Interaction of surface water and groundwater in a complex hydroclimatic system

Rahman Davtalab, Saba Ghotbi and Caroline Reynolds


Grace Lake and a series of interconnected stormwater retention and detention ponds as well as lakes play an important role in stormwater management and water quality in the region of central Florida. A significant variation in Grace Lake’s water level has been observed during the past couple of decades. In 1986, a significant sinkhole formed within Grace Lake causing a decrease in the water surface level, however, it was sealed shortly after formation. The sinkhole reopened in 1988 and was resealed again in 2015. After the latest sinkhole activity, the water level rose again resulting in road flooding downstream of the Lake during Hurricane Irma in 2017. 

There are numerous studies about climate change effects on surface water in different regions of the world, but studies on integrated surface water and groundwater are limited. The priority of the current study is evaluating the impact of climate change in an integrated method. This study developed a combination of 1 Dimensional (1D) and 2 Dimensional (2D) Integrated Surface Water and Groundwater Modelling (ISWGM) over 500-ha of the contribution area. The ISWGM was calibrated and validated for several historical tropical storms to reduce the potential uncertainties in hydrogeological conditions. The statistically downscaled rainfall and potential evapotranspiration time series from five Global Circulation Models (GCM) were extracted for the area, and the uncertainty of GCMs were addressed using a Multi-Model Ensemble method (MME). Using the ISWGM and MME time series, the hydro-periodic condition for Grace Lake and several other adjacent ponds were projected for mid-century (time horizon 2060) and end of the century (time horizon 2090).  Based on these projections, the Seasonal High Water (SHW) was estimated for each time horizon. A number of synthetic storms were simulated based on projected SHWs, and results were compared to the baseline. Results showed a moderate change (10 – 20 percent) in groundwater recharge in mid-century and end-century time horizons as well as an exacerbation in road flooding under future conditions.  

Key word: Stormwater, Groundwater, Climate Change, Grace Lake et

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