Today’s worst watershed stresses may become the new normal

Environmental Research Web via the University of Colorado at Boulder: Nearly one in 10 U.S. watersheds is “stressed,” with demand for water exceeding natural supply, according to a new analysis of surface water in the United States. What’s more, the lowest water flow seasons of recent years—times of great stress on rivers, streams, and sectors that use their waters—are likely to become typical as climates continue to warm.

“By midcentury, we expect to see less reliable surface water supplies in several regions of the United States,” said the study’s lead author, Kristen Averyt, associate director for science at the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado Boulder. “This is likely to create growing challenges for agriculture, electrical suppliers and municipalities, as there may be more demand for water and less to go around.”

Averyt and her colleagues evaluated supplies and demands on freshwater resources for each of the 2,103 watersheds in the continental United States, using a large suite of existing data sets.

They identified times of extreme water stress between 1999 and 2007, and they estimated future surface water stress—using existing climate projections—for every watershed. In the paper, published online in Environmental Research Letters on Sept. 17, the authors also diagnosed the reasons contributing to stress.

Across the United States, the team found that water supplies are already stressed (i.e., demands for water outstrip natural supplies) in 193 of the 2,103 watersheds examined....

The watershed of the Colorado River, created by  Karl Musser using USGS data, Wikimedia Commons,  Creative Commons Attribution-Share Alike 3.0 Unported license

Global warming to cut snow water storage 56 percent in Oregon watershed

Oregon State University: A new report projects that by the middle of this century there will be an average 56 percent drop in the amount of water stored in peak snowpack in the McKenzie River watershed of the Oregon Cascade Range -  and that similar impacts may be found on low-elevation maritime snow packs around the world.

The findings by scientists at Oregon State University, which are based on a projected 3.6 degree Fahrenheit temperature increase, highlight the special risks facing many low-elevation, mountainous regions where snow often falls near the freezing point. In such areas, changing from snow to rain only requires a very modest rise in temperature.

As in Oregon, which depends on Cascade Range winter snowpack for much of the water in the populous Willamette Valley, there may be significant impacts on ecosystems, agriculture, hydropower, industry, municipalities and recreation, especially in summer when water demands peak.

The latest study was one of the most precise of its type done on an entire watershed, and was just published in Hydrology and Earth System Sciences, with support from the National Science Foundation. It makes it clear that new choices are coming for western Oregon and other regions like it. “

In Oregon we have a water-rich environment, but even here we will have to manage our water resources differently in the future,” said Eric Sproles, who led this study as a doctoral student at OSU. “In the Willamette River, for instance, between 60-80 percent of summer stream flow comes from seasonal snow above 4,000 feet,” he said. “As more precipitation falls as rain, there will more chance of winter flooding as well as summer drought in the same season. More than 70 percent of Oregon’s population lives in the Willamette Valley, with the economy and ecosystems depending heavily on this river.”

...The study made clear, so far as snowpack goes, that temperature is the driving force, far more than precipitation. Even the highest levels of anticipated precipitation had almost no impact on snow-water storage, they said....

An aerial view of Crater Lake in the Cascade Range in Oregon, shot by Samion, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license. Subject to disclaimers

Paying farmers to protect forest watersheds in Vietnam & China: The long-term prognosis

Maya Thatcher in Forest News, a blog by the Center for International Forestry Research: As China and Vietnam move toward decentralised, market-based economies, they will need to improve the cost-effectiveness of ambitious programmes offering cash rewards to farmers who help protect forests, watersheds and other vulnerable ecosystems, a new study by the Center for International Forestry Research suggests.

Local communities, whose participation at the moment is generally mandatory, will also need to have a greater say in how they manage the land. “The key is to find a way to make these Payments for Ecosystem Services (PES) schemes sustainable in the long run,” said Vijay Kolinjivadi, lead author of the report looking at the governments’ driving role in the projects and what impact that has. “As currently designed, these schemes may eventually require external funding, from international donors or non-governmental organisations,” he said. “Local stakeholders need to understand the long-term benefits of ecological stewardship.”

Policymakers across the globe worry about how the food, water and shelter needs of seven billion people may be irreparably damaging our planet. The clearing of tropical forests, intensified farming production and industrial-scaled ranching have resulted in soil erosion, deterioration of water resources and a general loss of biodiversity. China and Vietnam, which have both experienced unprecedented economic growth in recent decades, are offering incentives to those who adopt land use practices that benefit society as a whole.

But these programmes, aimed at protecting forests and promoting watershed conservation, have cost tens of billions of dollars. And because they are carried out on state-controlled land, farmers have little choice but to take part and have little or no sense of ownership.

Kolinjivadi hopes district chiefs, farmer councils, and other local institutions will eventually play a larger, more significant role. “We have a unique opportunity here,” said Kolinjivadi, who sees the role of the government eventually shifting from primary driver to facilitator, promoting direct, fair negotiations between contracting parties....

A forest wetlands in Tịnh Biên and An Gaing, Vietnam, shot by Thuydaonguyen, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license

Ozone affects forest watersheds

Terra Daily via SPX: U.S. Forest Service and Oak Ridge National Laboratory (ORNL) scientists have found that rising levels of ozone, a greenhouse gas, may amplify the impacts of higher temperatures and reduce streamflow from forests to rivers, streams, and other water bodies. Such effects could potentially reduce water supplies available to support forest ecosystems and people in the southeastern United States.

Impacts of ozone, a global scale pollutant, on forests are not well understood at a large scale. This modeling study indicates that current and projected increases in ozone in the 21st century will likely enhance the negative effects of warming on watersheds, aggravating drought and altering stream flow. Using data on atmospheric water supply and demand and statistical models, researchers with the Forest Service and ORNL were able to show what effects ozone can have on stream flow in dry seasons.

Published in the November issue of the journal Global Change Biology, the study suggests that ozone has amplified the effects of warmer temperatures in reducing streamflow in forested watersheds in the southeastern United States.

"From previous studies, we know a lot about ozone's influences on crops and leaves of young trees. However, no studies have investigated the impacts of ozone on water flow in large forested watersheds," says Ge Sun, research hydrologist with the Forest Service Eastern Forest Environmental Threat Assessment Center "Our studies show that ozone has a possible connection in the reduction of streamflow in late summer when flow is generally lowest, particularly in areas with high ozone levels such as the Appalachian Mountains in the Southeast."

Researchers developed models based on 18 to 26 years of data and observed streamflow in response to climate and atmospheric chemistry during the growing season. The research team evaluated individual and interactive effects of ozone on late season streamflow for six southeastern forested watersheds ranging in size from 38 acres to more than 3,700 square miles. Estimates of ozone's influence on streamflow ranged from 7 percent in the area of lowest ozone in West Virginia to 23 percent in the areas of highest exposure in Tennessee....

Rim of the Gap trail in Georgia, shot by John Foxe, public domain

Drought demands wiser water decisions

Erica Gies in the Daily Climate: Midway through October, almost 64 percent of the contiguous United States remains in some form of drought, as the nation's most widespread drought since 1956 continues to threaten drinking water supplies, crops and livestock.

...The summer's epic Midwest drought has eased in the region's east, where Ohio, Indiana, and Illinois suffer only moderate drought. But farther west, Iowa still endures extreme drought, while Nebraska, Kansas and Oklahoma are gripped by exceptional drought.

...Droughts come and go, of course, but water scarcity is a looming problem, as growing populations increase demand and climate change makes supplies more erratic.  U.S. communities are responding in a number of ways that could be adopted across the nation:

A frequent response to water scarcity is lawsuits. In June, the U.S. Supreme Court declined to take a long-running case in which Alabama, Florida, and Georgia fought over the waters of Lake Lanier, allowing a lower court ruling to stand giving the Atlanta metro area much of the water. Of course, the problem with lawsuits is they don't increase water supply; they just reallocate it.

...Cooperative watershed management is an effective approach that considers an entire watershed for what it is: an integrated, natural system, as opposed to a mere source of a human commodity. It aims to meet the needs of all users in the water system, including cities, farmers, energy producers, plants and animals.

...Between 1950 and 2005, the U.S. population doubled while domestic, commercial and industrial water consumption tripled. However, conservation measures are closing this gap. Between 2005 and 2009, our population increased 5 percent while water withdrawals increased by just 2 percent, according to the U.S. Geological Survey....

A dry riverbed in California, shot by NOAA, Wikimedia Commons, public domain

Models simulate nitrate dynamics in a watershed

Science Daily: A new study details the first European application of two models that simulate the daily flow and dynamics of nitrogen in a watershed, which will help researchers prevent the over-enrichment of fresh, transitional, and marine waters with nitrogen, as well as understand the impacts of environmental change.

The over-enrichment of fresh, transitional, and marine waters with nitrogen (N) can lead to problems associated with eutrophication, such as a change in species composition of aquatic plants and nuisance algal blooms. In this context, dynamic models of flow and water quality are required to aid the implementation of the Water Framework Directive and to understand the impacts of environmental change.

Scientists from CNRS in Toulouse (France) and the University of Reading (U.K.) described the spatially and temporally complex flow and N dynamics of a major European watershed, the Garonne (62,700 km2) located in southwest France, using multivariate analysis before applying the linked rainfall-runoff HBV and the Integrated Catchment Model of Nitrogen (INCA-N) models to simulate daily flow and N dynamics…..

The Garonne river and a Pedestrian bridge in Agen, France. Shot by by Mike Peelwww.mikepeel.net), Wikimedia Commons, (under the Creative CommonsAttribution ShareAlike 2.5 License. Please visit Mike Peel's site to reward him for his generosity in making the image available