Water Quality Monitoring
Historical LUC (1660-200)
Effects of land use, soils, and human populations on export of water, C, N, and P from the Mid-Atlantic coastal plain
Related Student Projects

The Effects of Land Use Change--Overview

Over the last 300 years, the Atlantic coastal plain of North America has been vastly transformed by human activity. Native American populations existed at relatively low densities (0.15 individuals km -2), and they appear to have removed forest cover from only very small areas for crops, using the remainder for hunting and gathering activities (Benitez and Fisher in press). However, beginning in the 1600's, European settlers cleared the largely undisturbed forests primarily for low intensity agriculture. The coastal plain province was initially found due to the low topographic relief, good soils, and access to shipping, a trend that continued to ~1900 (Fig. A1). In the 20th century, human populations increased dramatically (Fig. A2), and urbanization has increasingly claimed more area, as both agriculture and secondary forests have declined in area. However, use of fertilizing and multiple crops greatly increased the intensity of agriculture in the 20th century.

The disturbance and intensive use of the coastal plain has led to greater export of C, N, and P in stream discharge (Fig. A3). The anthropogenically enhanced export of the fertilizing elements N and P has in turn led to eutrophication (nutrient enrichment) and declining water quality of lakes and estuaries, particularly in the last 50 years (Fig. A4), and there are local and regional plans attempting to improve water quality in many aquatic systems (e.g., EPA’s Chesapeake Bay Program).

Reversing eutrophication requires detailed information on watershed export. To reduce inputs of C, N, and P we have to know their sources. However, it is difficult to measure fluxes of water, C, N, and P from many places in coastal plain watersheds because of the low relief and tidal or salt intrusion. Most gauged areas on the coastal plain are quite far inland and represent only a small fraction of the basin draining into coastal waters (e.g., the gauged areas in the Choptank and Chester basins on the Delmarva Peninsula represent <20% of the total basin area (Fig. A5). Furthermore, areas of greatest anthropogenic impact are often closer to coastal waters, making the spatial extrapolation of fluxes from small gauged areas unrepresentative of the basin as a whole.

We are addressing this problem by regional application of the hydrochemical model GWLF. In a previous study in the Choptank basin on the Delmarva Peninsula, we estimated fluxes of water, N, and P from ungauged portions of the watershed using the local land use, soil characteristics, and human populations. We are currently extending the model capability to C export, and we are applying GWLF to 15-20 watersheds within the Mid-Atlantic region of the coastal plain, using local gauged areas as calibration and validation sites. The goal is to provide detailed maps of the Mid-Atlantic coastal plain (NY to SC) showing current land use, soil properties, human populations, and area-based export rates of water, C, N, and P. The results will be useful both for local and regional watershed nutrient management, and also for evaluating the terrestrial flux of C into the coastal zone.