How Is Earth's Water System Linked With Land Use, Climate Change and Ecosystems?

Answers may be in new NSF Water Sustainability and Climate research

How will climate change affect the connections between water sustainability and hydrologic processes?

To better understand how planet Earth's water cycle works, the National Science Foundation (NSF) and the United States Department of Agriculture's National Institute of Food and Agriculture (NIFA) awarded grants totaling almost $27 million through the Water Sustainability and Climate program.

WSC is part of NSF's Science, Engineering and Education for Sustainability investment.

NSF's Directorates for Geosciences; Engineering; and Social, Behavioral & Economic Sciences support the WSC awards.

"Among the most urgent challenges facing the world today is ensuring the adequate supply and quality of water, especially in light of burgeoning human needs and climate variability and change," says Marge Cavanaugh, NSF acting assistant director for Geosciences.

"Whereas the water imperative is global, WSC recognizes that water availability and quality issues must be examined at local scales where most water decisions are made," says Cavanaugh. "That's why WSC projects are placed-based, and each examines how global and regional climate changes are playing out in terms of water balance at the local scale."

WSC Category 1 awards are workshop planning grants; WSC Category 2 grants cover observatories and modeling; WSC Category 3 awards are for modeling.

"Water is a critical component to the success of American agriculture, yet there is a lack of understanding of how climate variability, land use and other environmental factors affect the water supply," says Sonny Ramaswamy, director of the National Institute of Food and Agriculture. "These projects will allow us to better understand water sustainability and allow our producers and rural communities to prepare for future changes."

The goal of the new WSC projects--including studies of Rocky Mountain pine beetles, Los Angeles' water supply and the Sierra Nevada snowpack--is to understand and predict the interactions of Earth's water system with climate change, land use, the built environment and ecosystem function and services.

For example, more than four million acres of forests in Colorado and Wyoming are dying. The main culprit is the mountain pine beetle, a species of bark beetle native to the woodlands of western North America. Recent hot, dry summers and mild winters have led to an infestation of the beetles.  It may be the largest forest insect blight ever seen in North America.

The result is stunning: dead trees lined up like so many fallen forest soldiers. But the invisible changes in watersheds in the Rocky Mountains, including the headwaters of the Platte and Colorado Rivers, may be a longer-lasting legacy.

Farther west, Los Angeles, like many cities in semi-arid regions, relies on centralized redistribution for its water supply. Water is transported hundreds of miles from mountain to city to support agricultural and urban needs in southern California. But water allocations from the mountain sources that feed L.A.'s water supply are declining.  Drought, over-extraction and competing water needs have taken their toll.

In many arid and semi-arid regions of the world, including much of the western United States, water resources management plans are based on the assumption that the snowpack that accumulates in winter holds the majority of the water. This snowpack gradually melts, replenishing reservoirs as their supplies are meted out to satisfy human water and power demands.

Nowhere is that more true than in California's Sierra Nevada. This remote and sparsely populated mountain range supplies water and power for millions of people downstream. Will the Sierras be able to sustain that supply in the decades and centuries to come?

Only 2.5 percent of Earth's water is freshwater, and 98.8 percent of that is locked away in ice or hidden in groundwater. Less than 0.3 percent of all freshwater is in lakes, rivers and the atmosphere.

How can we better manage and predict water availability for future generations, given alterations to the water cycle caused by climate change and by more direct human activities?

The answers require a holistic understanding of complex water cycle and water resource processes, the feedbacks in a water system, and the vulnerability and resilience of water systems to climate and other human-caused change.

A water system comprises a drainage basin and its physical, chemical and biological constituents, including water networks, ecosystems, the built environment, the oceanic and atmospheric systems that govern evaporation and precipitation in the basin and the source water bodies and terminal lakes or seas into which the water flows.

There have been few attempts to study the entire water system with an integrative, systems science approach. WSC researchers will do just that.

This analysis of the planet's water system--of the feedbacks and links among climate change, ecosystems, built environments and human activities--will lead to the improved understanding, prediction and management of water resources, scientists believe.

"Earth has approximately 1,386 million cubic kilometers of water, most of which is the saltwater of oceans and seas," says Cavanaugh.

"What decisions will we make about the rest, the freshwater that's 'technically' available to us? Those decisions are for societies to make, and water sustainability researchers are working through WSC to fully inform those complex decisions."