Transient Recharge Estimability Through Field‐Scale Groundwater Model Calibration

• Published in: Ground water 2017-11, Vol.55 (6), p.827-840
• Main Authors: Knowling, Matthew J., Werner, Adrian D.
• Format: Article
• Language: English
• Subjects: Aquifers; Calibration; Groundwater; Groundwater data; Groundwater levels; Groundwater recharge; Hydraulics; Mathematical models; Models, Theoretical; Parameter estimation; Parameters; Scale (ratio); South Australia; Spatial data; Spatial distribution; Specific yield; Statistical analysis; Statistical methods; Steady state models; Storage; Temporal resolution; Variability; Water levels; Water Movements
• ISSN: 0017-467X; 1745-6584
• DOI: 10.1111/gwat.12526

The estimation of recharge through groundwater model calibration is hampered by the nonuniqueness of recharge and aquifer parameter values. It has been shown recently that the estimability of spatially distributed recharge through calibration of steady‐state models for practical situations (i.e., real‐world, field‐scale aquifer settings) is limited by the need for excessive amounts of hydraulic‐parameter and groundwater‐level data. However, the extent to which temporal recharge variability can be informed through transient model calibration, which involves larger water‐level datasets, but requires the additional consideration of storage parameters, is presently unknown for practical situations. In this study, time‐varying recharge estimates, inferred through calibration of a field‐scale highly parameterized groundwater model, are systematically investigated subject to changes in (1) the degree to which hydraulic parameters including hydraulic conductivity (K) and specific yield (Sy) are constrained, (2) the number of water‐level calibration targets, and (3) the temporal resolution (up to monthly time steps) at which recharge is estimated. The analysis involves the use of a synthetic reality (a reference model) based on a groundwater model of Uley South Basin, South Australia. Identifiability statistics are used to evaluate the ability of recharge and hydraulic parameters to be estimated uniquely. Results show that reasonable estimates of monthly recharge (