PARENT SESSION
Oral Session #70: Riparian Ecology. Presiding: R. Cosgriff.
Thursday, August 9, 2001. 1:00 PM to 4:45 PM. Hall of Ideas I.

Middle Rio Grande riparian evapotranspiration, water balance, and restoration in space and time.

CLEVERLY, JAMES¹, THIBAULT, JAMES¹, GILROY, DAVID¹, ALLRED COONROD, JULIE¹, DAHM, CLIFFORD¹, ¹

ABSTRACT- Restoration of natural cottonwood-willow communities along the Middle Rio Grande may be achieved through removal of invasive Tamarix ramosissima and re-establishment of the flood pulse. As water resources become more scarce in the basin, the presumed water savings from restoration efforts may spell their political success or failure. This study uses 3-dimensional eddy covariance methods to quantify the actual evapotranspiration (ET) from native and invaded forests. Measurements of ET were compared at various temporal and spatial scales, with the objective of determining both the pattern and process of water loss to the atmosphere. ET over both T. ramosissima and Populus deltoides ssp. wislizenii forests was closely correlated to leaf area index (LAI) but not to groundwater depth during 2000. Daily average ET over a high LAI T. ramosissima stand was 4.25 mm day^-1, the same as over a combined P. deltoides-T. ramosissima-Elaeagnus angustifolia mixed forest of the same LAI. ET over a non-invaded P. deltoides forest was only 3.5 mm day^-1. The P. deltoides forest that experiences regular spring flooding has a less developed understory of invasive species and lower ET rate, suggesting P. deltoides is able to supress the development of an understory under normal flooding conditions. Restoration of both the native forests and the flood pulse is expected to be related to a savings in the water budget of this dry region.

KEY WORDS: Tamarix ramosissima, Populus deltoides ssp wislizenii, evapotranspiration, flood pulse