Aquifer Parameters from Constant Discharge Nonsteady‐Leaky Type Curves

Abstract

AbstractA drain function and set of type curves were defined for a simplified mathematical solution that represents one‐dimensional flow under nonsteady conditions in a leaky aquifer for the constant discharge boundary condition. The mathematical solution is in the form of exponential and complementary error functions, and it can be calculated using a polynomial approximation for the complementary error function. The mathematical solution and drain function are computationally easier to use than an equivalent integral‐form solution and drain function, which must be integrated numerically. A match‐point procedure was developed for determining aquifer diffuisivity (T/S), transmissivity (T), storage coefficient (S), and leakance (K′/b′) based on using the drain function and type curves. Use of the procedure is illustrated by an example that utilizes simulated aquifer drawdown and flowrate data. The match‐point procedure can be used to analyze drawdown data in leaky and nonleaky aquifers in cases where the flow is one‐dimensional and the discharge from the aquifer is constant. Applications of this procedure would include flow to a canal or river, flow to a highly permeable fracture that acts as a line sink, drainage of agricultural lands, and dewatering associated with strip mining operations.