State Guidance, Information and Tools

Account for Climate Change Adaptation in the WRE Analysis

​​To ensure adequate water and wastewater capacity to support planned growth and development, and to ensure the identification of suitable receiving waters given expected stormwater and wastewater impacts of planned growth and development, the WRE analyses should integrate climate change adaptation when assessing:

  1. Water supply availability
  2. Water demand projection
  3. Wastewater flow projection
  4. Stormwater quantity (local flooding impacts)
  5. Stormwater quality (pollutant impacts)
  6. Suitability of areas for septic systems, e.g., consider expected changes in water tables given that some areas proposed for septic systems could become waterlogged in the near future, preventing the proper functioning of these systems.
  7. Land use plans

Water-Related Risks: Climate Change Adaptation Needs

After considering the following climate change adaptation needs, local governments should include strategies within the WRE and Sensitive Areas Element to address them (see the S​trategies to Consider section below).

How will Climate Change Affect Water Resource Capacities?

  1. Water Supply Capacities: Although climate change is currently predicted to increase the average amount of precipitation in Maryland, variations are also expected to become more extreme. This includes the potential for drought. Therefore, a greater margin of safety should be considered in the expected availability from water supply sources that could be affected by climate change, whether within permits or intergovernmental agreements.
  2. Water Body Capacity to Assimilate Pollutants: Wastewater discharge limits already account for extreme flow conditions. In 2020, the Chesapeake Bay TMDL nutrient limits were tightened in acknowledgement of the effects of climate change. Similar tightening of limits should be anticipated in the future for other stressors, including temperature.
  3. Water Body Capacities to Manage Flooding: More extreme precipitation, resulting in more extreme flooding, is a hallmark of climate change predictions in the Eastern United States. Climate induced increases in precipitation impacts the ability of floodplains and wetlands to transport and store flood flows. This should be anticipated and accounted for in the planning related to both coastal and inland areas that play a role in mitigating the effects of flooding or are subject to flooding.

How will Climate Change Affect Water Infrastructure Capacity Needs?

  1. Water Supply System Capacities: Apart from water source availability, climate change could affect water supply systems capacity in various ways. Storage may need to be increased to account for source disruptions. Treatment may need to be improved to account for increased turbidity, which also increases treatment time and expense while reducing capacity, due to more intense rainfall events or increased algal blooms associated with increased temperatures. In some cases, more expensive technologies like potable reuse or desalination may be needed if backup supplies are not available. If local water sources play a role in power plant cooling, supply planning should anticipate increased usage needs during hot weather when energy demands rise. This can be particularly challenging if a drought corresponds with high heat.
  2. Wastewater Treatment Capacities: Higher water tables associated with climate change could exacerbate inflow and infiltration, which would consume wastewater treatment plant flow capacity thereby shortening the anticipated lifespan of the facility. In addition, greater precipitation can result in more combined or sanitary sewer overflows. At the other extreme, drought conditions could reduce wastewater flows while increasing wastewater pollutant concentrations. This could generate a water demand on drought-stressed water supplies to maintain a minimum flow to ensure the functionality of wastewater collection pipes and treatment systems.
  3. Water, Wastewater and SWM Infrastructure Stress: Climate change might cause more freeze/thaw cycles, and wet/dry cycles, which can place more stresses on infrastructure. Stormwater BMPs and conveyance systems will likely face physical stress and more rapid sedimentation from increased intensity of rainfall. Dry spells could stress the vegetation that is an integral part of some SW systems. Increased saltwater intrusion can hasten corrosion of infrastructure. Plans should account for greater maintenance needs and identify who should bear the cost burden for this infrastructure in the future.
  4. Water Conveyance System Capacity: Increased precipitation also impacts the ability of existing water conveyance infrastructure (culverts, channels, pipes, inlets, stormwater ponds and related dams, green infrastructure) to store, infiltrate and convey flood flows away from buildings, roads, and communities.

The EPA Climate Change Adaptation Resource Center’s Climate Impacts on Water Utilities section includes access to the Climate Resilience Evaluation and Awareness Tool (CREAT), which can help utilities identify current and future climate impacts and assess the vulnerability of water utility facilities. Go HERE for additional information on EPA’s CREAT tool.

How will Climate Change Impact Water Resources?​

  1. Greater Threat to Source Waters: More intense storms due to climate change increase the threat of chemical spills that could contaminate groundwater recharge areas, well heads (both community and individual) and surface water sources. This highlights the need to avoid certain types of development in these sensitive areas.
  2. Stormwater Treatment and Flood Control Effectiveness: More intense storms due to climate change are predicted to reduce the pollution removal effectiveness of stormwater BMPs. Similarly, to the degree SWM plays a role in localized flood management, current design criteria might need to be changed in the future. This suggests the potential need to set aside more land area for SWM associated with land development. Another approach is to ensure that current designs are resilient (e.g., they safely pass these intense rainfall events without overtopping or failing). This will depend on the current conveyance system and what is located in the overflow path. These details are probably more than would be typical of a planning level assessment; however, mapping the system, understanding its capacity and knowing where current problems exist are planning level assessments that should inform the WRE. Also, emergency action plans with alarm systems should be employed in areas where there is not enough room to build a large enough stormwater facility to manage an extreme event and peoples' lives are at risk.
  3. Higher Temperatures and Flows to Coldwater and Other Sensitive Streams and Waterbodies: The management of temperature impacts from development and other anthropogenic activities on coldwater streams can be difficult and costly. Climate change will exacerbate temperature and flow changes. Because this impact is not well accounted for in current development regulations, it is much better to avoid or significantly minimize development near these streams: maps of Maryland’s high quality (Tier II) waters and other sensitive waters include:
    • Tier II High Quality Waters, available HERE​.
    • 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 CBP within a Chesapeake Healthy Watersheds Assessment - see HERE for background 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 or 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, but 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.
  4. Erosion and Sediment Control: Extreme precipitation and weather events can result in unauthorized discharges, particularly during site construction and with respect to failure of onsite sediment and erosion controls. Soil Conservation Districts have the statutory authority to approve erosion and sediment control plans. A few local jurisdictions have delegated authority to ensure compliance with these plans. Local governments should consider whether a WRE strategy is needed to call for implementation of enhanced sediment and erosion control practices as an adaptation strategy for extreme weather events.

How might Climate Change Considerations Influence Land Use Decisions?

  1. Dams and Development: Climate change will place more stress on Maryland’s aging dams. Also, development in areas below dams could be inundated if a dam were to fail or emergency water releases are needed. Development upstream of some dams also could be flooded during large rain events, particularly if the dam height is required to be raised to account for larger rainfall events in the future.
  2. Floodplains and Development: Climate change is likely to extend the area near rivers and the coast that have a 1% chance of flooding in a given year (100-year floodplain) beyond their current boundaries. This should be considered when planning development near these areas. As a matter of equity, consider policies to prevent affordable housing from being located in areas at greater risk of flooding. Maryland’s Climate Ready Action Boundary maps the area of land inundated by water that ranges from 1-3 feet above the 100-year flood level.

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