Multiyear riparian evapotranspiration and groundwater use for a semiarid watershed

Riparian evapotranspiration (ET) is a major component of the surface and subsurface water balance for many semiarid watersheds. Measurement or model-based estimates of ET are often made on a local scale, but spatially distributed estimates are needed to determine ET over catchments. In this paper, we document the ET that was quantified over 3 years using eddy covariance for three riparian ecosystems along the Upper San Pedro River of southeastern Arizona, USA, and we use a water balance equation to determine annual groundwater use. Riparian evapotranspiration and groundwater use for the watershed were then determined by using a calibrated, empirical model that uses 16-day, 250–1000 m remotesensing products for the years of 2001–2005. The inputs for the model were derived entirely from the NASA MODIS sensor and consisted of the Enhanced Vegetation Index and land surface temperature. The scaling model was validated using subsets of the entire dataset (omitting different sites or years) and its capable performance for well-watered sites (MAD ¼ 0.32 mm day � 1 , R 2 ¼ 0.93) gave us confidence in using it to determine ET over the watershed. Three years of eddy covariance data for the riparian sites reveal that ET and groundwater use increased as woody plant density increased. Groundwater use was less variable at the woodland site, which had the greatest density of phreatophytes. Annual riparian groundwater use within the watershed was nearly constant over the study period despite an on-going drought. For the San Pedro alone, the amounts determined in this paper are within the range of most recently reported values that were derived using an entirely different approach. However, because of our larger estimates for groundwater use for the main tributary of the San Pedro, the watershed totals were higher. The approach presented here can provide riparian ET and groundwater use amounts that reflect real natural variability in phreatophyte withdrawals and improve the accuracy of a watershed’s water budget. r 2008 Elsevier Ltd. All rights reserved.

[1]  J. Cleverly,et al.  Evapotranspiration at the land/water interface in a semi‐arid drainage basin , 2002 .

[2]  W. Oechel,et al.  Energy balance closure at FLUXNET sites , 2002 .

[3]  D. Goodrich,et al.  Sensitivity of riparian ecosystems in arid and semiarid environments to moisture pulses , 2006 .

[4]  D. Goodrich,et al.  Hydrologic requirements of and consumptive ground-water use by riparian vegetation along the San Pedro River, Arizona. Chapters A-D. , 2006 .

[5]  Craig L. Westenburg,et al.  Evapotranspiration by phreatophytes along the lower Colorado River at Havasu National Wildlife Refuge, Arizona , 2006 .

[6]  N. U. Ahmed,et al.  Relations between evaporation coefficients and vegetation indices studied by model simulations , 1994 .

[7]  W. J. Shuttleworth,et al.  Interannual and seasonal variation in fluxes of water and carbon dioxide from a riparian woodland ecosystem , 2004 .

[8]  David C. Goodrich,et al.  Transpiration of cottonwood/willow forest estimated from sap flux , 2000 .

[9]  William P. Kustas,et al.  Utility of Radiometric–aerodynamic Temperature Relations for Heat Flux Estimation , 2007 .

[10]  A. Huete,et al.  Overview of the radiometric and biophysical performance of the MODIS vegetation indices , 2002 .

[11]  Carl Steinitz,et al.  Alternative Futures for Changing Landscapes: The Upper San Pedro River Basin In Arizona And Sonora , 2003 .

[12]  Yann Kerr,et al.  Seasonal estimates of riparian evapotranspiration using remote and in situ measurements. , 2000 .

[13]  Wim G.M. Bastiaanssen,et al.  Satellite surveillance of evaporative depletion across the Indus Basin , 2002 .

[14]  David C. Goodrich,et al.  Upper San Pedro Basin: fostering collaborative binational watershed management , 2004 .

[15]  D. Goodrich,et al.  Ecohydrological impacts of woody‐plant encroachment: seasonal patterns of water and carbon dioxide exchange within a semiarid riparian environment , 2006 .

[16]  D. C. Goodrich,et al.  The sensitivity of ecosystem carbon exchange to seasonal precipitation and woody plant encroachment , 2006, Oecologia.

[17]  W. J. Shuttleworth,et al.  The understory and overstory partitioning of energy and water fluxes in an open canopy, semiarid woodland , 2003 .

[18]  Pamela L. Nagler,et al.  Predicting riparian evapotranspiration from MODIS vegetation indices and meteorological data , 2005 .

[19]  W. J. Shuttleworth,et al.  The water use of two dominant vegetation communities in a semiarid riparian ecosystem , 2000 .

[20]  Pamela L. Nagler,et al.  Evapotranspiration on western U.S. rivers estimated using the Enhanced Vegetation Index from MODIS and data from eddy covariance and Bowen ratio flux towers , 2005 .

[21]  Andrew E. Suyker,et al.  Gap filling strategies for long term energy flux data sets , 2001 .

[22]  A. John Mallinckrodt,et al.  Data Reduction and Error Analysis for the Physical Sciences , 1993 .

[23]  David R. Maidment,et al.  Handbook of Hydrology , 1993 .

[24]  W. Kustas,et al.  A verification of the 'triangle' method for obtaining surface soil water content and energy fluxes from remote measurements of the Normalized Difference Vegetation Index (NDVI) and surface e , 1997 .

[25]  C. Campbell,et al.  Perpetual Succession of Stream-Channel Vegetation in a Semiarid Region , 1968 .

[26]  W. Kustas,et al.  Impact of Using Different Time-Averaged Inputs for Estimating Sensible Heat Flux of Riparian Vegetation Using Radiometric Surface Temperature , 2002 .

[27]  P. W. Scott,et al.  Evaporation from a riparian system in a semi-arid environment , 1998 .

[28]  J. Cleverly,et al.  Seasonal estimates of actual evapo-transpiration from Tamarix ramosissima stands using three-dimensional eddy covariance , 2002 .

[29]  James Cleverly,et al.  Bowen Ratio estimates of evapotranspiration for Tamarix ramosissima stands on the Virgin River in southern Nevada , 1998 .

[30]  Robert R. Gillies,et al.  A new look at the simplified method for remote sensing of daily evapotranspiration , 1995 .

[31]  D. Devitt,et al.  A REEVALUATION OF THE GROUND WATER BUDGET FOR LAS VEGAS VALLEY, NEVADA, WITH EMPHASIS ON GROUND WATER DISCHARGE 1 , 2002 .

[32]  J. Norman,et al.  Correcting eddy-covariance flux underestimates over a grassland , 2000 .

[33]  D. Or,et al.  Water balance for Great Basin phreatophytes derived from eddy covariance, soil water, and water table measurements , 2006 .

[34]  S. Sorooshian,et al.  A Shuffled Complex Evolution Metropolis algorithm for optimization and uncertainty assessment of hydrologic model parameters , 2002 .

[35]  Steven P. Loheide,et al.  A local-scale, high-resolution evapotranspiration mapping algorithm (ETMA) with hydroecological applications at riparian meadow restoration sites , 2005 .

[36]  R. Gillies.  A verification of the 'triangle' method for obtaining surface water content and energy fluxes from remote measurements of Normalized Difference Vegetation Index (NDVI) and surface radiant temperature , 1997 .

[37]  G. C. Lines,et al.  Riparian vegetation and its water use during 1995 along the Mojave River, Southern California , 1996 .

[38]  P. R. Bevington,et al.  Data Reduction and Error Analysis for the Physical Sciences , 1969 .

[39]  David C. Goodrich,et al.  Controls on transpiration in a semiarid riparian cottonwood forest , 2006 .

[40]  M. S. Moran,et al.  Estimating crop water deficit using the relation between surface-air temperature and spectral vegetation index , 1994 .