Large scale use of groundwater in California began during the 1920s and 1930s, due largely to the pumping of water for irrigation to feed rapid expansion of agriculture in the region. The pumping of groundwater for this purpose started moderately and remained constant until the mid-1950s. This baseline level of pumping then started to increase rapidly in response to yield level increases driven by the newfound use of high-performing synthetic fertilizers (worldwide). Current increases in groundwater pumping are driven more by mining, commercial and domestic needs rather than agriculture.

Use of groundwater is having a negative impact because the rate of use is higher than the rate of recharge. This leads to groundwater depletion which affects the lives and livelihoods of people in the state. The effects are largely felt through reduced water availability, issues of water quality, subsidence of the land, and impacts on biodiversity.

Reduced water availability

Reduced water availability is caused by groundwater depletion, a rate of groundwater extraction exceeding the rate of water replenishment from the natural hydrological system. This reduced water availability affects farmers, businesses, and residents alike. Farmers are perhaps the group who are most acutely impacted by this due to the higher costs, revenue impacts, tighter profits, and psychological stress.

Effects of low water availability on farmers

Higher costs to farmers include increased expenses for water pumping due to the need to drill deeper wells as the water table drops. Farmers also experience a drop in revenue caused by lower yields, because they are unable to irrigate crops as much or as frequently as they would like to. Higher costs and drops in revenue mean smaller margins, rendering businesses unprofitable. This can lead to significant personal stress, as many farms are family businesses, some of whom don't know if the next generation will even have a farm.

The business community

Businesses across the state impacted by reduced groundwater availability include food processing businesses, hospitality, property and construction, and beverage producers. The industry affected the most is perhaps the food processing industries due to the large volumes of water needed for equipment cleaning.

When confronted with water challenges, food processing businesses experience impacts to their profit-generating capabilities. They incur higher costs due to the investment needed in water efficiency technologies. These businesses are also expected to pay more for their water, and in the case of scarcity, may see revenue impacted by interruptions to production schedules.

Hospitality businesses face inconsistent water supplies which can reduce their capacity to serve customers, reducing guest satisfaction. As with food processing businesses, they may also face higher costs due to efficiency measures and may also face the risk of fines by exceeding water usage limits.

Property and construction businesses are impacted by significant threats to property values in areas of water shortages. The beverage industry is also affected, facing production capacity limitations due to the notable water use intensity of their processes.

Impacts of water shortages on residents

Residents feel the effects of groundwater shortages through variable water supply and increased water rates. The issue of supply variability is particularly pronounced in coastal regions such as Monterey and the Salinas Valley. This can result in strict water use regulations for residents in these regions. In parts of southern California such as the Los Angeles basin, annual water rates have increased for residents. These rates are necessary to pay for deeper drilling, water recycling, and water desalination.

Issues around water quality

Groundwater depletion reduces the quality of groundwater due to contaminants and seawater intrusion. Contamination occurs due to depletion because as the amount of water reduces, so the concentration of contaminants increases. Contaminants originate from agriculture, industry, and even from nature.

These contaminants include nitrates from agriculture which pose significant risks to residents of California. In high enough concentrations, high drinking water nitrates are known to cause infant mortality through Blue Baby Syndrome. They are also associated with increased cancer risks, hormonal disorders, and cardiovascular risks in adults.

Arsenic is another contaminant found in groundwater supplies in California. This can arise from agrochemical use and is associated with cancer risks, cardiovascular disease, and damage to the nervous system. Arsenic contamination can also originate from both natural rock weathering and industries such as aerospace.

The issue of groundwater contamination can be particularly acute for businesses such as beverage manufacturers who rely on putting water directly into their products. Manufacturers and other such businesses can face higher costs due to necessary water treatment processes. They also face risks to the quality and safety of their end products.

Seawater intrusion occurs when the loss of groundwater reduces the water pressure required to hold back seawater from entering freshwater supplies. The reduced groundwater pressure means that the denser seawater is pushed by the force of high ocean pressure through porous rock formations until it infiltrates groundwater aquifers. High water salinity makes water harmful to drink, dangerous to crops and useless for many industrial applications.

Land subsidence

Land subsidence occurs due to groundwater depletion because of the loss of water from the pores between the aquifer rocks that support the overlying land. Aquifers are comprised of sand, gravel, and other materials with pores in between them which fill up with water to form groundwater. If enough of the groundwater is extracted, the pressure in the aquifer drops and the solid parts (sand and gravel) start to collapse into one another. This causes the land above to drop (subside).

The issue of land subsidence in California affects farmers, businesses, and residents. Farmers face higher water management and distribution costs due to the damage caused to water delivery systems by subsidence. Property businesses are impacted by decreased property values in affected areas, and the construction industry faces higher operation costs because of the damage caused. Residents face disruption to their daily lives because of infrastructure damage caused.

Biodiversity impacts

Biodiversity in California is also impacted by groundwater loss, including both flora and fauna. In riparian zones (areas where land meets water), tree species such as willows and sycamores, which are reliant on steady groundwater levels, struggle to survive. These tree species are essential for stable riverbanks, for maintaining steady micro-climates as well as for their natural beauty.

The loss of essential flora has a cascading effect through the natural ecosystems. Habitats are lost due to unstable riverbanks as they wash away. The loss of habitat impacts other flora such as wetland plant species adapted to saturated soils. Wildlife populations threatened include California red-legged frog, invertebrates, beavers, and birds.

Invertebrates, an essential source of food for species higher up the food web become concentrated into smaller areas within the remaining habitat. This concentration increases predatory pressures, i.e., it becomes easier for predators to prey upon and consume the remaining invertebrates – leading to a cycle of further invertebrate population decline.

Summary

Groundwater is essential to the economy, society, and environment of California. The depletion of this resource has occurred due to extraction rates above replenishment. The depletion of groundwater impacts farming, industry, residents, and species dependent on riparian zones and other parts of the natural environment.

The California Department of Water Resources (DWR) introduced the Sustainable Groundwater Management Act in 2014 [5]. The Act requires authorities of all groundwater basins to make management plans bringing extraction rates back in line with replenishment rates by 2035 or before. Groundwater basin authorities ranked as at high-risk or critical by the DWR are concentrated in the Central Valley hydrological zone. The number of high-risk basins is 50 out of a total of 515 basins across the state.

California is at risk of major upheaval due to the impacts of groundwater depletion. Authorities have responded with a strict set of measures to address the problem basin by basin. There is still hope for a thriving agricultural industry, economy, society, and natural world in the years ahead.