Evaluation of water quality for drinking and agricultural suitability in the lower indus plain in Sindh Province, Pakistan

Indus Basin represents a conjunctive system for ground and surface water use. From it, originates the world’s largest irrigation system underlain a deep alluvium and well transmissive aquifer resulting in higher water table. At present, this area is at risk of ground water aquifer contamination due to extensive agricultural activities that needs to be constantly monitored. A total of 218 ground water samples were collected across the Sindh Province and were evaluated for drinking and agricultural purpose subjected to Hydrochemical analysis. The analytical parameters were compared with WHO and Pakistan water quality standards and majority of the samples were found not potable. 62.84% of EC samples, 34.86% TDS, 43% Na⁺, 17.88% Cl⁻, 26.60% SO₄²⁻, , 39.44% HCO₃⁻, 41.7% turbidity and 35.32% hardness in the samples were found to exceed the WHO standard limit of drinking water. Interpolation technique was used though Arc. GIS to determine the spatial distribution of major ground water quality parameters. Highest concentration was observed mostly at Lower Sindh (Thatta, Badin) where sea water intrusion takes place, Tharparker and central Sindh. Principal Component Analysis and correlation analysis confirms positive association of As with Fe which could be the possible cause of As mobilization in Sindh ground water. The hydrogeochemical facies indicates that alkali (Na⁺) exceeds over alkaline earth metals (Ca²⁺, Mg²⁺) and Cl⁻ and HCO₃⁻ exceeds over SO₄²⁻ indicating saline water and carbonate weathering as the source of solutes in Sindh groundwater. Suitability of groundwater for drinking and agricultural purpose indicates that majority of the samples were very far from drinking water standards while few samples were considered unsuitable for agricultural purpose especially in the lower southern Sindh( Thatta, Badin and Tharparker). Proper drainagepractices especially in the irrigated area and lower Sindh Province are recommended in order to reduce the water level and avoid sea water intrusion for better water quality.