Quality assessment of groundwater of Kadapa district, Andhra Pradesh, India for irrigation purpose and management options

Water samples collected from various locations in Kadapa district, Andhra Pradesh (AP), India were analysed for quality parameters, namely reaction (pH), salinity, Ca²⁺, Mg²⁺, Na⁺, and K⁺; CO₂, HCO, Cl^– and SO₂. The pH fell in the range 6.5–8.1, electri­cal conductivity (EC) from 0.4 to 11.1 (dS m^–1), sodium adsorption ratio (SAR) from 0.4 to 41.2 (mmol l^–1)1/2 and residual sodium carbonate (RSC) from –52.4 to 16.2 (meq l^–1). The presence of positively charged ions, namely calcium, magnesium, sodium and potassium varied from 0.4 to 46.0, 1.2 to 16.4, 0.76 to 60.1 and 0.002 to 11.78 meq l^–1 respectively. The concentration of bicarbonates, chlorides and sulphates varied from 0 to 2.0, 1.0 to 17.6, 0.4 to 76.0 and 0.3 to 14.8 me l^–1 res­pectively. The dominance of ions for majority of the samples was Na⁺ > Ca²⁺ > Mg⁺² > K⁺ for positively charged ions and HCO > Cl^– > SO₂ > CO for negatively charged ions. According to classification of irrigation water by the Central Soil Salinity Research Institute, Karnal, Haryana, India, 53.18% water samples is good, 21.88% marginally saline, 0.3% saline, 4.56% high SAR saline, 6.69% marginally alkaline, 7.90% alka­line and 5.47% highly alkaline. Spatial variability of pH, EC, SAR, RSC and groundwater quality in Kadapa district, AP was demonstrated using GIS maps.