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 sample and the digitized version of the 1:100,000 scale USGS map stream network as the sample population. Both classified Thematic Mapper (TM) and USGS Land Use/Land Cover (LULC) data were used to quantify land cover in the study watersheds. On average, the most common land cover was forest (77 %) followed by agriculture (20 %), and urban (1 %). Multiple regression analysis showed that concentrations of Cl-, nutrients, acid neutralization capacity, and base cations were the analytes most strongly related to watershed land cover. Despite large differences in resolution and age of the TM and LULC data sources, similar results were obtained with the two sources. Using a greater number of land cover subclasses did not greatly improve the land cover-chemistry relationships. Ecoregions with predominantly forested land cover had weaker relationships than ecoregions with more agricultural and/or urban land cover. In studies or databases without land cover information, Cl- concentration is a good surrogate indicator for general human disturbance in the watershed.