Abstract
Several recent studies have shown the significance of representing groundwater in land surface hydrologic simulations. However, optimal methods for model parameter calibration in order to realistically simulate baseflow and groundwater depth have received little attention. Most studies still use globally constant groundwater parameters due to the lack of available datasets for calibration. Moreover, when models are calibrated, various parameter combinations are found to exhibit equifinality in simulated total runoff due to model parameter interactions. In this study, a simple lumped groundwater model is incorporated into the Community Land Model (CLM), in which the water table is interactively coupled to soil moisture through the groundwater recharge fluxes. The coupled model (CLMGW) is successfully validated in Illinois using a 22-year (1984–2005) monthly observational dataset. Baseflow estimates from the digital recursive filter technique are used to calibrate the CLMGW parameters. The advantage obtained from incorporating baseflow calibration in addition to traditional calibration based on measured streamflow alone is demonstrated by a Monte Carlo-type simulation analysis. Using the optimal parameter sets identified from baseflow calibration, flow partitioning and water table depth simulations using CLMGW are improved, and the equifinality problem is alleviated. For other regions that lack observations of water table depth, the baseflow calibration approach can be used to enhance parameter estimation and constrain water table depth simulations.
Highlights
Numerous modeling studies [18,19,20,26,29,30,34,36,40,41,47,57, 64,65,67] have shown the importance of representing groundwater and soil moisture–groundwater interactions in land surface hydrologic simulations
The advantage obtained from incorporating baseflow calibration in addition to traditional calibration based on measured streamflow alone is investigated
Several recent land surface modeling studies have shown the importance of water table dynamics and various groundwater parameterizations have been developed, the problem regarding how to best specify groundwater parameters in order to realistically simulate baseflow and groundwater depth has received little attention
Summary
Numerous modeling studies [18,19,20,26,29,30,34,36,40,41,47,57, 64,65,67] have shown the importance of representing groundwater and soil moisture–groundwater interactions in land surface hydrologic simulations. [12,50,60]) have shown that with the same atmospheric forcing, the same amount of runoff, but with contrasting baseflow and surface runoff compositions can be simulated This deficiency leads to varying partitioning between runoff and soil water storage and different responses. We demonstrate that the use of baseflow estimates for calibration of relevant model parameters can improve simulations of water table depth and runoff partitioning. It has been widely shown [18,19,20,47,64] that water table depth can affect the soil moisture profile and land surface hydrologic fluxes.
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