Urban Industrial Water Supply and Demand: System Dynamic Model and Simulation Based on Cobb–Douglas Function

In order to meet the needs of water-saving society development, the system dynamics method and the Cobb–Douglas (C–D) production function were combined to build a supply and demand model for urban industrial water use. In this model, the industrial water demand function is expressed as the sum of the general industrial water demand and the power industry water demand, the urban water supply function is expressed as the Cobb–Douglas production function, investment and labor input are used as the control variables, and the difference between supply and demand in various situations is simulated by adjusting their values. In addition, the system simulation is conducted for Suzhou City, Jiangsu Province, China, with 16 sets of different, carefully designed investment and labor input combinations for exploring a most suitable combination of industrial water supply and demand in Suzhou. We divide the results of prediction into four categories: supply less than demand, supply equals demand, supply exceeds demand, and supply much larger than demand. The balance between supply and demand is a most suitable setting for Suzhou City to develop, and the next is the type in which the supply exceeds demand. The other two types cannot meet the development requirements. We concluded that it is easier to adjust the investment than to adjust the labor input when adjusting the control variables to change the industrial water supply. While drawing the ideal combination of investment and labor input, a reasonable range of investment and labor input is also provided: the scope of investment adjustment is 0.6 I 0 − 1.1 I 0 , and the adjustment range of labor input is 0.5 P 0 − 1.2 P 0 .