Submitted to: Ground Water
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/28/2003
Publication Date: 8/20/2003
Citation: Bosch, D.D., Lowrance, R.R., Sheridan, J.M., Williams, R.G., 2003. Groundwater storage affect on streamflow for a Southeastern Coastal Plain watershed. GROUND WATER. 41(7):903-912. Interpretive Summary: In the Southeastern United States, as in many other regions throughout the world, water resources are gaining considerably more public interest. There is a dramatic need to increase our understanding of the interactions between fresh water resources and the remainder of the ecosystem. Better data are required to evaluate how freshwater resources are distributed across the land. Interactions between climate, groundwater, and streamflow were examined using six years of climate and groundwater data and four years of streamflow data collected from two small agricultural watersheds in the Coastal Plain region of Georgia. Groundwater discharge was observed from December to March and intermittently throughout the remainder of the year. During periods when the aquifer was fully saturated streamflow peak discharge rates were greater and of shorter duration than periods during which the aquifer was not fully saturated. Groundwater discharge from the upland to the stream varied from 4 to 18% of the precipitation observed. Ponds within watersheds appear to offer a dramatic management tool. Ponds appear to reduce streamflow peaks and extend runoff duration. These data and relationships will be useful for improving flood forecasting and for water resource planning. Better groundwater data will improve our ability to prepare for climatic extremes and water resource problems related to those extremes.
Technical Abstract: Groundwater is known to have a significant impact upon streamflow in regions where the two are interconnected. Groundwater levels in the surficial aquifer and streamflow were examined for a six-year period for two small watersheds in south-central Georgia within the Coastal Plain Physiographic region of the U.S. Precipitation for the six-year period was below normal. The shallow water-table was elevated during normal precipitation conditions but receded as precipitation decreased. Over the three-year period from 2000 to 2002 the riparian buffer was fully saturated approximately 40% of the time. Lower available aquifer storage was observed for late winter and early spring due to higher rainfall and lower ET. During recharge periods, which normally coincided with the period from December to March, the groundwater gradient from the upland to the stream was approximately equal to the 3% land surface slope. During other times of the year the gradient fluctuated dramatically as a response to individual precipitation events, streamflow, and focused recharge. Assuming groundwater discharge to the stream existed for 40% of the year, groundwater discharge was found to be approximately 4% of the annual precipitation for the period from 2000 to 2002. Aquifer saturation was found to have a significant impact upon streamflow. During periods when the aquifer was fully saturated observed streamflow discharge peak rates were greater and of shorter duration. Comparison of similar magnitude events occurring in 1998 indicated that peak discharge was up to three times larger under saturated aquifer conditions than under non-saturated conditions. Watersheds with significant pond acreage appear to extend discharge over a longer duration. These data indicate the impact of aquifer and pond storage on peak and total discharge in Coastal Plain Watersheds.