## 2 Materials and Methods
### Water Demand  
Water demand was assumed to be equal to the actual evapotranspiration lumped at the field scale. In this study, we compare the results of two remote sensing-based evapotranspiration algorithms, i.e., CMRSET [51] and ETLook [37], both using the Sentinel-2 collection [51]. For the CMRSET algorithm, we assumed a similar wavelength range between Sentinel 2 and the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors, as the CMRSET methodology was developed and validated based on MODIS surface reflectance data. Thus, the crop coefficient (Kc) was calculated as:  
\[K_{c}=K_{c\ max}\ \Big{(}1-exp\Big{(}-a\times EVI_{r}^{a}-b\times RMI^{b} \Big{)}\Big{)} \tag{1}\]  
where \(K_{c}\) max, \(a\), \(a\), \(b\), \(\beta\) are parameters empirically calibrated for Australia and are 0.68, 14.12, 2.482, \(-\)7.991, and 0.89. In this case, \(EVI_{r}\) corresponds to the rescaled Enhanced Vegetation Index (\(EVI\)), where \(EVI\) was calculated based on:  
\[EVI=G\times\frac{\rho_{NIR}-\rho_{Red}}{\rho_{NIR}+C1\times\rho_{Red}-C2 \times\rho_{Blue}+L} \tag{2}\]  
In Equation (2), \(\rho_{NIR}\), \(\rho_{Rat}\), and \(\rho_{Blue}\) are the reflectances in the near-infrared, red, and blue wavelength spectrum, while \(G\) and \(L\) are the gain factor and a canopy background set to 2.5 and 1, respectively. \(EVI_{r}\) was then calculated by clipping \(EVI\) to a minimum of 0 and a maximum of 0.9. The \(RMI\) or Residual Moisture Index is a similar scaled index truncated at 0 and 1, and was calculated by first calculating:  
\[RMI=GVMI-(K_{RMI}\times EVI+C_{RMI}) \tag{3}\]  
where \(K_{RMI}\) and \(C_{RMI}\) parameters have been calibrated in Australia, and correspond to 0.775 and \(-\)0.0757, respectively. \(GVMI\) is the Global Vegetation Moisture Index, which can be calculated as:  
\[GVMI=\frac{(\rho_{NIR}+0.1)-(\rho_{SWIR2}+0.02)}{(\rho_{NIR}+0.1)+(\rho_{SWIR 2}+0.02)} \tag{4}\]  
where \(\rho_{SWIR2}\) is the reflectance for the shortwave infrared wavelength of the spectrum. The actual evapotranspiration (\(AET\)) was then calculated using the FAO56 methodology [52]:  
\[AET=ET_{r}\times K_{c} \tag{5}\]  
And \(ET_{r}\) is the reference evapotranspiration calculated using the FAO Penman-Monteith equation [52]:  
\[ET_{r}=\frac{0.408\Delta(R_{n}-G)+\gamma\frac{C_{n}}{T+273}u_{2}(e_{s}-e_{a})} {\Delta+\gamma(1+C_{d}u_{2})} \tag{6}\]  
where \(R_{n}\) is the net radiation, G is the soil heat flux, \(\Delta\) the saturation vapor pressure-temperature slope, \(u_{2}\) the mean wind speed measured at 2 m, \(T\) the mean daily temperature, \(\gamma\) corresponds to the psychrometric constant, \(e_{s}\) to the saturation vapor pressure, \(e_{a}\) the actual pressure vapor, while \(C_{d}\) and \(C_{n}\) are constants for standard short crops, equivalent to 0.34 and 900, respectively. The second approach was to use the ETLook algorithm to calculate the \(AET\). This algorithm is based on the energy budget equation [37]:  
\[R_{n}-G=\lambda E+H \tag{7}\]  
In this budget, \(\lambda E\) is the latent heat flux and H is the sensitive heat flux. In the ETLook algorithm, evapotranspiration is split into the evaporation component:  
\[E=\frac{\Delta(R_{n,\ soil}-G)+\rho c_{p}\Big{(}\frac{\Delta_{c}}{r_{s,\ soil}} \Big{)}}{\Delta+\gamma\Big{(}1+\frac{r_{\ soil}}{r_{s,\ soil}}\Big{)}} \tag{8}\]  
and the transpiration component:  
\[T=\frac{\Delta\big{(}R_{n,\ canopy}-G\big{)}+\rho c_{p}\Big{(}\frac{\Delta_{c} }{r_{s,\ canopy}}\Big{)}}{\Delta+\gamma\Big{(}1+\frac{r_{\ canopy}}{r_{s,\ canopy}} \Big{)}} \tag{9}\]  
both following typical Penman Monteith descriptions. Here, \(\rho\) is the air density and \(C_{p}\) the specific heat or dry air, with radiation inputs for soil (\(R_{n,soil}\)) and canopy (\(R_{n,canopy}\)), and resistances for soil (\(r_{soil}\)) and canopy (\(r_{canopy}\)), and associated aerodynamic resistances for soil (\(r_{a,soil}\)) and canopy (\(r_{a,canopy}\)). The meteorological data necessary to derive these parameters were acquired from the Goddard Earth Observing System (GEOS) [53].