Evaluation of groundwater quality for irrigation in a semi-arid region of South India

Abstract

Groundwater quality was evaluated for irrigation purpose by collecting the groundwater samples from 36 locations during pre- and post-monsoon seasons. These groundwater samples were analyzed for physico-chemical parameters like pH, EC, TDS, major cations, and anions. Furthermore, irrigation quality indices like salinity hazard, chloride hazard, magnesium hazard, carbonate and bicarbonate hazard and sodium hazard were calculated using the analytical results. These parameters were compared with standard limits for irrigation use for the prevailing crops. The hydrochemical results indicate that the groundwater in the study area is neutral to slightly alkaline in nature. Based on the EC and TDS classification, most of the groundwater samples are falling under medium salinity hazard category. The order of abundance of major anions and cations in groundwater was found as ${\text{HCO}}_{3}^{ - }>{\text{C}}{{\text{l}}^ - }~$ > $~{\text{NO}}_{3}^{ - }~$ > $~{\text{SO}}_{4}^{{2 - ~}}$ > $~{\text{CO}}_{3}^{{2 - }}>{{\text{F}}^ - }$ and ${\text{N}}{{\text{a}}^+}~$ > $~{\text{C}}{{\text{a}}^{2+}}~$ > $~{\text{M}}{{\text{g}}^{2+}}~$ > ${{\text{K}}^+}$. The Chadha’s diagram revealed the dominance of ${\text{N}}{{\text{a}}^+} - {\text{HCO}}_{3}^{ - }$, mixed ${\text{C}}{{\text{a}}^{2+}} - {\text{M}}{{\text{g}}^{2+}} - {\text{C}}{{\text{l}}^ - }$, and mixed ${\text{C}}{{\text{a}}^{2+}} - {\text{M}}{{\text{g}}^{2+}} - {\text{HCO}}_{3}^{ - }$ and ${\text{N}}{{\text{a}}^+} - {\text{C}}{{\text{l}}^ - }$ types of hydro-geochemical facies. Based on the EC and SAR, classification more than 50% of the samples is falling under slight to moderate reduction in infiltration rate category in both seasons. The study revealed that most of the water samples are exceeding the critical levels of irrigation water quality and it may require careful management to growth suitable crops in the study area. In addition, the study also points out that usage of such a high TDS groundwater for irrigation may cause soil salinity.