The Cobb-Douglas production function is not suitable for estimating the benefit of water use and the value of water resources. When looking at data from the US, Japan, and Beijing, it was found that economic growth can still increase even when water use decreases. This means that the value of water resources is not negatively linked to economic production as the Cobb-Douglas function suggests. The function also fails to account for the full contribution of water resources to economic growth, as factors like technology and investment in water-saving methods play a significant role in total output.