2012 AGU Chapman Conference on Remote Sensing of the ...

model was used to demonstrate that both the channelnetwork (including the connectivity provided by floodplainchannels) and floodplain storage are necessary to simulatethe correct wave propagation. The calibration of the sub-gridchannel model from the available remotely sensed data setsand prospects for assimilating data with the model on ungaugedrivers were also evaluated.Neale, Christopher M.Water balance of Large Irrigation Systems usingRemotely Sensed ET EstimatesNeale, Christopher M. 1 ; Taghvaeian, Saleh 1 ; Geli, Hatim 11. Civil and Environmental Eng., Utah State University,Logan, UT, USADemand for water for urban/municipal uses continuesto rise in the Western US with the growing population. Mostfresh water is tied up in irrigated agriculture thusunderstanding the pathways of irrigation water and theconsumptive use of water within large irrigation systemsbecomes of vital importance for improved rivermanagement, policy decisions and water transfers. In thispaper we examine the use of different remote sensingmethods for estimating evapotranspiration (ET), namely theenergy balance method and the reflectance-based cropcoefficient method for estimating seasonal ET at the PaloVerde Irrigation District (PVID) in southern, CA. Two energybalance methods are tested, namely the Two-source model by(Norman et al., 1995) and the Surface Energy Balance forLand (SEBAL) method (Bastiaansen et al., 1998). Thereflectance-based crop coefficient method as originallydescribed by Neale et al, 1989, Bausch and Neale, 1987 is alsoapplied. The PVID system diverts water from the ColoradoRiver through an extensive network of canals. Water flowmeasurements are conducted in the inflow to the system aswell as the main outflow drain and all spill locations at theend of lateral canals, allowing a complete water balance to beestimated for this 53000 ha irrigation system. An extensivenetwork of groundwater wells allowed for the monitoring ofdeep percolation and drainage. We close the yearly waterbalance using estimates of ET from the different remotesensing based models. Daily ET values from the differentmodels are compared to Bowen ratio and eddy covariance ETmeasurements from towers placed in alfalfa and cottonrespectively. The PVID is located in the overlap zone betweentwo Landsat TM paths, which resulted in 21 usable imagesduring 2008 (Taghvaeian, 2011) and allowed for a detailedexamination of seasonal ET by the different models.Nearing, GreyEstimating Thermal Inertia with a MaximumEntropy Production Boundary ConditionNearing, Grey 1 ; Moran, Susan 2 ; Scott, Russell 21. Hydrology and Water Resources, University of Arizona,Tucson, AZ, USA2. Southwest Watershed Research Center, USDA-ARS,Tucson, AZ, USAThermal inertia, P [Jm-2s-1/2K-1], is a physical propertythe land surface which determines resistance to temperaturechange under seasonal or diurnal heating. It is a function ofvolumetric heat capacity, c [Jm-3K-1], and thermalconductivity, k [Wm-1K-1] of the soil near the surface:P=ck. Thermal inertia of soil varies with moisture contentdue the difference between thermal properties of water andair, and a number of studies have demonstrated that it isfeasible to estimate soil moisture given thermal inertia (e.g.Lu et al, 2009). One common approach to estimatingthermal inertia using measurements of surface temperatureis to model the Earth’s surface as a 1-dimensionalhomogeneous diffusive half-space and derive surfacetemperature as a function of the ground heat flux (G)boundary condition and thermal inertia; a daily value of P isestimated by matching measured and modeled diurnalsurface temperature fluctuations. The difficulty in applyingthis technique is in measuring G, and a number ofapproaches have been suggested (e.g. Xue and Cracknell,1995). We demonstrate that the new maximum entropyproduction (MEP) method for partitioning net radiationinto surface energy fluxes (Wang and Bras, 2011) provides asuperior boundary condition for estimating P. Adding thediffusion representation of heat transfer in the soil reducesthe number of free parameters in the MEP model from twoto one, and we provide a sensitivity analysis which suggests,for the purpose of estimating P, that it is preferable toparameterize the MEP model by the ratio of thermal inertiaof the soil to the effective thermal inertia of convective heattransfer to the atmosphere. Estimates of thermal inertia attwo semiarid, non-vegetated locations in the Walnut GulchExperimental Watershed in southeast AZ, USA are madeusing time series of ground heat flux measurements andthese are compared to estimates of thermal inertia madeusing the boundary condition suggested by Xue andCracknell (1995) and those made with the MEP ground heatflux boundary condition. Nash-Sutcliffe efficiencycoefficients for predictions made using the MEP boundarycondition are NSE = 0.44 and NSE = 0.59 at the two sitedcompared to NSE = -12.31 and NSE = -6.81 using the Xueand Cracknell boundary condition. Thermal inertiameasurements made using the MEP boundary condition areextrapolated to daily near-surface soil moisture estimatesusing the model developed by Lu et al (2009). In very dryconditions, thermal inertia is less sensitive to changes in soilmoisture than in moderate-to-wet conditions. Overall wefind the correlation between measured and modeled soilmoisture at these semiarid sites to be approximately 0.5.Lu, S., Ju, Z.Q., Ren, T.S., & Horton, R. (2009). A general110