Comparison of sap flux, moisture flux tower and MODIS Enhanced Vegetation Index methods for estimating riparian evapotranspiration

Pamela L. Nagler, Edward P. Glenn, Kiyomi Morino

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Riparian evapotranspiration (ET) was measured on a salt cedar (Tamarix spp.) dominated river terrace on the Lower Colorado River from 2007 to 2009 using tissue-heat-balance sap flux sensors at six sites representing very dense, medium dense, and sparse stands of plants. Salt cedar ET varied markedly across sites, and sap flux sensors showed that plants were subject to various degrees of stress, detected as mid-day depression of transpiration and stomatal conductance. Sap flux results were scaled from the leaf level of measurement to the stand level by measuring plant-specific leaf area index and fractional ground cover at each site. Results were compared to Bowen ratio moisture tower data available for three of the sites. Sap flux sensors and flux tower results ranked the sites the same and had similar estimates of ET. A regression equation, relating measured ET of salt cedar and other riparian plants and crops on the Lower Colorado River to the Enhanced Vegetation Index from the MODIS sensor on the Terra satellite and reference crop ET measured at meteorological stations, was able to predict actual ET with an accuracy or uncertainty of about 20%, despite between-site differences for salt cedar. Peak summer salt cedar ET averaged about 6 mm d-1 across sites and methods of measurement.

Original languageEnglish (US)
Title of host publicationRemote Sensing and Hydrology
Number of pages4
StatePublished - 2012
EventRemote Sensing and Hydrology Symposium - Jackson Hole, WY, United States
Duration: Sep 27 2010Sep 30 2010

Publication series

NameIAHS-AISH Publication
ISSN (Print)0144-7815


OtherRemote Sensing and Hydrology Symposium
Country/TerritoryUnited States
CityJackson Hole, WY


  • Colorado River
  • Groundwater
  • Invasive species
  • Tamarix

ASJC Scopus subject areas

  • General Earth and Planetary Sciences

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