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Watershed Hydrologic and Contaminated Sediment Transport Modeling in the Tri-State Mining District
Citation:
Rahman, K., Mohamed M. Hantush, A. Hall, AND J. McKernan. Watershed Hydrologic and Contaminated Sediment Transport Modeling in the Tri-State Mining District. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-18/247, 2019.
Impact/Purpose:
A sediment transport component of SWAT was constructed and calibrated using three years-worth of bi-weekly flow and suspended sediment concentration data (2014-2016) sampled from stations in seven different tributaries upstream from Empire Lake. Sediment loading was calibrated at Spring River and Shoal Creek. The model met the threshold performance statistics recommended for sediment and explained 65% of the variance in the observed data at the Spring River Watershed. However, sediment calibration at Shoal Creek was not as good as for Spring River, with the model explaining only 45% of the variance in the observed data. Calibration of sediment loading at smaller tributaries of mainstem Spring River produced R2 ranging from 0.69 to 0.99, thus explaining more than about 70% of the variance in the observed data. Average annual sediment loading in the watershed were estimated for the period (2010-2016) using the calibrated SWAT model, and areas contributing most of the sediment were identified. The two largest sub-basins, the Spring River and Shoal Creek Watersheds, contributed most of the annual sediment loading. SWAT computed average annual sediment loading for 2014-2016 and reported studies on historical lead and zinc occurrence within the TSMD were used to make qualitative inferences on efficacy of hypothetical sediment traps as a potential remedial strategy for mining-affected tributaries. While installation of sediment traps in Short, Center, and Turkey Creeks may reduce less than 14% of annual average sediment loading to Empire Lake (based on 2014-2016 data), these tributaries historically have been associated with highest concentrations of dissolved and sediment-bound zinc and lead. However, effectiveness of sediment filtration in reducing heavy metals input to Spring River would be limited by the percentage of fine sediment particles and percentage of total lead and zinc in the dissolved phase. These results are useful for identifying critical source areas of sediment and can be used to inform management decisions on lake dredge and sediment traps as viable remedial measures for metal contamination in heavily contaminated tributaries of Spring River and Empire Lake.
Description:
The Tri-State Mining District (TSMD) encompassing the Kansas, Missouri and Oklahoma conjunction was the center of historic mining activity, ceasing in 1970. Although mining activity ended almost 50 years ago, its legacy as a source of cadmium, lead, and zinc to the environment continues to this day. This mining activity left 165 million tons of improperly contained piles of mine waste (chat) across the 2,500 square mile region. Chat piles were the dominant geographic feature in the TSMD, especially in Short Creek, Center Creek, Turkey Creek, and Shoal Creek, among others. These features, along with waste rock and mine tailings, have contributed to metal contamination of the waterways of the Spring River Watershed (located in the TSMD), and led to the transport of heavy metal-laden (primarily zinc and lead) sediments into the Empire Lake Reservoir in Cherokee County, Kansas. Years of sedimentation have reduced the capacity of the reservoir, leading to the pass-through of contaminated sediments - affecting downstream communities and Indian Tribes. The Soil and Water Assessment Tool (SWAT) was used to construct a distributed watershed model for streamflow and sediment loading simulations in the Spring River Basin watershed that feeds into Empire Lake, KS. The objective of the watershed model simulations is provide information on metal-laden sediment transport and loading from source areas needed to support remediation efforts for the Spring River Watershed and Empire Lake. Geospatial and hydro-climate input data resolution analysis was conducted to identify optimal input data resolution for best model performance in simulating flow and sediment transport within the Spring River Watershed. Input data resolution analysis was conducted prior to model calibration to insure optimal watershed model performance. The SWAT hydrologic model was successfully calibrated and validated both at the monthly and daily time scales using streamflow data downloaded from two USGS gauge stations in the watershed. The flow watershed model at the Spring River and Shoal Creek gauges met the threshold performance statistics and explained more than 60% of the variance in the observed data for both the calibration and validation periods. The model reproduced observed low and high streamflows adequately, but deviated from middle range observed values.