The Mississippi River never runs less than 100,000 cubic feet per second as it braces the western side of the Delta. And yet, the copious flow hides a growing problem for Mississippi farmers — the Delta’s water supply is no longer sustainable.
Skeptics and scoffers take note: A 10- to 20-year window is projected which could see progressively larger areas of the central Delta burdened by poor well production.
Dean Pennington, executive director, Yazoo-Mississippi Delta Water Management District, says water demand has outpaced supply.
“What has happened, as in many parts of the country — when you have a very useful, natural resource like water, that plays a major roll in how your production works in an area, you begin to use that natural resource to produce economic value,” he said, speaking at the Agronomic Crops Field Day at the Delta Research and Extension Center, Stoneville, Miss.
“More people see the value; more people want to use the resource, and eventually in most cases you finally reach the point where the demand for the resource exceeds the supply. That’s where the Mississippi Delta is now.”
The Delta is covered with a 10- to 30-foot deposit of clay, the same rich layer that allows for high-yielding production. Underneath the clay lies the alluvial aquifer — a 100- to 150-feet layer of sand and gravel, meshed with a tremendous volume of water. The water from this alluvial layer is pumped up and onto the clay to irrigate Delta crops.
The recharge and resupply for the aquifer comes the Mississippi River in the west, and the bluff hills in the east.
“Basically everybody who has a groundwater well in the Delta is taking water out of that same alluvial aquifer. We’re all pumping water out of the same supply,” notes Pennington. Approximately 75 percent of Mississippi water use permits are in the Delta.
The coming shortfall of Delta water is stark when measured by the intake and outtake numbers. Pennington notes that on the 2 million acres of irrigated Delta farmland, producers annually use 1.5 million acre feet of water. Through natural means, the aquifer is replenished with 1.2 million acre feet per year.
“The end result: we’re using a tremendous amount of water every year. Each year, Mother Nature puts back almost that same amount, but over the long term, year-in-year-out, we’re taking 300,000 acre feet of water too much every year.”
The deficit of 300,000 acre feet has become the target for Pennington and the Water Management District — a vital number that is the focus of objectives and future accomplishments.
“If we can find ways to reduce our groundwater use by 300,000 acre feet per year — we’ll have a long-term, sustainable water supply that will be here 30, 40, 50, and 100 years from now.”
The Water Management District has a network of 550 wells that are monitored biannually during April and October. The wells are measured from the top of the casing to the water level, and the findings expose an area in the central Delta with consistent long-term declines — as much as 1 foot per year.
“Because we see these declines year after year, there is a really simple conclusion: The aquifer will not continue to support water use at our current rate.”
According to Pennington, the water problem will “first be expressed in Leflore and Sunflower counties.” If the top level of clay was removed, and the aquifer laid bare, the water level would appear high along the western edge (Mississippi River) and eastern edge (bluff hills), and then slope toward the central Delta. Combined pumping across the whole Delta is influencing the recharge back to the central area; Leflore and Sunflower counties are serving as the proverbial canary in the coal mine.
“The problem of running out of water in the short-term is in the central Delta, but we don’t view this as just a central Delta problem. Water runs downhill and as water recharges the Mississippi River or the bluff hills and flows toward the central Delta, everybody who takes some of that water out of the systems is contributing to the problem of using more water than our recharge. Therefore, everyone needs to be part of the solution to balancing our water budget,” says Pennington.
The Water Management District has maintained a study area of 1 million acres in the central Delta, and since 2004, 1,100 wells have been drilled. The data describes soil conditions and depth, as well as recording screen and casing measurements. The distance between the tops of the screens and the water level serves as a bellwether for Pennington.
“The typical depth of a Delta well will be 100 to 140 feet deep. Most wells will have 40 feet of screen. You have a static water level that we measure twice a year. But as soon as you turn a well on, you get a drawdown around the well — a cone of depression.
“For a typical 40-horsepower motor pumping 1,500 gallons per minute, this drawdown is about 15 feet. The drawdown in the aquifer is about 1 foot per 100 gallons per minute of flow. It’s the distance between the operating water level or draw-down level and the top of the screens that really tells you how much usable water is left in the aquifer.”
He believes water levels in some areas of the central Delta will reach the tops of well screens in as little as 10 years. When the water level declines to the top of a well screen, it doesn’t equate to a well being dry; but rather that well production decreases — screens and pumps wear out.
The results will include: biofouling, mineral deposits, air in the screens, and a drop in flow rate. “There will still be usable water, but you’re reaching the point where you have to start tinkering with how wells are constructed. It might take three wells to do what you’d previously done with two wells.”
Pennington admits there is not a “magic bullet” to stem the outtake flow from the aquifer by 300,000 acre feet. However, he is adamant that change is viable. “Long-term in the Mississippi Delta, if we do this right we can have one of the most dependable water supplies in the entire country.”
One option for change relates to a natural advantage of the Delta — water supply development has barely been tapped.
“We’re not using our rainfall as effectively as we could. The Mississippi River never runs less than 100,000 cubic feet per second. If we could use the flow from the Mississippi river for two days, we could meet our entire water need for the year in the Delta. That will give you an idea of how much water is in the river.
“The flood control reservoirs around Grenada hold a couple million acre feet of water in each one. Not a drop of that is used for anything other than navigation and flood control. We have some huge resources we could develop.
“We need to look at ways to store water in the thousands of miles of channels that we have: storm water runoff, irrigation runoff — instead of extra water making its way to Vicksburg… it can be re-used for irrigation.”
Specifically, the Water Management District is considering the possibility of transferring water to the central Delta from the Tallahatchie River. The Tallahatchie runs near to the Quiver River close to Glendora, Miss., and Pennington is reviewing the potential to take 1,000 cubic feet per second of flow out of the Tallahatchie and into the Quiver.
The Quiver River runs over the top of the Delta area with the most significant water decline. In essence, the Quiver would be used as a canal to deliver water from the Tallahatchie to the central Delta — with the aim of replacing 50,000 acre feet to 100,000 acre feet of groundwater use with surface water.
Pennington also advocates a second option for balancing the water budget — conservation and efficient water use. Indicative of such change, he notes, “If we could change all of our straight levees to zero grade, we could balance our water budget. That would reduce our demand on rice alone, by almost all the water we need.
“Zero grade rice still has a long way to go to determine whether it’s a viable option — some like it and some don’t. We’re certainly not advocating everyone be pushed toward zero grade rice. But I use that as an example of how going from poor conservation to better management can make a big difference in water balance.”
Pennington believes the time is now to implement change in Mississippi Delta water management. The Delta has 3 million acres of farmland, of which roughly 2 million acres are irrigated. Therefore, the roughly 1 million acres of non-irrigated farmland represent a long-term potential increase on an already strained water demand.
Changes in water use rules are approaching fast for Delta farmers, and the permit process will soon look different. In the past, water permits were gained with ease. Generally, $10 gained a producer 10 years of water. “Don’t call us; we’ll call you in 10 years. That’s the good old days,” describes Pennington.
Beginning Jan. 1, 2010, a Class 1, 10-year permit will require a producer’s well to fit into a minimum of one of the following four categories:
1. Is irrigation runoff from the given well captured and reused?
2. Is the well water applied through a sprinkler system?
3. Is over 90 percent of the application area precision leveled with straight levees or zero grade with permanent pads on three sides?
4. Can water from an existing surface water permit be applied to at least 75 percent of the irrigated area?
If a particular well doesn’t match up affirmatively with any of the four categories, a three-year permit will be issued. At the end of three years, the Water Management District will then consider if any conservation practices are being applied to a Class 1 standard. If no conservation practices are in place, a flow meter will be installed allowing for annual water use reports.
Also starting Jan. 1, 2010, producers will be required to obtain a permit prior to drilling a well. “We’ve been living in luxury where you drill the well, and then get the water use permit.”
Currently, if a farmer needs a well, a call is made to a driller, and drilling might begin days later. But under the new regulations in 2010, farmers can expect to wait a month for completion of the permit process. However, in cases of emergency, a farmer will be allowed to bypass the mandatory wait and complete the paperwork after the well has been completed.
Pennington believes that if done right, the Mississippi Delta can have one of the most dependable water supplies in the United States. He emphasizes that the changes will be made in small, incremental steps; with the aim of minimal intrusion into farming operations.
“The worst thing we can have happen is for folks not to have the water they need for their crops. So we’re probably looking at some minor burdens along the way and minor changes of business. The good old days are behind us in water use in the Mississippi Delta, but with just a little bit of common sense and change, we can make sure we have enough water for the next 100 years. There aren’t many places in the United States that can say that.”
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