|Scott, R. - UNIV. OF ARIZ.|
|Shuttleworth, W. - UNIV. OF ARIZ.|
Submitted to: American Meteorological Society
Publication Type: Proceedings
Publication Acceptance Date: January 21, 1998
Publication Date: N/A
Interpretive Summary: For many of the human settlements in the Southwest, groundwater from regional aquifers has become the largest single source of fresh water for human communities. This reliance on groundwater has led to a large effort to further our understanding of the water balance of these large regional groundwater systems. In the basin and range physiographic province of the Southwest the main natural inlet and outlet of the underlying groundwater systems are mountain front recharge and riparian zone recharge/discharge areas. The Upper San Pedro River Basin in southeastern Arizona and northern Sonora, Mexico is an ideal area in which to investigate these poorly understood processes of regional aquifer water balance. A critical component of this water balance is amount of water used by the sacaton grass and a mixed grass/mesquite community within the San Pedro riparian system. Numerous observations indicate that these plants are deep rooted; thus, they have been thought to rely mainly on water taken up from the near-surface water table when they exist in riparian corridors. An experiment was conducted to measure the amount of water used by both of these communities over several seasons. Early results suggest that the vegetation is less of a groundwater user than previously assumed.
Technical Abstract: The work described in this paper is focused on the water use of a sacaton grass flood plain and a mixed grass/mesquite community. These two types of vegetation communities are often associated with riparian areas across the Southwest. Numerous observations indicate that these plants are deep rooted; thus, they have been thought to rely mainly on water taken up from the near-surface water table when they exist in riparian corridors. Curren basin aquifer modeling studies often rely upon coarse, empirical estimates of riparian corridor evapotranspiration (ET), to validate their modeling calibrations. Such estimates of ET are often based on indirect measurements taken elsewhere and then extrapolated (in this case) to the San Pedro Basin using local meteorological information. In this study we employ micrometeorological techniques to measure the fluxes of water and energy in both of these communities over several seasons. Early results suggest that strength of the vegetation water demand (for these two vegetation types) in this area is not as high as previously estimated, and the vegetation is less of a groundwater user than previously assumed.