Although much of the discussion about climate change impacts has focused on increases in temperature and the rise in sea level, changes that impact our nation’s water resources could have the greatest impact on society. A quick glance at recent newspaper headlines—heavy spring rains leading to massive flooding of the Mississippi River, historic drought covering large parts of Texas, and extensive wildfires spreading across Arizona—provides more than enough evidence of how vulnerable we are to water-related extreme events.
While these events have led some to ask whether they are caused by climate change, this question misses the mark. Individual weather events are not “caused” by any single phenomenon—and climate change’s contribution to individual events will not be resolved cleanly in the years to come. What virtually all climate scientists agree on, however, is that the climate is already changing, all weather events now form under different conditions than they used to, and this change is increasing the probability of extreme weather events happening. It makes sense to learn what we can from actual events and avoid getting caught up in an irresolvable debate about why a particular event happened. We would be better served by learning more about what is at risk from extreme events and what we can do to better manage and minimize those risks.
A recent interagency draft report, National Action Plan: Priorities for Managing Freshwater Resources in a Changing Climate , highlights both the extensive economic and social risks that we face as a nation from the impact of climate change on water resources and the critical steps we need to take to begin facing up to these challenges.
The report documents the changes in our climate system that are already evident and are likely to increase over time. Warmer air and sea surface temperatures and rising sea levels are only part of the picture. Total precipitation has increased by about 5 percent over the past 50 years, and the amount of precipitation that occurs during the heaviest downpours has increased by 20 percent . However, regional variations appear likely with increased precipitation in the northern part of the country while areas in the south, particularly in the southwest, are likely to get drier. The strengthened hydrologic cycle puts wet areas at risk of getting wetter while dry areas are at increased risk of drought. Areas dependent on water from melting snow packs may also face substantial changes as more precipitation falls as rain rather than snow and as earlier snowmelt changes the timing and quantity of water availability.
The implications of these changes cut a wide swath across our economy and environment. Water availability is critical in sectors as diverse as agriculture, electricity generation (hydroelectric, but also fossil fuel generation and nuclear power), heavy transport, mining and mineral exploration, and storm water management. Beyond economic factors, water is also critical to ecosystem wellbeing, wildfire management, and public health.
In order to more effectively manage these risks, and to enhance the resiliency of our water resource systems, the report sets out six general recommendations and 24 specific actions that should be undertaken by federal agencies and their partners. It calls for a more formal planning process, highlights the need for improved information, enhanced capacity building, better integration across related issues, and better tools for assessing vulnerabilities, and recommends expanded water use efficiency.
These actions are by no means a cure-all for the challenges we face in managing the increasing demands on our water resources in a changing climate. Nor are they a substitute for slowing the rate and magnitude of climate change through reducing emissions of greenhouse gases. The most effective risk management strategy is to avoid the risk all together. But with climate change already underway, we are too late to avoid some changes, and adaptation will be critical to reducing economic and environmental costs. We need only to look at the costs and suffering from recent extreme weather events to understand the risks we face.
Comments on the draft plan are being accepted until July 15, and can be submitted to: http://www.whitehouse.gov/administration/eop/ceq/initiatives/adaptation/freshwater-plan 
Steve Seidel is Vice President for Policy Analysis