Using remote sensing to evaluate the spatial variability of evapotranspiration and crop coefficient in the lower Rio Grande Valley,New Mexico |
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Authors: | Zohrab Samani A Salim Bawazir Max Bleiweiss Rhonda Skaggs John Longworth Vien D Tran Aldo Pinon |
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Institution: | (1) New Mexico State University, Las Cruces, USA;(2) New Mexico Office of the State Engineer, Las Cruces, USA |
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Abstract: | Pecan is a major crop in the lower Rio Grande Valley (LRGV), New Mexico. Currently, about 11,000 ha of pecan orchards at various
stages of growth are consuming about 40% of irrigation water in the area. Pecan evapotranspiration (ET) varies with age, canopy
cover, soil type and method of water management. There is a need for better quantification of pecan ET for the purpose of
water rights adjudication, watershed management and agronomical practices. This paper describes a process where remote sensing
information from Landsat-5 and Landsat-7 were combined with ground level measurements to estimate pecan ET and field scale
actual crop coefficient (K
c) for the LRGV. The results showed that annual pecan water use for 279 fields ranged from 498 to 1,259 mm with an average
water use of 1,054 mm. For fields with NDVI > 0.6 (normalized difference vegetation index), which represented mature orchards
(total of 232 fields), the annual water use ranged from 771 to 1,259 mm with an average water use of 1,077 mm. The results
from remote sensing model compared reasonably well with ground level ET values determined by an eddy covariance system in
a mature pecan orchard with an average error of 4% and the standard error of estimate (SEE) ranging from 0.91 to 1.06 mm/day.
A small fraction (5%) of the pecan fields were within the range of maximum ET and K
c. |
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Keywords: | |
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