Targeted Adaptation Strategies for Climate Impacts on Water Quality

Climate Impacts

Stormwater Runoff

  • Use Bioretention to collect stormwater runoff
    Bioretention is an adapted landscape feature that provides onsite storage and infiltration of collected stormwater runoff. Stormwater runoff is directed from surfaces to a shallow depression that allows runoff to pond prior to infiltration in an area that is planted with water-tolerant vegetation. As runoff accumulates, it will pond and slowly travel through a filter bed where it either infiltrates into the ground or is discharged via an underdrain. Small-scale bioretention areas are often referred to as rain gardens.
  • Use a blue roof to hold precipitation after a storm event and discharge it at a controlled rate
    A blue roof is designed to hold up to eight inches of precipitation on its surface or in engineered trays. It is comparable to a vegetated roof without soil or vegetation. After a storm event, precipitation is stored on the roof and discharged at a controlled rate. Blue roofs greatly decrease the peak discharge of runoff and also allow water to evaporate into the air prior to being discharged. Precipitation discharge is controlled on a blue roof through a flow restriction device around a roof drain. The water can either be slowly released to a storm sewer system or to another green infrastructure practice such as a cistern or bioretention area.
  • Use permeable pavement to allow runoff to flow through and be temporarily stored prior to discharge
    Permeable pavement includes both pavements and pavers with void space that allow runoff to flow through the pavement. Once runoff flows through the pavement, it is temporarily stored in an underground stone base prior to infiltrating into the ground or discharging from an under drain. Permeable pavers are highly effective at removing heavy metals, oils and grease in runoff. Permeable pavement also removes nutrients such as phosphorous and nitrogen. Soil and engineered media filter pollutants as the runoff infiltrates through the porous surface. The void spaces in permeable pavement surfaces and reservoir layers provide storage capacity for runoff. All permeable pavement systems reduce runoff peak volume.
  • Use underground storage systems to detain runoff in underground receptacles
    Underground storage systems vary greatly in design. They detain runoff in underground receptacles that slowly release runoff. Often the underground receptacles are culverts, engineered stormwater detention vaults or perforated pipes. One of the benefits of underground storage is that it does not take up additional surface area and can be implemented beneath roadways, parking lots, or athletic fields. Underground storage systems are typically designed to store large volumes of runoff and therefore can have a significant impact in reducing flooding and peak discharges.
  • Use a stormwater tree trench to store and filter stormwater runoff
    A stormwater tree trench is a row of trees that is connected by an underground infiltration structure. At the ground level, trees planted in a tree trench do not look different than any other planted tree. Underneath the sidewalk, the trees sit in a trench that is engineered with layers of gravel and soil that store and filter stormwater runoff. Stormwater tree trenches provide both water quality and runoff reduction benefits.
  • Use a retention pond to manage stormwater
    A retention pond is one of the earliest prototypes of green infrastructure, and is now considered a more traditional type of stormwater infrastructure because it has been integrated into gray infrastructure design. It is an engineered stormwater basin designed to store runoff and release it at a controlled rate while maintaining a level of ponded water. Pollutants and sediment loads are reduced as the runoff is retained in the basin. Retention ponds are a very common stormwater management practice and may be designed with sustainable elements to increase water quality and decrease peak discharges. Vegetated forebays may be added to increase sediment removal as well as provide habitat. Another enhancement to traditional stormwater retention ponds is the addition of an ironenhanced sand filter bench that removes dissolved substances such as phosphorus from runoff.
  • Use extended detention wetlands to reduce flood risk and provide water quality and ecological benefits
    Extended detention wetlands may be designed as a flood mitigation strategy that also provides water quality and ecological benefits. Extended detention wetlands can require large land areas, but come with significant flood storage benefits. Extended detention wetlands can be created, restored (from previously filled wetlands) or enhanced existing wetlands. Wetlands typically store flood water during a storm and release it slowly, thereby reducing peak flows. An extended detention wetland allows water to remain in the wetland area for an extended period of time, which provides increased flood storage as well as water quality benefits. Extended detention wetlands are distinct from preservation of existing wetlands, but the two practices often are considered together as part of a watershed-based strategy.

  • Consider how current design standards are formulated as a starting point to the discussion
    Rather than starting a conversation with a discussion of climate change projections, understand the current design standard for stormwater management. Then, engage decision makers to seek agreement on a threshold (e.g., the community will prepare for X storm) that is informed by historic data and reflects the risk tolerance of the community (e.g., what level of damage or disruption the community can tolerate at different costs). This also entails understanding the current design standard and whether performance can be enhanced for projects in the region.
  • Demonstrate the use of dynamical downscaling on research projects at the site scale
    Decision makers can use local resources for climate change data from researchers at organizations within the area, such as universities, state meteorological agencies and other organizations that may be involved in downscaling of climate change scenarios.
  • Develop a "wish-list" of data that should be collected to improve understanding of climate changes
    Stormwater managers and geographic information system (GIS) staff can begin to collect this needed local data (e.g., establish and maintain more local weather gauges and monitoring stations). Partners in the community or neighboring jurisdictions may also be interested in pooling resources to develop or improve data sets.
  • Use resources to show historical and future trend lines
    To understand future climate changes, techniques that use historic data, such as analogue events or other sensitivity and threshold information in the historic record, can be used as illustrations (e.g., see the Intergovernmental Panel on Climate Change report, Climate Change 2001: Working Group II: Impacts, Adaptation, and Vulnerability, Section 3.5. The U.S. Environmental Protection Agency's National Stormwater Calculator and Storm Water Management Model Climate Adjustment Tool provide regional downscaled climate projections. The USEPA also offers the Global Change Explorer, a web application for visualizing and downloading climate model output.

  • Build swales and rain gardens
    Water temperature benefits include getting water underground and maintains aquifers. Other benefits can included keeping stormwater runoff out of waterways.
  • Control stormwater runoff
    Water temperature benefits include reducing high peak flows that contribute to erosion and channel changes. Other benefits can include restoring natural hydrology, returning to natural sediment transport and geomorphology, reestablishing natural disturbance and raising water quality.
  • Plant trees
    Water temperature benefits include shading the ground and keeping water temperature cooler. Other benefits can include controlling stormwater runoff and promoting infiltration.
  • Promote stormwater infiltration
    Water temperature benefits include getting water into aquifers and away from exposure to sun, and recharging groundwater that supplies baseflow that regulates stream temperature. Other benefits can include restoring natural hydrology, returning to natural sediment transport and geomorphology and reestablishing natural disturbance.

Erosion and Sedimentation

  • Use Underground storage systems to detain runoff in underground receptacles
    Underground storage systems vary greatly in design. Underground storage systems detain runoff in underground receptacles that slowly release runoff. Often the underground receptacles are culverts, engineered stormwater detention vaults or perforated pipes. One of the benefits of underground storage is that it does not take up additional surface area and can be implemented beneath roadways, parking lots or athletic fields. Underground storage systems are typically designed to store large volumes of runoff and therefore can have a significant impact in reducing flooding and peak discharges.
  • Use a retention pond to manage stormwater
    A retention pond is one of the earliest prototypes of green infrastructure, and is now considered a more traditional type of stormwater infrastructure because it has been integrated into gray infrastructure design. It is an engineered stormwater basin designed to store runoff and release it at a controlled rate while maintaining a level of ponded water. Pollutants and sediment loads are reduced as the runoff is retained in the basin. Retention ponds are a very common stormwater management practice and may be designed with sustainable elements to increase water quality and decrease peak discharges. Vegetated forebays may be added to increase sediment removal as well as provide habitat. Another enhancement to traditional stormwater retention ponds is the addition of an ironenhanced sand filter bench that removes dissolved substances such as phosphorus from runoff.

  • Consider long-term benefits of green infrastructure in economic analysis of stormwater management plans
    Train local appraisers/commissioners to capture the full value of green infrastructure. Incorporate cobenefits into ROI calculations, such as ecosystem services and quality of life factors.

  • Control soil erosion in the watershed
    Water temperature benefits include keeping sediment from clogging streambeds and interfering with groundwater exchange and keeping heat-trapping particles out of waterways. Other benefits can include returning to natural sediment transport and geomorphology, and raising water quality.
  • Control stream bank erosion
    Water temperature benefits include keeping stream channels from getting wider and shallower and warming more easily. Other benefits can include maintaining natural sediment transport and geomorphology, and raising water quality.

Harmful Algal Blooms

  • Develop models to understand potential water quality changes
    In many areas, increased water temperatures will cause eutrophication and excess algal growth, which will reduce drinking water quality. The quality of drinking water sources may also be compromised by increased sediment or nutrient inputs due to extreme storm events. These impacts may be addressed with targeted watershed management plans.
  • Manage reservoir water quality
    Changes in precipitation and runoff timing, coupled with higher temperatures due to climate change, may lead to diminished reservoir water quality. Reservoir water quality can be maintained or improved by a combination of watershed management, to reduce pollutant runoff and promote groundwater recharge and reservoir management methods, such as lake aeration.
  • Install effluent cooling systems
    Higher surface temperatures may contribute to making water quality standards or make temperature criteria more difficult to attain, as well as lead to greater outbreaks of harmful algal blooms. Therefore, efforts to reduce the temperature of treated wastewater discharges, such as additional effluent cooling systems, may be needed to help maintain water quality.
  • Visit the Water Utility Source Water Quality Page to view more Adaptation Strategies that can help support efforts to reduce water quality impacts from harmful algal blooms.

Source Documents

These strategies are adapted from existing federal sources including the U.S. Environmental Protection Agency, the Centers for Disease Control and Prevention and others. Please view these strategies in the context provided by the primary source documents: