If asked to name a water crisis hot spot, few people would point to the Mississippi Delta. That's low country filled with creeks and bogs and cursed with not infrequent floods. The Mississippi River flows by at 100,000 cu. ft. per second or even more. To a casual observer, the region appears overly blessed with water.
Wrong. Like so many other areas across the U.S., Mississippi's biggest-producing agricultural counties, those in the northwest quadrant of the state, face groundwater shortages. Dean Pennington, Yazoo-Mississippi Delta Water Management District executive director, says intense groundwater usage means the region now tallies a yearly deficit of 300,000 acre-feet.
"Our water use must change. The alluvial aquifer will not support current irrigated acres and certainly not additional acres. Managing our water supply protects and maintains our economy and land values. The question is not if change will occur but how will we change,” Pennington says.
That part of the state pumps up to 2 million acre-feet per year from the aquifer. Recharge falls far short of that, however.
"Everybody in the Delta is taking water out of that aquifer,” Pennington says.
Long-term monitoring of 550 wells shows water level declines of a foot per year in some areas. "Where we have the most significant water use, we see declines. In 10 to 20 years, some wells will have problems. We're not in a long-term marathon over water use. It's really a sprint. What we have to think about is what can we accomplish in 10 years,” Pennington says.
Along the border of Mississippi's Sunflower and Leflore counties, an area filled with fields of irrigated cotton, corn, soybeans and rice as well as catfish ponds, is where water levels have dropped most dramatically. "The water problem is going to be first expressed as a production problem in this area. We are looking for ways to balance our water budget,” Pennington says.
The issue, he explains, is not lack of rainfall. The area gets 50" of annual rainfall. The issue is keeping it where it's needed.
"Most of the rain runs off to the Gulf of Mexico,” Pennington says.
More water storage could help. The water management district is eyeing the transfer of water from the Tallahatchie River to the Quiver River, which flows in the area with the most serious water decline. Once there, that additional water could replace as much as 100,000 acre-feet per year. In addition, flood control reservoirs near Grenada, Miss., could store 2 million acre-feet of water for irrigation use. Flood control channels throughout the area could also hold water for irrigation.
Changing irrigation techniques would help, too. Pennington suggests that farmers consider planting rice on zero-grade fields, which requires half the water of rice fields with straight levees. "If we could change our straight rice levees to zero grade, it would balance our water budget,” he says.
Reusing irrigation runoff water could be another partial answer. Starting Jan. 1, 2010, in order to get a Class 1, 10-year well permit, producers will have to tell how they plan to reuse water runoff, if water is applied through a sprinkler irrigation system, whether or not the land is precision leveled with straight levees or zero grade with permanent pads on three sides, and whether water from an existing surface water permit can be applied to at least 75% of the irrigated area. Respond positively to those questions and you'll get a 10-year permit.
If you can't, you'll likely get a three-year permit requiring a flow meter and water use reporting.
The long-term viability of irrigated agriculture in the highly productive region largely depends on how farmers respond to the impending crisis. "I'm not saying everybody should change, but if some would change that would help a lot. If we get a one-tenth of an acre-foot reduction on each of our million acres of irrigated land that would take a big bite out of our water problem,” Pennington says.
"If we do it right, we will have water here for 100 years. Not many places in the U.S. can say that,” he says.
You can e-mail Charles Johnson at firstname.lastname@example.org.
- December 2009