Water Resources Research Act Program

Details for Project ID 2007UT87B

Two-Zone Temperature and Solute Model Testing and Development in the Virgin River

Institute: Utah
Year Established: 2007 Start Date: 2007-03-01 End Date: 2008-02-29
Total Federal Funds: $24,264 Total Non-Federal Funds: $52,328

Principal Investigators: Bethany Neilson

Project Summary: Water shortages and drought resulting in low stream flows are commonplace in Utah. Although water quantity tends to be the focus of efforts to cope with low flows, the effects on instream temperatures are additionally a high profile aspect of water quantity management in this arid region. Water temperature is important in an aquatic system because of its integral relationship with chemical and biological reaction rates. Temperature-related water quality impairments are ninth on the U.S. Environmental Protection Agencys Top 100 Impairments list. Many rivers in Utah support species, including endangered fish species that are sensitive to small temperature fluctuations. To enable management strategies that control small temperature fluctuations, modeling techniques that provide a detailed understanding of all important heat exchange processes are needed for more accurate predictive capabilities. Temperature models that are currently available to assist in heat load allocations are limited in that they do not represent all of the important heat fluxes (e.g., hyporheic and dead zone processes).

The proposed project consists of a data-centric approach to collecting information about energy and mass fluxes in streams that can be used in temperature and solute model parameter estimation for high-gradient watersheds. Past efforts for modeling river hyporheic and dead zone processes have used a lumped or one-zone approach where the total of the surface (dead zones) and subsurface (hyporheic zone) storage was referred to as transient storage. A two-zone temperature and solute model was formulated and tested at Utah State University that includes hyporheic and dead zone effects on the transport and fate of contaminants through exchange and biochemical transformations. The two-zone model, coupled with the observations of temperatures and solute concentrations in different zones, allows for separation of transient storage into surface and subsurface storage zones. The results of two-zone model calibration in a desert river for solute fate and transport have proven to be more representative of the surface storage zone than the lumped, one-zone approach. Similarly, the two-zone model calibration for temperatures in each zone resulted in more accurate temperature estimates in each zone and, therefore, in the main channel. There is still, however, a need to predict how these storage zones and the resulting instream temperatures change under different flow regimes. This project will provide for: 1) the testing and possible enhancement of the two-zone temperature and solute stream model by collecting more spatially intensive data required for calibration and corroboration of the model under a number of flow conditions, and; 2) the testing of parameter transferability between different flow regimes in a portion of the Virgin River, Utah.