Water, Climate, and You: the 2014 National Climate Assessment

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Today we expect to have water flowing at our kitchen sink and our food supplied by farms with sufficient water. The 2014 National Climate Assessment, released today, points to opportunities and challenges with the U.S. water resource infrastructure.

This post is part of a series on the National Climate Assessment. Learn more about climate change where you live by attending a UCS webinar.

This post is part of a series on the National Climate Assessment. Learn more about climate change where you live by attending a UCS webinar.

This infrastructure must keep pace with a growing population and increased water demand in a rapidly warming world.  Take a look at the change in water withdrawals figure that projects a marked increase in most regions of the continental U.S. (except some of the Midwest), when climate change is included on top of population and socioeconomic conditions.

The difference between the projections with climate change and without is primarily due to higher temperatures and potential for evapotranspiration (water is released to the atmosphere from surface water, soil water, and plants).

National Climate Assessment Chapter 3 Water Resources Figure 3.11

2014 National Climate Assessment Chapter 3, Figure 11: The effects of climate change, primarily associated with increasing temperatures and potential evapotranspiration, are projected to significantly increase water demand across most of the United States. Maps show percent change from 2005 to 2060 in projected demand for water assuming (a) change in population and socioeconomic conditions based on the underlying A1B emissions scenario, but with no change in climate, and (b) combined changes in population, socioeconomic conditions, and climate according to the A1B emissions scenario (gradual reductions from current emission trends beginning around mid-century). (Figure source: Brown et al. 2013 available at adapted in Climate Change Impacts in the United States (2014) Chapter 3 available at

Weaknesses in existing water law regimes – “stationarity” principle may no longer apply

What is striking about the water resources chapter of the report is the identification of a possible barrier to improving U.S. water systems that are increasingly stressed by future impacts of climate change. Current U.S. water law regimes assume that natural systems fluctuate within an “unchanging envelope of variability” or “stationarity.”  With climate change shifting over the lifetime of major water infrastructure projects, this assumption of “stationarity” breaks down.

Streamflow Projections for River Basins in the Western U.S. Source: National Climate Assessment 2014 Figure 3.4

2014 National Climate Assessment Chapter 3, Figure 4: Annual and seasonal streamflow projections based on the B1 (with substantial emissions reductions), A1B (with gradual reductions from current emission trends beginning around mid-century), and A2 (with continuation of current rising emissions trends) CMIP3 scenarios for eight river basins in the western United States. The panels show percentage changes in average runoff, with projected increases above the zero line and decreases below. Projections are for annual, cool, and warm seasons, for three future decades (2020s, 2050s, and 2070s) relative to the 1990s. (Source: U.S. Department of the Interior – Bureau of Reclamation 2011; Data provided by L. Brekke, S. Gangopadhyay, and T. Pruitt available at adapted in Climate Change Impacts in the United States (2014) Chapter 3 available at

Water, Climate, and You

Who is stepping up to ensure you have clean water at your tap and enough “virtual water” via the food on your plate? Steps are being taken by some water utilities to ensure drinking water supply projects include climate risks in the design.

A key message from the 2014 National Climate Assessment is that seasonal droughts are expected to intensify in most U.S. regions and longer-term droughts are expected to intensify in large areas of the Southwest, southern Great Plains, and Southeast. This is a huge challenge for improving our water systems to support crops and livestock yields in these regions. The report suggests that as the risk of drought increases, groundwater may be tapped more during periods of drought even though there are limits to this resource given current management and institutional frameworks.

Another key message is “flooding may intensify in many U.S. regions, even in areas where total precipitation is projected to decline.” The good news is that municipalities are increasing porous pavement, rainwater harvesting, roadside plantings to limit sewer backups, and investing in systems that avoid sewer overflows into surface water.

My favorite aspect of the Third National Climate Assessment is that more than ever before, there is the ability to look at what is behind the figures, graphs, and key findings for those who are taking steps to prepare and protect communities. Take a look at the region where you live and see what the climate assessment has to say and tell us what you think.

Posted in: Global Warming Tags: , , ,

About the author: Brenda Ekwurzel is a senior climate scientist and assistant director of climate research and analysis at UCS. She has expertise on many aspects of climate variability including Arctic Ocean and sea ice, wildfires, groundwater, and coastal erosion. She holds a Ph.D. in isotope geochemistry from Columbia University (Lamont-Doherty Earth Observatory). See Brenda's full bio.

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