When in Drought…

December 12th, 2011 by Sarah Pryputniewicz

New groundwater and soil moisture drought indicator maps produced by NASA are available on the National Drought Mitigation Center’s website. They currently show unusually low groundwater storage levels in Texas. The maps use an 11-division scale, with blues showing wetter-than-normal conditions and a yellow-to-red spectrum showing drier-than-normal conditions. (Credit: NASA/National Drought Mitigation Center)

GRACE groundwater map of continental U.S.

The map (above) shows the change in stored groundwater in the contiguous United States.  Texas, which experienced record heat and wildfires this summer, is experiencing a very severe drought.  The change in stored water should not be a surprise given the weather conditions of the past year.  (By contrast, New England has a surplus of water from a very wet summer and the remnants of Hurricane Irene.)

Drought maps offer farmers, ranchers, water resource managers and even individual homeowners a tool to monitor the health of critical groundwater resources. “People rely on groundwater for irrigation, for domestic water supply, and for industrial uses, but there’s little information available on regional to national scales on groundwater storage variability and how that has responded to a drought,” Matt Rodell, a hydrologist at NASA’s Goddard Space Flight Center, said. “Over a long-term dry period there will be an effect on groundwater storage and groundwater levels. It’s going to drop quite a bit, people’s wells could dry out, and it takes time to recover.”

The question is: how long will it take to replenish the water that has been removed from the aquifers in Texas? Matt Rodell estimates, “Texas groundwater will take months or longer to recharge.  Even if we have a major rainfall event, most of the water runs off. It takes a longer period of sustained greater-than-average precipitation to recharge aquifers significantly.”

Water is a resource that everyone needs.  In dry environments, such as southwestern Texas, water is especially precious.  Water is used for the usual personal purposes, for agricultural purposes, and in natural gas wells.  For example, accessing the natural gas in the Eagle Ford shale deposit, which runs from the Mexican border towards Houston and Austin, requires millions of gallons of water to fracture the shale and release the stored hydrocarbons.

The prolonged Texas drought is putting more pressure on local officials about how best to use the limited amount of groundwater.  What is the best way to use the water supply?  Who gets first dibs?  How much should different businesses pay for water?  These are highly-important questions that can only be answered with a full understanding of how groundwater works.

You can explore how groundwater flows and propose solutions to water-supply issues in the High-Adventure Science water investigation.

http://www.nasa.gov/topics/earth/features/tx-drought.html

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