The Evaluation of an Integrated Land Surface – Groundwater Model Through Remote Sensing
Abstract:Integrated land surface-groundwater models simulate the variability of water dynamics and land surface fluxes in both time and space while explicitly incorporating the role of groundwater dynamics in soil moisture distribution. The ParFlow.CLM modelling platform is an integrated hydrologic model and was used here for simulating land surface and groundwater dynamics over the Baldry sub-catchment in Australia at hourly time intervals. Baldry is located in the central west of New South Wales, has an ephemeral creek and is located in a temperate climate class with hot summers. Here, a multi-criteria evaluation strategy was employed using a range of observed catchment responses, including surface energy fluxes and states of land surface temperature, soil moisture and groundwater level for the period from 2005-2010. Particularly, the use of remotely sensed soil moisture and land surface temperature products obtained from downscaled microwave observations from the Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) were explored to test the feasibility of these products for model evaluation at the catchment scale.
Results suggest high agreement between the temporal dynamics of the model simulations and remotely sensed surface soil moisture and land surface temperature products, with correlation coefficient values of 0.79 and 0.92 respectively. Model comparisons with observed daily groundwater levels show satisfactory model performance (correlation coefficient > 0.5) considering the simple conceptual geological model developed for the study site. Our analyses indicate that the depth to the water table (DTWT) has an important role in controlling evaporation rates and top layer soil moisture distributions in the catchment. The relationship between evaporation rates and DTWT distribution for the six years of simulations shows increased sensitivity during dryer periods. Our results highlight that soil moisture distributions obtained from a physically based integrated hydrologic model have the potential to bridge the spatial scale gap inherent in satellite soil moisture products.