Author(s)

H. M. Al-Ghobari

Abstract

The main source of water in the Najran region is the unconfined shallow aquifer along the Najran Wadi (valley). Ground water quality of the Najran region was studied in 43 well water samples collected from different wells in the region. Water samples were chemically analyzed and evaluated using water quality criteria. The investigated water quality parameters revealed the following: water salinity (ECw dS m-1) ranged from 0.35 to 5.99 dS m-1 (i.e. 227 to 3843 meq/l) with an average of 1.95 dS m-1 (i.e.1248 meq/l), pH value ranged from 7.28–7.80 with an average of 7.55. The dominant cation was Ca followed by Na, Mg and K while Cl was the dominant anion followed by HCO-3 with an average of 432.4 and 180.2 meq/l, respectively. The suitability of this water for irrigation was slight to moderate saline water. Also, \“48.8%” of the water had salinity above the recommended level for drinking water. The values of adjusted sodium adsorption ratio (adj. SAR) and residual sodium carbonate (RSC) were in the range of 0.53 to 17.22 and –1.69 to –41.85 with an average of 4.17 and –12.94 meq/l, respectively. These results indicated no expected problems with either sodium or permeability from most of the studied wells. Concentration of (NO3-N) ranged from 0.30 to 33.1 meq/l with an average of 9.48 meq/l. All the tested samples have (NO3-N) concentrations lower than the recommended level for drinking water. Also, it was found that in the Najran region a large fraction of farms (more than 35%) which have been equipped with tube wells and irrigation systems have abandoned business and farming as a result of groundwater depletion, this is because the annual groundwater discharge far exceeds the recharge. The excessive extraction of groundwater resources have caused that water for human

Keywords

groundwater, water quality, extraction, environment, Najran