## 2 Data and Methods
### Methods  
#### 2.3.1 PT-JPL Model  
For the inland surface of the basin, the PT-JPL model was used to estimate the actual evapotranspiration (ETa) per pixel (raster). The PT-JPL model (Priestley-Taylor Jet Propulsion Laboratory Model) is an actual evapotranspiration estimation model developed by [PERSON], [PERSON] [25] based on the Priestley-Taylor equation, which can be divided into soil evaporation (ETs), canopy interception evaporation (ETi) and vegetation transpiration (ETc). The model is driven by remote sensing data and meteorological data and is suitable for situations where soil moisture data, surface impedance data, and wind speed data are lacking. The model equations and parameters are shown in Table 1.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameter** & **Description** & **Equation** & **Unit/** & \\  & & **Value Range** & \\ \hline ETa & Actual evapotranspiration & ETa = (Ev + Es + Ei)/ & mm & [34] \\ ETc & Vegetation transpiration & Ev = (1 - fwet)fgff1m & W/m2 & [25] \\ ETs & Soil evaporation & Es = (fwet + fsm(1 - fwet)) & W/m2 & [25] \\ ETi & Canopy interception evaporation & Ei = fwet & W/m2 & [25] \\ Rns & Net radiation reaching the & Rns = exp(-kRnLAI) & W/m2 & [35] \\  & soil surface & & \\ Rnc & Net radiation intercepted by & Rnc = Rn - Rn & W/m2 & [35] \\ Rnc & the canopy & & \\ G & Soil heat flux & G = Rn[Tc + (1 - Fc)(Ts - Tc)] & W/m2 & [35] \\ Fwet & Relative surface humidity & fwet = RH4 & 0–1 & [25] \\ Fg & Proportion of green canopy & fg = fblack & 0–1 & [25] \\ Ft & Temperature limiting factor & f1 = exp (- & 0–1 & [25] \\ Fm & Water limiting factor & fm = & 0–1 & [36] \\ Fsm & Soil moisture limiting factor & fsm = RHD/g & 0–1 & [25] \\  & Canopy absorption PAR & fAPAR & fAPAR = m1 EVI + b1 & 0–1 & [36] \\ FiPAR & Conopy intercept PAR coefficient & fIPAR = m2 NDVI + b2 & 0–0.95 & [36] \\ Fc & Vegetation coverage & & 0–1 & [35] \\ \hline \hline \end{tabular} Note: \(\lambda\) is the latent heat of evaporation, taken as 2.45 MJ/kg; \(\alpha\) is the Priestley–Taylor model coefficient, taken as 1.26; \(\gamma\) is the psychrometric constant, kPa/\({}^{\circ}\)C, taken as 0.066; \(\Delta\) is temperature-saturated water vapor pressure slope, kPa/\({}^{\circ}\)C; parameters m1 = 1.2, b1 = 0; m2 = 1.0, b2 = \(-\)0.05 [36]; EVI is enhanced vegetation index; NDVI is normalized vegetation index; \(\delta\) is the sensitivity of fsm = RHD/g. Kn is the extinction coefficient, valued at 0.6, RH is the relative humidity, % Topi is the optimum growth temperature of vegetation, \({}^{\circ}\)C, which is the average temperature of the basin in the multiyear growing season; Tmax is the maximum temperature, \({}^{\circ}\)C; D is the saturated water vapor pressure difference, kPa; parameter \(\delta\) value: shrub \(\delta\) = 0.2; fall \(\delta\) = 0.8; broad-leaved forest: \(\beta\) = 0.5; coiferous forest: \(\beta\) = 1; tropical rainforest: \(\beta\) = 0.1; typical grassland: \(\delta\) = 0.4; mixed forest: \(\beta\) = 0.2; meadow: \(\beta\) = 0.2; ice: \(\beta\) = 0.2; dyland farmland: \(\beta\) = 0.6; wetland: \(\beta\) = 0.8; town: \(\beta\) = 1 [35].  
\end{table}
Table 1: Model equations and parameters.