2007 Annual Report
The following subordinate ARS projects are being conducted under the auspices of this project to assist in achieving the milestone and research objectives of this project and its predecessor.
5342-13610-007-14S - Remote Sensing and GIS for Improved Characterization of Landscapes for Hydrologic Modeling and Estimation of Soil Moisture 5342-13610-010-01R - Spatially Integrated Environmental Modeling 5342-13610-010-02R – Prediction of Seasonal to Inter-Annual Hydro-Climatology including the Effects of Vegetation Dynamics and Topography over Large River Basins 5342-13610-010-03R - Forecasting Water Quality and Quantity Hazards Using Spatially Distributed Watershed Models and Biophysical Data 5342-13610-010-05S - San Pedro Riparian National Conservation Area (SPRNCA) Riparian Water Needs Study 5342-13610-010-06S – Geospatial Watershed Modeling for Improved Water Management
The effect of rainfall events on riparian ecosystems in semiarid environments. The influence of different hydrological processes on the structure and functioning of riparian vegetation in semiarid basins is not well understood and this information is critical to the management of these important and ecologically diverse ecosystems, which are threatened by human groundwater use in the western U.S. The results of many studies along the San Pedro River conducted in southeastern Arizona were synthesized to show that rooting depth and access to groundwater are key factors that control the vegetations water use and carbon dioxide exchange. Depth to groundwater, which varies substantially across the riparian landscape, is a key factor controlling the sensitivity of cottonwood transpiration, leaf photosynthetic metabolism, and plant water sources to pulsed inputs of growing season moisture. Because mesquite accesses groundwater in these habitats, ET and gross ecosystem production are decoupled from precipitation, but ecosystem respiration remains highly coupled to rainfall due to the dominant contribution of litter and bulk soil organic matter decomposition. Responses of net ecosystem exchange of carbon dioxide to rainfall variability in riparian floodplain is therefore not simple, but depends on vegetation structure and the connection of dominant plants to the water table. The complex vegetation patterns, hydrologic setting and disturbance dynamics in the riparian landscape offer unparalleled opportunities to investigate fundamental processes linking water and carbon exchange. NP 201/211, Problem Area 5, Problem Statement: More accurate quantitative components of basin water budgets that consider ecosystem feedbacks affecting watershed states and fluxes and enhanced instrumentation (in-situ soil moisture, eddy-covariance, etc.) applications coordinated with ecosystem and biogeochemical observations.
A space-based approach for mapping regional surface roughness. When runoff occurs on a watershed, the roughness of the surface of the watershed plays an important role in how rapidly water moves on the watershed, which in turn is very important determining the magnitude of flooding and erosion. Surface roughness, as it affects water flow and erosion, is typically estimated is a relatively subjective manner and is very difficult to do consistently over large areas. Often empirical methods are used or gross extrapolations are made from laboratory studies. In this study, ARS and Univ. of Arizona scientists developed a new approach to derive roughness data from satellite-based radar images. The result is a quantitative, and consistently derived, roughness map applicable to large drainage areas. This estimates can be directly input into hydrologic models to improve estimates of erosion and runoff. NP 201/211, Problem Area 5, Problem Statement: Improved watershed simulation, plant growth, and weather generation model components and data assimilation tools for water budget, water quality assessment, and flood and drought risk and impact assessment.
Estimating soil texture and hydraulic properties from remote sensing data and modeling.
Soil texture and hydraulic properties are critical components of energy and water balance studies, but are not easily determined over heterogeneous regions. This study conducted by NASA, ARS scientists in Tucson, AZ and the U.S. Army used estimates of soil moisture derived from satellite imagery to infer soil texture and hydraulic properties from a land surface model. This operational approach is useful for mapping soil information using available technology for a better understanding of water availability in semiarid watersheds. Research is useful for farmers and managers of semiarid watersheds. NP 201/211, Problem Area 5, Problem Statement: Improved watershed simulation, plant growth, and weather generation model components and data assimilation tools for water budget, water quality assessment, and flood and drought risk and impact assessment. (Also addresses Obj. 1 in Coordinated Plan of Work (CPW) entitled “Remote Sensing for Parameters and States of Watershed Models for Improved Watershed Management."
SWRC scientists are heavily involved in the NSF Sustainability of semiArid Hydrology and Riparian Areas (SAHRA) Science and Technology Center. This program has a very active program in outreach and education of Native American communities to increase hydrologic awareness career opportunities in science.
Bryant, R., Moran, M.S., Thoma, D., Holifield Collins, C.D., Skirvin, S.M., Rahman, M., Slocum, K., Starks, P.J., Bosch, D.D., Gonzalez-Dugo, M.P. 2007. Measuring surface roughness height to parameterize radar backscatter models for retrieval of surface soil moisture. IEEE Geosci. and Rem. Sens. Letters 4(1): 137-141.
Nagler, P.L., Glenn, E., Kim, H., Emmerich, W.E., Scott, R.L., Huxman, T., Huete, A. 2007. Relationship between evapotranspiration and precipitation pulses in a semiarid rangeland estimated by moisture flux towers and modis vegetation indices. Journal of Arid Environments. 70:443-462.
Nichols, M.H. 2007. The walnut gulch experimental watershed - 50 years of watershed monitoring and research. In: Monitoring and Evaluation of Soil Conservation and Watershed Development Projects. de Graaff, J, Cameron, J., Sombatpanit, S., Pieri, C., Woodhill, J.(eds.). World Association of Soil and Water Conservation, Bangkok. 496 p.
Potts, D.L., Huxman, T.E., Scott, R.L., Williams, D.G., Goodrich, D.C. 2006. The sensitivity of ecosystem carbon exchange to seasonal precipitation and woody plant encroachment. Oecologia 150(3): 453-463.
Santanello, Jr., J.A., Peters-Lidard, C.D., Garcia, M.E., Mocko, D.M., Tischler, M.A., Moran, M.S., Thoma, D.P. 2007. Using Remotely-Sensed Estimates of Soil Moisture to Infer Soil Texture and Hydraulic Properties across a Semi-arid Watershed. Remote Sensing of Environment. 110:79-97. doi:10.1016/j.rse.2007.02.007.
Tischler, M., Garcia, M., Peters-Lidard, C., Moran, M.S., Miller, S., Thoma, D., Kumar, S., Geiger, J. 2007. A GIS framework for surface-layer soil moisture estimation combining satellite radar measurements and land surface modeling with soil physical property estimation. J. of Environmental Modeling and Software 22:891-898.