Abstract: The accurate forecasting of water demand is highly crucial for both economic and social development planning and water supply planning and management. Any very large or small water demand forecasts that are a result of blind predictions will bring different degrees of misdirection to water conservancy planning and water supply project construction and lead to very serious consequences. Therefore, there is a need to predict the different levels of actual water demands from the perspective of the water user. This paper firstly analyzes the connotations and impact factors of water resources demand; then, Maslow's Hierarchy of Needs Theory is introduced and a preliminarily water resources demand hierarchy theory is established; then, the different levels of actual water demands are discussed from the perspectives of life, production and ecology; finally, taking Puer as an example, the demand for water is forecasted from different hierarchies. In 2020, under the water frequency of 50%, 75%, 90% and 95%, the total quantity of the water demand forecast outside a river under the development level is smaller by 28.2%, 22.6%, 22.6% and 18.1% respectively when compared with planning results; while that under the basic level is even smaller. Under the harmonious level, the forecast results are smaller by 1.8%—13.8%. Under the water frequency of 75%, water demands under the development level are overall smaller by about 0.8%—1.7%, almost the same as the forecast results obtained by using the method of integrated water consumption per capita. The results show that the forecast results under different frequencies and different levels are generally smaller than conventional ones, which makes up for the deficiency of the conventional forecasting that is always larger.