Reducing the delivery of nutrients to the Chesapeake Bay is one of the most important components of restoration efforts to achieve a healthy Bay ecosystem. The United States Geologic Service (USGS) has developed a new method for tracking the progress toward reducing nitrogen and phosphorus delivery from the watershed to the Bay. When evaluating the quality of the water entering the Bay, this new method takes into consideration seasonality, variations in river flow, and the long-term trends that are driven by the wide range of human activities in the watershed, such as wastewater treatment and changing land management practices.