Abstract
Global water scarcity is becoming a major issue for billions of people. WHO and UNICEF estimate that billions of people are not available to clean drinking water and many more experience pollution and scarcity of water according to the report of World Health Organization and UNICEF in 2017. Policymakers and stakeholders have significant challenges in allocating water resources to optimize water use for every user. One of the concerning issues facing the modern world is water scarcity, thus many experts in the field are interested in water allocation and its thoughtful usage. With careful planning and design, this issue can be effectively resolved. Sustainable development requires a multidisciplinary approach to water resource planning. Water-based irrigation is one of the most essential inputs for agricultural production worldwide and a way to achieve the highest level of sustainability in production systems. Since water is abundant on Earth, perhaps one refers to Earth as the "blue planet." Regretfully, more than 97.5 percent of the water readily available to us is saline water, which must be desalinated before it can be used. The remaining 2.5 percent of freshwater is available to us. Surface water accounts for around 1.2% of the total freshwater supply and meets the majority of human demands. Twenty-nine percent of freshwater is located in lakes, and the remaining portion is frozen in ice. Surface freshwater is composed of 0.49% rivers. If water supplies were dispersed equally over the planet, the remaining proportion of freshwater would be more than sufficient to practically meet the demands of every individual on Earth. Freshwater availability becomes crucial if any plans or development projects are to be carried out for the protection of the environment, health enhancement, hygiene, and sanitation, establishing housing projects, or changing the use of land. The absence of Freshwater water can impede the growth of industrialization, food
production, and society, and ultimately cause harm to natural resource systems. The current work offers a thorough analysis of the applications of the WEAP Version 21 is used as a decision-making tool in water resource planning and distribution issues across a range of domains, such as groundwater modeling, climate change simulations, and water quality analysis. This paper reviews various WEAP models and presents an overview of their results. WEAP offers a broad range of applications, including groundwater evaluation, irrigation, and water quality. There have been many previous research investigations that have used WEAP modeling to maximize the water resources during water administration in India during the past 20 years, taking into account a variety of factors and distinct water resources across the nation. To determine the fields of focus, study limits, and outcomes of the fourteen prior investigations, a review of those studies was conducted to determine the reliability of the WEAP modeling for optimizing the management of sources of water. The Model of WEAP was shown to be dependable for evaluating, organizing, and optimizing the management of water resources.