Development and Application of a Predictive Model for Treated Wastewater Irrigation Management in a Semiarid Area

ABSTRACT The use of treated wastewater (TWW) as an alternative resource to fresh water (FW) for irrigation purposes is becoming increasingly important, especially in semiarid and arid regions. However, achieving success in crop production largely depends on the adoption of appropriate on‐farm management strategies aimed at optimizing crop yields, maintaining soil productivity and safeguarding the environment. For this purpose, predictive models are of particular interest. A safe irrigation management (SIM) model developed and tested in this research was used to schedule irrigation under controlled management tailored to the use of 1) TWW and 2) FW and to reproduce farmers' strategies. These management strategies aim to improve actual irrigation practices, accounting for water quality, soil characteristics, and crop yield. The results of the application of SIM on a citrus farm in Souss‐Massa, Morocco, show that the management strategy adopted by farmers withdraws considerable amounts of water and results in substantial drainage volumes compared to those in the SIM strategy. In the specific case of TWW, the strategy simulated by the SIM model resulted in a decrease in yield of approximately 4%, compared to the 23% decrease derived from the farmers' traditional strategy. Moreover, SIM allowed for great savings in terms of fertilizing elements and for the reduction in the movement of water and salts beyond the root zone, usually considered the main source of groundwater contamination. These results confirm the appropriateness of using prediction models and the accuracy of the SIM model in adapting irrigation strategies to TWW, which will be an integral part of the strategies that encourage their use in irrigated agriculture. Integr Environ Assess Manag 2020;16:910–919. © 2020 SETAC KEY POINTS A model is developed that incorporates subroutines for 1) irrigation scheduling with treated wastewater, accounting for water quality and soil properties and combining water and salt conservation equations, and 2) simulating bacterial movement and assessing the infection risk of exposed farmers. For the first time, accurate irrigation management scenarios are defined that are tailored specifically to the use of treated wastewater on citrus, a strategic crop for Souss‐Massa, Morocco, that is experiencing a growing deficit of water resources. The appropriateness of using accurate prediction models that enable the adaptation of irrigation strategies to treated wastewater (TW