FAQ: Droughts & California’s Coastal Regions

San Elijo Lagoon, Encinitas. Photo by Marcel Fuentes.
San Elijo Lagoon, Encinitas. Photo by Marcel Fuentes.

In the past century, multiple severely dry periods have occurred across the state of California, commonly referred to as droughts. The hot, dry weather associated with droughts raises questions about how and why these droughts occur and what the implications are for coastal regions. Explore this FAQ to learn more about what’s causing droughts and their impacts on California’s coastal regions.

This FAQ was developed by Sarah Farnsworth, 2021 California Sea Grant State Fellow at the Delta Stewardship Council.

What is a drought?

A drought is a period of time during which drier-than-normal conditions result in water supply shortages and water quality issues. Droughts can be categorized in three ways: (1) meteorological (lack of precipitation); (2) agricultural (reduced soil moisture); and (3) hydrologic (reduced stream flows and groundwater storage). The primary impacts of a drought can vary depending on location, meaning a particular drought period can be labeled under multiple categories. A drought period often occurs slowly, building up over years before notable impacts are seen by communities and a drought is officially declared- a process that varies across different states and regions.

What droughts have occurred in California recently?

Droughts are not new to California. Over the past few thousand years, the region has experienced many dry periods, with several notable events in the past century. This includes a more than ten-year period in the 1920s and 1930s, 1976 to 1977, 1987 to 1992, 2007 to 2009, the five-year event of 2012 to 2016, and the most recent drought California finds itself in, which was announced in 2021. Some are even considering the possibility that we are in a decade-long drought that began in 2012 due to the limited number of wet years between the two most recent events. As major droughts have continued to increase in frequency over recent decades, California has issued proclamations of emergency and imposed water use reduction requirements to try to recover from the conditions.

What causes droughts in California?

Complex systems of water infrastructure and groundwater resources buffer impacts in California, but droughts still occur due to reduced rainfall and water storage. One of the primary sources of water storage in California is in its snowpack, which accumulates along the Sierra Nevada, Klamath, and Cascade Mountains. Since less snow usually falls and accumulates in times of drought, seasonal snowpack decreases significantly during long periods of drier conditions and warmer temperatures. Additionally, as temperatures rise over time, the moisture in the soil evaporates more quickly. When the reduced snowpack melts, it soaks directly into the dry soil rather than flowing into rivers and streams (and thus, water reservoirs). Droughts can worsen during the period they are occurring, as the reduced water supply in reservoirs gets carried over into following years and leading to a consistently declining water supply.

How do droughts impact the coastal ecosystems of California?

Coastal ecosystems are integral to the health of California and they do not remain untouched by droughts. With a rapidly declining fresh water supply during a drought period, water allocations for restoration and habitats can be reduced, or even stopped, negatively affecting fishes’ and other species’ survival as well as the quality of these coastal habitats.

Estuaries, one of California’s major coastal habitats, play an important role in filtering pollutants and sediments, providing better water quality, and offering essential habitat for numerous plant and animal species. They even act as nursery areas for young fish, including commercially important species such as salmon and trout, to obtain necessary nutrients early in their life and be protected from the ocean’s strong currents and tides. During a drought, reduced inflows of freshwater from rivers and streams can lead to increased salinity in these normally brackish habitats, causing high mortality of plants which can significantly impact the habitat and water quality for many species and allow for a shift in ecosystem structure to support more marine or invasive, nonnative species. Many fish, invertebrate, and bird species depend on these coastal ecosystems in the early stages of life, so droughts pose threats that can reverberate through the food web.

Prolonged drought can also impact coastal chaparral and sage scrub habitats. These habitats are two of the most widely distributed shrubland ecosystems along the coast of California and play an important role in hosting habitat for a large variety of organisms. Although they are adapted to seasonal drought periods, the increasing frequency of multi-year droughts are making it difficult for these habitats to thrive. Decreasing soil moisture poses a serious threat to their survival and higher temperatures are expected to exacerbate these impacts and decrease the resiliency of these habitats to survive these longer droughts.

How do droughts impact aquaculture?

Aquaculture, a way of producing seafood for human consumption, has a growing presence in California’s economy with nearly $102 million in sales in 2012 in California alone. Numerous freshwater and saltwater species are grown in California for food products for consumption, stocking lakes to support recreational fishing, and supplementing wild populations. Aquaculture is a growing industry, but drought conditions pose a serious threat to these operations and could lead to a decline in production and loss of jobs. Reduced availability of freshwater for many of these facilities can reduce the volume of water available for the species, ultimately crowding them into smaller areas and leading to a high concentration of toxins. For aquaculture that depends on seawater, drought can also lead to phytoplankton blooms that reduce the available oxygen in the water. In marine aquaculture, it is common to culture species in natural bodies of water, which can face an unfavorable increase in salinity with a reduction in freshwater inflow.

How do droughts impact communities?

Public health and safety and economic consequences are at the forefront of impacts communities face due to droughts. This includes drinking water and irrigation shortages, especially in rural communities, more severe wildfire and smoke inhalation risks, and a decrease in agricultural production. Alongside these many serious issues, habitat degradation can also have economic consequences, whether it be through fishery declines or recreational opportunities. In California, indigenous communities are particularly at risk due to their reliance on land and water supplies.

Are droughts evidence of climate change?

Yes, climate change has been linked to the increased frequency and severity of these drought periods. Climate change favors the extremes and heightens variability, so areas that are historically dry, such as California, can expect droughts to only increase in frequency with more severe impacts as years with reduced precipitation and contracted seasons of wet weather occur more often. Warming temperatures associated with climate change will lead to drier soils and earlier melting of snowpack, kicking off the cycle within which the reduced snowpack melts into the soil rather than supplementing streams and rivers, therefore limiting the supply that enters water reservoirs.

What can we do to prepare, prevent, or recover from droughts?

Droughts vary by region, so it can be difficult to determine when a drought begins or ends. Often, regions consider the storage in the water reservoirs or when there is a sustained period of rainfall, but in order to prepare, prevent, and recover from droughts more efficiently, more research and planning must be done. California has taken many steps to move towards drought resilience, with collaborative planning across agencies, statewide water reductions during severe periods, and programs to fund essential research that can improve the ability for long-range climate predictions so that more proactive steps can be taken to prepare for potential drought periods. The State’s Water Resilience Portfolio is a leading example of these initiatives and incorporates actions that many state agencies are implementing to achieve resilience statewide.

California Sea Grant is also part of these actions and regularly funds research that is integral to understanding and approaching questions related to droughts. For example, researchers are assessing the needs for hatchery fishes in the face of drought and are looking into San Francisco Bay fishes as impacts of droughts and climate change grow in intensity.

Ultimately, we need to identify where our vulnerabilities lie regarding drought periods; identify potential alternative water sources and increase storage opportunities; implement drought-resistant crops and landscaping as well as increase and implement conservation and efficiency practices to reduce water demands; plan collaboratively and proactively; and take steps to reduce the impacts of climate change. 

Expert Reviewer:

Anthony Navasero, Senior Engineer, Water Resources, Delta Stewardship Council

Further Reading: