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Return to Archive/SALSA DocumentsPurpose
Cooperative hydrologic investigations and monitoring efforts, conducted by the USDA Agricultural Research Service (ARS), Bureau of Land Management (BLM), United States Geological Survey (USGS), Arizona Department of Water Resources (ADWR), Cochise County Flood Control District, and the University of Arizona (UofA), are attempting to quantify and characterize major hydrologic fluxes and processes in the upper San Pedro Basin including evapotranspiration in the riparian corridor and stream/aquifer interactions. The objectives of these studies are to:
1) quantify evapotranspiration, on a seasonal basis, from mesquite, sacaton, and cottonwood/willow vegetation communities in the Lewis Springs, Little Boquillas, and Escapule Wash study sites in the San Pedro Riparian National Conservation Area (SPRNCA); 2) identify sources of waters subject to evapotranspiration at several seasons and for several riparian vegetation communities; 3) measure evapotranspiration effects on streamflow, and water levels in the flood plain and regional aquifers in the Lewis Springs study site; and 4) investigate the relationships and water movement between the river, flood plain aquifer and regional aquifer systems. Need
The BLM manages the SPRNCA in southeastern Arizona to protect the riparian ecosystem and the related values found in this area. These values are closely associated with the presence of shallow groundwater and perennial streamflow. Successful management of the conservation area requires a thorough understanding of the hydrologic system and the factors that influence it. The ADWR's Hydrologic Survey Report (1991) identified evapotranspiration from the riparian area as one of the largest components of the water budget of the upper basin, estimated at about 14,450 acre feet per year. Understanding the hydrologic processes that define the relationships between evapotranspiration, streamflow, and groundwater flow is of critical importance if we are to understand the ecological effects of water resource management decisions in the SPRNCA. Better characterization of the rates and quantities of water movement between the river and aquifer systems are of interest to federal, state, and local government land managers, as well as private landowners.
Description Of Research
The study is a coordinated hydrologic investigation that will quantify the effects of evapotranspiration and characterize the relationship between streamflow and the flood plain and regional aquifers in the Lewis Springs study site. Meteorological towers, piezometers (monitoring wells), soil moisture probes, and other equipment have already been installed at the study sites. Satellite and airborne remote sensing data will supplement the field measurements to help extrapolate the results over a broader area. The results from this study will directly and more accurately quantify evapotranspiration and source waters being transpired on a daily, seasonal, and annual basis. This information will be used in model calibration, testing and refinement, as well as to assist water resource management decisions.
The research is being conducted under the auspices of the ARS's Semi-Arid Land-Surface-Atmosphere (SALSA) Program, a multi-disciplinary, multi-agency effort to monitor and model hydrological and ecological processes in semi-arid regions. Other agencies cooperating in the San Pedro riparian study (in addition to those mentioned above) include the ARS Water Conservation Laboratory (Phoenix), ARS Remote Sensing Research Unit (Texas), ARS Hydrology Laboratory (Maryland), US Army-Fort Huachuca, Jet Propulsion Laboratory, Los Alamos National Laboratory, and US EPA (Nevada). SALSA emphasizes "participatory science," and includes students and volunteers in the research effort. To date, over 60 students and volunteers, representing the University of Arizona, Cochise County, City of Sierra Vista, Huachuca Audubon Society, and the Friends of the San Pedro, or simply acting on their own, have contributed hundreds of hours to the project and, in the process, have helped educate the community about water resources issues within the San Pedro River watershed.
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