Draft CARP Selections, Water Quality and Stormwater

Deterioration in water quality limits the availability of clean water for human and ecosystem use, thereby eliminating otherwise viable supplies or increasing treatment costs. Section 3.3.3 of the draft CARP focuses on the water quality issues in the CWPA. Water quality parameters of concern in the CWPA include, but are not limited to, those for which impairments have been noted (sediments, nutrients, dissolved oxygen, total phosphorus, and nitrite nitrate). The figure below shows locations of impaired waterways in the CWPA.

Causes for these impairments include agriculture, industry, development, and urban land uses. Water quality impacts from point sources are most notable during low flows, when concentration of contaminants peaks. However, non-point source pollutant transport is primarily driven by unmanaged stormwater which carries diverse pollutants across the landscape and into the waterways.

These water quality concerns do not appear to present immediate risks to human uses of ground- or surface-water in the watersheds; however, aquatic benthic communities are severely impaired at most CWPA sampling locations. Future growth and development may exacerbate these problems if not managed.

Stormwater and floodplain management are an important component of water resources management in the CWPA, analyzed in Section 3.3.4 of the draft CARP.  The table shows average seasonal storm-flows in inches from 1997-2010.

Stormwater management and reuse could aid in meeting current and future water demands.  When compared to the quantity of water available in the CWPA, the stormwater analysis demonstrated that sufficient quantities of stormwater typically exist to alleviate much of the potential water shortfall. A key to making this a reality will be selecting effective stormwater practices for implementation, both in terms of cost and amount of water made available. Management of floodplain areas would also protect water quality and enhance water availability.

Comments on the water quality, stormwater and floodplain management, and any other CARP section are welcome and can be submitted via email (marshrockpa@gmail.com), phone (301.274.8116), or at the upcoming July 11 combined CAAC and Potomac Regional Committee meeting.