Ecological Modeling in the
Chesapeake Bay Watershed

Increasingly, the maintenance of water quality in streams, lakes and coastal waters, is focusing on the watersheds which supply them. Stream quality is greatly affected by land uses and land cover changes within watersheds, including the important riparian zones. Excessive riverine and groundwater discharges of sediment and nutrients (N, P) have had major negative impacts on water quality, biological integrity, commercial fisheries, and recreation value of coastal ecosystems, including the Chesapeake Bay, the nation’s largest estuary.

Reducing the delivery of nutrients from the Chesapeake’s 167,000 square kilometer catchment to its waterways has been identified as the key priority in the Chesapeake Bay Program, a major, intergovernmental, multi-state/federal effort. Although some nutrients come from well-monitored point sources, such as sewage treatment plants, the largest amount comes from non-point sources distributed diffusely across the landscape. A critical tool for quantifying, modeling and controlling nutrient runoff is satellite remote sensing of land cover properties and associated modeling of ecosystem processes.

Watershed simulation models are often used to help understand the sources and transport pathways for materials, to predict future conditions, and to evaluate management alternatives (for example, at the SERC). The models differ widely in their objectives, temporal resolution, spatial resolution, geographic extent, however, all share a need for accurate land cover/ use data. To meet the needed improvements in available land use/ cover data, the Mid-Atlantic RESAC is developing and distributing land cover maps that more accurately resolve croplands from pastures, hayfields, and other grassy covers. We are also testing the application of the high spatial resolution sensors that are currently being assessed in the CRESS program for mapping and monitoring the riparian buffers that can greatly reduce chemical runoff into the Bay’s waterways.

Remote sensing also provides the means to map and monitor wetland loss, restoration and maintenance, in both tidal and non-tidal areas. Wetlands are particularly important parts of the landscape and large areas have been lost or are threatened by human activities and sea-level rise.

Finally, modeling of forest growth (net primary production), water yield, and N retention of forested watersheds in the Chesapeake Bay basin is an important contribution of the Mid-Atlantic RESAC. We plan to provide regional remote sensing applications to the US Forest Service Global Change Program which, in turn, supplies validation data sets such as forest inventory and analysis data for the Mid-Atlantic. These applications include mapping, detection of land use change, disturbance (e.g., defoliating insect outbreaks), historic land use change (particularly with respect to N retention modeling), and estimation of forest biomass and production.

Landcover Mapping   Planning and Urban Growth   Land Manager Information System   Integrated Monitoring    Outreach