Maps

Long-term trends were computed by state partners using the Seasonal Kendall non-parametric technique for annual data collected from 1999-2013. Highly significant trends are indicated with triangles and possible trends are show with colored circles. Bottom total phosphorus concentrations are decreasing/improving significantly at 27 stations, possibly decreasing at 13 stations, increasing/degrading significantly at 12 stations, and possibly increasing at 10 stations.

Long-term trends were computed by state partners using the Seasonal Kendall non-parametric technique for annual data collected from 1999-2013. Highly significant trends are indicated with triangles and possible trends are show with colored circles. Surface total phosphorus concentrations are decreasing/improving significantly at 36 stations, possibly decreasing at 23 stations, increasing/degrading significantly at 2 stations, and possibly increasing at 6 stations.

Watershed Yield: Total Phosphorus yields ranged from 0.036 to 0.57 tons per square mile. Each of the 17 sites in the high yield category carries more than 0.19 tons of phosphorus per square mile of watershed. High yielding sites were found in the Eastern Shore, Susquehanna, Potomac, and Rappahannock Watersheds. The lowest yields are generally in the western areas of the Bay watershed and the York River Basin.

Short Term Trend: Over the past 10 years, 63 percent of the monitoring stations show little or no change in flow-adjusted phosphorus concentrations. Between 2003 and 2012: - 9 out of 43 sites show improving flow-adjusted trends for phosphorus concentrations, - 7 site shows degrading trends, and - 27 sites show small changes that are not statistically significant.

Long Term Trend: Seventy-three percent of long-term stream monitoring sites in the Chesapeake Bay Watershed show improving flow-adjusted concentrations of phosphorus. Between 1985 and 2012: - 22 out of 30 sites show improving flow-adjusted trends for phosphorus concentrations, - 4 sites show degrading trends, and - 4 sites show small changes that are not statistically significant.

Average yields for total phosphorus (TP) were estimated for the last five years at 65 sites and classified into thirds as high, medium, and low. While the distribution was spatially variable, there were some general patterns in location. Generally, higher yields for TP are dominant in the middle of the watershed, areas that also coincide with large urban and agricultural land uses. The lowest yields are generally in the western areas of the Bay watershed, an area dominated by forests.

Over the past 10 years, the majority of phosphorus concentration trends are non-significant monitoring at sites within the Bay watershed with many sites showing improving condition and only a few are degrading. The trend results indicate that in many locations, management actions, such as improved wastewater treatment and nonpoint-source pollution controls (i.e. urban stormwater runoff and agricultural runoff controls), have reduced phosphorus concentrations in streams.

Changes in phosphorus concentrations have been determined for the period 1985-2011 at 31 stream sites in the Chesapeake Bay watershed. Of these, the majority of the flow-adjusted trends were downward, with 22 sites showing decreasing trends, 4 sites showing increasing trends, and 5 sites showing trends that were not statistically significant.

Long-Term Flow-Adjusted Trends for Total Phosphorus for 31 Sites in the Chesapeake Bay Watershed, 1985-2010

This map is a key to monitoring stations used to depict flow-adjusted concentration data for nitrogen, phosphorus, and sediment.