SURFACE AND SUBSURFACE WATER QUALITY ASSESSMENT IN SEMI-ARID REGION: A CASE STUDY FROM QUETTA AND SORANGE INTERMONTANE VALLEYS, PAKISTAN

Present investigation is an exertion to explore safe means of water for the community in the water scare region. In order to accomplish such goal origin of springs as well as chemical analyses of groundwater samples from different locations were carried out. Four zones are discovered on the basis of nature of water points, rock types and water chemistry. These zones are Hard Rocks Springs (HRS), Valley Springs (VS), Recharge Areas Aquifers (RAA) and Central Valley Aquifers (CVA). HRS are originated from thick successions of limestone (Kirthar Limestone) and thick packages of channelized sandstone and conglomerates of the Siwalik Group. It is recommended that Chiltan, Parh, Kirthar, Dhok Pathan and Soan formations may be focused for future needs of safe water supply in the Quetta valley. This study includes the analysis of different physico-chemical parameters such as Total dissolved solids (TDS), pH, turbidity, Electrical conductivity (EC), hydrochemical facies, Sodium Adsorption Ration (SAR), Sodium Percent (Na%), Kelleys Index (KI), Permeability Index (PI), major cations and anions to assess the quality of groundwater sources. The outcomes of groundwater analyses were equated with various drinking water standards e.g., NSDWQ-Pak, USEPA, and EU. The results are plotted for determination of lateral variations and to empathize the reasons of these variations. The affects of rock types, geological structures as well as anthropogenic causes on origin and results are discussed systematically. The hydrochemical facies identified show that the alkaline earth exceeds alkalies, strong acids exceeds weak acids, mixed type (no cation, anion exceeds 50%), no dominant cation and anion types but water of VS is calcium chloride and sulfate type. The water is classified as C2-S1 (HRS), C3-51 (CVA & RAA) and C3-S2 (VS) based on SAR and EC values, which intend that most water samples can be used for irrigation safely except water samples collected from VS. Based on the Na% the water samples are categorized as excellent to good and good to permissible limits. The water is suitable for irrigation as all samples bear KI less than 1. The PI values in the water samples studied (less than 40) also contemplate that the water is desirable for irrigation use, although caution is needed of VS water.