Earthquakes today

Current and latest world earthquakes breaking news, activity and articles today


Geological news

New Maps Provide Crucial Information for Water Managers



New Maps Provide Crucial Information for Water Managers

Long-Term U.S. Evapotranspiration Rates Mapped for the First Time

RESTON, Va. — For the first time, U.S. Geological Survey scientists have mapped long-term average evapotranspiration rates across the continental United States – a crucial tool for water managers and planners because of the huge role evapotranspiration plays in water availability.

Why are evapotranspiration rates so important to know? It’s because the amount of water available for people and ecosystems is the amount of annual precipitation – that is, snow or rain – minus the amount of annual evapotranspiration.  Evapotranspiration itself is the amount of water lost to the atmosphere from the ground surface.  Much of this loss is the result of the “transpiration” of water by plants, which is the plant equivalent of breathing. Just as people release water vapor when they breathe, plants do too.

“Since evapotranspiration consumes more than half of the precipitation that happens every year, knowing the evapotranspiration rates in different regions of the country is a solid leap forward in enabling water managers and policy makers to know how much water is available for use in their specific region,” said Bill Werkheiser, associate director for water at the USGS. “Just as importantly,” he added, “this knowledge will help them better plan for the water availability challenges that will occur as our climate changes since transpiration rates vary widely depending on factors such as temperature, humidity, precipitation, soil type, and wind.”

In spite of its importance, evapotranspiration has been difficult to measure accurately on a regional or continental scale.  To produce these maps, USGS scientists Ward Sanford and David Selnick examined Landsat satellite imagery for climate and land-cover data from 1971 to 2000 and streamflow data for more than 800 watersheds for the same time period.  This information allowed them to generate a mathematical equation that can be used to more precisely estimate long-term evapotranspiration at any location in the continental United States.  

“The map of the long-term average annual evapotranspiration rates for different areas should be immensely helpful for ensuring the long-term, sustainable use of water in different regions, especially since forecasted climate change will, in many places, change the amount of precipitation and evapotranspiration that occurs,” Sanford said. “This tool, for example, allows water managers to quantify surface water runoff to reservoirs or water recharge to aquifers. It will also enable natural resource planners to understand the water needed for healthy-functioning ecosystems.”

One interesting finding illustrated in the maps is that in certain regions of the United States, such as the High Plains and the Central Valley of California, evapotranspiration exceeds the amount of precipitation because water is imported from other regions.  The map also shows that the Pacific Northwest has many areas with low evapotranspiration to precipitation rates because of the area’s very high rainfall and low-to-moderate temperatures.  In contrast, counties in the arid Southwest have evapotranspiration rates that usually exceed 80 percent of precipitation.  

The research was published this week in the Journal of the American Water Resources Association.  To read the article and see the maps, click here.

 

USGS Newsroom



More information

Parameter Value Description
Magnitude mb The magnitude for the event.
Longitude ° East Decimal degrees longitude. Negative values for western longitudes.
Latitude ° North Decimal degrees latitude. Negative values for southern latitudes.
Depth km Depth of the event in kilometers.
Place Textual description of named geographic region near to the event. This may be a city name, or a Flinn-Engdahl Region name.
Time 1970-01-01 00:00:00 Time when the event occurred. UTC/GMT
Updated 1970-01-01 00:00:00 Time when the event was most recently updated. UTC/GMT
Timezone offset Timezone offset from UTC in minutes at the event epicenter.
Felt The total number of felt reports
CDI The maximum reported intensity for the event.
MMI The maximum estimated instrumental intensity for the event.
Alert Level The alert level from the PAGER earthquake impact scale. Green, Yellow, Orange or Red.
Review Status Indicates whether the event has been reviewed by a human.
Tsunami This flag is set to "1" for large events in oceanic regions and "0" otherwise. The existence or value of this flag does not indicate if a tsunami actually did or will exist.
SIG A number describing how significant the event is. Larger numbers indicate a more significant event.
Network The ID of a data contributor. Identifies the network considered to be the preferred source of information for this event.
Sources A comma-separated list of network contributors.
Number of Stations Used The total number of Number of seismic stations which reported P- and S-arrival times for this earthquake.
Horizontal Distance Horizontal distance from the epicenter to the nearest station (in degrees).
Root Mean Square sec The root-mean-square (RMS) travel time residual, in sec, using all weights.
Azimuthal Gap The largest azimuthal gap between azimuthally adjacent stations (in degrees).
Magnitude Type The method or algorithm used to calculate the preferred magnitude for the event.
Event Type Type of seismic event.
Event ID Id of event.
Event Code An identifying code assigned by, and unique from, the corresponding source for the event.
Event IDS A comma-separated list of event ids that are associated to an event.

Leave a Reply