Abstract

Shahram Ashraf*, Hossein Afshari and Abdol Ghaffar Ebadi

In order to evaluate the quality of groundwater in Damghan plain for irrigation purposes, 199 surveyed wells with GPS data used to produce the map. The features that generally had considered for evaluation of the suitable quality of groundwater for irrigation are salinity, water infiltration rate, and specific ion toxicity. The SAR , ions Ca2+,Mg2+, Na+ , K+ , CO3 2- , HCO3- – , SO4 2- , Cl- , electrical conductivity (EC), total dissolved solids (TDS), pH were analyze as the evaluation indexes. The EC map indicates the presence of about 0.04% of the study area; groundwater lie in good range (none degree of restriction on use) 61.38% slight to moderate and 38.58% severe for irrigation purposes. The suitable zones for ECw are in the central and northwestern and portion of south of the study area (61.42%). The quality of groundwater for the sodium hazard on infiltration is in 98.9% of study area none degree of restriction on use and in 0.6% slight to moderate and 0.5% severe. The suitable zones for infiltration have no degree of restriction on use in majority of the study area. The maps result of crops yield potential as influenced by irrigation water salinity (ECw) indicates that crops barley>wheat > Alfalfa respectively have yield potential more against ECW in study area (99.42,92.3 and 0.23%). The results of thematic maps of sodiumw, choloridw were overlaid with maps of sodiumplant, choloridplant showed that the crops yield potential of barley and wheat. Alfalfa in all the study area is 100%.