Two new climate change studies offer a fascinating, if deeply troubling, view of California's water future. The noted climate scientist Jim Hansen and his NASA colleagues have analyzed decades of global temperatures and found a steep increase in the frequency of extremely hot summers. The statistical likelihood of extreme heat, drought and heavy downpours in certain regions is so huge that from a mathematical perspective these cannot be random or normal events.

Here at home, the California Climate Change Center tells us that the state can expect hotter springs and summers, and longer and more frequent heat waves. California will see less rain and snow by at least 10 percent, and more wildfires.

As in the rest of the American West, climate change is already making itself felt through our water supplies. How much rain or snow California receives, and when, as well as evaporation and runoff rates, are already changing. In the face of these changes, water security must be an increasingly critical focus – both for our communities and for statewide policymakers.

While much recent media attention has been devoted to the future of water exported by the large state and federal water projects out of the Sacramento-San Joaquin Delta, it's time to explore what climate change means for the 85 percent of California's water supply that does not depend on those Delta exports.

California's farms, commerce, industry and 38 million residents rely in large part on water that flows from headwaters forests – many of them on public land from the Feather River to the Owens Valley to Hetch Hetchy.

Whether remote or right in our backyards, the headwaters of California's rivers and streams are essential to our water security. These forests capture and hold snow in the winter. Their soils soak up water from snowmelt like enormous sponges, providing a natural cleansing filter, replenishing aquifers, and moderating floods and high flows as the water moves downhill toward its many users. Headwaters forests are the savings accounts for water security in California and the West.

Today, these watershed regions are at risk. Emerging threats include severe drought, higher levels of insect infestations, invasive species and excessive erosion. Wildfires like those now blazing around the state bring massive post-fire washouts of sediment – clogging rivers and streams. Many headwaters are also weakened by past forest management legacies.

These challenges imperil our headwaters' ability to continue to provide clean, dependable supplies of water to the millions of people, farms and businesses that rely on them.

With growing awareness of these problems, new allies for healthy headwaters forests are emerging. There are plenty of success stories from around the West that California would do well to emulate.

In Denver, for example, water managers partner with the U.S. Forest Service to protect and restore the forests that provide the city with drinking water. Their Forest to Faucet Partnership will protect nearly 40,000 acres of headwaters forests at a cost of about $33 million. The tab for water customers? A tiny 14 cents per month.

As Ron Lehr, former president of the Denver Water Board, says: "We realized water doesn't come out of the stream – it comes out of the forest."

Headwaters protection efforts linking cities to their water sources are also under way in Oregon, New Mexico, Arizona, Utah and elsewhere.

In California, we have an opportunity to make the same connections. Water and climate can become the drivers for a new era of public lands management, securing funding and incentives to protect the best headwaters forests and restore the rest. Doing so will go a long way toward ensuring the long-term water security of our communities in the face of a changing climate.

Former California Natural Resources Secretary Lester Snow and Gap Inc. Director Bob Fisher recently called for a different way of thinking about water issues, urging investments in multi-benefit local supply projects, water reuse and other efficiency measures.

This direction makes sense for California, particularly in combination with a renewed focus on protection of water supplies at their source. Investing in the natural infrastructure provided by headwaters ecosystems connects upstream and downstream communities in a shared mission for water supply and ecological resilience.

The climate news is sobering. But we have the opportunity now to advance innovative policies that will help modernize our approach to water. Only then will we be able to ensure that we have enough water to meet all of the needs of a 21st century economy and environment.

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