HR: 1330h
AN: H12B-0979    [PDF]
TI: Ground Water Depth and Water use by Phreatophyte Communities During Drought
AU: * Thibault, J R
EM: jrtebo@sevilleta.unm.edu
AF: Department of Biology, MSC 03 2020, 1 University of New Mexico, Albuquerque, NM 87131-0001 United States
AU: Cleverly, J R
EM: cleverly@sevilleta.unm.edu
AF: Department of Biology, MSC 03 2020, 1 University of New Mexico, Albuquerque, NM 87131-0001 United States
AU: Dahm, C N
EM: cdahm@sevilleta.unm.edu
AF: Department of Biology, MSC 03 2020, 1 University of New Mexico, Albuquerque, NM 87131-0001 United States
AB: Demand for limited water resources along the middle Rio Grande of New Mexico has been exacerbated by drought in recent years. Since the last wet year in 1999, river flows have been well below normal and ceased in some reaches. Alluvial ground water elevations have declined steadily. Riparian vegetation consists primarily of native cottonwoods and introduced saltcedar, phreatophytes which are commonly groundwater-dependent. We investigated how drought-induced lowering of local water tables affects riparian water use. Since 1999, we have quantified rates of evapotranspiration (ET) and water table (WT) depths at two sites with relatively deep WTs ($>$ 1.5 m) dominated by saltcedar, and since 2000 at two relatively shallow WT sites ($<$ 1.5 m) dominated by cottonwood. Our results indicate that drought conditions and lowered ground water levels do not influence water use in the shallow WT cottonwood forests but do appear to limit water use in deeper WT saltcedar stands, particularly where seasonal WT fluctuations are large. As facultative phreatophytes, saltcedars are more flexible in their use of water resources. It is unlikely cottonwoods could compete effectively with saltcedars in sites characterized by relatively deep groundwater and dynamic WT hydrographs. Restoration efforts along the middle Rio Grande, such as cottonwood planting, saltcedar thinning, and managed flooding must plan for drought. Restoration will likely be more successful in more stable, shallow WT environments, where cottonwood forests are able to sustain access to water resources during drought.
DE: 1812 Drought
DE: 1818 Evapotranspiration
SC: Hydrology [H]
MN: 2003 Fall Meeting