Home » Climate Change » Drought in California Part 9: Summary of the Water Deficit and Strategies to Cover It

Drought in California Part 9: Summary of the Water Deficit and Strategies to Cover It


This is the ninth post in my series about drought in California. The previous posts have appeared once weekly over 8 weeks, so perhaps it is time for a recap and summary of what is known about California’s water deficit and the strategies that might be used to cover it.

California faces a serious water deficit, both right now and in the future. There are regions in California that receive a lot of precipitation, but much of the state is dry. Even in the wet areas, the bulk of the precipitation falls during the winter, while the spring, summer, and fall are dry. The vast majority of people live in the dry regions of the state. California has thrived by developing one of the most extensive water collection, storage, and transportation systems in the world. This system diverts surface water from Northern California, the Sierra Nevada Mountains, and from the Colorado River. In addition, California pumps groundwater out of its aquifers, the largest and most important of which is the Central Valley Aquifer. Seventy-six percent of the water is delivered to California’s agricultural areas, where it is used for irrigation, and 24% is delivered to its urban areas, where it supports the famous lifestyle for which California is famous.

Estimates of the size of the current California water deficit vary, but the best sources I could find suggest that it may be more than 6 million acre-feet per year. The deficit is covered by draining down both aquifers and surface reservoirs. Part of the shortfall in water has been caused by development. The population of California has skyrocketed, and so has agricultural consumption of water. Most projections expect California’s population to continue to grow, and thus, the water deficit will grow.

However, climate projections suggest that California’s water supply will decrease in the future. In California, much of the winter precipitation falls as snow in the mountains. The California snowpack is particularly important because it serves as the state’s largest “reservoir,” storing water during the winter and releasing it slowly during the rest of the year. This slow release is essential, because it allows the maximum amount of water to nourish vegetation, recharge aquifers, and be collected into reservoirs. Unfortunately, climate projections suggest that by mid-century California’s snowpack will decline by 40%. Such a decline would significantly reduce the water supply.

I found no studies that included climate change in their calculations of California’s future water deficit, so I constructed my own. I calculated that California’s future water deficit will be 25.1 million acre-feet, which is about 39% of California’s current water supply. The most important cause of the deficit will be the decline in the snowpack. The second most important cause will be the projected increase in population.

Theoretically, California could cover the projected deficit by obtaining additional water supplies or by reducing consumption. The possibilities for gaining additional water to cover the deficit include finding additional groundwater resources, diverting additional rivers either inside or outside of California, and desalination. The possibilities for reducing water consumption include reducing the population, reducing the amount of water used to sustain the environment, reducing agricultural consumption, and reducing urban consumption. Whether any of these hold any practical potential is hard to know. But even theoretically, only desalination, agricultural conservation, and urban conservation seemed to hold any potential; the other possibilities seemed unfeasible.

California’s groundwater system has been extensively mapped. The system is already being depleted, and it is unlikely that new aquifers will be discovered.

All but a few of California’s surface rivers have already been impounded and tapped. Looking at the few that have not been impounded revealed very significant problems that would make impounding them difficult, expensive, and highly objectionable.

The possibility of importing water from rivers out-of-state, like the Columbia River, would require a huge public works project to bring the water to California, and then re-engineering and rebuilding the existing California water distribution system to handle the increased capacity. It seemed impractical.

Desalinating enough water to cover the deficit would require the construction of many desalination plants, plus the infrastructure to distribute their water. In addition, it would require the construction of new electricity generation and storage facilities to power them. There would be a nightmare of problems that had to be overcome, and the cost would be high, but it did not seem impossible on the face of it. I wasn’t sure what context to put the cost in, but I calculated the annual cost to be roughly equal to 1/4 of the entire state budget, or 1% of the gross state product.

The notion of reducing population to reduce water consumption was felt to be unrealistic. It is typically abhorrent to governments and to the business community, as fewer people mean lower tax receipts and lower sales. I felt that California might eventually depopulate, but if it does, it would be because people migrated away on their own, not because of a policy choice by the state.

Diverting additional water away from the environment was felt to be impossible without causing severe damage. The environment in California has already suffered significant degradation due to water diversion. For instance, salt water is intruding into the San Francisco Bay Delta, and they are having to build an emergency barrier to try to prevent it.

Because agriculture consumes 76% of California’s water, it is the natural place to look for reduced consumption. I found some sources that suggested consumption could be significantly reduced using a few simple strategies, but other sources that suggested that the optimism was based on faulty analyses and fundamental misunderstandings. Estimates ranged from 0.5 – 3.4 million acre-feet. I felt the true potential lay somewhere between, but it was impossible to know precisely where. In any event, even at the full amount, it represents only a small fraction of the total deficit. I felt that ultimately water would be cut off from many California farms, causing many of them to fail, leading to significant unemployment and dislocation.

And finally, because California’s urban areas consume only 24% of California’s water, water conservation in urban areas can only make good a small percentage of the projected future deficit. Paired with strategies to recycle urban wastewater, it seemed that urban water consumption could make good up to 16% of the deficit. Each water saving strategy, however, saved only a small fraction of the amount that needs to be saved, required an up-front capital expenditure, required the acquisition of new knowledge and expertise, and contrary to claims, reduced the quality of service provided by the water. Thus, consumers would have to implement many strategies. Together, they would impose a noticeable, and possibly significant, burden that would meaningfully degrade the quality of life for which California has become famous.

Thus, California faces a very large projected future water deficit, and covering the deficit will not be easy. Only 3 of the potential solutions seem feasible: agricultural conservation, urban conservation, and desalination. Agricultural conservation and urban conservation are not sufficient to cover the deficit, either alone or in combination. Thus, it seems that California will have to implement some combination of all three.

The remaining posts in this series will attempt to look at how California might go about implementing such a combined program, and will discuss what the costs might be. I will finish with some discussion of how the drought and the attempts to make good the water deficit will affect California economically.

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