Economic Impact Assessment of Quantity and Quality Changes in Irrigation Water on Agriculture in Kerman Province

Excessive extraction and depletion of groundwater aquifers and critical water status in more than 120 plains of the country have resulted in decreased water quality. In addition, the productivity of agricultural water of Iran in different years is on average lower than other countries. The results of most salinity studies show that high concentrations of salt in soil solution have significantly reduced the yield of crops and horticultural products in the country. More profitability and high market value of pistachio crops in comparison with other crops has led to many efforts by Kerman farmers to develop pistachio groves. Various studies show that over- extraction of groundwater resources in Kerman province and decreasing water quality of wells and consequently increasing salinity has reduced root growth and crop yield. In the present study, economic analysis of the effects of quantitative and qualitative changes of water in different scenarios on concepts such as yield, cropping pattern, water consumption and productivity and gross profit of farmers in major county of Kerman province has been investigated.

To achieve the goals of present study, we first obtained the salinity-water-yield function for each product. Then, by regarding this function in the positive mathematical programming model, the effect of different scenarios including changing water salinity level and changing water supply, on factors such as water productivity, crop yield, cropping pattern and gross profit of farmers especially pistachio growers are analyzed and investigated. In this regard, scenarios of 15% reduction of available water resources in different regions and increase of one salinity unit individually in combination with the above mentioned indicators are evaluated by conducting positive mathematical programming model and are identified by studied areas.

Investigation of the data reveals that discharge of aquifers is higher for recharge in all studied areas and consequently reduction of groundwater level has occurred. The result shows that the yield sensitivity of pistachio and barley crops to one unit soil salinity is lower than other crops. However, the highest yield loss as a result of increasing one unit in soil salinity as a scenario for canola and potato crops is 13 and 12 percent, respectively. Due to the decrease in quality and quantity of water resources, the total area under cultivation has decreased, with the lowest and highest reduction being in Kerman and Rafsanjan County, respectively. The results show that the scenario of 15% reduction in available water resources would just increases the area of Bardsir and leads to a decrease in one cubic meter economic productivity for other areas. On the other hand, by applying all three scenarios including decrease in quantity and quality of water resources, gross margin and water use will be reduced due to the decrease in the cultivated area of high yield and water based crops such as alfalfa and pistachio in Kerman region. Also, the results indicate that for all studied areas, increase in salinity by one unit has the most negative effect on economic productivity of one cubic meter of water consumption. In addition, the results reveal that decreasing the quality of water resources due to the increase in salinity encouraged the pistachio growers to cultivate less pistachio crop which would result in reducing their gross profit. Also, decreasing the quality of water resources caused by one unit increase in water salinity has a negative effect on the gross margin (gross profit) of farmers in different regions. This is mainly due to reduction in total area of cultivated pistachio in Rafsanjan County.

In general, decreasing the quantity and quality of water resources will cause irreparable damages to the agricultural economy of all studied areas except Bardsir. Therefore, it is vital to adopt appropriate policies to control the quantity and quality of water resources so improving livelihoods and water demand management in the pistachio areas of the province. The increasing salinity poses a serious challenge to the economic productivity of water use and water resources management in Rafsanjan, applying economic productivity improvement tools, such as the use of modern irrigation systems or crop pattern reform strategies and product insurance can be effective in boosting gross margin.