American Society of Civil Engineers


Impact of Shallow Groundwater on Evapotranspiration Losses from Uncultivated Land in an Irrigated River Valley


by Jeffrey D. Niemann, (corresponding author), M.ASCE, (Associate Professor, Dept. of Civil and Environmental Engineering, Colorado State Univ., Campus Delivery 1372, Fort Collins, CO 80523-1372 E-mail: jniemann@engr.colostate.edu), Brandon M. Lehman, (Master of Science Candidate, Dept. of Civil and Environmental Engineering, Colorado State Univ., Fort Collins, CO, 80523-1372.), Timothy K. Gates, M.ASCE, (Professor, Dept. of Civil and Environmental Engineering, Colorado State Univ., Campus Delivery 1372, Fort Collins, CO 80523-1372.), Niklas U. Hallberg, (Civil Engineer, U.S. Army Corps of Engineers, 109 St. Joseph St., Mobile, AL 36602.), and Aymn Elhaddad, (Research Scientist, Dept. of Civil and Environmental Engineering, Colorado State Univ., Fort Collins, CO 80523-1372.)

Journal of Irrigation and Drainage Engineering, Vol. 137, No. 8, August 2011, pp. 501-512, (doi:  http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0000356)

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Document type: Journal Paper
Abstract: In many agricultural regions of the West, decades of intensive irrigation have produced shallow water tables under not only cultivated fields but also the nearby uncultivated land. It is possible that the high water tables under the uncultivated lands are substantially increasing evapotranspiration (ET) rates, which would represent an unnatural and potentially nonbeneficial consumptive use. The objective of this paper is to quantify loss of water that occurs from uncultivated lands in a semiarid irrigated river valley (the Lower Arkansas River Valley in southeastern Colorado). A remote-sensing algorithm is used to estimate actual ET rates on 16 dates on the basis of Landsat satellite images. On the same dates, water table depths, soil moisture values, and soil water salinities are measured at up to 84 wells distributed across three study sites. On the basis of a water balance of the root zone, it is estimated that 78% of the ET is supplied by groundwater upflux at these sites. It is also observed that the ET and groundwater upflux decrease with increasing water table depth. A regression analysis indicates that the spatial variations in ET are most closely related to variations in vegetation-related attributes, whereas soil moisture and water table depths also explain substantial amounts of the variation. Valley-wide implications for reducing nonbeneficial ET through water table control also are discussed.


ASCE Subject Headings:
Evapotranspiration
Groundwater
Alluvium
Conservation
Colorado
Water loss
Irrigation

Author Keywords:
Evapotranspiration
Groundwater
Alluvium
Conservation
Colorado