ASSESSING IMPACT OF IRRIGATION AND DRAINAGE NETWORK ON SURFACE AND GROUNDWATER RESOURCES – CASE STUDY: SAVEH PLAIN, IRAN

摘要

In the present study, the environmental impacts of Saveh irrigation and drainage network and the associated dam, especially on surface and groundwater bodies have been evaluated. Space-time changes of groundwater quality and quantity have been analyzed using Geostatistics Software version 5.1 and the relevant maps were created based on Wilcox method, involving GIS software, Version 9.3. Using Standardized Precipitation Index (SPI) for three meteorological stations in the study area including; Shah Abasi, Imamabad and Ahmadabad, it was found that extreme drought had occurred through years,1970, 1978, 1979, 1980, 1983 and 1985. According to the result, the average flow of Qarachay river after operation of Saveh dam has been reduced to 0.67 m3/s in contrast with 6.03 m3/s, which had been recorded before of the dam operation. Downstream of Qarachay river, water quality analysis shows that it had deteriorated from 1971 to 2006. According to Wilcox method the water quality had reduced from C3-S1 to C4-S2 class. Groundwater quality for agricultural usages in Saveh aquifer were classified into 4 including; 16% in class C4-S2, 46% in class C4-S1, 30% in Class C3-S1 and 8% in Class C2-S1. Generally speaking, the effects of irrigation and drainage networks on environment and water bodies need to be determined to have a sustainable development.