NEAR-SURFACE SOIL-WATER MONITORING FOR WATER RESOURCES MANAGEMENT ON A WIDE-AREA BASIS IN THE GREAT PLAINS

In the Great Plains, soil water is one of the most critical factors related to sustainable production on cropland and rangeland, while the need for better water management grows in the face of increasing water demand during dry years. Soil water is also an important factor related to flood modeling and quantification of the boundary conditions in atmospheric models such as global circulation models. The objectives of this study were to install a wide-area automated soil-monitoring network, determine effective calibration procedures, and develop new products to illustrate the status of soil water. Soil-monitoring sensors were established at 51 sites across Nebraska under rain-fed conditions and under a grass cover. Four sensors were installed at each site at depths of 10, 25, 50, and 100 cm. The sensors were calibrated for three soil types: sandy, loamy, and clay. Data are collected daily, assessed for quality, and archived. Six quality-assurance (QA) tests were developed based on the properties of soil water, the statistical characteristics of the measurements, the soil properties, and the precipitation measurements. The quality-assured data from the network are used in maps to determine the spatial status of soil-water availability as expressed by the percentage of maximum available water in the layer (or profile). Data is also presented on the interannual and mean annual patterns of soil water across a range of climates, from semiarid to subhumid, in the Great Plains. The results of this study demonstrate the feasibility of monitoring soil water. This capability will be valuable in drought mitigation, water management planning, ecosystem research, and other studies. The dataset will be of great value for researchers in the Great Plains to quantify weather forcing, climate change, and the water balance, especially in rangeland areas.