Water Quality Protection Process
Where monitoring data indicate that waterbodies meet or have higher water quality than applicable WQS, that level of water quality should be protected and maintained (green box in Figure 1). To protect high quality waters, MDE has adopted an avoid, minimize, and mitigate approach. As a first line of protection, local governments should seek to first avoid new discharges to high quality waters by planning new growth and development outside of high quality watersheds or if growth is needed, redeveloping existing developed areas in the watershed using lower impact development practices than what currently exists. Some mechanisms for doing so include enacting more ecologically protective zoning in high quality watersheds, targeting those watersheds for agricultural and forest preservation, and adopting Rural Legacy Program designations. This could also include consideration of redeveloping existing developed areas in the watershed using lower impact development practices than what currently exists.
Maps of Maryland’s high quality (Tier II) waters and other sensitive waters include:
- Tier II High Quality Waters, available HERE. See the Water Quality Protection Implementation Process section of this guidance for additional information.
- Stronghold watersheds, which are priority watersheds for protecting Maryland’s aquatic biodiversity. A description is available HERE. Stronghold watersheds can be viewed HERE and downloaded as GIS data HERE.
- Additional potentially high quality watersheds are planned to be mapped by the Chesapeake Bay Program (CBP) within a Chesapeake Healthy Watersheds Assessment - see HERE for background information and HERE for the assessment.
- Maps showing the water quality status of watersheds in Maryland is available HERE.
- Drinking source water protection areas for both surface and groundwater sources can be found within MDE Water Supply Program’s Source Water Assessments which can be found HERE.
- Maryland Coldwater Resources Mapping Tool is available HERE.
- Maps of streams and wetlands with state or federal rare, threatened, or endangered species within Sensitive Species Project Review Areas (SSPRAs) is available HERE.
- Streams with significant freshwater mussel populations (freshwater mussels contribute to nutrient and sediment reduction in streams and are also important components of freshwater biodiversity) - freshwater mussel mapping will be available soon; please contact DNR for preliminary information.
- Anadromous fish spawning habitat (this includes striped bass spawning areas) whose watersheds are rural (impervious surface is 5% or less, highest priority), approaching suburban development (5-10%, medium priority), and greater than 10% (lowest priority). See HERE.
Where new growth and development cannot be avoided in high quality watersheds, the WRE should ensure new stormwater and wastewater (WWTP and septic) impacts are minimized as much as possible. The WRE should include strategies for identifying and ensuring implementation of applicable minimization techniques such as pollution offsets, maintaining or expanding existing forest cover, protecting or expanding riparian buffers of 100-230 feet (depending upon soil types and slopes), building up rather than out to reduce impervious surfaces, using underground stormwater storage, implementing green roofs and other innovative low impact development techniques, and using the best available technology for onsite disposal systems. The WRE should include strategies for identifying and ensuring implementation of a sufficient number of offsets for watershed impervious surface and nutrient load increases to mitigate the impacts associated with any new development in high quality watersheds.