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OCH BLOG

Chasing Water

California is no stranger to drought. Many of our ecosystems, especially here in Southern California, have adapted to naturally arid conditions. Drought deciduous shrubs shed their leaves during dry periods and some plants go dormant every summer to survive our Mediterranean climate of hot, dry summers and low rainfall in the winter. However, as climate change leads to higher temperatures and more variable weather patterns, our droughts have increased and worsened, making life difficult for even the most drought-tolerant wildlife. Because of warmer temperatures, snow melts sooner, which means there is less moisture later into summer, and the dry season lengthens. Over the past 50 years, California has been through many droughts including 1976 to 1977, the driest period on record, 1987 to 1992, the second driest period on record, the most recent drought from 2012 to 2016, and now the drought we are currently experiencing. All of California has experienced historically low rainfall recently. From July 2020 to June 2021, L.A. received 5.82 inches of rain, only 41% of typical rainfall. Northern California, the source of much of the state’s water, is experiencing one of the driest two-year spans since the Gold Rush in 1849.

Early June Drought Conditions in the West. Photo by U.S. Drought Monitor

Within California, much of our water comes from snowpack, or condensed snow, that accumulates at high elevations and melts throughout the summer to replenish our water. However, when winter brings unusually low levels of precipitation to our snowpack as well as surface water, we must turn to other sources. In Southern California, we often resort to water transported from Northern California or the Colorado River and, all across the state, people depend on groundwater. Groundwater is found in underground layers of water-bearing permeable rock called aquifers. In normal years we acquire about 40% of our water from underground aquifers, but in dry years this increases to as high as 60%. This dependence can become an issue if water is not being used consciously and conserved.


California splits its water use among three different uses: environmental, agricultural, and urban. Environmental water includes water in rivers protected as “wild and scenic” and wetlands in wildlife preserves are required to maintain freshwater habitats and water quality in urban and agricultural sources. This takes up roughly half of our water while agriculture and urban uses 40% and 10% respectively. These percentages vary depending on the region and if it is a wet or dry year. This infographic from the Department of Water Resources shows there is a high urban use in the South Coast region where population is high while in the north a greater percentage of water goes to the environment due to many protected rivers. In addition, the pie charts display the difference between a wet and dry year: when water is scarce, environmental water use takes a hit, dropping from 62% to 28% in favor of agriculture and cities.

California Water Plan Update 2018 (Public Review Draft). Photo by Department of Water Resources

Use of water for agriculture has been decreasing since 1995 due to a combination of more efficient irrigation and the downward trend of farming across the nation. However, agriculture still uses a considerable amount of California's water. A transition to more perennial crops, such as trees and vines, has made farming more vulnerable to water shortages since these crops require more water. Agricultural irrigation is the largest human use of freshwater in California and even in the world, taking about 70% of freshwater for both. California’s large agricultural industry includes approximately 9.6 million acres of irrigated land which in an average year receive roughly 34 million acre-feet of water, or enough to cover 31 million football fields with one foot of water. Unfortunately, some of our current methods of irrigation lose much of the water to evaporation and runoff. One example is surface irrigation, a traditional method still used today since it is inexpensive and low-tech. However, as it relies on gravity to distribute the water, a percentage of it is lost on the edges of the field to runoff. Another more modern method, spray or sprinkler irrigation, also has efficiency issues. It wastes less water to runoff than surface irrigation but more to evaporation and wind. To avoid these issues, farmers can use more efficient microirrigation. Drip irrigation, a type of microirrigation, lessens water loss by slowly delivering water through perforated hoses and targeting the plants that need moisture. Though not implemented often due to its expense, this system could conserve much of our irrigation water if more widely used.


Urbanization has a large impact on the hydrologic cycle. As we expand cities and suburbs for an increasing population, native plants are removed and replaced with buildings, streets, parking lots, and sidewalks. We cover the land with concrete and asphalt, creating miles of impermeable surfaces that prevent water from soaking into the ground. In addition, most Southern California rivers are channelized and have artificial stream beds that add to this issue. There is only one remaining unchannelized and natural stream in Orange County, the San Mateo Creek. Negative effects of urbanization include an increase in evaporation and runoff, as when rain does fall, it does not soak into the ground. This in turn means less infiltration of water to recharge aquifers. The water instead goes through storm drains straight into rivers and streams. Because water is not able to absorb into the ground and so much is channeled into rivers, urbanization leads to increased risk of floods.

Model of saltwater intrusion. Photo by Lenntech

Of all Earth’s freshwater, 30% is found in underground aquifers that are naturally recharged by rain. When this recharge is inhibited by urbanization, and when cities and farms rely heavily on groundwater, we can draw from aquifers faster than they are naturally replenished. Depleting aquifers can lower the water table, causing wells to dry up unless they are dug deeper, increasing pumping costs. It can also lessen water in rivers and lakes by interrupting the normal flow of underground water between surface water and aquifers. If the aquifer is near the coast, over-drawing can lead to saltwater intrusion in which underground saltwater moves inland and upward, contaminating the water supply. Another impact of groundwater depletion is the compacting and collapsing of soil as the water is taken from it, known as land subsidence. This happens slowly, but can cause considerable damage to infrastructure as well as a permanent loss of aquifer storage.

Land surface subsided due to aquifer-system compaction from 1925 to 1977 in San Joaquin Valley, California. Photo by Richard Ireland (U.S. Geological Survey)

Due to California’s numerous water struggles, we must find ways to be more conscious about water use and proactive about conservation. One way to do this is through incentives for homeowners to update water systems, or tiered pricing that charges heavy water users more. Farmers can use more efficient irrigation methods like drip irrigation, level fields to reduce runoff, or capture and reuse runoff. Cities can install green spaces, like rain gardens, or permeable concrete to allow infiltration of water as well as new storm drainage systems that aid reuse of wastewater. Sustainable groundwater management and artificial recharge (returning water to the ground) can help us avoid depleting aquifers. As individuals, we can observe and limit water use in our homes by investing in water-efficient or low-flow appliances, keeping plumbing up to date, and immediately fixing any leaks. If you have a yard, the biggest change you can make is replacing lawns with drought-tolerant natives since landscape watering accounts for half of urban water use. These changes, along with voting, communicating with your congresspeople, and supporting local efforts to conserve water, are all ways you can help California with its water struggles. To learn more about California’s relationship with water watch the recording of our recent Coffee & Conservation on our website!


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