Submitted to: Proceedings of the USCID Wetlands Seminar
Publication Type: Proceedings
Publication Acceptance Date: 9/1/2006
Publication Date: 10/1/2006
Citation: Colaizzi, P.D., Gowda, P., Marek, T.H., Porter, D.O. 2006. Reducing Ogallala withdrawals by changing cropping and irrigation practices in the Texas High Plains. Ground Water and Surface Water Under Stress: Competition, Interaction, Solutions. A USCID Water Management Conference, October 25-28, 2006, Boise, Idaho. p. 113-126.
Interpretive Summary: Irrigated crop production is a vital component of the economy in the Texas High Plains. Major crops include cotton and peanuts in the Southern High Plains and cotton, corn, and winter wheat in the Northern High Plains. Irrigation is dependent on the Ogallala Aquifer, which has a declining water volume because withdrawals have greatly exceeded natural recharge (predominately from precipitation) since irrigation development began in the 1930-40s and accelerated during the major drought in the 1950s. Cotton has recently expanded northward again and replaced corn in some areas because both crops have similar revenue potential but cotton has about half the water requirement. Furthermore, cotton has much greater drought tolerance than corn, achieving profitable yields under dryland or limited (deficit) irrigated conditions. We computed potential water savings by converting portions of currently irrigated corn area to cotton. We also computed additional water savings by reducing irrigation application volumes to cotton, corn, wheat, and grain sorghum and the associated reductions in crop yield. Cotton appears to be a good candidate for deficit irrigation management because significant water savings can result without undue reductions in crop yield. The potential water savings of grain sorghum and winter wheat were much less than that of cotton because these crops are already produced under mostly dryland or deficit-irrigated conditions. Corn would have significant potential water savings if its water use efficiency could be improved. Peanuts were not analyzed due to limited data on dryland or deficit-irrigated conditions within our region.
Technical Abstract: Irrigated crop production in the Texas High Plains is dependent on the Ogallala Aquifer, which has declined by up to 50 percent in some areas since irrigation development began in the 1930-40s. About 6.5 million ac-ft (8.0 x 109 m3) of water was pumped to irrigate 4.6 million ac (1.9 ha) in 2000, with most irrigation demand being for corn and cotton production. Cotton is produced primarily in the Southern Texas High Plains, with corn and winter wheat comprising most of the irrigated area in the Northern Texas High Plains. However, cotton production is expanding northward again and replacing corn in some areas because both crops currently have similar revenue potential but cotton has about half the irrigation water requirement, and may result in profitable yields under dryland and deficit irrigated conditions. In the Northern Texas High Plains, combined annual irrigation demand for corn and cotton could be reduced from 2.6 to 2.0 million ac-ft (3.2 x 10**9 to 2.5 x 10**9 m**3) by replacing 50 percent of the irrigated corn area with cotton, and combined irrigation demand could be reduced to 1.6 million ac-ft (2.0 x 10**9 m**3) if cotton irrigation applications were reduced to 50 percent of full crop evapotranspiration minus rainfall. In the Southern Texas High Plains, annual irrigation demand for cotton could be reduced from 1.4 to 1.0 million ac-ft (1.7 x 10**9 to 1.2 x 10**9 m**3) if overall irrigations were reduced to 50 percent of full crop evapotranspiration minus rainfall. Deficit irrigation results in some yield penalty; however, this may be offset somewhat by the reduced energy costs of pumping.