Summary

Water, as limited and necessary a resource for humanity's survival and the development of civilizations, has been and always will be the object of multiple studies. Space and seasonal variables, as well as constantly increasing demands have provoked the interest of engineers specializing in the field of water resource management. Collaboration on a global level, between engineers and other specialists, will improve the use of this increasingly scarce resource.  

An integral instrument for the management of water resources systems is hydrological planning, where the strategic management and usage this systems must be clearly defined. The main objective of this planning is to improve water systems management, and to establish specific guidelines for the utilization of water basins or systems of basins with the goal of mitigating droughts. Droughts and overflows are an inevitable factor in water resources systems, given the unpredictability of time and space on these systems.

In this thesis, a methodology to obtain and evaluate operating rules is presented. The governance of these operating rules is directed at policymakers and the goal is to provide information about how much water a given system is able to deliver to the end users, at the beginning of each agricultural campaign. 

This thesis will focus on specific situations where little water is available, seeking methods for minimizing annual water deficits, while at the same time, managing the likelihood of water deficits throughout the lifecycle of an agricultural campaign.  This planning will allow the establishment of cultivation patterns which consider the adequacy of water resources. Through better water management and planning, unforeseen shortages, which often have serious economic consequences, can be avoided. 

This kind of operation rules, known as hedging rules, allow users a certain guarantee that service during the next campaign is assured and that the probability of water shortages is minimized.

In order to establish these rules and implement a cohesive policy, it is necessary to integrate several tools, such as: synthetic streamflows generating models (Model MASHWIN, [UPV, 2002], SERENA [Ochoa J.C, 2002] modified Svanidze’s model [Arganis J.M., 2004]), techniques of analysis and characterization of droughts (theory of runs, [Guerrero-Salazar and Yevjevich, 1975]), optimization’s models (OptiGes, [Andreu, J.1992]) and simulation models for management of water resources systems (SimGes, [Andreu, J. et to the, 1996]) or similar models.

The integration of these models within the realm of policymaking, places importance on practical management rules which are easily assimilated by different groups of users.  Since reliance on water resources permeates so many different aspects of life, indicators such as the initial stored volume or stored volume plus a certain inflow quickly establish the necessity of a restriction.

The generation of rules consists of four main processes: determination of the best restriction levels for a system, the definition of a specific rule who's function is to activate the restriction, the adjustment of the parameters that define the rules considering the simulation of the system and the evaluation of the management rules. Furthermore, it is important that during the policymaking process many different factors be considered, which would include historical data, an analysis of periods of droughts and studies of flows and of selected droughts during these times.

The case study selected for this analysis is the system "San-Lorenzo-Culiacán-Humaya-Mocorito", located in the northwest of Mexico. It is formed of four reservoirs and three aquifers which supply three watering districts that encompass an area of 325,850 ha, with a total concession volume of 3,185.28 hm³, of which 2945.10 hm³ or 92.45% comes from surface waters (CNA-IMTA, 2000).  This stresses the importance of making an efficient use of the surface waters of the system. Besides the agricultural demands, this system must also supply the urban and industrial centers of Culiacán and Guamúchil and the populations of the San Lorenzo river basin, considering the maximum and minimum hydroelectric volumes of this region.

When applying the methodology three types of operation rules are obtained: 1) function of the volume stored to the beginning of the agricultural year, 2) function of the volume to the beginning of the cycle with review every 6 months, since during each year, two cycles are observed; autumn-winter and spring-summer and; 3) function of the stored volume with an inflow for antecedent contribution which provides information of the possible presence of a drought. If one simulates the system under different scenarios, the following observations can be made: 1) restrictions are applied only in dry seasons, 2) given equal conditions of availability (stored volume and inflows) the incidences of shortages diminish the monthly unforeseen deficit and 3) if droughts occur during the middle or the end of period of analysis they are easier to manage than if they show up at the beginning.