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

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...

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Bibliographic Details
Published in:Journal of irrigation and drainage engineering 2011-08, Vol.137 (8), p.501-512
Main Authors: Niemann, Jeffrey D, Lehman, Brandon M, Gates, Timothy K, Hallberg, Niklas U, Elhaddad, Aymn
Format: Article
Language:English
Subjects:
Agricultural and forest climatology and meteorology. Irrigation. Drainage
Agricultural and forest meteorology
Agronomy. Soil science and plant productions
Biological and medical sciences
Evapotranspiration
Freshwater
Fundamental and applied biological sciences. Psychology
General agronomy. Plant production
Groundwater
Irrigation. Drainage
Land
Rivers
Soil moisture
TECHNICAL PAPERS
Valleys
Water balance and requirements. Evapotranspiration
Water table depth
Water tables
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Summary: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.
ISSN:0733-9437
1943-4774
DOI:10.1061/(ASCE)IR.1943-4774.0000356