Multi-criteria decision making techniques for water allocation planning: A case study of Seyhan watershed area

Water is of vital importance to socio-economic development. The world's water resources are deteriorating due to population growth, climate change, global warming and rapidly growing industrialization and urbanization. Increased water demand brought about by rapid population growth has created the necessity to increase food production through the expansion of irrigation and industrial production to meet basic human needs. Therefore, water has become a scarce resource in almost all countries. In response to this, equitable and efficient water allocation policy should be developed to supply the water demands of various competing water-use sectors. These competing sectors are urban water supply, irrigation, industry and ecosystem. Decrease in water storage poses new challenges to water resources managers. Therefore water resource managers apply to new plans and work to ensure a more effective, efficient and sustainable use of available water resources. The water allocation plan, developed by water resources managers, stakeholders, scientists, and water users, involves the potential of water resources (i.e.groundwater and surface water), existing water use, expected future water demand, water requirement for environmental purposes, short and long term planning conditions, drought conditions, and precaution to be taken against these conditions. Additionally, the water allocation plans provide coordinated, planned and sustainable management of natural resources within a river basin. The plans requires coordinated action by various government authorties, because no single authority can have the expertise, experience and legislative powers to be solely responsible for providing sustainable water allocation. The water allocation plan is an acceptable and rational framework for the allocation of the total water resources within the a river basin. The plan tries to mention the inherent stress in a water resource limiting situation between the need to protect the environment and basic human rights of access to the water resources and consumptive use of the resource for economic development. All of thes details, required for water allocation plan, are used for developing different allocation scenarios in consideration of social, economic, and environmental consequences. Water allocation plans should be based on the principle of water resources planning and management that involve all types of interrelated freshwater bodies, and take into consideration water quantity and quality. This plan should improve the efficiency of water utilization among sectors, ensure that all potential water resources are identified and protected in the river basin and prevent contamination of known resources. This plan should also consider inherent linkage of economic and social development via protecting natural ecosystems, surface water and groundwater supplies. In this thesis, a framework that aims to ensure sustainable water sharing among water users has been created in considering the water potential of a river basin. The water allocation plan is established and implemented by 9 key steps. These key steps are described respectively: planning initiation; situation assessment; scenario development and analyses; selection of decision making techniques; identification and assessment of objectives; performance measures and alternative operating rules; elicitation and modelling of preference parameters; results; sensitivity analysis, robustness measures and derivation of optimum operating rules; and suggestion and planning. Consultation and coordination among stakeholders and decision makers are required for preparation of a water allocation plan at various stages in these mentioned planning process. Consultation provides information to assist stakeholders in understanding the problem, alternatives, opportunities and solutions. The main elements of the framework are illustrated on a case study of the Seyhan River Basin allocation system. Seyhan River Basin is located in the east of the Mediterranean Region of the southern Turkey. Seyhan River Basin is one of the most important agricultural regions in Turkey. So, there is a huge irrigation demand. 40% of the land is agricultural land in the Seyhan River Basin. The water allocation plan that has been created in this thesis is applied for the water pontential of Seyhan River Basin in 2015, 2020 and 2030. A detailed technical and scientific evaluation are referred to determine the right balance between water requirements. Objectives are determined for sustainable water allocation plans. The study illustrates how the water users or stakeholder preferences on the multiple objectives related to ecological, economic, environmental and social aspects can be incorporated into the decision analysis of the alternatives. In this research, decision support framework is created to evaluate alternative operating rules taking into consideration of competition between sectors, the demand scenarios, existing water potential and the preferences of stakeholders. The Seyhan water allocation system demonstrates its capabilities for evaluating alternative operating rules under single or group decision-making situations. Nine performance measures (PMs) were identified under four main objectives to evaluate the system performance related to four pre-selected alternative operating rules. The resource allocation model, REALM, provides the values of performeance measures with regard to each operating rule under defined demand and streamflow scenarios. The major groups inculuding water users and resource managers were represented in hypothetical decision making situations. An interview by questionnaire, one of the type of survey, was used to derive performance measures, preference functions and their weights as required by the PROMETHEE, which is a one of the multi-criteria decision making techniques. Finally, an overall ranking for alternative operating rules is obtained. This overall ranking focuses on which alternative operating rules is the best choice for water allocation planning. According to this ranking, reuse of domestic wastewater for irrigation is the best alternative operating rule for Seyhan River Basin. On the other hand, the second alternative operating rule is reducing seepage looses, third one is demand restriction that can be applied by water license, the last one is flood control. The most important result of this research is to evaluate alternative operating rules for water allocation plans and to develop a decision support framework that can be used for the other water allocation plans. In paralel with these purposes, minimizing the negative effects on environment, maximizing the revenue in a river basin, minimizing the costs, maximizing the level of service to water users and maximizing the sustainable water supply are targeted.