Location: Watershed Management Research2013 Annual Report
1a. Objectives (from AD-416):
1) Evaluate the impact of landscape change on fluxes of energy, water and CO2 for Great Basin rangeland ecosystems. 2) Quantify soil-water plant growth relationships and complex terrain effects on soil temperature and moisture using the Reynolds Creek Experimental Watershed as a model system. 3) Expand integrated snow hydrology modeling to larger scales, coupling to belowground processes, including wind effects on precipitation input, and helping to incorporate snow-related processes into ARS watershed and management simulation models (e.g., SWAT, AnnAgNPS, KINEROS, AgES, AGWA, RHEM, ISNOBAL, PIHM, etc).
1b. Approach (from AD-416):
This project is motivated by the following two interconnected aspects of water resources in the western U.S.: 1) water resources and covarying biological resources are concentrated in snow dominated mountainous terrain in which critical processes vary dramatically over short distances; and 2) climate change is affecting hydrologic processes, particularly snow accumulation and melt, in ways that may drastically alter water supply and land management. There are three objectives, two of which focus on field measurement and modeling of critical processes using the Reynolds Creek Experimental Watershed facilities and infrastructure. Those two objectives provide fundamental verification and evaluation data for the third, modeling objective. In the first objective, we combine innovative application of eddy covariance in mountainous terrain with intensive measurement and modeling to evaluate the impacts of ongoing landscape (vegetation) change on the net ecosystem flux of water and CO2. In the second objective, we measure soil water and temperature, along with important climatic parameters, and simulate the water balance and plant production across the rain/snow transition elevation. The third objective focuses on integrated hydrologic modeling to assess the impact of climate warming and landscape change on the seasonal snow cover, soil moisture, groundwater recharge, evaporation and streamflow in mountainous terrain. Model development includes upscaling process models from research to management scales and extending the modeled features to improve management models. The second and third objectives include multi-location research projects in which hydrologic trends at Reynolds Creek are analyzed and compared in a broader, nationwide context. Replacing 5362-13610-008-00D (02/12)
3. Progress Report:
This report documents progress for the parent Project 5362-13610-010-00D "Understanding Snow and Hydrologic Processes in Mountainous Terrain with a Changing Climate," which started February, 2012. Eddy covariance (EC) is a sophisticated measurement technique used to determine the rate of water movement from the earth to the atmosphere, or evapotranspiration. The Northwest Watershed Research Center (NWRC) has processed and error-checked EC data for the Upper Sheep Creek watershed, which is part of the Reynolds Creek Experimental Watershed (RCEW), through water year 2012. Estimates of evapotranspiration using EC, soil water measurements and model simulations have been compared and a manuscript is ready for submission. These efforts will aid in assessing the hydrologic impact of the 2007 prescribed fire and 2008 vegetation removal within the Upper Sheep Creek watershed. At the South Mountain watersheds, which are about 100 km south of the RCEW, correlations of measured streamflow, observed precipitation, and model simulations have been evaluated. Further modeling will be conducted when vegetation data for the watersheds have been assessed. These efforts will characterize the hydrologic response of the watersheds prior to juniper removal. ARS scientists in Boise, Idaho, have completed the Soil Ecohydrology Model (SEM) simulations and have written a draft manuscript that should be submitted before the fiscal year end detailing long-term productivity at three sites at Reynolds Creek Experimental Watershed. At Johnston Draw within the RCEW, NWRC has complete soil water and soil temperature data for opposing north and south aspects along with two seasons of extensive field survey and are currently analyzing those data. The fiber optic Distributive Temperature Sensor system has been evaluated for use in characterizing soil temperature as affected by topography and snow cover at Upper Sheep Creek and ARS scientists in Boise, Idaho, are currently writing a manuscript. In regards to the site inter-comparison work, the unit has carefully reviewed data from Tucson and Little River to be included. NWRC has also modified software to generate model inputs of precipitation, wind, temperature, and humidity in the complex terrain of Reynolds Creek. ARS scientists in Boise, Idaho, are using this type of data to run combined snow and hydrology models over increasingly large parts of Reynolds Creek and have completed a comparison of Simultaneous Heat and Water-type approaches to snowmelt with those in Isnobal (an energy-balance snowmelt model). During this time NWRC has worked extensively with other agencies, especially with the National Aeronautics and Space Administration and the National Science Foundation, to obtain funding in support of most of the objectives in this project.
1. Energy balance modeling improves description of hydrology in complex terrain. Modeling hydrologic processes in complex terrain for purposes of water supply forecasting, flood forecasting and quantifying ecosystem services has been based on empirical correlations and relatively crude averaging techniques. ARS researchers in Boise, Idaho, used meteorological and extensive eddy covariance data from the Reynolds Creek Experimental Watershed to improve and test linked snow (Isnobal) and soil (Penn State Integrated Hydrologic Model) energy and mass balance hydrology models. Results demonstrate that the energy balance approach is the most accurate way to simulate snow accumulation and melt, that relatively robust parameters can be used to drive the simulation approach, and that this approach is critical to determining patterns of soil moisture and soil water use during and following snow melt. The close linkage of eddy covariance data to hydrologic models in complex terrain demonstrates the potential for expanding research to carbon flux across the landscape. These findings further demonstrate the potential for applying a physically-based approach to management-oriented modeling of water supply and flood forecasting.
Flerchinger, G.N., Caldwell, T.G., Cho, J., Hardegree, S.P. 2012. Simultaneous heat and water model: Model use, calibration and validation. Transactions of the ASABE. 55(4):1395-1411.