Modeling influences of canal stage raises on groundwater and soil water in the C-111 basin of south Florida

The study purpose was to develop modeling tools to investigate how raises in canal stage proposed under the C-111 spreader canal project could impact groundwater and soil water content in the C-111 basin. The objectives were to: 1) evaluate the impact of surface water management on soil and limestone water content using Dynamic Factor Analysis (DFA), 2) estimate hydraulic parameters governing canal-aquifer interaction using analytical modeling, 3) simulate water table response to the proposed incremental raises in canal stage and 4) simulate soil and bedrock water content dynamics in response to proposed changes in canal stage.;Canal stage significantly (t > 2) drives temporal variation in soil and bedrock water contents, followed by net surface recharge. The effect of water table evaporation was not significant at all sites. DFA Model performance was better at sites with smaller depths to water table (< 1 m) highlighting the effect of micro-topography on water content dynamics. The following hydraulic parameters were estimated: specific yield (0.07 to 0.14), horizontal hydraulic conductivity (11,000 to 14,300 m/day), aquifer thickness (13.4 to 18.3 m), and canal leakance (99.8 to 279 m). The estimated values were within the range of values estimated using more complex methods at nearby sites.;The developed MODFLOW based model was able to reproduce measured water table elevation, with average Nash-Sutcliffe (NSE) > 0.9 and Root Mean Square Error (RMSE) <0.05 m. Model predicted that incremental raises in canal stage resulted in significant differences (p<0.05) in water table elevation. Increases in canal stage of 9 and 12 cm resulted in occasional root zone saturation of low elevation sites and shortening of growing season. The model also predicted that lowering canal stage prior to large storms reduced water table intrusion into the root zone. Considering measurement uncertainty in the WAVE based models resulted in NSE values less than zero to 0.89 and RMSE values between 0.22 and 1.61 m m-3. Soil water content before and after the incremental raises in canal stage were predicted to be significantly different (p<0.001), sites that had surface elevation less than 2.0 m NGVD29 were predicted to experience root zone saturation.