Spatial trends in saturated hydraulic conductivity of vegetated dunes in the Nebraska Sand Hills: Effects of depth and topography

In the Nebraska Sand Hills (NSH), the largest vegetated dune field in the Western Hemisphere, dunes have relatively high hydraulic conductivities, and surficial aquifers can partially retain a significant fraction of precipitation as groundwater recharge and return it for preservation of plants. This important mechanism for maintaining the stability of the ecosystem in the NSH requires knowledge of saturated hydraulic conductivity (K-fs) in the vadose zone. A unique 3D dataset for the distribution of K-fs was collected within the framework of the Grassland Destabilization Experiment (GDEX) at the Barta Brothers Ranch site, Nebraska, using direct in situ measurements. The results show that K-fs increases with depth towards the lower boundary of the root zone (up to 2 m). For the topographic effects, highlands generally present higher K-fs values than lowlands, and there exists a significant correlation between K-fs and absolute elevation. It is found that the effect of short-term vegetation disturbance on K-fs was minimal that may not hold in the long run. (c) 2007 Elsevier B.V. All rights reserved.