Assessment of Changes in Groundwater Quality and Quantity of Mianab Shushtar Plain after the Construction of Irrigation and Drainage Network

Irrigation and drainage networks construction are affecting the quality and quantity of groundwater. This study aims to evaluate the quantitative and qualitative changes of Mianab Shushtar plain aquifer after the construction of irrigation and drainage network in 2008. First by checking annual hydrograph of the plain, the changes of ground water storage volume during years of before and after the implementation of irrigation and drainage network were evaluated. During 2005-06 to 2008-09 in the third year, 6.4 million cubic meters of underground water reservoir storage volume decreased and from 2008-09 to 2013-14, 9.07 million cubic meters of underground water storage volume has been added. With comparison in the same period, it was found that change in the reservoir is largely influenced by the amount of annual precipitation. Then calculate the groundwater balance, factors affecting the reservoir volume changes were studied. The results showed that 2008-09 and 2009-10 balance was -3.59 and 5.44. Most important factor in changes in groundwater reservoir was the amount of annual rainfall and operation of the network had not a significant impact in increasing the groundwater level. In the following to investigate qualitative changes of underground water sources, the Wilcox diagram for two years before and after the construction of irrigation and drainage network was used. The results showed that due to high groundwater level before the network operation, more sampling points was in class of too salty and unusable for agriculture. Therefore network operation had not significant effect in the quality of groundwater resources.