Spatial interpolation and mapping groundwater quality using geostatistical method: case study in Jakham River Basin

Abstract

The determination of groundwater quality is the utmost priority for conserving freshwater supplies in semi-arid and hard rock areas, which is necessary for the development of a sustainable water utilization system. This study investigated the potability of water collected from open wells in a basaltic hard rock region interpolated the groundwater quality (WQ) parameters' concentration, and generated a map. During the years 2019 & 2020, in pre and post-monsoon seasons (PRM & POM), a total of 76 samples were taken from the open wells of Jakham River Basin. In this analysis, groundwater quality parameters ranges for the pH (6.50–8.90), EC (< 650– > 1550 μS/cm), TDS(< 300– > 1200 mg/L), Cl⁻ (0.60–12.20 mg/L), SO₄²⁻ (0.20–9.70 mg/L), NO₃⁻(0.05–3.0 mg/L), Ca²⁺ (0.80–10.30 mg/L), Mg²⁺ (0.60–13.50 mg/L), Na⁺ (0.80–9.85 mg/L), K⁺ (0.04–1.60 mg/L) and F⁻ (0.20–1.20 mg/L) in hard rock region. Water quality index (WQI), indicates the qualitative status (excellent, good, poor, very poor, and unsuitable) of groundwater in the study area. The spatial maps were developed using ArcGIS 10.5 software. In PRMseason, the generated value of WQI ranges from 28.28 to 116.74, while for post-monsoon season, it varies from 29.49 to 111.98. As per the findings of GIS-based WQ,index a total of 63.42 percent of the groundwater samples during PRM and 42.02 percent during the POM season were classed as ‘good’ and could be consumed for drinking. Based on the WQI index, it is concluded that the groundwater in the study area is consumable, with the exception of some discrete patches in the eastern and northern parts of the basin. The high WQ index readings in some samples from the basin imply that the water is inappropriate for direct consumption and must be treated sustainably before being used for drinking. The physico-chemical investigation revealed that rock-water chemistry, dissolution, ion-exchange processes, and human activities controlled groundwater chemistry in the region.