OBSERVATIONS OF STREAM-GROUNDWATER INTERACTION AT PARCEL, RANCH, AND REACH SCALE, WEST-CENTRAL NEBRASKA

This paper identifies the benefits of developing sensor networks designed to improve the spatial and temporal resolution of stream-groundwater interaction observations. Nebraska water managers make water-quantity management decisions using spatially and temporally discretized computer models that simulate the effects of water use on stream-groundwater interactions. These models, however, are calibrated using historical measurements of aquifer head that have comparatively fine (township-level) spatial distribution, but coarse (1-2 data points/year) temporal resolution. Likewise, measurements of stream flow on main-stem reaches typically have hourly temporal resolution, but a spatial distribution at the scale of tens of kilometers. Accordingly, there is uncertainty regarding the local results of simulations developed at spatial and temporal resolutions unsupported by observations.

Between 2014 and 2016, I deployed 31 pressure transducers along the North and South Platte Rivers in Keith and Lincoln Counties in west-central Nebraska. Study areas include a 20 ha parcel near the city of North Platte, an 850 ha ranch along the North Platte River, and a 110 km reach of the South Platte River. The transducers record temporally synchronized and spatially correlated measurements of groundwater head, stream stage, and temperature. Initial results indicate that it is possible to: 1) track stresses across the surface water-groundwater interface; 2) identify stream-aquifer interactions; 3) improve the designs of computer models through better estimation of parameters; and 4) enhance the basis for water-management decisions. It is likely that the potential improvements described herein will make the effects of water conservation and consumptive-use reduction better understood by producers and regulators across management scales.