Effective monitoring strategies for demonstrating water quality changes from nonpoint source controls on a watershed scale

Demonstrating water quality improvements from nonpoint source (NPS) controls by monitoring both land treatment and water quality in at least a subset of watershed projects is necessary to provide feedback to project coordinators Feedback to regional and national policy makers is also essential to achieve political and economic support for NPS control programs. To meet this objective, two challenges must be met in designing the monitoring network and analyzing the data: (1) Detecting significant (or real) trends in both water quality and land treatment implementation and (2) Associating water quality trends with land treatment trends. Land treatment and water quality monitoring requirements for meeting these challenges are discussed based on lessons learned from the Rural Clean Water Program, a 10-15 year experimental program designed to control agricultural NPS pollution in rural watersheds. At minimum, monitoring of land treatment and water quality should be multi-year before and after best management practice (BMP) implementation. The paired watershed design is the best for documenting BMP effectiveness in the shortest number of years (a minimum of 3-5 years). The water quality and land treatment data bases should be temporally related. All significant sources of variability in the land treatment and water quality data should be taken into account to increase the chances of isolating true water quality changes due to BMPs.