Water-Energy Dependency May Put a Damper on Water Banking in California

By Meaghan Daly, Water Matters @ Columbia. Posted June 16, 2009.

We've been following some of the issues related to the drought in California. In response to water shortages, a "water bank" has been implemented to allow users who do not use all of their water to sell it to other users. In theory, such a system allows water to be used in an efficient manner, with higher priority users gaining the ability to purchase water when there are shortages.

In looking at the reality of implementing such a system, however, it becomes clear that there are challenges on many levels. This is evidenced by the fact that despite the state's efforts, it will likely only promote the trade of 82,000 acre feet of water this year -- less than 15% of what it had been hoping for.

One major challenge is related to the price of food crops, which have risen drastically in the last year, making the sale of water less appealing to farmers.  Additionally, there is the fundamental challenge of getting the water where it needs to be once it has been purchased, a task that requires vast amounts of energy.

In many places, where water-energy dependency is already an issue, this may detract from the potential benefit that could be derived from systems like water banking.

In California, this is a particularly serious problem.  A study conducted by the California Energy Commission in 2005 found that 19% of the state's energy use is water related, being used to pump, treat, transport, heat, cool, and recycle water.  Additionally, 30 percent of California's natural gas consumption and 88 billion gallons of diesel fuel combustion per year are tied to supplying water to municipal, agricultural, and industrial users.

This scenario is likely to be exacerbated by ever-increasing demand for water due to high rates of population growth and the likely implications of climate change. The state's water plan anticipates minimizing expected water deficits in the next 25 years through the use of desalination and water recycling. Both of these, however, are energy intensive processes. As a result, the interwoven nature of water and energy in California will undoubtedly grow more complex -- and strained -- in the years to come.

Therefore, the prospect for water banking in California in the future becomes more dubious when considered in the context of energy demand, as the whole concept of a water bank necessitates an increase in the transport of water - sometimes over great distances.  Water conveyance can have widely fluctuating energy intensity, depending on the distance and the elevation covered, and can comprise a significant portion of the water related energy use, especially in years when there are shortages.

Source: The Future is Now: An Update on Climate Change Science Impacts and Response Options for California

As you can see from the chart, the energy intensity for water supply and conveyance can range from 0 to 14,000 kWh per million gallons. This is because in a typical hydrological year, 60% of California's water supply comes from more easily accessed surface water sources. In years of shortage, however, groundwater can account for the majority of supply, as pumping is necessary, thus increasing energy use dramatically. Water banking may only amplify this problem.

While significant precipitation events during the past month have helped to slightly ease the current water shortage crisis, 35 local water management agencies have mandated conservation measures and 94% of agricultural businesses have been impacted by drought conditions this year. (For current updates on the drought in California, click here.) But drought is not a problem that is likely to disappear any time in the near future in the state of California. Thus, any solutions should necessarily take long-term impacts into account - including increased energy use.

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