Numerical groundwater-flow modeling to evaluate potential effects of pumping and recharge: implications for sustainable groundwater management in the Mahanadi delta region, India | Modélisation numérique des écoulements d'eau souterraine pour évaluer les effets potentiels d'un pompage et de la recharge: conséquences pour la gestion durable des eaux souterraines dans la région du delta de Mahanadi, en Inde Modelización numérica del flujo de agua subterránea para evaluar los efectos potenciales del bombeo y la recarga: implicancias para el manejo sostenible del agua subterránea en la región del delta de Mahanadi, India 数值地下水流量模拟来评估抽水和补给的潜在影响: 对印度马哈纳迪三角洲地区可持续地下水管理的影响 Modelagem numérica do fluxo das águas subterrâneas para avaliar os potenciais efeitos do bombeamento e da recarga: implicações para a gestão sustentável das águas subterrâneas na região do delta de Mahanadi, Índia

Process-based groundwater models are useful to understand complex aquifer systems and make predictions about their response to hydrological changes. A conceptual model for evaluating responses to environmental changes is presented, considering the hydrogeologic framework, flow processes, aquifer hydraulic properties, boundary conditions, and sources and sinks of the groundwater system. Based on this conceptual model, a quasi-three-dimensional transient groundwater flow model was designed using MODFLOW to simulate the groundwater system of Mahanadi River delta, eastern India. The model was constructed in the context of an upper unconfined aquifer and lower confined aquifer, separated by an aquitard. Hydraulic heads of 13 shallow wells and 11 deep wells were used to calibrate transient groundwater conditions during 1997–2006, followed by validation (2007–2011). The aquifer and aquitard hydraulic properties were obtained by pumping tests and were calibrated along with the rainfall recharge. The statistical and graphical performance indicators suggested a reasonably good simulation of groundwater flow over the study area. Sensitivity analysis revealed that groundwater level is most sensitive to the hydraulic conductivities of both the aquifers, followed by vertical hydraulic conductivity of the confining layer. The calibrated model was then employed to explore groundwater-flow dynamics in response to changes in pumping and recharge conditions. The simulation results indicate that pumping has a substantial effect on the confined aquifer flow regime as compared to the unconfined aquifer. The results and insights from this study have important implications for other regional groundwater modeling studies, especially in multi-layered aquifer systems.