\(GPP=f\left(ET\right)\)                                                                                  (2)
        The above formula reflects the relationship between GPP and ET, which can also be interpreted as water use efficiency (WUE).
        Based on the relationship obtained from the above fitting, when using all of  Wveg for vegetation growth, we were able to calculate the GPP that could be supported.
                                                                    \(GPP'=f\left(Wveg\right)\)                                                                             (3)  
        and the vegetation restoration potential was defined as the ratio of GPP’ to GPP, which was in the percentage form:
                                           \(Restoration\ potential=\frac{GPP'}{GPP}\times100\%\)                                                   (4)