Groundwater resource vulnerability and spatial variability of nitrate contamination: Insights from high density tubewell monitoring in a hard rock aquifer

摘要: Agriculture has been increasingly relying on groundwater irrigation for the last decades, leading to severe depletion and/or nitrate contamination. Understanding links between concentration and resource is a prerequisite assessing sustainability of irrigated systems. The Berambadi catchment (ORE-BVET/Kabini Critical Zone Observatory) in Southern India typical example intensive agriculture then an ideal site study relative influences land use, management practices aquifer properties NO3 spatial distribution groundwater. monitoring >200 tube wells revealed concentrations from I 360 mg/L. Three configurations level elevation gradient were identified: i) hot spots associated deep levels (30-60.m) low suggest small reserve with absence lateral flow, degradation quality due recycling through pumping return flow; ii) high gradient, moderate that significant flow prevented enrichment; iii) concentrations, shallow indicate large reserve. We propose mapping could be used delineate zones vulnerable intensification catchments where low-yielding aquifers only source irrigation. Then, located are likely suitable impacts local agricultural systems, while would reflect average catchment, hence should regional quality. Irrigatiori concentrated induces ``hidden'' input nitrogen crop which can reach 200 kgN/ha/yr hotspot areas, enhancing Such fluxes, once taken into account fertilizer management, allow optimizing consumption mitigate (C) 2016 Elsevier B.V. All rights reserved.