## 1 Introduction  
According to the annual report of Phuket Province in 2010, water demand for consumption was approximately 51 million m\({}^{3}\)/year, whereas water supply was about 46 million m\({}^{3}\)/year. The water supply is categorized into three groups: surface water, groundwater, and seawater. Surface water accounts for about 38 million m\({}^{3}\)/year, or 82% of the total water supply. In comparison, groundwater accounts for about 4 million m\({}^{3}\)/year or 9% of the total water supply, and seawater accounts for 4 million m\({}^{3}\)/year or 9% of the total water supply. The average water demand increases by about 2% per year according to economic growth and tourism. Thus, the water demand estimates for 2017, 2027, and 2037 are approximately 61 million m\({}^{3}\), 78 million m\({}^{3}\), and 101 million m\({}^{3}\), respectively [1]. Accordingly, balancing water supply and demand for consumption is very important for water resources management, in particular water scarcity, in Phuket Island. Phuket Island is the largest island in Thailand and a highly popular tourist destination. In the past 30 years, Phuket Island has seen considerable tourism growth [2]. Information from TAT Intelligence Center, Tourism Authority of Thailand and Economics Tourism and Sports Division, Ministry of Tourism and Sports, shows that the total number of domestic (Thai) and international (foreign) tourists dramatically increased between 1993 and 2019, from 2,088,179 people in 1993 to 14,576,466 people in 2019. There has been a threefold increase in tourists in the last decade, although the number of tourists declined in some years. For instance, the number of tourists declined to 2,510,276 in 2005 after the Indian Ocean Tsunami on 26 December 2004. During the H1N1 pandemic in 2009, tourist numbers dropped from 5,313,308 in 2008 to 3,375,931 in 2009. Similarly, due to the COVID-19 pandemic, tourist numbers dropped from 14,576,466 in 2019 to 4,003,290 in 2020 [3,4]. Between 1993 and 2020, the registered population of Phuket province continuously increased from 194,178 people in 1993 to 414,471 people in 2020 [5]. Recently, the balance between water demand and supply has been investigated to mitigate water shortage problems in many countries. [PERSON] et al. applied the SWAT model to assess the impact of land-use change on the water balance of the Narmada River basin in Madhya Pradesh, India [6]. [PERSON] et al. applied the Water Evaluation and Planning (WEAP) hydrological model and used population growth trends and climate change scenarios to forecast the water demand and supply in Addis Ababa, Ethiopia [7]. [PERSON] applied Multi-Criteria Decision Analysis to assess water supply and demand management in Santa Cruz, Galapagos Island, Ecuador, from the environmental, technical, economic, and social aspects and relevant stakeholders' perspectives [8]. [PERSON] et al. applied a system dynamics approach to simulate and optimize the water supply and demand balance in Shenzhen, China [9]. [PERSON] et al. applied the Soil and Water Integrated Model (SWIM) to assess gaps between water demand and supply for water resources planning in Upper Niger and Bani River Basins (UNBB) in West Africa [10]. During the last three decades, many researchers have conducted studies on Phuket Island's water supply, demand, and balance. Using statistical and field data, [PERSON] explored the location and distribution of water resources to assess the water demand situation and trend and delineate areas to develop as water storage sites [11]. [PERSON] applied spatial data and stepwise regression to assess the streamflow characteristics of Phuket Island [12]. Thepunan applied System Dynamics (SD) to develop a system tool to analyze and explain significant variables that affect the tourism development carrying capacity of water resources [13]. [PERSON] et al. applied the runoff coefficient to assess water supply and demand in terms of quantity and time, evaluate the future water situation, and propose water resource management strategies [14].