Author(s): Aksara Putthividhya; Sasin Jirasirirak; Wimolpat Bumbudsanpharoke Khamkanya
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Keywords: Groundwater contamination; Irrigation; Nitrate; Agricultural contamination; Contaminant transport and migration; MODFLOW; MT3D
Abstract: Irrigation has contributed significantly to poverty alleviation, food security, and improving the quality of life for rural populations. However, infiltration of irrigation water in excess of available root zone storage from agricultural lands with poorer water quality may carry both agricultural chemicals and naturally recharge to groundwater, rivers, and lakes. In recent years water security concerns have centered on groundwater depletion by withdrawals for irrigated agriculture and groundwater quality degradation both from natural and anthropogenic origin, and only limited attention has been paid to the more insidious (and more chronic) problems of progressive aquifer contamination of groundwater recharge by irrigation return flows, which is occurring in major intensive agricultural practices. Environmental vulnerability and risk assessment is a step towards identification, analysis, and classification of vulnerable and risk factors as well as its long -term implications, and thus reduction of the possibility of adverse consequences from irrigation, are the primary objective of this present study. A novel approach for environmental impact of irrigation to groundwater contamination and aquifer vulnerability assessment is initiated and applied by combining a novel aquifer vulnerability DRASTIC map with pollution severity and prioritization based in probability of occurrence of pollution using TOPSIS ranking method. 9% of the total study area is categorized as high risk level which needs intensive groundwater samples from domestic and monitoring wells at various depths (100 samples from <30 m deep, and 60 samples from >60 m deep) are collected and analyzed for nitrate (as NO3 -), K. 2-) and other water quality parameters. NO3 - level in groundwater ranged from 0.18 to 151 sulphate (as SO4 mg/L. Consistent K and NO3 - trends from municipal wells in the study area indicate that nitrate source is likely agricultural origin. Detection of high nitrate concentration in shallow groundwater suggests the direct association of major nitrate concentration in groundwater aquifer with potential surficial source on the ground.
Year: 2020