Desalination and Water Treatment | 2021
Comprehensive evaluation of urban water saving based on AHP-TOPSIS
Abstract
1. Research background Water is the source of life, the key to production, and the basis of ecology. With the gradual construction of ecological civilization, water ecology, and water environment have been paid more attention. China’s rapid development in recent decades is at the cost of environmental damage and over-exploitation of resources, including over-exploitation and pollution of water resources. Due to China’s large population and rapid industrial and technological development, China has a huge demand for water, therefore, under these prerequisites and backgrounds, water conservation has become an important goal. It is urgent to construct a water-saving evaluation system to evaluate the current water-saving status and put forward suggestions on the future direction and key points of water-saving. 1.1. Research progress Scholars at home and abroad have done research on the water-saving evaluation system. In 1959, the former China National Construction Commission proposed the city’s water-saving slogan for the first time. New water-saving ideas were put forward by General Secretary Xi in 2014 at the Fifth Meeting of the Central Financial and Economic Leading Group. During this time, in 1989, Zhu made quantitative evaluations of industrial water-saving levels in 18 cities in North China. Xu and Shan [1] made a brief introduction to water-saving agriculture and its physiological and ecological basis. Kang et al. [2] conducted research on water-saving irrigation in farmland. Feng [3–5] summarized and considered the current water-saving work in China. Chen et al. [6] explained the connotation of 203 X. Zhang, T. Liang / Desalination and Water Treatment 213 (2021) 202–213 water-saving society and conducted a preliminary study on the index system of water-saving society. Liu [7] researched and explained the water-saving evaluation of large-scale irrigation areas. Li [8] established an urban watersaving evaluation system based on the most stringent water resources management methods. In the beginning, foreign water-saving evaluations considered economic costs, and then gradually transformed them into holistic ones [9]. For example, Israel’s drip irrigation technology, which mixes water and nutrients by the drip irrigation center, greatly improves the utilization of irrigation water. Horton first proposed a water quality evaluation index system in 1965, the Howden Water Quality Index. Renato and Fibeiro [10] applied neural networks to construct optimal irrigation schemes to achieve water-saving effects in 1998. Tsadilas and Vakalis [11] proposed a long-term model framework for river basin framework and regional development. These studies are aimed [12], to a certain point to water-saving evaluation models for cities, irrigation districts, watersheds, etc., do not take the environment into account in which the evaluation subjects are located. It should be noted that any subject exchanges material energy with the surrounding environment [13–15]. The interaction of water, the most basic substance of nature, with its surroundings should be considered. The scientific evaluation of water-saving management and capacity in a region is an important basis for formulating water-saving development management and policies. In recent years, the comprehensive evaluation of watersaving capacity has developed from qualitative evaluation to quantitative evaluation and from simple main indicators to build an evaluation system to multiple indicators to build a comprehensive evaluation system. Analytic hierarchy process, fuzzy comprehensive evaluation, factor analysis, gray correlation method, etc., have been applied to the comprehensive evaluation of water-saving among them, the analytic hierarchy process is based on the hierarchical structure model and the construction of the judgment matrix to find the eigenvalues to determine the weight of each index factor. The judgment matrix is dominated by the evaluation criteria, and the objectivity of the evaluation criteria is difficult to reflect. Fuzzy comprehensive evaluation needs to construct a complicated membership function for a more complicated water-saving capacity evaluation system. When the factor analysis method processes the normal standardization of indicators, information loss and feature extraction decline will occur. The gray correlation method is based on the results of the correlation and comparison of indicators for objective evaluation, but it cannot reflect the interaction between water-saving management and the objective environment. Technique for order preference by similarity to an ideal solution (TOPSIS) is a new method for solving multi-attribute decision-making problems proposed in recent years. The principle is to sort according to the closeness of the evaluation object to the ideal target. The good value and bad value in the actual sample can be introduced into the final result, which can well reflect the objectivity of each indicator. Therefore, the analytic hierarchy process (AHP) and TOPSIS are combined to construct a water-saving evaluation model, which avoids decision-making errors caused by the one-sidedness of single-factor decisionmaking and differences in human subjective understanding. This can make more scientific and comprehensive judgments, and provide guidance for reality. 1.2. Research purposes The research direction of this article is based on a macro perspective and a large area of human activity, including urban factors, irrigation area factors, and natural environment factors within this area. The main carrier of water conservation assessment is the city. The city and its surrounding water environment are inseparable, interacting, and interdependent. This article explains the concept of the water environment, analyzes the operating mechanism of the water environment to show the interaction between the city and the surrounding environment, and proposes a new concept of the water environment. Through, the coupling of AHP and TOPSIS method, an urban watersaving evaluation model is built for water-saving evaluation of the water environment of Henan Province in the past 10 y. Its water-saving status and future water-saving development trends and priorities are analyzed. 1.3. Water-saving analysis of urban operation The water cycle in nature forms precipitation through evaporation, surface water is then formed, which penetrates into the groundwater and replenishes it. At the same time, during non-rainfall periods, groundwater will replenish surface water. This is the operating mechanism of the water environment in nature. Due to the construction of urban asphalt pavement, and the existence of a large number of concrete buildings. As a result of this, its mechanism is different from the natural water environment operation mechanism. Firstly, urban surface water is dominated by urban water landscape (lakes and rivers in some cities), but water landscapes are generally less, and most water landscapes often have no other water supply except rainwater replenishment. This has caused most water landscapes to consider anti-seepage measures. This has mixed a lot of artificial measures and human factors. At the same time, due to the construction of asphalt pavements and a large number of concrete buildings, the soil surface is hardened, and the water cycle cannot be performed effectively. In normal urban water cycle, surface water (mainly refers to temporary surface water formed by rainfall) is drained underground through the urban pipe network. Therefore, it is often necessary to comprehensively consider the degree of urban pipe network construction and pipe network bearing capacity when a water-saving model is constructed. At the same time, urban operation cannot be separated from economic production, and industrial production. Both of them will consume a lot of water resources. In industrial production, it is measured by the water consumption per unit of output value. So in industrial production, it is often measured by the water consumption level of 10,000 yuan GDP (Gross Domestic Production) in industrial production. 2. Overview of Henan Province Henan Province spans the Yangtze River Basin, Huaihe River Basin, Yellow River Basin, and Haihe River Basin. X. Zhang, T. Liang / Desalination and Water Treatment 213 (2021) 202–213 204 Most of the rivers in the province originate from the mountain areas in the west, northwest, and southeast. There are 493 rivers with a basin area of more than 100 km2. The province’s average water resources totalled 40.5 billion m3, ranking 19th in China, and its per capita water resources were <420 m3. This is equivalent to one-fifth of China’s average. Henan Province is the only province in China that flows through four major river basins. It is also the largest province in China with a long history and has bred Chinese civilization. Currently, under the strategy of the rise of the Central Plains, the water environment in Henan Province is relatively complicated, and so it is particularly important to evaluate urban water conservation. 2.1. Evaluation index selection and system construction The index screening is conducted from the perspective of urban water conservation, including the urban area and the surrounding environment, fully reflecting the urban operation and ecological cycle and the interaction between them. The indicators should fully reflect the state of urban development and the state of the natural environment in a region. The indicators are selected from the aspects of the city’s economic development status, social progress, and surrounding environment status. In terms of urban operation, the selected indicators should reflect the city’s water-saving capacity and efficiency. This is done by selecting indicators from the perspectives of people’s lives, industrial and commercial production, and economic construction. At the same time, the policy of a region is also an indicator of water-saving capacity. In