State Water Resources Research Institute Program


Project ID: 2011NE220B
Title: High-resolution imaging of the Platte River streambed using combined electromagnetic induction and hydraulic parameter estimation techniques
Project Type: Research
Start Date: 3/01/2011
End Date: 2/29/2012
Congressional District: 1
Focus Categories: Groundwater, Surface Water, Methods
Keywords: Groundwater-Surface Water Interaction, Geophysical methods, Streambed, Hydrogeology
Principal Investigators: Korus, Jesse Thomas (University of Nebraska-Lincoln); Chen, Xun-Hong (University of Nebraska-Lincoln)
Federal Funds: $ 19,000
Non-Federal Matching Funds: $ 35,676
Abstract: The purpose of this study is to characterize the spatial variability of geophysical properties in relation to hydraulic properties in the streambed of the Platte River, central Nebraska. This river system is the focus of many current water issues in the state. Understanding streambed characteristics provides information on the temporal and spatial variability of flows between streams and aquifers, providing data and tools for managing water resources and critical wildlife habitats. Previous research on the Platte River has focused on direct measurement of hydraulic properties using in-situ and lab-based parameter estimation techniques. This research is critical, but is time-consuming and provides only point-based data over relatively small regions. Geophysical tools can be used to rapidly characterize stream-aquifer systems over large regions. The relationships between indirectly measured geophysical properties and directly measured hydrologic properties, however, are not well established. Preliminary data from the Platte River suggests that an inverse correlation exists between electrical conductivity (EC) and hydraulic conductivity of the streambed. Furthermore, separate sites with relatively homogenous versus heterogeneous streambed materials have been identified. We hypothesize that the spatial variability in EC of the streambed are related to channel morphology and hydrostratigraphic heterogeneity in the shallow aquifer beneath the stream. Ground-based electromagnetic induction (EMI) will be used to measure subsurface electrical conductivity as a function of water content, porosity, salinity, temperature, soil texture, and mineralogy. Direct comparisons between hydraulic and geophysical properties will be made based on co-located profiles at two sites along the Platte River. Three-dimensional visualizations will be produced using an EMP-400 field portable, mulit-frequency EMI tool and commercially available data integration/visualization software (Encom PA®). Areas of highly contrasting, frequency-dependent EC values should correspond to areas with underlying silt/clay layers and low Kv values. Areas with less depth-dependent and cross-channel variability in EC should correspond to areas without silt/clay layers and more uniform Kv values. Variations in EC that cannot be explained by silt and clay content may be related to other factors, such as porosity and water chemistry. By relating electrical conductivity to material properties and thence to hydraulic properties, the internal architecture of channel sediments and shallow aquifer materials can be characterized, improving our understanding of streambed processes and facilitating quantitative, regional analysis of stream systems, possibly using airborne geophysical platforms.

Progress/Completion Report, 2011, PDF

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