improvement [2].

(0.56), and chickpea (0.18) kg/m3

secondary salinity and/or sodicity [8].

wheat are about 1.09 kg/m3

of such a climate are hot summers with the temperatures reaching up to 55°C in the interior and southern parts. Evaporation demand is much higher than precipitation in most areas of the country. Consequently, water resource management under these conditions is an important issue and a great challenge especially in the agricul-

Despite reliance of the country on agriculture, especially irrigated agriculture,

. This

water resources required for agricultural production are limited but provide a vital input to agricultural production in Iran. Currently more than 93% of water consumption (84 billion cubic meter; BCM) is used to irrigate 8.2 million hectares (Mha) of lands. Considering the growing demand for water in industrial and municipal sectors, combined with the environmental concerns, in the near future, there will be lesser freshwater resources available for agriculture in the country. The latest agricultural statistics reveal that Iran produced 77 million tons of agricultural products from 84 BCM of water consumed. Therefore, currently the average water productivity (WP) in agriculture is almost 0.92 kg/m3

value is quite low and necessitates the use of appropriate approaches for its

values of WP during the past 25 years, it was found out that the average WPs of

However, there is no information available or accessible that addresses assessment of WP in the Lower Karkheh River Basin (L-KRB). Preliminary estimates that are based on farmers' field visits and questionnaire on crop yield and applied water

Soil and water salinity are major threats and barriers to the optimal crop production systems in most parts of the world, especially in arid and semiarid regions, including Iran [6, 7]. The salinization of land and water resources has been the main consequence of two factors including naturally occurring phenomena and anthropogenic activities. The first factor has caused primary fossil salinity and/or sodicity, while the second factor, which is more prominent, has caused human-induced or

Soil and water resource salinities are the major threats to the crop production and sustainability of natural resources, especially in irrigated agriculture based on groundwater resources in Iran. Salt-affected soils are the major features of many parts of the country, particularly in the Central Plateau, which is surrounded by two main ranges of high mountains along with the northwest to northeast (Alborz

Irrigated agriculture is the main cropping system in the country, while out of which at least 4.1 Mha of 8.2 Mha of total irrigated lands (nearly 50%) suffer from different levels of salinity and sodicity [9]. This is under conditions that irrigated agriculture is the main focus of government plans for increasing agricultural

Irrigated agriculture with low irrigation efficiencies has been one of the causes of human-induced salinization of land and water resources. This phenomenon has occurred mostly in unique topographic conditions of semi-closed or closed intermountain basins where irrigated agriculture has been practiced for many years. Distribution of land salinity in Iran is diverse. The extent and characteristics of salt-affected soils in Iran have been investigated and are reported by several

range) and northwest to southern parts and southeast (Zagros range).

products and food security, especially in the recent decades.

[5].

suggest WP of irrigated wheat to be about 0.6 kg/m3

Studies conducted on farmers' fields in five regions in the country (Kerman, Hamedan, Moghan, Golestan, and Khuzestan provinces) revealed that WP for the irrigated wheat varies in the range of 0.56–1.46, sugar beet (0.59–1.28), sugarcane (0.31), potato (1.45–3.0), silage corn (6.46), cotton (0.73), alfalfa (1.48), barley

[3, 4]. Based on the review of 84 references on

in this region.

**176**

In the upper KRB, the dryland agriculture prevails. The challenges for the rural households in such areas are similar to the ones in other dryland areas, i.e., agricultural options are limited, and wheat, barely, and pulses are dominant cropping patterns in the landscape. Agricultural outputs are usually low and unstable, due mainly to the resource degradation, drought spells, and climate change impacts [16]. Irregular rainfall on poorly vegetated hill slopes results in severe soil erosion, downstream flooding, and sedimentation. Consequently, the lifetime of the Karkheh Reservoir Dam in the downstream basin is dwindling rapidly. These environmental constraints combined with their economic problems make this southwest corner of Iran one of the poor areas of the country with a high outmigration rate [16].

KRB had been selected as one of the nine benchmark basins of the CGIAR Challenge Program on Water and Food (CPWF<sup>1</sup> ). One of the CPWF Phase 1 projects focuses on interventions for the improvement of on-farm agricultural WP in KRB. This project was carried out jointly by the International Center for Agricultural Research in the Dry Areas (ICARDA) and Agricultural Research, Education and Extension Organization (AREEO) of Iran. The objectives of the project were to develop biophysical interventions to improve the farm and basin level of WP and sustainable management of the natural resources and to develop appropriate policies and institutions supporting the project interventions to help the poor communities for the improvement of their income and livelihoods. Moreover, the project aimed at strengthening and enhancing the capacity of the National Agricultural Research and Extension Systems (NARES) of Iran.

KRB is becoming a water-scarce area, and droughts and climate change are becoming permanent features of this region. Because of water scarcity and degradation of land and water resources, livelihoods of rural communities are at stake. With the current rate of deterioration of natural resources if no remediation is taken, the situation will worsen in the near future. However, there are great potentials for the improvement of land and water productivities in the KRB. Therefore KRB was well adapted to be a pilot area for the development-oriented research activities to be implemented under Phase 1 of CGIAR Challenge Program on Water and Food (CPWF). KRB situation provided a unique opportunity for the CPWF to make an impact through improvements in land and water productivities, which in turn will improve the livelihoods of rural poor living in this basin. The issues of KRB have a great similarity with other basins located in the similar hydrological conditions, e.g., West Asia and North Africa (WANA) region.

This chapter provides an overview of the soil and water potential of the L-KRB and the salinity and waterlogging constraints to agricultural production and agricultural WP improvement under saline areas of L-KRB. The findings are mostly based on the research results conducted during the CPWF Phase 1 comprehensive project in KRB.

**179**

**Figure 1.**

*Geographical location and boundaries of KRB.*

*Water Productivity Improvement Under Salinity Conditions: Case Study of the Saline Areas…*

KRB is located in the west to southwest of Zagros ranges in Iran (**Figure 1**). It is located between 56°, 34′–58°, 30′ north latitude and 46°, 06′–49°, 10′ longitude.

areas of KRB are mostly in the eastern and central parts. The plains are mostly in the northern and southern parts and cover almost 45% of the basin area. Hypsometric studies indicate that 75% of the basin is located in altitudes of 1000–2000 and 0.6%

The Karkheh River arises from the confluence of numerous large and small tributaries including the three large rivers, namely, Gamasiyab, Ghareh-So, and Kashkan. The Karkheh River has various names along its route and is locally best known as the Saymareh River at the point where the Gamasiyab and Ghareh-So Rivers combine, and later the point where the Kashkan River flows into the main waterway is known as the Karkheh River. When approaching to the Khuzestan province hypsometric and slope of the basin decrees and gently the river ultimately flows into the Hawr-al-Azim (HAA) wetland at the basin outlet. Therefore KRB

Based on general hydrological classification of basins in Iran, the KRB is consid-

The pattern of precipitation in KRB is affected by Mediterranean regime. It means

that the dry season is coinciding with summer and rainy season match with cold months. The rainfall distribution in the basin is very scatter, but most of the rain falls in winter and autumn seasons. The annual precipitation of the basin is 219 mm in Hamidieh (in L-KRB) to 765 mm in the northern dryland farming areas (in upper KRB). Based on climatic maps, the hottest areas of the basin are located in its southern parts (L-KRB) and are surrounded by the 25°C iso-temperature (isohyets) contours. The coldest areas of the basin are located in altitude higher than 3000 m and are mostly located in the north and northeast of the basin and are surrounded by the

Evaporation in KRB varies between 1800 and 3600 mm depending on the altitude. For example, it is around 3561 mm in Abdul-Khan Station in an altitude of 40 m in L-KRB. Almost 79% of annual evaporation occurs from May to September.

). Out of which

are plains and hills. The mountainous

The area of the basin (inside Iran) is 50,764 square kilometers (km2

ered as one of the sub-basins of the Persian Gulf Great Basin.

*DOI: http://dx.doi.org/10.5772/intechopen.86891*

of the basin is above 2500 m altitude.

could be classified as a closed basin.

5°C isohyets' contour map.

27,645 km2

**2. Karkheh River Basin characteristics**

are mountains and 23,119 km2

<sup>1</sup> The Challenge Program on Water and Food (CPWF) is one of the pilot programs designed to reinvent the business model for the CGIAR. The CPWF was launched in 2002 as a reform initiative of the CGIAR, the Consultative Group on International Agricultural Research. CPWF aims to increase the resilience of social and ecological systems through better water management for food production (crops, fisheries, and livestock). CPWF does this through an innovative research and development approach that brings together a broad range of scientists, development specialists, policymakers, and communities to address the challenges of food security, poverty, and water scarcity. CPWF Phase 1 worked in nine river basins globally: Andean system of basins, Indo-Gangetic, Limpopo, Mekong, Nile River, Yellow River, Sao Francisco, Volta, and Karkheh River Basin.

*Water Productivity Improvement Under Salinity Conditions: Case Study of the Saline Areas… DOI: http://dx.doi.org/10.5772/intechopen.86891*
