THE RELATIONSHIP BETWEEN STREAM CHEMISTRY AND WATERSHED LAND-COVER DATA IN THE MID-ATLANTIC REGION, US

In order to investigate the relationship between stream chemistry and watershed land cover at the regional scale, we analyzed data from 368 wadeable streams sampled in the mid-Atlantic region of the U.S. during spring 1993-1994. Study sites were selected using a probability sampl e and the digitized version of the 1:100,000 scale USGS map stream net work as the sample population. Both classified Thematic Mapper (TM) an d USGS Land Use/Land Cover (LULC) data were used to quantify land cove r in the study watersheds. On average, the most common land cover was forest (77 %) followed by agriculture (20 %), and urban (1 %). Multipl e regression analysis showed that concentrations of Cl-, nutrients, ac id neutralization capacity, and base cations were the analytes most st rongly related to watershed land cover. Despite large differences in r esolution and age of the TM and LULC data sources, similar results wer e obtained with the two sources. Using a greater number of land cover subclasses did not greatly improve the land cover-chemistry relationsh ips. Ecoregions with predominantly forested land cover had weaker rela tionships than ecoregions with more agricultural and/or urban land cov er. In studies or databases without land cover information, Cl- concen tration is a good surrogate indicator for general human disturbance in the watershed.