2007 Annual Report
1a.Objectives (from AD-416)
1) Conduct detailed field experiments to quantify how fluxes of water and energy control snow accumulation and melt, and affect soil moisture, streamflow, and water supplies in western watersheds.
2) Develop methodology for detailed characterization of terrain and canopy structure over mountainous regions using high resolution LiDAR data.
3) Develop improved coupling of surface and below-ground models for spatial simulation of snowmelt, runoff, soil temperature and moisture, and streamflow.
4) Develop methodology for generating cold-season runoff distributions to improve RUSLE erosion predictions in agricultural regions dominated by winter snow and frozen soil.
5) Test and validate new instrumentation, databases, and model interfaces for use by the NRCS and other action agencies and potential users.
1b.Approach (from AD-416)
(1) Five Eddy Co-variance systems will be deployed across a range of landscape and vegetation types to measure atmospheric fluxes over vegetation and snow. Within and above canopy radiation exchange, simulated by the SHAW model, will be tested using solar and long-wave radiation data collected for a variety of plant canopies (wheat, soybean, maize, and forest). ETRS integrated flux measurement systems will be established to accurately measure fluxes from the bedrock to the atmosphere. (2) LiDAR data will be acquired over a large area of southwestern Idaho, including RCEW, the Boise Front, and the Juniper Impact area of the Owyhee Mts. A voxel-based canopy model will be developed to estimate canopy transmissivity to direct and diffuse solar radiation and thermal radiation enhancement due to canopy emissivity and heating effects. The simulations will be validated against detailed sub-canopy radiation and canopy temperature measurements completed as part of Objective 1. (3)a. Detailed models of snow deposition, redistribution and melt, including adjustments for canopy effects will be scaled from plots the relatively small Reynolds Mountain, Upper Sheep Creek and Johnston Draw catchments and then scaled to the much larger Tollgate sub-basin. b. A spatially distributed soil water model will be used to simulate streamflow generation and plant water use for two water years for which extensive data have been collected. c. The hydrologic effects of fire will be evaluated at the Upper Sheep Creek catchment comparing historical, pre-fire data and validated modeling to and measured data and simulations following prescribed fire. (4) The SHAW model will be modified as necessary to accurately simulate frozen soil runoff. The model will then be applied for a series of climate and crop/residue cover scenarios to generate a distribution of runoff events to assess the influence of crop/residue cover on cold-season runoff to be incorporated in the RUSLE erosion model. (5) A state-of-the-art hydrological relational database that enhances user data accessibility will be developed and populated, the ISNOBAL snow accumulation and melt program will be incorporated into the NRCS OMS modeling system, and there will be continued work on snow water equivalent and soil water content measuring devises in cooperation with the NRCS.Replaces 5362-13610-006-00D (1/07).
Simpler approach for simulation of radiation transfer though plant canopies. Simplified equations were developed that very close approximate the extremely complex mathematical expressions to compute radiation transfer through plant canopies. The exchange of solar radiation within plant canopies is critical to the plant’s thermal environment, photosynthesis, and growth. Scientists from the USDA-ARS-NWRC, Boise, Idaho and the Institute of Geographical Sciences and Natural Resources Research, Beijing, China developed regression equations that very closely approximate complex integral functions for the transmission and scattering of radiation through a plant canopy. These simplified equations can be more easily implemented into computer simulation models and will lead to more reliable models for evaluation of management and climate scenarios on plant microclimate and plant response. This accomplishment addresses National Program 201, Problem Area 5 – Watershed Management, Water Availability, and Ecosystem Restoration.
Hydrologic impact of shrub removal in a semiarid environment.
Managers of western rangelands are under increasing pressure to remove woody vegetation and part of the justification for this expense is that it is assumed that water supply will increase as a result. We conducted a field study removing woody vegetation to measure and model the impact on the soil water balance and groundwater recharge. Scientists from the USDA-ARS-NERC, Boise, Idaho conducted a field study in the Reynolds Creek Experimental Watershed (located near Boise) removing… woody vegetation to measure and model the impact on the soil water balance and groundwater recharge. Based on the results, a modeling/evaluation approach to estimating water supply impacts of woody vegetation removal was proposed. This information should prove very helpful for managers who must decide where limited restoration money would be best applied.
National Program 201, Problem Area 5 – Watershed Management, Water Availability, and Ecosystem Restoration
5.Significant Activities that Support Special Target Populations
|Number of web sites managed||2|
|Number of non-peer reviewed presentations and proceedings||15|
|Number of newspaper articles and other presentations for non-science audiences||4|
Flerchinger, G.N., Seyfried, M.S., Hardegree, S.P. 2006. Using Soil Freezing Characteristics to Model Multi-Season Soil Water Dynamics. Vadose Zone Journal. 5:1143-1153.
Essery. R., and Marks, D., (2007) Scaling and parametrization of clear-sky solar radiation over complex topography, Journal of Geophysical Research, Vol. 112, D10122.
Flerchinger, G.N., Q. Yu. 2007. Simplified Expressions for Radiation Scattering in Canopies with Ellipsoidal Leaf Angle Distributions. Agricultural and Forest Meteorology. 144:230-235.
Seyfried, M.S., Wilcox, B. 2006. Soil Water Storage and Rooting Depth: Key Factors Controlling Recharge on Rangelands. Hydrological Processes, 20:3261-3275.
Flerchinger, G.N., Marks, D.G., Seyfried, M.S., Pierson Jr, F.B., Nayak, A., Hardegree, S.P., Winstral, A.H., and Clark, P. 2007. 45 years of climate and hydrologic research conducted at the reynolds creek experimental watershed. pp 135-143. In: J.R. Rogers (ed.), Environmental and Water Resources: Milestones in Engineering History. Sponsored by ASCE Environmental and Water Resources Institute (EWRI) National History & Heritage Committee. American Society of Civil Engineers, Reston, VA. 168p.