Larry Hogan, Governor Boyd Rutherford, Lt. Governor Mark Belton, Secretary Tidewater Ecosystem Assessment Joanne Throwe, Deputy Secretary Potomac River Water Quality and Habitat Assessment Overall Condition 2012-2014 The Potomac River watershed includes area in Maryland, Virginia, Pennsylvania, West Virginia and Washington D.C. For the purpose of this report, the basin is divided into four regions: the Upper Potomac, Shenandoah, Middle Potomac and Lower Potomac (Figure 1). Land use in the upper Potomac River watershed was estimated to be 69% forest and 22% agriculture (Figure 1, Table 1).1 The Upper Potomac watershed is largely within West Virginia (54%), with other portions in Pennsylvania (22%), Maryland (18%) and Virginia (7%). Impervious surfaces cover 1% of the Maryland potion of the Upper river basin (Table 1).2 Land use in the Shenandoah watershed was estimated to be 56% forest and 34% agriculture. The Shenandoah watershed is almost entirely in Virginia (96%), with a small area in West Virginia (4%). Land use in the Middle Potomac watershed was estimated to be 44% agriculture, 32% forest and 20% developed. The Middle Potomac watershed includes areas in Maryland (55%), Virginia (34%), Pennsylvania (13%) and Washington D.C. (0.1%). Impervious surfaces cover 7% of the Maryland potion of the Middle river basin. Land use in the Lower Potomac watershed was estimated to be 41% forest, 30% developed, and 16% agriculture. The Lower Potomac watershed includes Figure 1 Potomac River basin Top panel shows state boundaries and the individual watersheds. Bottom panel shows the land use throughout the basin for 2011.1 Potomac River Water Quality and Habitat Assessment Overall Condition 2012-2014 1 areas in Virginia (56%), Maryland (42%) and Washington D.C. (2%). Impervious surfaces cover 9% of the Maryland potion of the Lower river basin. For the Maryland portion of the Potomac River basin, agriculture is the largest source of nitrogen, phosphorus and sediment loadings to the upper portion of the basin; stormwater is also a large source of nitrogen, phosphorus and sediment loadings, and wastewater is a large source of nitrogen loadings (Table 2). 3 Stormwater is the largest source of nitrogen, phosphorus and sediment loadings to the lower portion of the basin; agriculture is also large source of nitrogen, phosphorus and sediment loadings and forest lands are a large source of nitrogen loadings. Loadings sources from the other states are shown in Table 2. Table 1. Land Use in the Potomac River Basin. Dominant land use1, percent of the watershed in each State and percent impervious surfaces (MD only)2 within each watershed. All values are in percent (%). Abbreviations include: Ag (Agriculture), Dev (Developed), For (Forest). % of Basin Land Use by State % Impevious Watershed Dominant land use MD VA DC PA WV (MD only) Upper Potomac For (69), Ag (22) 17.8 7.1 0.0 21.5 53.6 1.0 Shenandoah For (56), Ag (34) 96.1 3.9 n/a Middle Potomac Ag (44), For (32), Dev (20) 55.4 34.2 0.1 10.3 6.8 Lower Potomac For (41), Dev (30), Ag (16) 41.5 56.3 2.2 9.1 Total Potomac For (55), Ag (27), Dev (14) 24.2 39.6 0.4 11.2 24.7 5.6 Basin Table 2. Loadings sources from the Potomac River Basin. Dominant loadings sources3 by Chesapeake Bay Program segment and State (only sources accounting for approximately 20% or larger are shown). Columns include TN (Total Nitrogen), TP (Total Phosphorus) and Sed (Sediment) loadings. All values are in percent (%). Loading information is available based on Chesapeake Bay Program segment. The loads from the upper portion of the Potomac River basin (including the Upper Potomac, Shenandoah, Middle Potomac and the upper portion of the Lower Potomac watersheds (Figure 1, Table 1) are summarized as the total loads for two segments: POTTF (Potomac Tidal Fresh) and ANATF (Anacostia Tidal Fresh). The loads from the lower portion of the Potomac River Basin (including most of the Lower Potomac watershed) are summarized as the total loads for four segments: PISTF (Piscataway Tidal Fresh), MATTF (Mattawoman Tidal Fresh), POTOH (Potomac Oligohaline) and POTMH (Potomac Mesohaline). Sources are Agriculture (Ag), Non Regulated Stormwater (Urban), Regulated Stormwater (Stormwater), Wastewater-CSO (CSO), Wastewater, and Forest. MD VA DC PA WV Watershed Segments Source % TN % TP % Sed % TN % TP % Sed % TN % TP % Sed % TN % TP % Sed % TN % TP % Sed load load load load load load load load load load load load load load load Ag 41 51 54 37 61 62 70 70 75 45 55 62 Urban 17 POTTF, Stormwater 25 26 33 19 18 62 ANATF Lower CSO 26 Upper, Wastewater 17 85 52 Shenandoah, Middle, part of Forest 29 PISTF, Ag 27 37 45 39 61 30 MATTF, Urban 23 POTOH, Lower Stormwater 17 33 26 29 Potomac POTMH Forest 23 17 25 17 Potomac River Water Quality and Habitat Assessment Overall Condition 2012-2014 2 How healthy is the Potomac River? Maryland Department of Natural Resources (MDDNR) measures water and habitat quality at 36 non-tidal long- term monitoring stations and at 13 tidal long-term monitoring stations in the Potomac River (Figure 2). Current conditions are determined from the most recent three years of data; trends are determined from the 1999-2014 data. Maryland DNR also participates in the Non- tidal Network, a partnership with the United States Geologic Survey (USGS), the Chesapeake Bay Program, and the other states in the basin, to measure non-tidal water quality using the same sampling and analysis methods. Six of Maryland’s long-term non- tidal stations are also part of the Non-tidal Network (Figure 2, Table 3); three additional stations are only part of the Non-tidal Network. USGS completes the trends analysis for all Non-tidal Network stations. USGS combines river flow data and the nutrient and sediment data for the most recent 10-year period. The USGS method accounts for changes in river flow so that underlying changes in nutrient and sediment levels can be 4 Figure 2 Water quality sampling stations in the Potomac River basin. determined. Trends results from the Non- MD DNR sampling stations (non-tidal and tidal) and the Non-tidal tidal Network stations from the other states Network stations in the basin where trends were determined for 2014. are included below because of the consistency The River Input station for loadings trends is also shown. in monitoring and analysis methods. USGS and MDDNR also measure the nutrient and sediment loadings at the fall-line station located at Chain Bridge (River Input station on Figure 2) to determine trends in loadings at this station.4 Upper Potomac: This portion of the river includes from the headwaters down to the confluence with the Shenandoah River, and is all non-tidal. Measured nitrogen levels decreased at most of the stations in the upstream portion of the Upper Potomac, but increased at some stations in Conococheague Creek and Antietam Creek (Table 3, MDDNR method). However, when changes in river flow are accounted for, the underling nitrogen levels in Conococheague Creek decreased and the nitrogen trend in Antietam Creek is not significant (at the stations that are also part of the Non-tidal Network, USGS method). Phosphorus levels also decreased at many of the stations throughout the Upper Potomac basin, even after changes in river flow are accounted for. Measured sediment levels decreased at some of the stations in the downstream portion of the Upper Potomac, but increased in Georges Creek. However, most stations do not have a significant sediment trend when changes in river flow are accounted for. While decreased nutrients indicate improvement overall, they do not necessarily indicate healthy stream habitat. Non-tidal river habitat is influenced by many issues beyond nutrient and sediment conditions (for example, acid Potomac River Water Quality and Habitat Assessment Overall Condition 2012-2014 3 mine drainage, pollutants, impervious surfaces, etc.). Also, newer concerns include harmful algal blooms in this farthest upstream region of the Potomac River and the occurrence of invasive species such as Didymo. Shenandoah: Virginia measures water quality at six Non-tidal Network stations. Phosphorus levels decreased at the North Fork Shenandoah station when changes in river flow are accounted for. Middle Potomac: This portion of the river extends from the confluence of the Shenandoah downstream to the head of tide at Chain Bridge. The Monocacy River drains to this portion of the river. This portion of the river is all non-tidal. Measured nitrogen levels decreased in the Monocacy River and Seneca Creek and at one of the main river stations (though none of these stations are part of the Non-tidal Network so the effect of changes in river flow cannot be determined). Catoctin Creek nitrogen levels decreased when changes in river low are accounted for. Measured phosphorus levels decreased at most of the stations in the Middle Potomac, but the trends were not significant when the effect of changes in river flow is accounted for. There are no significant trends in sediment levels in the Middle Potomac. Lower Potomac: This portion of the river extends from the head of tide at Chain Bridge downstream to the mouth of the river at Point Lookout. Loadings and water quality are determined at the fall-line station at Chain Bridge (River Input station, Figure 2). Four additional stations are monitored in non-tidal areas, and thirteen stations are monitored by Maryland in tidal portions of the Lower Potomac basin. Non-tidal areas: Nitrogen, phosphorus and sediment loadings have decreased at the fall-line station at Chain Bridge.4 Nitrogen levels in the water also decreased at this station when the effects of river flow are accounted for.