The latest US National Climate Assessment is warning that climate change is putting water security in the United States increasingly in jeopardy and deteriorating water infrastructure at greater risk.
The analysis comes in a detailed chapter on US water resources in the Fourth National Climate Assessment report prepared by the U.S. Global Change Research Program (USGCRP) and delivered to Congress and the President last week.
The National Oceanic and Atmospheric Administration (NOAA) served as the administrative lead agency for the preparation of the report.
The report says that climate change is a major driver of changes in the frequency, duration, and geographic distribution of severe storms, floods, and droughts. The shifts have led to protracted exposures to extreme floods or droughts in different parts of the country that are “extraordinary compared to events experienced in the 20th century.”
The Assessment is warning that US water systems are already facing considerable risk, even without anticipated future climate changes.
Limited surface water storage, as well as a limited ability to make use of long-term drought forecasts and to trade water across uses and basins, has led to a significant depletion of aquifers in many regions in the United States, the report says.
Much of the critical water and wastewater infrastructure across the United States is aging and, in some cases, deteriorating or nearing the end of its design life, presenting an increased risk of failure.
Despite this, to date, the national exposure to this risk has not yet been fully assessed and no comprehensive assessment exists of the climate-related vulnerability of U.S. water infrastructure, the potential resulting damages, or the cost of reconstruction and recovery. Key assets at risk include:
- water and wastewater distribution and treatment systems
More than 15,000 aging and deteriorating dams in the United States are listed as high risk due to the potential losses that may result if they failed.
Several recent heavy rainfall events have led to dam, levee, or critical infrastructure failures, including:
- the Oroville emergency spillway in California in 2017
- Missouri River levees in 2017
- 50 dams in South Carolina in October 2015/16
- New Orleans levees in 2005 and 2015
The report is flagging up the need to plan for plausible future climate conditions wider in range than those experienced in the 20th century as a central challenge to water planning and management.
“Doing so requires approaches that evaluate plans over many possible futures instead of just one, incorporate real-time monitoring and forecast products to better manage extremes when they occur, and update policies and engineering principles with the best available geoscience-based understanding of planetary change.”
“Infrastructure design, operation, financing principles, and regulatory standards typically do not account for a changing climate,” the report says.
Current risk management does not consider potential cascading infrastructure failure
According to the report, current risk management does not typically consider the impact of co-occurrence of multiple events and the risk of cascading infrastructure failure.
The Assessment warns that compound extreme events—the combination of two or more hazard events or climate variables over space and/or time that leads to an extreme impact—have a multiplying effect on the risk to society, the environment, and built infrastructure.
Compound extremes can also increase the risk of cascading infrastructure failure – the failure of one system can lead to the failure of interconnected systems, such as water–energy infrastructure, the report warns.
Despite this, traditional infrastructure design approaches and risk assessment frameworks often consider these drivers in isolation.
Recent examples of compound events cited in the report include:
- the 2016 Louisiana flood, which resulted in simultaneous flooding across a large area
- Superstorm Sandy in 2012, when extreme rainfall coincided with near high tides
- Hurricane Isaac in 2012 and Hurricane Matthew in 2016 – events which combined storm surge and extreme precipitation
Estimated reconstruction and maintenance costs total trillions of dollars
Based on data from a variety of different sources, the report says the estimated reconstruction and maintenance costs aggregated across dams, levees, aqueducts, sewers, and water and wastewater treatment systems total in the trillions of dollars, including:
- An estimated $384 billion in capital improvement needs for public water systems for projects from 2011 through 2030
- An estimated $271 billion over a 20-year period for capital investment needs for publicly owned wastewater conveyance and treatment facilities, combined sewer overflow correction and storm water management to address water quality or water quality-related public health problems
Diagram source: adapted from NOAA NCEI 2018 1
The report also points out that flooding on the Mississippi and Missouri Rivers in May 2011 caused an estimated $5.7 billion in damages (in 2018 dollars). One year later, drought conditions in 2012 led to record low flows on the Mississippi, disrupting river navigation and agriculture and resulting in widespread harvest failures for corn, sorghum, soybean, and other crops. The nationwide total damage from the 2012 drought is estimated at $33 billion (in 2018 dollars).
To date, however, no comprehensive assessment of the climate-related vulnerability of U.S. water infrastructure has been undertaken, while the climate risks to existing infrastructure systems remain unquantified.
No common infrastructure design standards or operational guidelines in face of growing climate risk
The report says that tools, case studies, and other information are already available that can be adopted into design standards and operational guidelines to account for future climate and/or integrate climate projections into infrastructure design.
However, currently there are no common design standards or operational guidelines in place that address how infrastructure should be designed and operated in the face of changing climate risk.
Existing procedures for the design, estimation of probability of failure, and risk assessment of infrastructure rely on 10–100 years of past data about flood and rainfall intensity, frequency, and duration.
The report says numerous studies suggest that the severity and frequency of climatic extremes, such as precipitation and heat waves, have been changing, unlike the current approach which assumes that the frequency and severity of extremes do not change significantly over time.
Other significant challenges highlighted in the Assessment include:
- Limited surface water storage and a limited ability to make use of long-term drought forecasts and to trade water across uses and basins have led to the significant depletion of aquifers in many regions of the United States.
- Extreme precipitation and rising sea levels associated with climate change make the built environment in the Southern Great Plains increasingly vulnerable to disruption
- Storm water management systems and other critical infrastructure in the Midwest are already experiencing impacts from changing precipitation patterns and elevated flood risks
- Harmful algal blooms (HABs) in western Lake Erie have been steadily increasing over the past decade. In 2014 in Toledo, Ohio, half a million people were warned to avoid drinking the water due to toxins overwhelming a water treatment plant in Lake Erie’s western basin as a result of a harmful bloom.
- Northwest and Alaska: Pacific salmon populations in the Northwest are being affected by climate stressors, including low snowpack (such as in 2015), decreasing summer streamflow and habitat loss through increasing storm intensity and flooding
- Water supplies for people and nature in the Southwest are decreasing – intensifying droughts, heavy downpours, and reduced snowpack are combining with increasing water demands from a growing population, deteriorating infrastructure, and groundwater depletion to reduce the future reliability of water supplies
- Glaciers are continuing to melt in Alaska and the western United States which will alter stream water volume, water temperature, runoff timing, and aquatic ecosystems in these regions.
- Higher temperatures also result in increased human use of water, particularly through increased water demand for agriculture, In the United States, groundwater provides more than 40% of the water used for agriculture (irrigation and livestock) and domestic water supplies
- Groundwater use for irrigation has increased substantially since about 1900 and in some areas has exceeded natural aquifer recharge rates
- In the High Plains Aquifer, the largest freshwater aquifer in the contiguous United States that supports an important agricultural region, the rate of groundwater withdrawal for irrigation is nearly 10 times the rate of natural recharge, resulting in large groundwater depletions.
- Continued warming will add to the stress on water supplies and adversely impact water supply reliability in parts of the United States
- Without efforts to increase water-use efficiency in rural and urban areas, increased future demand due to warming could exceed future supply in some locations
The Assessment says that the lack of coordinated management of surface water and groundwater storage is limiting the United States’s ability to address climate variability. “Management of surface water and groundwater storage and water quality are not coordinated across different agencies, leading to inefficient response to changing climate,” the report says.
Water management in a changing future
The Assessment says that water management strategies designed in view of an evolving future which can only partially be anticipated will help to prepare for the water- and climate-related risks of the future. However, the report warns:
“While there are examples of promising approaches to manage climate risk, the gap between research and implementation, especially in view of regulatory and institutional constraints, remains a challenge.”
The report says that learning to plan for plausible future climate conditions that are wider in range than those experienced in the past is a central challenge to water planning and management and is calling for the reassessment of water planning and management principles developed in the 20th century.
“Doing so requires approaches that evaluate plans over many possible futures instead of just one, incorporate real-time monitoring and forecast products to better manage extremes when they occur, and update policies and engineering principles with the best available geoscience-based understanding of global change,” the Assessment suggests.
For example, Tampa Bay Water employed 1,000 realizations of future demand and future supply to evaluate their preparedness for future conditions.
The report also points out that:
“Developing new water management and planning approaches may require updating the regulatory, legal, and institutional structures that currently constrain innovation in water management, community planning, and infrastructure design.”
“Furthermore, adequate maintenance and sufficient funding to monitor, maintain, and adapt water policy and infrastructure would help overcome many of these challenges.”
It also proposes that continued collaboration on transboundary watershed coordination and agreements on both surface water and groundwater with Canada and Mexico are among actions that could facilitate more sustainable binational water management practices.
Finally, the report says financial instruments and water trading can also provide avenues for managing the effects of variability on water competition, especially between urban water supply and agricultural water use.
The World Bank has published a set of specific guidelines for implementing such robustness-based approaches in water investment evaluation.
Click here to access the Water chapter in full
- NOAA National Centers for Environmental Information (NCEI) U.S. Billion-Dollar Weather and Climate Disasters (2018)