A water allocation indicator for hydrographic basins

Abstract

Water is fundamental to the development of life and the environment, becoming its stress and scarcity severe problems worldwide. Chile is among the top thirty countries under hydric risk. Based on the global and country situation, there is a need to solve the hydric resource allocation problem and to have a broader concept of protecting the resource. This work creates a vectorial water allocation indicator (VWAI), which assesses how much the hydric resource allocation in a basin is fair or equitable. The indicator is tested in a case study to assess the current situation and how it can be improved through an optimization problem. The first step is to define a Water Accounting System (WAS) for the main water uses in Chile. Eight uses are defined and classified into consumptive and non-consumptive use. The WAS comprises three categories: consumptive uses, non-consumptive uses, and pollution of both uses. The first determines the water supply for a specific activity, the second quantifies how much water is used in the process, and the last determines the water pollution caused by each use. The VWAI definition depends on two WAS: one indicates an ideal context, and the another indicates the current context. The vectorial indicator is a comparison through the deviation, which aims to show the basin state regarding the water requirements and contamination caused. This structure allows the assessment and gauging of how close or far the current context is from the desired one, facilitating decision-making for involved entities. The indicator is three-dimensional, and its components are the same as for the WAS: a) consumptive uses, in which the evaluation is about the demand fulfillment, determining if a use is under-supplied or over-supplied; b) non-consumptive uses, in which the evaluation is about the water requirements difference; and finally, c) it assessment of the pollution caused in both uses. The assessment is about how much the current case has reduced the pollution regarding a base case (previous year). The Food and Agriculture Organization developed the concept of water tenure to refer to a water assignment instead of rights. The tenure concept is more general than the water rights concept by including the understanding and determining of how society relates to water and natural resources. This work analyzes the indicator results and how they can improve the allocation with a water tenure perspective, aiming to protect and preserve the water resource. The indicator shows where the allocation issues prevail and works as a base for analyzing water allocation, the social, economic, and environmental consequences, and the advantages and disadvantages of the allocation. Finally, this thesis presents recommendations to improve the indicator, have a better basin status approach, and globalize it to make it adaptable to any country.