December 1, 2011 – Drought and Flooding Map of the United States: The map, above, uses an 11-division scale, with blues showing wetter-than-normal conditions and a yellow-to-red spectrum showing drier-than-normal conditions. The extreme drought conditions in the south western United States, especially Texas, are clearly shown.
The record-breaking drought in Texas that has fueled wildfires, decimated crops and forced cattle sales has also reduced groundwater levels in much of the state to the lowest levels in more than 60 years.
The latest groundwater map, released on Nov. 30th, shows large patches of maroon over eastern Texas, indicating severely depressed groundwater and drought levels.
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.
To make the maps, scientists use a sophisticated computer model that combines measurements of water storage from satellite images, with a long-term meteorological dataset to generate a continuous record of soil moisture and groundwater that stretches back to 1948.
The color-coded maps show how much water is stored now as a probability of occurrence in the 63-year record. The maroon shading over eastern Texas, for example, shows that the level of dryness occurred less than two percent of the time between 1948 and the present.
These maps would be impossible to generate using only ground-based observations. There are groundwater wells all around the United States, and the U.S. Geological Survey does keep records from some of those wells, but it’s not spatially continuous and there are some big gaps.
The maps also offer farmers, ranchers, water resource managers and even individual homeowners a new 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. 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 a very long time to recover.
The Master of Disaster