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Figure 4. Locations of 48 water-quality monitoring sites for which in-stream nutrient load data were retrieved from the U.S. Geological Survey National Water Information System and analyzed.

Loads of Nutrients and Suspended Sediment

In-stream loads of 13 nutrient and suspended-sediment concentrations were estimated for selected sites in the Southeast (table 12), including most of the USGS NWIS sites that were included in the trend analyses. Identification and location of the 48 sites for load estimation are presented in table 12 and figure 4.

Annual load estimates (in kilograms) for the period 1973–2005 are presented in table 13. Annual yield estimates, calculated as load per unit area, are given in table 14 (in tons per square mile) and in table 15 (in kilograms per square kilometer). Summary statistics of the annual load and yield estimates at each site also are presented in tables in appendix A2; these summary tables include mean annual load (in kilograms; table LDR4), median annual load (in kilograms; table LDR5), mean annual yield (in kilograms per square kilometer; table LDR6), median annual yield (in kilograms per square kilometer; table LDR7), mean annual yield (in tons per square mile; table LDR8), and median annual yield (in tons per square mile; table LDR9). The time periods used for the summary statistics of the annual load estimates vary by station and constituent because they are limited to available data. The time periods can be inferred by inspecting data availability in table 12.