Groundwater response to changing water‐use practices in sloping aquifers

Abstract

Groundwater flow is examined for recharge and extraction within a sloping aquifer. Fundamental equations are commonly formulated either in s‐n coordinates where s is tangent to the base or in x‐z coordinates where x is horizontal. Consistency between these two formulations is achieved here by incorporating the slope of the base directly into the hydraulic conductivity and aquifer diffusivity terms. A stepping model is developed for steady and transient flow, and comparisons between stepping and sloping models show that the stepping model approaches the exact solutions as the number of steps increases. This model is used to develop a set of nomographs and dimensionless parameters relating drawdown over time to distance upgradient or downgradient from a point of water use. While upgradient and downgradient responses differ with respect to the quantity of water removed or injected, it is shown that the response proportional to the change in saturated thickness is the same in both directions.