Automatic estimation of aquifer parameters using long-term water supply pumping and injection records

Ning Luo,Walter A. Illman

doi:10.1007/s10040-016-1407-x

Abstract

Analyses are presented of long-term hydrographs perturbed by variable pumping/injection events in a confined aquifer at a municipal water-supply well field in the Region of Waterloo, Ontario (Canada). Such records are typically not considered for aquifer test analysis. Here, the water-level variations are fingerprinted to pumping/injection rate changes using the Theis model implemented in the WELLS code coupled with PEST. Analyses of these records yield a set of transmissivity (T) and storativity (S) estimates between each monitoring and production borehole. These individual estimates are found to poorly predict water-level variations at nearby monitoring boreholes not used in the calibration effort. On the other hand, the geometric means of the individual T and S estimates are similar to those obtained from previous pumping tests conducted at the same site and adequately predict water-level variations in other boreholes. The analyses reveal that long-term municipal water-level records are amenable to analyses using a simple analytical solution to estimate aquifer parameters. However, uniform parameters estimated with analytical solutions should be considered as first rough estimates. More accurate hydraulic parameters should be obtained by calibrating a three-dimensional numerical model that rigorously captures the complexities of the site with these data.

Highlights

Planning for the optimized use of groundwater resources is of paramount importance to water managers worldwide in the face of increased demands on groundwater resources, the protection of groundwater resources from contamination, and the increasing energy costs of community water systems
This paper presents the analyses of existing long-term pumping/injection and water-level records from a municipal well field in a complex multi-aquifer/aquitard system utilizing an approach proposed by Harp and Vesselinov (2011)
The approach estimates homogeneous hydraulic properties of the aquifer in well fields consisting of multiple water-supply boreholes operating with rapidly varying pumping/injection rates

Summary

Introduction

Planning for the optimized use of groundwater resources is of paramount importance to water managers worldwide in the face of increased demands on groundwater resources, the protection of groundwater resources from contamination, and the increasing energy costs of community water systems. The Theis (1935) solution is the first analytical model developed for transient analysis of a pumping test in a confined aquifer, but numerous type curve solutions have since been developed over the few decades for different aquifer types and boundary conditions (e.g., Hantush and Jacob 1955; Neuman 1974; Moench 1997; Mathias and Butler 2006; Mishra and Neuman 2011). The application of these analytical models is sometimes restricted in complex hydrogeological conditions, where some features that significantly affect groundwater flows are not considered (e.g., Mansour et al 2011). The use of analytical models may lead to good matches between observed drawdowns and type curves, the estimated hydraulic properties may be scenario-dependent—for example, Wu et al (2005) demonstrated that the conventional analysis of aquifer tests yields biased T estimates that evolved with time and depended on the location of monitoring boreholes, and the Hydrogeol J (2016) 24:1443–1461 estimated S is mainly affected by the geology (i.e., heterogeneity) between the water-supply and monitoring boreholes

Objectives

Methods

Results

Conclusion