National Climate Assessment: Will U.S. Water Problems Worsen?

Glen Canyon dam, on the Colorado River, a major supplier of water for the U.S. West (Kevin Krajick/Earth Institute)

Upmanu Lall is director of the Columbia Water Center, and the lead author of the chapter on water resources in the latest U.S. National Climate Assessment. The report, issued last week, paints a troubling picture of the nation’s climate future, including projected droughts and extreme precipitation events that could worsen already existing problems with U.S. water supplies and infrastructure. We spoke with Lall about the challenges, and ideas for how the nation can respond.

Your chapter in the National Climate Assessment says that infrastructure for storing and delivering water is already outdated, and new investments are not keeping up. Could climate change compound this problem?
Current water infrastructure is beyond its design life. Plus, system operations and allocation rules do not account for a changing climate, nor even for the range of droughts and floods experienced over the last 1,000 years. As a result, we face compound risks. A major dam failure due to overtopping could lead to a cascading failure of downstream dams and levees, thermoelectric power plants, water and wastewater treatment systems, and transportation networks, including airports, which are often sited near rivers. Regionally, one could experience severe drought and flood in the same year or in succession, as we have seen in Texas and California recently. We have no planning to address the joint risk of such events. We could face a perfect storm in some part of the United States. Just last February, we saw the near failure of the tallest U.S. dam, in Oroville, Calif.

Federal investments in water infrastructure today are lower in real dollars than they were in 1983. Local and state financing has gone up, but it has not covered the gap. This has led to significant fragmentation of planning and investment, so that only very local projects are typically looked at. Since the local ability to pay is limited, aging systems continue to be operated with deferred maintenance.

How important is surface water for the United States? How might higher temperatures and more frequent extreme bouts of precipitation affect those supplies?
Surface water is the primary renewable supply. Most of it goes toward irrigation, ecosystems preservation, thermoelectric generation and urban use, in roughly that order. Higher variability in this supply portends a risk to all these sectors, and will most likely be accompanied by poorer water quality. That is because pollutants will be mobilized by more extreme precipitation, and because warmer temperatures will facilitate their accumulation and transformation into chemical forms that people and wildlife can more readily absorb.

The White House claims the National Climate Assessment “is based largely on  the worst-case scenario” for global warming. Is this true of the outlook for water?
We tried to frame the water chapter as a water chapter rather than a climate change chapter. We did this largely to draw attention to the fact that the water situation in the United States is quite dire even just considering past climates, never mind future ones. So, for water, it is not the worst case; it is a serious current concern that could be aggravated by any future scenarios. In reporting on the National Climate Assessment, the media are focusing on potential climate change, where uncertainty clouds the issue. Our point is that water is a current and urgent problem.

What should we do to meet future challenges?
First, we should use climate and paleoclimate scenarios to assess local, regional and national infrastructure exposure to severe, sustained drought and floods. Second, we need precision agriculture to improve crop yields per unit land and per unit water. This has to be complemented by mechanisms for monetizing the water saved or not polluted by transferring it to other systems, including natural areas, that could beneficially use this water. Third, we need decentralized water and wastewater networks in urban areas that focus on an integrated approach to locally  capturing rain and storm water, and treating and distributing it for reuse. Fourth, let’s increase the use of financial instruments that can leverage climate forecasts across different users to mitigate climate risk. To help with that, we should develop publicly accessible databases that can support better investments and decision making at corporate, urban and regional levels. We could integrate access to information on water availability and use in the same way that the Energy Information Administration provides information on the state of the energy sector.

— Kevin Krajick, Earth Institute

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