The third National Climate Assessment (NCA) was released on May 6, as reportedreported by AMWA. The NCA can be explored online or downloaded as PDF files. The report assesses the current science of climate change and its impacts across the U.S. now and through the end of this century. The NCA describes several climate impacts that are of interest to water utilities, noted below and organized by section or chapter.
The Highlights section describes impacts related to freshwater and ocean temperatures, frost-free days and heavy downpours, among others:
- Overall increases in extreme weather, specifically regional floods and droughts.
- A rising intensity and frequency of Category 4 and 5 hurricanes and more rainfall that will occur in conjunction with these hurricanes.
- A rising intensity and frequency of winter storms, and a northward-shifting track for these storms.
- Observed increases in heavy precipitation across all regions, but particularly in the Northeast and Midwest.
- An observed increase in average precipitation across the U.S. since 1990. However, less precipitation is expected to fall over the Southwest and more will fall over the northern U.S. in the winter and spring in the coming decades.
- A thaw of the permafrost in Alaska.
- An 8-inch increase in global sea level since 1880. Sea level in the U.S. is expected to rise an additional one to four feet by 2100.
- The global ice melt will not only affect sea level rise but could also lead to increased snowfall over northern land areas and increase north-south meanders of the jet stream.
- An increase in the number of frost-free days, which could result in an increased water demand on crops.
- An increasing duration of heat waves, which are tied to drought and also to increasing water loss rates due to evaporation.
- An increase in floods, particularly flash floods in urban areas, and also increases in river flood magnitude in the Midwest, Northern Appalachians and New England.
The Water chapter is supported by many predictions, examples and graphics illustrating observations of changing precipitation, runoff patterns, droughts, flooding and other impacts:
- Climate change is expected to impact water demand, groundwater withdrawals and aquifer recharge.
- Increases in pollutant loads and other adverse impacts to water quality are expected as a result of increasing air and water temperatures as well as more intense precipitation and runoff.
- Climate change will impact the way water resources are used and managed across regions and economic sectors. The Southwest, Great Plains and Southeast are particularly vulnerable to change in water supply and demand.
- The likelihood of water shortages will increase in many areas, due to expected changes in precipitation and runoff coupled with changes in consumption and withdrawal.
- In most regions of the U.S., water resources managers will encounter new risks, vulnerabilities and opportunities that may not be adequately addressed using existing practices.
- By increasing resilience and enhancing the ability to adapt, water resources managers will have opportunities to strengthen water resources management and plan for the impacts of climate change. However, many types of barriers exist which present challenges to implementing adaptation strategies.
The Urban chapter notes that because climate change often presents a series of challenges for the most densely populated parts of the U.S., many cities have become early responders to climate challenges, particularly given the vulnerabilities of urban infrastructure:
- Essential infrastructure systems including water will increasingly be compromised by interrelated climate change impacts. The nation’s economy, security and culture all depend on the resilience of urban infrastructure systems.
- In urban settings, climate-related disruptions of services in one infrastructure system will almost always result in a cascading effect on one or more other infrastructure systems.
- Climate vulnerability and adaptive capacity of urban residents and communities are influenced by pronounced social inequalities.
- Many cities have started adaptation plans that focus on infrastructure systems and public health. But, to be successful, these adaptation efforts require integration into everyday city operations and governance as well as cooperative private sector and governmental activities.
The Adaptation chapter notes that while substantial adaptation planning is occurring in public and private sectors as well as across all levels of government, few measures are being implemented. This is due in part to legal and policy barriers as well as difficulty for policymakers to anticipate local-level climate impacts. The chapter provides a generalized adaptation process, lists many federal, state and local adaptation activities and provides four illustrative case studies.
AMWA members may also find other sections of the report useful, such as the chapters on regional issues and coastal zones.