Hydrologic Model Development for Evaluation of Long-Term Water Levels in Lake Miona
Interflow completed a successful pilot study of a potential HSPF-based tool that may be used to predict potential lake level impacts resulting from current and future groundwater withdrawals. Lake Miona in Sumter County, Florida was chosen as the setting for the test case. Using HSPF, Interflow simulated the lake’s watershed processes including hourly rainfall, evapotranspiration, infiltration, percolation, runoff, and baseflow. Interactions between the lake and the Upper Floridan Aquifer (UFA) were simulated using the “Special Actions” routine with a user-input time series of UFA head elevations and a lumped lake bed conductance term.
Interflow calibrated the model using measured rainfall and lake level data, and then used the results to develop annual and multi-decadal (60-year) water budgets. Projected groundwater drawdowns based on MODFLOW simulations were used in the long-term simulations of lake level impacts.
The calibrated model was applied in a series of 60-year simulations in an effort to quantify lake level impacts resulting from an artificial lowering of heads in the UFA associated with future groundwater withdrawals for water supply. In settings similar to the Lake Miona area, it is sufficient to assume a constant UFA drawdown as opposed to a monthly variable drawdown. This may not be true in other lakes that are more directly connected to the UFA.
A limited sensitivity analysis was performed on the lumped conductance parameter (K’) used in the Special Actions routine. The resulting range of uncertainty attributed to K’ was then applied to simulations of lake level impacts, in order to characterize this uncertainty with respect to the estimated impacts. The analyses described above resulted in a number of insights into the strengths and weaknesses of this approach.
Client: Southwest Florida Water Management District
Month/Year Initiated: April 2010
Month/Year Completed: April 2011
- Integrated Groundwater/ Surface Water Modeling
- Continuous Simulation
- Environmental Flows and Levels
- Uncertainty Analysis