Abstract
The current study emphases on hydrochemicalevaluation of groundwater in Northwestern part of Saudi Arabia and particularly in Tabuk, Jauf and Hail regions. In this region, the aquifers are appeared to be as confined aquifers. The main aquifer has extensive outcrop areas along the boundary with the Arabian Shield in the west, where it receives some recharge which is less than the volumes abstracted from the aquifer. Groundwater samples were gathered from about 60 groundwater wells and tested for various physico-chemical parameters such as electrical conductivity (EC), pH, temperature, total dis-solved solids (TDS), Na+, K+, Ca2+, Mg2+, CO3-, HCO3, Cl, SO4, and NO3. Groundwater in the area is slightly alkaline and hard in nature. Electrical conductivity (EC) varies between 171 and 5061 mu S/cm with an average value of 982 mu S/cm. The distribution of major ions in the groundwater is Ca++> Na+ > Mg++ > K+ and Cl- > SO4-2>HCO3-. Using Pipers classification, groundwater was classified under Na-C-SO4 water type. The GW has acquired unique chemical characteristics through prolonged rock water interactions, percolation of irrigation return water and reactions at vadose zone.