Submitted to: USDA Miscellaneous Publication 1343
Publication Type: Abstract Only
Publication Acceptance Date: 9/15/2006
Publication Date: 10/5/2006
Citation: Garbrecht, J.D., Brown, G.O., Steiner, J.L., Schneider, J.M., Starks, P.J. 2006. Soil Water Trends During the 2005 - 2006 Drought in Oklahoma. Oklahoma Water Conference, Oklahoma State University, October 5-6, 2006, Oklahoma City, Oklahoma. Available: http://environ.okstate.edu/okwater/index.asp Interpretive Summary: Abstract Only.
Technical Abstract: Soil water depletion is an early consequence of a meteorological drought, with the latter defined as a precipitation deficit lasting a few months to several years. Soil water in the upper soil profile (approximately first meter) is limited and highly variable because of its rapid response to precipitation and evapotranspiration. Depletion of the soil water due to meteorological drought stresses rangeland, pastures and rainfed crops, hence the name “agricultural drought”, even though natural ecosystems can also be stressed. Soil water patterns from January 1998 through July 2006 were analyzed for a tall grass prairie site on the grounds of the Grazinglands Research Laboratory at Fort Reno, about 35 miles west of Oklahoma City. The soil at this site is characterized as a silt loam. Soil moisture data were obtained from the Atmospheric Radiation Measurement (ARM) Program, sponsored by the U.S. Department of Energy. Soil water patterns in three layers (0-50 cm, 50-100 cm, and 100-200 cm) showed clear signs of higher soil water depletion from September 2005 through July 2006 compared to previous years, with the lowest layer being the most impacted and having practically no soil water recharge during the 2005-2006 fall and winter months. The 1998-2004 soil water patterns and corresponding precipitation records were used to estimate the minimum amount of precipitation required during fall and winter to refill the soil profile. On average it took a minimum of 16 cm fall-winter precipitation to replenish the top layer, 28 cm to replenish the top and middle layer, and 35 cm to replenish all three layers. While such minimum precipitation amounts may be sufficient to break an agricultural drought, these precipitation minimums are likely not sufficient to break any co-existing hydrologic or water resources droughts which unfold over longer periods and, once established, tend to be more persistent than agricultural droughts.