ABSTRACT
Watershed research and analysis will increasingly center on large-scale, multi-year studies of mixed land use. This shift from small-scale mechanistic studies is motivated by the urgent need to prevent or reduce water quality degradation by identifying sources of streamflow alteration and pollutants (primarily nonpoint source). Scientists and managers need to develop and validate field and modeling methods that will accurately identify sites that have a disproportionate influence-either positive or negative-on the aquatic environment. It is especially important to quantify the relative effects of specific areas and land uses on streamflow and water quality as the foundation for watershed management efforts. Furthermore, it is necessary to understand the interactions and cumulative effects of land and resource uses and changes with respect to space (location and area/extent) and time. One example of this large-scale emphasis is the U.S. Geological Survey (USGS) National Water Quality Assessment (NAWQA) program, described in Box 9.1.
