An efficient GIS-based approach for sustainability assessment of urban drinking water consumption patterns: A study in Tabriz city, Iran

Highlights

• An navel approach for urban drinking water consumption patterns has proposed

• The efficiency of the proposed approach was examined in Tabriz city as a case study

• Urban texture and demographic have a significant impact on the water consumption

• Results makes significant contribution for sustainability assessment in urban areas

Abstract

The importance of freshwater for human societies and sustainable urban development is paramount. This study presents a new approach and framework for spatial modelling of urban drinking water consumption patterns (UDWCP) in light of a drinking water sustainability assessment. The approach was developed based on the GIS multi-criteria decision analysis (MCDA) and its efficiency was evaluated for spatial UDWPC mapping in Tabriz city, Iran. To achieve this goal, we identified the main water consumption indicators (WCI) (e.g. urban fields, population, land use/cover and their related sub-spatial factors), and determined their significance using the analytical network process. In addition, the sensitivity and uncertainty analyses was applied to reduce the inherent error in criteria weights. A GIS-based aggregation function was applied to discern the UDWCP map. Finally, regression analysis was used to determine the spatial correlation of the water consumption with different urban fields as well as the ratio of each WCI for the sustainability assessment objects were computed. According to results, urban fields, texture and demographic properties have a significant impact on the water consumption ratio. In the context of the urban texture, this study revealed that water consumption rates in both run-down and slums/informal settlements are relatively high. Results of this research provide a comprehensive understanding of UDWCP and their contribution to urban water consumption in Tabriz city. The importance of fresh water for human societies and the numerous issues related to water scarcity around the world is undisputed, and our proposed approach can be employed to efficiently model UDWCP and provide critical information for decision-makers and authorities worldwide to assist with the sustainable development of urban environments.

Introduction

The concept of urban water sustainability gained the attention of authorities, decision-makers and planners over the past two decades (Motevallian, Tabesh, & Roozbahani, 2014). The sustainable development of urban environments demands renewable freshwater resources, which are vital for supporting human life and socio-economic activities (Jaramillo & Nazemi, 2017). Water sources have always been critical for the well-functioning and sustainable development of human communities; they influence the development of societies and determine the location of settlements. However, based on the impact of climate change, population growth, and environmental issues such as water scarcity, the water supply of human societies has been facing severe challenges that require sustainable solutions for both water supply and consumption. Thus, having access to sufficient and renewable sources of drinking water to sustain the demand in quantity and quality has always played a fundamental and critical role for human life and societies (Yang et al., 2017).

The World Economic Forum (2015) identified water crises as one of the eight major global risks and ranks them among the most severe international challenges in the coming years (WEF: World Economic Forum, 2020). This statement underpins the importance of access to safe freshwater, which has increased around the world in the last few decades (Yang et al., 2017). In addition, as developing countries are becoming wealthier, new challenges emerge related to the management of freshwater sources (Chen, HuaYang, Yang, & Chen, 2015). One of these serious challenges relates to urbanisation and population growth, which is one of the predominant trends of the 21^st century. The global population has increased from 3 to 7 billion in the past five decades (Chen et al., 2015; Sadr et al., 2016). According to a United Nations (2015) report, there will be about 2.5 billion additional urban dwellers by the year 2050 (Chen et al., 2015). In terms of water consumption, it is believed that a number of relevant factors (e.g. climate, food habits, cultural background, working status, level of development, physiology) determine the quantity of water consumption (Chen et al., 2015). As a result of the rapid global population growth, improvement in living standards, and, more recently, the impacts of climate change impacts, drinking water demands are increasing, and the threats of water shortages and water scarcity are becoming more severe (Sadr et al., 2016).

Due to the serious limitations in the availability of freshwater resource in urban environments and the increasing water demand for the sustainable development of human societies under the impact of serious environmental challenges, decision-makers and authorities need to consider the local natural environments and socio-economic conditions impacting the water consumption ratio. To facilitate decision-making processes in reclaimed water management, it is important to measure how stakeholders form opinions and make choices based on the local water supply and the possibility and necessity of using reclaimed water (Li et al., 2019).

In the context of urban water, the term sustainable development requires a paradigm shift in conventional and traditional planning approaches that enables the maximisation of economic benefits of water and sanitation services in the short term, regardless of the long-term environmental and social impacts (Motevallian et al., 2014). Thus, it is critical to analyse urban water consumption patterns and provide detailed information for decision-makers and authorities. It is widely known that comparative urban water research is critical for making generalisations about sustainability and for developing approaches for adapting lessons from one set of cities for consideration in other urban environments (Noiva et al., 2016). The detailed information derived from these studies can be used to identify the areas with the most extensive water consumption and accordingly develop essential plans for the reduction of water consumption. In this context, several studies show that population growth and rapid urbanisation, together with climate change, increase the risk of droughts and significantly impact freshwater availability (Chen et al., 2015). A review of the literature and research background indicates that most of the early studies examined single case studies (e.g., Gandy, 2014). Some research also employed cases based on the authors’ expertise (e.g. Novotny, Ahern, & Brown, 2010; Wörlen et al., 2016). Noiva et al. (2016) pointed out that the sustainability of urban water systems is often compared in a small number of selected cases based on their familiarity, similarities and differences. Therefore, proposing and applying a comprehensive and efficient approach that can be used for urban water consumption pattern modelling is considered to be lacking in sustainable urban development.

In this context, consumer segmentation studies based on spatial analysis and pattern analysis using consumption data reveal characteristic stakeholders/customers and develop spatial drinking water consumption patterns (Shaban & Sharma, 2007). The obvious application of water consumption patterns is to obtain an overview of the spatial drinking water patterns in urban environments. Such detailed information can support authorities to raise the awareness of consumers. Authorities can develop a plan for changing consumer behaviour and attitudes by clarifying the challenges of water scarcity and its respective issues (Chen et al., 2015 l, Babaei, 2019). It is assumed that spatial modelling of urban drinking water consumption patterns (UDWPCs) enables us to observe and map the contribution of different urban fields for urban water use efficiently. Spatial modelling of UDWPCs also helps us to obtain valuable information for the sustainability assessment of urban drinking water.

The spatial modelling of water consumption patterns in urban environments is very complex due to the numerous relationships between freshwater systems and human systems that dynamically change across various temporal and spatial scales (Jaramillo & Nazemi, 2017). Thus, an integrated approach of GIS and spatial decision support systems (SDSS) shall enable the development of a spatial model of the water consumption patterns in urban environments. Nowadays, digital spatial data has replaced the old process and hard copy maps for gathering information and is helping to resolve urban water issues (Seteh, 2013). Based on the GIS's capabilities for integrating spatial analysis and hydrologic models, the GIS-SDSS can be transformed from a simple spatial query and visualisation tool to a powerful analytical- and efficient spatially distributed modelling tool (Satti & Jacobs, 2004). In the domain of GIS-SDSS, the multi-criteria decision analysis (MCDA) is identified as one of the major decision support techniques (Feizizadeh & Blaschke, 2014; Jiang & Eastman, 2000). To support the growing interest in integrating GIS spatial analysis with MCDA processes, the GIS-MCDA is an efficient methodology for a large number of applications such as sustainable planning and development (Chen, Khan, & Paydar, 2007; Joerin, Theriault, & Musy, 2001). In recent years, GIS-based MCDA methods have been widely employed by researchers and scientists in various fields of science, such as geography, engineering, management, economics and business science for supporting decision-makers to make the right decisions and validate results (Behzadian, Kazemzadeh., Albadvi, & Aghdasi, 2010; Kheybari, Mahdi Rezaie, & Farazmand, 2020). Compared to the capabilities of MCDA methods, the GIS-MCDA methods turned out to be critical for operations research and management sciences because they provide a robust collection of methods and techniques for organising decision issues, evaluating, designing, ranking and proposing the alternative decisions (2006, Boroushaki & Malczewski, 2010; Malczewski, 1999). Due to multiple natures of UDWCPs in urban environments and "large number of factors that impact the urban water consumption ratio, the GIS-MCDA can be applied for characterising and mapping the UDWCPs. The water consumption patterns in urban environments have developed in each society based on the socio-economic conditions, cultural backgrounds, religious beliefs and tradition and customs. As a result of a variety of parameters contributing to the water consumption patterns, the GIS-MCDA, with the inability to handle a large number of criteria, is able to model the spatial pattern of water consumption trends appropriately. Therefore, the main objective of this research is to present a GIS-MCDA approach and framework for spatial modelling of UDWCPs. The proposed approach is examined in Tabriz city, the fourth largest city in Iran, which has been facing significant water scarcity problems over the past decades. In focusing on the concept of sustainability of water supply in urban environments, this research presents a novel indicator-based framework that can be applied for the sustainability assessment of UDWCPs as well as water supply issues.