Irrigation conservation effort a necessary start
Soybean producers in Mississippi irrigate the third most acres in the U.S., second only to Nebraska and Arkansas. The vast majority of these irrigated soybean acres are in the Delta.
Each year, the Yazoo Mississippi Delta Joint Water Management District (YMD) estimates number of irrigated acres and amount of irrigation water applied to the major crops grown in the Delta. Most of this water is pumped from the Delta alluvial aquifer.
click image to zoom In March 2011, I posted a blog using 2010 data (see below table) that outlined how reducing the amount of irrigation water applied to soybeans could significantly reduce the amount of water withdrawn from the alluvial aquifer for that purpose. The numbers may have changed in the subsequent two years, but the facts have not.
Each year, the YMD also makes measurements throughout the Delta to estimate water volume changes in the alluvial aquifer. During the 2005-2010 period, the estimated change in the aquifer level averaged a loss of about 234,000 acre-ft/year-the change was negative in 5 of the 6 years. In fact, over the last 24 years that these measurements have been made, 15 years have shown estimated declines in the aquifer level. Obviously, this is a matter of concern.
In a Delta Farm Press article, Dr. Dean Pennington, Executive Director of YMD, gave an update on the state of the alluvial aquifer. He outlined numerous changes to permit regulations that took effect on Jan. 1, 2011, to abate the aforementioned decline in the aquifer and ensure its sustainability. His bottom-line message as reinforced by the new water conservation regulations guiding the permitting process is that the continued overuse of water from the aquifer cannot continue.
The changes he outlined deal with the physical aspects of irrigation management; i.e., land leveling to zero grade, reducing runoff and/or recapturing excess irrigation water, on-farm surface water storage (OFWS), etc.
Three points about OFWS for irrigation purposes:
- This is not a new concept. In an Oct. 3, 1986, Delta Farm Press article (Vol. 43, No. 34, p. 1,5), this option was discussed at length and its utility was touted.
- Water captured in impoundment structures for future irrigation use provides positive downstream water quality benefits.
- Impounded water from winter rains can be used for early irrigations, thus reducing the amount of groundwater needed or used for irrigation during the season. This conservation measure is currently being evaluated to determine just what the savings will be for a given amount of land that is 1) irrigated, and 2) used for impounding water.