Physicochemical differences Reasons of the Alvand basin’s main karst springs

The Alvand basin is located in the northwest of Zagros in Kermanshah province.Some main karst springs discharge the aquifers of the basin and supply the drinking and irrigation water of the residences. In order to determine the controlling factors on the water quality and assess the origin of waters, the physicochemical parameters of springs were studied for two years. According to Factor Analysis (PCA), the springs were classified into two groups: (1) Low EC, ions concentration especially sulphate and temperature, light isotope composition and high elevation of catchment area. (2) High EC, ions concentration especially sulphate, low elevation of catchment area, heavy composition of stable isotopes and some evaporation from waters.This study demonstrated that the extent of the gypsum bearing Gachsaran formation around the catchments or passing water through Pabdeh-Gurpi formation (lithology effect), elevation of catchment area (elevation effect) and more or less karst system development (karstification factor) are the main parameters affecting the different quality of spring waters. The water of the first group is supplied by the areas with no Gachsaran and has higher altitude and consequently higher precipitation (mostly in the form of snow) and lower temperature. It is believed that karst system more developed in their catchments. The catchment area of the second group has partly contact with Gachsaran or Pabdeh-Gurpi, lower catchment elevation and consequently lower precipitation (in the form of rain) and higher temperature, which could affect the quality of input water by evaporation and less developed karst system.

Keywords:

Karst , herbivores , Alvand basin , karst springs , zagros