Assessment of trends in groundwater quality and quantity of Kashan plain

Abstract

In this study, the groundwater level depletion and electrical conductivity (EC) were chosen to assess the water quality and quantity changes in Kashan plain, Iran. The relevant hydrographs were drawn using Thiessen polygons based on the piezometric data. Moreover, the groundwater depletion, the elevation contour line and iso- electrical conductivity maps were provided using GIS. Also, the relation between EC and Anions and Cations (such as Ca2+, Mg2+, K+, Cl-, Na+, SO42-, HCO3-) were determined. The calculated Standard Index of Annual Precipitation (SIAP) in five meteorological stations showed that normal precipitation has the most percentage of frequency. Also, the results of drawn maps showed that the groundwater flows from south of the plain towards the Kavir in the north part of the plain. The most depletion of groundwater level and the withdrawal have also occurred in the south and south-eastern parts of the plain mainly due to the concentration of agricultural lands. Electrical conductivity has direct relation with concentration of ions in all cases, except bicarbonate. According to the hydrographs; the average level of groundwater has decreased 10.02 meters over 19 years and the groundwater level depletion has consequently decreased poor water quality.

Keywords

• groundwater
• depletion
• hydrograph
• electrical conductivity