One of the centerpieces of the argument I make in my book, Water is for Fighting Over: and Other Myths about Water in the West, is that changing patterns in water demand (specifically, that we’re using a lot less of it than we used to, across all sectors of the economy) create significant new flexibility in managing water in the West. I drilled down into that argument in a piece published this summer by the Breakthrough Institute:

Unfortunately, a deeply entrenched water management paradigm continues to stand in the way. Consider the Los Angeles Department of Water and Power, one of the nation’s largest municipal water retailers, serving 4 million people. In a major 2005 planning effort, LADWP managers projected that over the coming decade their water demand would rise by 7 percent. In reality, it dropped by 18 percent. Yet despite steady declines, the 2016 version of the agency’s draft water management plan again projects the trend that has resulted in a long term water use decline dating back to the 1990 will reverse itself, with water use rising again from their current low levels.

This pattern of overestimating future demand and underestimating consumer conservation is widespread, and is the major impediment to capturing the benefits that decoupling offers.

Into this public policy mess come Matthew Heberger and colleagues at the Pacific Institute with a helpful new white paper – A Community Guide for Evaluating Future Urban Water Demand:

For much of the 20th century, water use in American cities grew in proportion to population and the economy. Since the 1980s, however, water use in communities across the United States has remained steady or declined despite continued population and economic growth, due to improved water conservation and efficiency and structural changes in the American economy.

While the water sector has undergone a fundamental transformation, the practice of water demand forecasting has been slow to keep pace. Water suppliers routinely overestimate future water demand based on often overstated estimates of population and economic growth and underestimates of the effects of water conservation and efficiency improvements. These inflated estimates of future water needs can result in unneeded water supply and treatment infrastructure, higher costs to ratepayers, and unnecessary environmental impacts.