Deep drainage sensitivity to climate, edaphic factors, and woody encroachment, Oklahoma, USA. Issue 17 (1st April 2015) - Wine, Michael L.
Abstract Because groundwater is Earth's largest pool of freshwater, understanding the sensitivity of deep drainage to climate, soils, and land cover is critical in managing water resources. To better understand controls on this critical flux in the context of woody encroachment, we determined the sensitivity of deep drainage to climate, soil texture, soil compaction, rooting depth, growing season duration, and plant–water stress response using Hydrus‐1D to simulate deep drainage. To evaluate the simulation results, we compared these results with ground measurements at two anchor sites. At both anchor sites, Hydrus‐1D predictions of deep drainage matched measured values within the errors inherent in ground measurements. Sensitivity analysis suggested greatest sensitivity of deep drainage to climate (24 mm yr−1) and rooting depth (12 mm yr−1), moderate sensitivity to growing season duration (5 mm yr−1) and soil texture (4 mm yr−1), and lowest sensitivity to topsoil compaction and plant–water stress response (3 mm yr−1). The sensitivity analysis indicated the relative importance of the plant‐related factors considered, which, in decreasing order, were rooting depth, growing season duration, and plant–water stress response – factors that change concomitantly as a result of forestation or woody encroachment. Further ground‐truth measurements of woody encroachment effects on deep drainage are needed to confirm or refine the results of this simulation modelling study. Copyright © 2015 John Wiley & Sons, Ltd.