Research

Stream Temperature and Dissolved Oxygen Modeling in the Lower Flint River Basin, GA

The tributaries of the Lower Flint River in southwest Georgia are incised into the Upper Floridan semi-confined limestone aquifer, and thus seepage of relatively old groundwater sustains baseflows and provides some influence over temperature and dissolved oxygen fluctuations. This hydrologic and geologic setting creates unique aquatic habitats. Groundwater withdrawals for center-pivot irrigation and proposed water supply reservoirs threaten to exacerbate low flow conditions during summer droughts, which may negatively alter stream temperature and dissolved oxygen conditions. To evaluate these possible impacts, we developed a one-dimensional Dynamic stream Dissolved Oxygen and Temperature (DDOT) model. The major contributions of DDOT to existing water quality models include the integration of an easy to use SHADE module and a BED module. The SHADE module generates accurate estimation of riparian vegetation shading of direct solar radiation on the water surface, while the BED module calculates streambed layer vertical temperature and DO profiles necessary to account for groundwater input effects on surface water quality. The model allows robust exploration of system sensitivities and responses to management actions. DDOT predicts that reduced streamflow rates lead to increased maximum stream temperatures and lower minimum DO levels, that reduced groundwater inputs exacerbate stream temperature problems, that problematic DO levels occur only at very low flows, and that stream width and riparian vegetation strongly effect temperature and dissolved oxygen.