1. SUSTAINABLE OPERATION OF THE YAQUI RESERVOIR SYSTEM

2. Yaqui Hydrologic-Agronomic-Economic Model Short-term Model Objective function Multi-objective function Constraints Reservoirs storage constraints Releases constraints Continuity constraints Irrigation constraints Urban use constraints Long-term Model Risk criteria a) Reliability (how likely the system is to fail) b) Vulnerability (how severe the consequences of failure may be) c) Reversibility (how quickly it recovers from failure) Equity criteria

3. Objectives To develop a sustainable reservoirs’ operating policy (a formula for computing the optimal storage capacity in each reservoir) and to determine releases to be made at the beginning of each period, maximizing agricultural net benefits and minimizing the risk of shortages or spills in each reservoir. To explore equity, and risk questions about reliability, reversibility and vulnerability of reservoirs’ storage water under different RMSC and their association to agricultural activities and its economic benefits.

4. Historical Yaqui Reservoir Runoff, 1965-2004

5. The Yaqui System is being Affected for both, Natural (droughts) and Anthropogenic (excessive releases) Causes. October 1 st 2004 1,820 MCM

6. Annual Model Output for the Agricultural Year 2004-2005

7. Crop Pattern and Economic Benefits for the Agricultural Year 2004-2005

8. The Yaqui Basin has been Faced with a Severe Drought (SPI 24 Months) Present drought

11. Real and Simulated Runoff in the Yaqui Basin Real RunoffSimulated Runoff

12. Simulated Runoff from 1965-2019 in the Yaqui Basin

13. Structure of the Long-term Model

14. Ratios of Model’s Planted Area to the Total Irrigable Area and Available Volume at October 1 st. to the Required Volume under Different Pumping Scenarios IAB = Planted area using 600 MCM of pumped water IAWB = Planted area using 370 MCM of pumped water SVB = Storage volume in October 1st. Using 600 MCM of pumped water SVWB = Storage volume in October 1st. Using 370 MCM of pumped water

15. Parameters of Irrigable Area and Reservoir Storage Volume Reliability, Reversibility and Vulnerability under two Pumping Scenarios

16. Changing Rate of Water use Pumping 600 MCM.

17. Changing Rate of Water Use Pumping 370 MCM.

18. Conclusions The short-term model is a tool that can be used in the irrigation district yearly planning process. Sensitivity analysis shows that this model is sensible to economic and hydrologic parameters. The long-term model shows that the irrigated area can be sustained, even during dry periods, but at expenses of the reservoirs’ storage volume, which declines under drought conditions. Excessive releases for agricultural use from the reservoir system will reduce storage volume reliability, making the system more vulnerable, inequitable and increasing the probability to have failure conditions. After the economic analysis we conclude that large increase in irrigated area is not economically efficient, but it has negative consequences in reservoirs’ storage volume because farmers waste water planting no profitable crops.

19. Conclusions Equity analysis shows that irregular annual water allocation can be minimized applying the appropriate operation policies. We can also conclude that there is a relationship between equity and economic efficiency and between reservoirs’ storage volume reliability and irrigated area reliability. We conclude that a sustainable margin of sustainability of at least 2500 MCM should be used in the Yaqui reservoirs’ system, to give more certainty in the planning process. Finally, we conclude that this model can be used to develop the Yaqui river reservoirs’ operation rules.

20. Contribution The short-term model has been used during the planning process of the Irrigation Districts No. 041 and 018, during the Agricultural years 2003-2004 and 2004-2005. The C.N.A is developing the “Water Resources Management Plan under Drought Conditions in the Yaqui Basin” and the long-term model is being used. The Yaqui River reservoir operation rules document developed in this study is being revised by the C.N.A for its application in the Irrigation District N0. 041.

21. Future Research Groundwater allocation for irrigation was assumed as a known value. It is necessary to develop a groundwater model to be operated simultaneously with the reservoirs’ allocation model (surface model) minimizing the possibility of mining underground water reserves. According to the evolution of the modernization of the hydraulic infrastructure, the conveyance and application efficiencies should be actualized for its incorporation in the model. Forecast crops’ prices and costs. Forecast crops’ yields. Future research is required to include other priorities in the objective function (institutional and environmental).

22. Muchas Gracias