GROUNDWATER QUALITY ASSESSMENT AND SUITABILITY FOR DRINKING AND IRRIGATION IN TEHSIL BELA, DISTRICT LASBELA, BALOCHISTAN, PAKISTAN

Abstract

Groundwater underpins domestic water supply and agriculture across District Lasbela, Balochistan, and its chemical quality is a key determinant of public health and crop productivity in this semi-arid coastal region. This study assesses the groundwater quality of Tehsil Bela, District Lasbela, based on twenty-six samples collected from bore wells, dug wells and hand pumps across thirteen union councils between November 2022 and August 2023. Fifteen physico-chemical parameters – pH, electrical conductivity (EC), total dissolved solids (TDS), salinity, total hardness (TH), alkalinity, chloride, sulphate, nitrate, total phosphate, orthophosphate and the essential metals sodium, potassium, calcium and magnesium – were determined by standard spectrophotometric, titrimetric and flame atomic absorption spectrometric methods and benchmarked against the World Health Organization (WHO), the Pakistan Council of Research in Water Resources (PCRWR), the National Environmental Quality Standards (NEQS) and the United States Environmental Protection Agency (UEPA) permissible limits.

The mean pH (7.93), sodium, magnesium and nitrate values largely conformed to WHO guidelines, and 73% of samples were classified as non-saline on the TDS scale. However, chloride exceeded the WHO limit in 80.7% of samples, potassium in 80.7%, total hardness placed 73% of samples in the hard-to-very-hard categories, and total/orthophosphate exceeded WHO limits in 46–54% of samples. Irrigation-suitability analysis showed that 92.3% of samples satisfied Kelly's Index, while only 30.8% met the Sodium Adsorption Ratio (SAR) suitability criterion. Overall, groundwater in Tehsil Bela is chemically more favorable than in neighboring Uthal for several key parameters, but chloride, hardness and sodium-hazard indices indicate that treatment and continued monitoring remain necessary before unrestricted drinking and irrigation use. This enhanced edition additionally reports mean-ion hydrochemical facies, five supplementary derived indices (Na%, Residual Sodium Carbonate, Permeability Index, Magnesium Hazard ratio and Kelly's Ratio), a multi-standard compliance comparison, and an expanded discussion of public-health implications and management recommendations.