WATER-QUALITY FUNCTIONS OF RIPARIAN FOREST BUFFERS IN CHESAPEAKE BAY WATERSHEDS

Maryland, Virginia, and Pennsylvania, USA, have agreed to reduce nutri ent loadings to Chesapeake Bay by 40% by the year 2000. This requires control of nonpoint sources of nutrients, much of which comes from agr iculture. Riparian forest buffer systems (RFBS) provide effective cont rol of nonpoint source (NPS) pollution in some types of agricultural w atersheds. Control of NPS pollution is dependent on the type of pollut ant and the hydrologic connection between pollution sources, the RFBS, and the stream. Water quality improvements are most likely in areas o f where most of the excess precipitation moves across, in, or near the root zone of the RFBS. In areas such as the Inner Coastal Plain and P iedmont watersheds with thin soils, RFBS should retain 50%-90% of the total loading of nitrate in shallow groundwater, sediment in surface r unoff, and total N in both surface runoff and groundwater. Retention o f phosphorus is generally much less. In regions with deeper soils and/ or greater regional groundwater recharge (such as parts of the Piedmon t and the Valley and Ridge), RFBS water quality improvements are proba bly much less. The expected levels of pollutant control by RFBS are id entified for each of nine physiographic provinces of the Chesapeake Ba y Watershed. Issues related to of establishment, sustainability, and m anagement are also discussed.