2000 BES Abstracts

Baseline hydrologic data collection in and near the Gwynns Falls watershed

Gary T. Fisher, P.E., Edward J. Doheny

Characterizing the movement of water in an ecological study area is essential for understanding physical, chemical, and biological processes and their interrelationships. All components of the hydrologic cycle must be considered: precipitation, evaporation, surface water, and ground water, as well as their many subcomponents. Monitoring is required to obtain continuous time-series data for process studies and to determine an accurate water balance. One of the most time-consuming and expensive monitoring tasks is continuous stream gaging. Streamflow represents output from a watershed, and is the component of the hydrologic cycle that can be determined with the least uncertainty, so it is very important that data be obtained with a high level of accuracy. The accuracy of water balance determinations, chemical loading computations, and physical-chemical-biological interrelationship studies are highly dependent on accurate streamflow records. Changes over time can best be evaluated where long-term records have been maintained. The Baltimore Ecosystem Study (BES) has established a network of continuous stream-gaging stations that represent the urban-rural gradient and the range of ecosystem types within the study area. Gaged basins range from a 41 hectare forested watershed to a 17,100 hectare urban-suburban watershed at the mouth of Gwynns Falls. Periods of record for 8 stream-gaging stations providing data to BES range from 1 year to 35 years. At least 31 additional stream-gaging stations, with periods of record from 1 year to 55 years, are operated by the U.S. Geological Survey in nearby watersheds to provide a regional context for data interpretation or transfer of BES results to other watersheds.