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October 6, 2015

Drought has left the West parched and thirsty. Families, businesses, and farmers all need water, as do fish, wildlife, and their habitats.

Image: USGS Documents 2015 Western U.S. Drought
A hydrologic technician from the USGS Idaho Water Science Center measures streamflow, or the lack thereof, in Lightning Creek at Clark Fork, ID. The USGS is collecting data at hundreds of sites on rivers and streams in six western states to document te 2015 drought. USGS scientists will analyze the data to identify which rivers and streams may be most vulnerable to future droughts.

Drought has left the West parched and thirsty. Families, businesses, and farmers all need water, as do fish, wildlife, and their habitats.  And shortages have dire impacts. Choosing where the water goes – and where it does not – involves complex tradeoffs and hard decisions. Good science is essential for making the best of this bad situation and is the foundation for wise choices.

In June, Deputy Secretary of the Interior Mike Connor testified before Congress on the state of the Western drought. At that hearing, Connor offered thoughts on how USGS science is informing sound decisionmaking.

“The USGS is an integral part of the Department’s drought response and is providing actionable, science-based information and tools as a participant in the National Drought Resilience Partnership,” said Connor. “During drought, forecasting stream low-flow conditions can be critical for water apportionment and ecosystem protection.”

Such low-flow conditions are monitored by more than 8,000 streamgages nationwide operated by the USGS and its many partners. During high-flow conditions, this network warns communities of flooding. But in the opposite situation, when there is not enough water to go around, those same streamgages provide real-time data to help local and state authorities make critical decisions on the fly.

Image: USGS Documents 2015 Western U.S. Drought
A hydrologic technician from the USGS Idaho Water Science Center measures streamflow in the St. Joe River at Red Ives Ranger Station in northern Idaho as an effort to identify drought-stricken areas.

“Data collection and drought science analysis performed by federal agencies, including the Natural Resources Conservation Service, the U.S. Geological Survey, and the National Oceanic and Atmospheric Administration, are all essential to understanding and managing drought,” testified James D. Ogsbury, Executive Director, Western Governors’ Association, before Congress at the June Western drought hearing.

It is also important to monitor discharge from power generators during times of drought because the impacts from these discharges may vary under drought conditions. Lastly, groundwater levels also play an important role in understanding how much water is available for household use or for growing crops.

But the effects of drought are felt beyond water. As Mark Sogge, USGS Pacific Regional Director, points out, “Groundwater pumpage during drought conditions is associated with land subsidence, or sinking, in the Central Valley of California. So we are monitoring this phenomenon and updating existing groundwater models to predict the effects of different withdrawal scenarios. The drought is literally moving the ground under Californians’ feet.”

Groundwater and surface water are very closely connected in the Central Valley and across in California. Groundwater pumpage has increased and groundwater levels have decreased during the drought. This is because while less surface water is available for withdrawal, more permanent crops are being produced, increasing the demand for water just when its availability is constrained. The result has been greater rates of land subsidence. In turn, this subsidence threatens to damage infrastructure, imperils irrigation, and makes it more difficult to manage flood risks.

“We have developed a computer simulation of groundwater-surface water interactions in central California, the Central Valley Hydrologic Model, that is an important tool to understand what is going on to help managers to assess the impact of future changes in pumpage, land use, surface water availability, and climatic conditions, on groundwater levels and  land subsidence,” says Sogge.

Sogge also said that to assist the California Department of Water Resources with their runoff calculations, researchers are providing soil moisture data. This information helps wildlife refuges manage their water resources. Not only is this good for the birds, it also supports hunting in the state. Waterfowl comprise about one-third of California’s nearly $1 billion hunting business.

Satellites Used with Ground Activities

Satellite-based technology offers newfound opportunities to closely monitor the West’s water resources. One example of this is the Vegetation Drought Response Index, or VegDRI. “It integrates space based observations with other information about climate, land cover and land use, ecological setting and soil characteristics,” explains Bill Cunningham, USGS Drought Coordinator. “We can use this and other space-based tools to compare past snow coverage, reservoir water levels and fallowed field coverage. Taken altogether, it helps paint a complete picture of the water situation. And we can do it all down to a 1-kilometer resolution.”

In the interest of providing the public in California with a comprehensive overview of the drought, the USGS recently launched an interactive California Drought Visualization website. The application compiles data from a variety of open sources and presents this valuable water data in a more user friendly, easily accessible, and understandable format. The USGS hopes to expand this tool to cover the West.

New USGS Study

The USGS is collecting streamflow and water temperature information from more than 500 rivers and streams to document the severity of this year’s drought across six western states: California, Idaho, Nevada, Oregon, Utah, and Washington. The goal of the study is to assess how warmer winter temperatures, reduced mountain snowpack, and a shift in precipitation from snow to rain may affect water availability. Partners include the U.S. Bureau of Reclamation, Northwest Indian Fisheries Commission, Nevada Division of Water Resources, Oregon Department of Water Resources, and Washington Department of Ecology.

Image: USGS Documents 2015 Western U.S. Drought
A hydrologic technician from the USGS Idaho Water Science Center measures streamflow in Homer Creek near Herman, ID. The USGS is collecting data at hundreds of sites on rivers and streams in six Western states to document the 2015 drought.

The West is Not Alone

California and the West are not alone in their struggles with drought. Similar conditions are impacting Puerto Rico and the Caribbean. Reservoirs supply most of the drinking water to the San Juan metropolitan area, and with less rain, the streams that supply these reservoirs are not replenishing them. Meanwhile, water levels in the south coast aquifers used for public and agricultural water supply have also dropped, letting salt water intrude and reduce the quality of the water. In response to these challenges, several agencies have begun rationing water along the northeast and south parts of the island. On some areas of the south coast, public water supplies are also subject to a rationing period of 8 hours each day. The USGS Caribbean-Florida Water Science Center, as with their colleagues in the West, is providing data that helps guide the drought response. This includes information about the condition of reservoirs and aquifers and rates of streamflow and rainfall.

Across the country, the USGS is working with local partners, sharing our knowledge and helping people make tough decisions.  Decisions about water quantity and quality, wildlife and endangered species management, habitat restoration, water storage options, and more.  These decisions are not just for today, but for future generations.

As Sogge says, “All of this science is designed to assist decision making during the drought crisis. It is a public service.”

Image: Vegetation Drought
The Vegetation Drought Response Index (VegDRI) incorporates satellite observations of vegetation to monitor at a finer spatial detail than other commonly used drought indicators.

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