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Playa wetlands in the Rainwater Basin area in south-central Nebraska perform the important functions of protecting water quality by trapping and filtering sediments and other pollutants, but they are highly vulnerable to the culturally accelerated sediment accumulation from the surrounding watershed. Culturally accelerated accumulation of sediment will overwhelm playa wetlands in many respects by reducing wetland volume and altering the hydro-period of wetlands, and subsequently decrease their value as biotic habitats.
This study aims to use EM38-MK2 to map sediment vertical depth to Bt (clay) layer for the hydric soil footprints at 93 publicly-managed wetland watersheds to determine if electromagnetic induction (EMI) technique can be used as a technique to more efficiently detect the depth of sediment to Bt layer, and to generalize sediment accumulation conditions in the 93 publicly-managed playa wetlands in Nebraska Rainwater Basin area. At each site, the sample data with three replicates was taken with the EM38-MK2 in both east-west and north-south directions in vertical mode with transmitter receiver coil separation at 1 meter within certain hydric soil type. The EM data were processed using Interpex Limited 1X1Dv3 inversion software to generate one dimensional conductivity versus depth profiles, and the depth of sediment to Bt layer can be derived from the inversion results. The results in this research indicate that the depth of sediment in all 279 sites ranged from 21.00 to 78.00 cm, and the average of sedimentation accumulation is 39.00 cm. The annual average depth of sedimentation ratio is 0.26 cm/year. This project can fill the critical knowledge gap about the vertical profile of playa wetland sediments, and future wetland restoration plans can be developed based on the results of this research.
Advisor: Zhenghong Tang