Airborne electromagnetic imaging of canal‐induced recharge on groundwater quality improvement in saline‐ affected alluvial region of NW India

Abstract Canals have been important structure for transporting water from one place to another for irrigation purposes across the globe. In the present scenario of increasing water scarcity, the significance of canals has increased manifold. Canals also suffer water leakages, which in turn contributes to the groundwater recharge. Thus, there is a strong need to study how the long‐term canal flow impacts groundwater recharge and improves its quality, especially in saline environments. The paper presents a detailed analysis of airborne electromagnetics (AEM) data acquired from a highly saline groundwater zone in the semi‐arid region of northwest India, where most of the irrigation has been met from the canal network for the past several decades. The study focuses on using AEM data, supported by borewell lithology and borehole electrical logs, to analyse the subsurface recharge induced by the canals and its impact on groundwater quality. Over the dense and sparse canal networks, AEM has identified different resistivity signatures. It shows high resistivity over the dunes and low resistivity in the clay‐dominated areas. A crescent‐shaped, 20–100 m thick zone with moderate to high resistivity has been observed below the canals within the low resistivity background, which indicates seepage and discharge from the canal. Moreover, changes in water quality (1994–2019) from borewells near the canal recharge zones show significant improvement in the groundwater quality, evidenced by a lowering of the electrical conductivity of groundwater. This recharge affects approximately 20% of the total study area. The total volume of canal‐induced recharge inferred from AEM resistivity is estimated to be ∼12,000 to ∼18,000 MCM.