2018 CSDMS meeting-007
Coupled groundwater and surface water modelling to visualise lake extent and total terrestrial water storage under a changing climate
Large-scale flow-routing algorithms efficiently route water to the ocean, often neglecting inland basins which may be able to form lakes. We combine groundwater and surface water routing components to allow visualisation of changing groundwater levels and lake locations and sizes through time. The groundwater component is based upon the model developed by Reinfelder et al (2013), and surface water is a simple downslope-flow algorithm. Our model requires as inputs topography, climatic data (recharge and winter temperature), and an approximation of hydraulic conductivity. The two outputs are depth to water table, and a surface water layer showing any lakes that would form under the starting conditions. The model can be run either to equilibrium in both surface and groundwater, or, if a starting depth to water table input is provided, the model can be run for any user-selected length of time with respect to groundwater movement. Since surface water movement is significantly faster than groundwater, it is always run to equilibrium. The model allows infiltration when surface water flows across cells that are not fully saturated in the groundwater, and it allows groundwater-fed lakes to form at locations where the topography and climate allow for this. We show sample results from this model on a test area. Future work using this model will include global model runs since the last glacial maximum, with ground truthing possible using past lake shoreline data. Changing depth to water table plus the surface water storage computed using this model allows computation of changing terrestrial water storage volume through time.