where Dr,i refers to the cumulative water depletion depth for day i, and it is estimated from soil water balance, see Eq. (1). s is the total available water in the root zone, which is the target parameter to be estimated by the optimization procedure proposed in this work. Readily available water (q) is the amount of water that can be used by a given canopy without the reduction of transpiration and is related to s by the parameter ps.