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Characterization and mass balance modeling of dissolved solids concentrations and loads in the South Platte River system, northeastern Colorado




Haby, Paul Andrew, author
Loftis, Jim C., advisor
Garcia, Luis A., committee member
Steele, Timothy D., committee member
Waskom, Reagan M., committee member

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Driven by an increasing population in the South Platte River Basin, water which was historically used for agricultural purposes is being diverted to urban areas in order to satisfy increasing municipal and industrial demands. This trend is changing the timing, location, volume, and quality of return flows to the river. The quality of return flows is of particular concern in the lower reaches of the South Platte River Basin where salinization of irrigated soils has emerged as a concern. This study addresses the critical need for a comprehensive understanding of salinity status and provides the basis for understanding the processes involved in the origin, flux, and ultimate destination of salts throughout the basin. The first phase of this research utilized historical monitoring data in order to characterize dissolved solids status and trends within the basin. Specific objectives of this phase were: (1) the compilation and assessment of available historical streamflow and dissolved solids concentration data, (2) the estimation of daily dissolved solids loads at selected monitoring sites, (3) the characterization of spatial patterns in dissolved solids concentrations and loads, and (4) the determination of temporal trends in dissolved solids concentrations and loads. The second phase of this research provides a quantification of salt balance and prediction of future streamflow and dissolved solids concentrations resulting from proposed water resource projects. The salt balance of the mainstem of the South Platte River was evaluated through the development of a reach-based water and dissolved solids budget. Components of the budget included upstream inflow, tributary contributions, major point sources, diversions, and downstream outflow. Residuals of the mass balance were used to quantify unmeasured streamflow and salt contributions to the river, the majority of which occur via ground water inflows. In the final phase of this study, a dynamic streamflow and salt mass simulation model was developed to assess water-quality impacts of water development projects. Based on mass balance concepts, this model allows for the evaluation of changes in streamflow, dissolved-solids loads, and dissolved-solids concentrations along the middle and lower portions of the South Platte River resulting from single or multiple user-configurable upstream water diversion and reuse projects. Details of the model development and operation are presented along with results of simulations of several case studies. The results of these simulations highlight the utility of a dynamic streamflow and salt mass simulation model in the evaluation of future water-quality conditions and demonstrate the importance of combined evaluation of multiple proposed water development projects.


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South Platte River
dissolved solids
dynamic systems modeling
water-quality monitoring
water-quality modeling


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