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Water On Earth: Floods, Droughts And Prediction

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Today is World Water Day, a time to think about how water interacts with the environment. Too much water leads to floods and landslides; too little water results in droughts. Better predictions of when either situation is going to occur will reduce risk through better disaster preparation, in turn making everyone safer and happier.

Too Much Water: Floods

On May 1st and 2nd, 2010, the Mississippi drainage basin received record-breaking rainfall, resulting in flooding in Tennessee, Kentucky, Arkansas and Missouri.


The Mississippi River in Tennessee flooded its banks after record-breaking rainfall on May 1st and 2nd, 2010.

After the floods, water (bright blue in the images) flooded not just the banks of the main branch of the Mississippi River, but overflowed along all the smaller tributaries draining into the river. By the time the river receded, several days after rainfall, 31% of the Tennessee (including Nashville) was declared a disaster area, and 31 people had died from the flood in all four states.


Constant monitoring by satellites provided ways to measure and monitor how the devastating storm impacted the landscape, guiding disaster response activities.

Too Little Water: Droughts

Droughts aren't always severe, news-worthy stories like the dry winter in California this year. Sometimes, the story is subtler.

The Cheyenne Bottoms Wildlife Wetlands in Kansas is a wetland resting area for millions migrating birds each fall. It is feeding spot, a regular resting area, and a nesting zone. In 2010, the wetlands had enough water, showing up in satellite images as vivid cobalt blue water with a thick fringe of wet green wetlands so dark it's almost black.


The Cheyenne Bottoms Wildlife Wetlands in Kansas shrank and dried up between 2010 and 2012 after extended droughts.

The following year, the drought besetting large areas of the western US had a visible impact: the clear blue open-water regions were interrupted by patches of newly-exposed land as the water level dropped and the fringe of wetlands had shrunk. Outside the wetlands, the drought was also impacting agricultural lands, with a scattering of yellowing fields and the absence of pale blue water stockpiles. A white fringe along the southern edge of the wetlands marked mineral deposits left behind by evaporating water.


By 2012, the wetlands have no trace of blue water or dark green swamps. Instead, dead, dry expanses of brown fill the region. Outside the park, the drought has also impacted agricultural lands with a larger proportion of dry fields.

While they can't control the weather, wildlife officials can use satellite images like these as reliable, objective data sources to guide their policies and actions on how to make this area a sustainable habitat for the annual bird migrations.


A Data-Rich Future

Disasters happen, and will keep happening. At this point, we can't redirect storms, or break a drought with a call for rain. But we are getting better at predicting weather and even long-term climate patterns through the acquisition of better and better data.


The most recent improvement in getting high-quality data is the Global Precipitation Measurement (GPM) satellite. GPM was successfully launched this February, and is currently in it's testing phase. Soon it will provide global images of all precipitation (rain and snow) every couple of hours. This rich data feed will hopefully result in better models for predicting weather patterns, particularly areas that will be deluged or dried out in the near future.

All images credit Landsat. To read more about the Tennessee flood, see NASA Climate's Images of Change, or the USGS Landsat's Tennessee Flood. To read more about the Kansas drought, see NASA Climate's Images of Change, or the USGS Landsat's Effects of Drought. For more on how NASA is monitoring water on Earth, check out When Water Rises.