Sure, 90% is an overestimate of the portion of water applied for irrigation that returns as recharge to the groundwater system. However that number is not zero

Sure, 90% is an overestimate of the portion of water applied for irrigation that returns as recharge to the groundwater system. However that number is not zero in the Lower Colorado River basin. I work in groundwater modeling for various clients in the desert southwest, the number we assume for agricultural return flow recharge varies based on crop type and other factors. 90% is an overestimate, 0% is an underestimate