Dry conditions increase pressure on Mississippi Delta aquifer

Published 9:12 pm Tuesday, April 3, 2007

The Mississippi River Valley Alluvial Aquifer contains trillions upon trillions of gallons of water and serves as a vital safety net for farmers and catfish producers in the Mississippi Delta.

After 30 years of increasing agricultural pressure and a recent yearslong dry spell, though, researchers are beginning to see signs that the aquifer might not be bottomless after all.

“The Delta area of the state used way too much groundwater to irrigate and dewatered that aquifer considerably,” state climatologist Charles Wax said. “And now here we are in 2007 coming into a very dry spring.”

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Increased use and long-term drought conditions dating back to 2000 have led to falling water levels in the aquifer. While it would take decades to tap the reserve because it naturally recharges itself in time, researchers are beginning to see a net loss.

Wax and other researchers have secured grant money to get a better understanding of the loss-recharge cycle of the aquifer and to come up with ideas to slow down the steady pull from farms and ponds.

Dean Pennington, executive director of the Yazoo Mississippi Delta Joint Water Management Council, said on average researchers are seeing a net loss of 200,000 acre-feet of water a year or about 65 billion gallons of water.

Over the last year the aquifer dropped 2 feet in some places and it’s unclear how this spring’s dry conditions will affect its natural recharge, Pennington said. In a really bad year, the aquifer might lose 228 billion gallons. It might also gain that much in a year where rain and snow are plentiful.

“It’s like I like to say about Mississippi — it’s feast or famine,” Wax said. “We’ve either got too much or too little. There are a lot of flood years in there as well as drought years.”

Rainfall this March in the Delta was the second lowest since 1950 and the Climate Prediction Center calls for the possibility of moderate to extreme drought through June.

“This is a really bad time to be having a drought,” Wax said.

The introduction of irrigation helped increase the number of crops grown in the Delta and the overall profitability of farming when it started in the mid-1970s. But water usage has continued to increase.

Mississippi rice farmers alone would need about 195 billion gallons of water a year under total drought conditions, Pennington said. And now that corn is taking hold in the Delta for use in ethanol, groundwater usage likely will spike.

Pennington will work with Wax this summer to compare aquifer water-level and climate data over the last three decades. They will then work on recommendations to help reduce the draw.

The sand and gravel aquifer extends out on both sides of the Mississippi River and touches parts of Mississippi, Louisiana, Tennessee, Missouri and Arkansas, where the bulk of it is located.

It sits 20 to 40 feet below the surface and extends 100 to 150 feet down.

The water is iron-heavy and tastes bad, so it isn’t suitable for drinking water, Pennington said. It’s perfect for rice, soybeans, corn and catfish.

The aquifer is naturally recharged from the Mississippi River and runoff from surrounding hills in the watershed. Wax said it’s unlikely the entire aquifer could be drained, but it could be lowered enough that certain areas would no longer be able to pull water from wells.

Farmers are looking at ways to lower their use of water. Ronnie Aguzzi, chairman of the water management district’s board of directors and a lifelong rice and soybean farmer from Cleveland, Miss., said he has leveled his fields so water doesn’t run off as easily.

There has been increased use of ditches to hold surface water for later use.

“That’s how we pick up extra surface water, letting rain water go in these ditches,” Aguzzi said. “But it looks like we’re getting less of that, too.”

Which means more of a reliance on the aquifer. Pennington’s group is hoping to help farmers cut use of the aquifer by 20 percent in the coming years.

“And that’s a very attainable goal,” he said. “If we had to cut our water use by 70 percent, that’s more serious. We’d be sweating this.”