Through the efforts of the CBP and its partner agencies, various types of data have been collected that document the extent of nutrient loading and the environmental factors that affect it. Stream-discharge and nutrient-concentration data have been collected at many locations throughout the watershed. Data sets that document major sources of nutrients have also been developed, including those that quantify point-source discharges, agricultural-fertilizer application, manure generation and atmospheric deposition. In addition, data sets that describe the geographic characteristics of the watershed that may affect loading, such as land cover, physiography, and soil characteristics, have been compiled. All of this information is important for understanding nutrient loading and accomplishing the goals of the CBP. The environmental factors that affect loading are interrelated; thus the different types of data that describe these factors must be integrated to understand the role of any individual factor