Temperatures are rising, snow and rainfall patterns are shifting, and more extreme climate events—like heavy rainstorms and record high temperatures—are already taking place. Increasing temperatures have been observed to lead to reduced lake levels due to increased evaporation. Anticipated expansion of water use is also likely to impact the quality and quantity of available surface and ground water resources.
As the climate continues to warm, evaporation is expected to increase. While flooding due to larger rain events is projected in many regions of the United States, higher temperatures and reduced lake ice are expected to outpace increases in precipitation falling as rain in the winter and spring, leading to lower surface-water levels in lakes and rivers as well as declining reserves of groundwater in some regions.
While changes in water levels are anticipated throughout the nation, marked changes in water levels have already been observed in the Great Lakes, impeding navigation and impacting water quality and aquatic ecosystems. Average lake levels depend on a balance between precipitation and runoff and evaporation and outflow.
The Lake Mead and Lake Powell reservoirs of the Colorado River system, which provides water for vulnerable ecosystems as well as millions of people in the Southwestern United States have been receding – in large part due to human withdrawals, however, changing climatic conditions are expected to exacerbate water scarcity in this region.
Although future climate change is expected to produce increases in precipitation throughout the United States, in most locations rising evapotranspiration due to increasing temperatures will offset this change and overall, water yields are expected to undergo substantial declines – exceeding 30% of current levels by 2080 under some scenarios
Altered water levels from declining surface and groundwater levels to flooding affect the built and the natural environment. Changing water availability and quality will likely to impact infrastructure – from water supplies and utilities, to power generation from hydroelectric and nuclear power plants – as well as commercial navigation, property owners, marine recreation and tourism, and marinas, as well as the ecosystems and species dependent on these systems. Throughout the country, lower water levels may result in diminished water quantity and quality. As waters recede lakefront property and water dependent infrastructure will be farther away from the water’s edge, reducing accessibility and raising issues of public trust.
Decreasing water levels are also likely to have broad impacts on ecosystems – watersheds and wetlands as well as coastal areas and ocean waters are vulnerable to extreme changes in water levels, temperatures, and chemical composition. Coastal wetlands fronted by barrier beaches may be cut off from the lakes, and as water levels drop, lakes, wetlands, and streams may dry up. In addition, lower water levels is likely to result in an increase in the concentration of nutrients and pollutants and a decrease in dissolved oxygen concentrations, which in conjunction with associated warmer air and water temperatures may exacerbate harmful algal blooms and hypoxia, where low dissolved oxygen levels create expansive “dead zones”. Changing ecological conditions may also facilitate “invasions” by new species or encourage expansion of previously established non-native invasives.
Land trusts are responding to on-the-ground impacts of altered surface and groundwater levels in various ways. Some groups are implementing adaptation projects such as removing barriers to surface waters or planting less water-dependent tree species. In addition to employing strategic conservation planning to reduce risks and enhance resilience, some land trusts are also supporting efforts to mitigate greenhouse gas emissions to reduce the extent of future climate change.
Land trusts must determine the right planning approach for their organization, however, more and more, conservation organizations are working with their communities to identify opportunities to reduce vulnerabilities and prepare for changing temperatures. Agencies are making similar strides to implement projects that reduce risks and plan for resilience by incorporating adaptation, mitigation, and engagement into their strategic goals and objectives. For example, the U.S. Fish and Wildlife Service’s Strategic Plan for Responding to Accelerating Climate Change identifies seven planning and development goals to support sustainable landscapes. Conservation groups are increasingly partnering with agencies as well as other nonprofits and for-profit organizations to respond to this global challenge at local levels.
Resilience describes the ability of a system to persist through extreme change. By working to identify and reduce potential threats land managers can build resilience and achieve multiple management objectives. Assessing vulnerabilities is a critical step in the strategic conservation planning process that helps land trusts identify key threats to resources. Adaptive management planning enables conservation practitioners to implement interventions to reduce vulnerabilities and to monitor and revise strategies as new information becomes available. There is no one-size-fits-all solution to addressing management challenges associated with warming average temperatures, however, planning that acknowledges vulnerabilities can help land trusts better achieve their conservation objectives.
Increased frequency and duration of droughts as well as greater extraction of water resources lowers water levels. Lower water levels increase nutrient concentrations and residence times in streams, potentially increasing the likelihood of harmful algal blooms and low oxygen conditions.
Models indicate an increase in the length of dry periods across most of the United States. The US Climate Resilience Toolkit describes that as higher temperatures lead to greater evaporation and earlier snowmelt, the threat of seasonal drought will increase. In some regions, changing conditions and increased demand will challenge the reliability of municipal water supplies, which draw on surface and groundwater resources. Cases of water use conflicts between human uses and ecosystem needs have already been arising across the United States.
Did you know land trusts are working to mitigate climate change? Learn more.