The Santa Clara valley aquifer is a groundwater aquifer located in the southern San Francisco Bay Area. The geology of the Santa Clara valley aquifer consists of a complex stratigraphy of permeable and impermeable units. [1] Management of aquifer resources is associated with the Santa Clara Valley Water District.
In the early parts of the 20th century, the Santa Clara Valley was a vegetable and fruit growing region. Ground water was pumped heavily, leading to the Santa Clara valley being the first region recognized to be affected by land subsidence in the 1940s. [2] Between 1912 and 1966, artesian pressure levels dropped more than 200 feet (61 m). The decreasing pressure heads resulted in land subsidence of up to 15 feet (4.6 m). [3] The Santa Clara Valley Water District and other water purveyors have work to refined management practices which have halted land subsidence. During the 1960s due to the substantial decrease in ground water the SCVWD began to import surface water. [4] The Central Valley Project and the California State Water Project provide the surface water which has been beneficial to the region.
The groundwater aquifer can be separated into two major regions: the Upper and Lower Aquifers. The alluvial boundary which surrounds the valley allows for water to permeate through the ground which then flows horizontally into the confined region of the aquifer. [5] This system creates a convergent flow within the area which is bound by the topography of the region. The faults in the region also play a role in how groundwater is controlled, which furthermore subdivides the aquifer into three subregions. The hydrogeology of the aquifer has been significantly altered by surface water, which is treated and recharged to the aquifer while also providing water to local users. [6]
Well core data indicate that the Santa Clara Valley Aquifer consists of between four and six different water-bearing units. The aquifer is composed of both confined and unconfined units. Water-bearing units are generally coarse-grained and separated by relatively fine-grained units. The thicknesses of coarse-grained sections vary between 10–25 feet (3.0–7.6 m) in the southeast and between 50–200 feet (15–61 m) in the south-central and southwestern areas of the valley. Temperature data from monitoring wells indicate that horizontal groundwater flow occurs primarily above 775 feet (236 m) in southern-central regions and above 510 feet (160 m) in southeastern areas. [7] Faults also play a big role in how water is controlled; depending on the sediments' permeability, the Silver Creek fault creates seasonal subsidence or uplift on the west side or long term uplift on the east side. [5] The uplift has been associated with the dam on the eastern side of the Valley.
Subsidence has been a key issue in the region, which led to 17 square miles (44 km2) of dry land to sink beneath high tide levels in the 1969; this region was adjacent to the San Francisco Bay. The region is now[ as of? ] heavily rigged with ring dikes and control levees, which work as flood control and prevent saltwater intrusion. Land subsidence created a need for controlling stream channels to ensure that water flowed into the Bay. [2] [6] The majority of land subsidence has occurred in the confined region of the aquifer. [5]
The effort conducted in the valley to halt subsidence resulted in uplift from 1992 to 1998: the mean uplift surveyed was 6.4 ± 2.2 mm/yr, which was noted in Sunnyvale and eastern San Jose. However, there is still a lot of land deformation from subsidence, but not notable from fault movement. [5] The majority of notable uplift has been noted to be in the southernmost region of the confined zone of the aquifer, which has been seen as seasonal. [5]
Decades of ground water depletion due to urban development and agriculture resulted in substantial land subsidence. The Santa Clara Valley Water District and other water purveyors have replenished ground water levels by artificial recharge, which is occurring in the upper 500 feet (150 m) of the upper aquifer. [6]
Percolation ponds were built in the margins of the Santa Clara Valley to help increase the rate of recharge with rainfall runoff. However, the percolation ponds did not produce any uplift, due to the compacted interbeds of the upper aquifer. [5] Recharge wells pump treated water into the confined region of the aquifer, which has produced uplift.
The quality of the groundwater is considered "good", but if the demand for ground water exceeds the amount replenished, then there would be increased the risk of seawater intrusion, which may degrade the water quality. [6] The characteristic of the water is identified to be calcium bicarbonate, which occurs in the region of 200 feet (61 m) and above the subsurface, while in-between 200–1,000 feet (61–305 m), it is sodium bicarbonate. [8]
An aquifer is an underground layer of water-bearing material, consisting of permeable or fractured rock, or of unconsolidated materials. Aquifers vary greatly in their characteristics. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology. Related terms include aquitard, which is a bed of low permeability along an aquifer, and aquiclude, which is a solid, impermeable area underlying or overlying an aquifer, the pressure of which could lead to the formation of a confined aquifer. The classification of aquifers is as follows: Saturated versus unsaturated; aquifers versus aquitards; confined versus unconfined; isotropic versus anisotropic; porous, karst, or fractured; transboundary aquifer.
Santa Barbara County, officially the County of Santa Barbara, is a county located in Southern California. As of the 2020 census, the population was 448,229. The county seat is Santa Barbara, and the largest city is Santa Maria.
Goleta is a city in southern Santa Barbara County, California, United States. It was incorporated as a city in 2002, after a long period as the largest unincorporated populated area in the county. As of the 2000 census, the census-designated place (CDP) had a total population of 55,204. A significant portion of the census territory of 2000 did not include the newer portions of the city. The population of Goleta was 32,690 at the 2020 census. It is known for being close to the University of California, Santa Barbara (UCSB), campus.
The water table is the upper surface of the zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with groundwater, which may be fresh, saline, or brackish, depending on the locality. It can also be simply explained as the depth below which the ground is saturated.
Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available fresh water in the world is groundwater. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock become completely saturated with water is called the water table. Groundwater is recharged from the surface; it may discharge from the surface naturally at springs and seeps, and can form oases or wetlands. Groundwater is also often withdrawn for agricultural, municipal, and industrial use by constructing and operating extraction wells. The study of the distribution and movement of groundwater is hydrogeology, also called groundwater hydrology.
The Governor Edmund G. Brown California Aqueduct is a system of canals, tunnels, and pipelines that conveys water collected from the Sierra Nevada Mountains and valleys of Northern and Central California to Southern California. Named after California Governor Edmund Gerald "Pat" Brown Sr., the over 400-mile (640 km) aqueduct is the principal feature of the California State Water Project.
Fossil water, fossil groundwater, or paleowater is an ancient body of water that has been contained in some undisturbed space, typically groundwater in an aquifer, for millennia. Other types of fossil water can include subglacial lakes, such as Antarctica's Lake Vostok. UNESCO defines fossil groundwater as "water that infiltrated usually millennia ago and often under climatic conditions different from the present, and that has been stored underground since that time."
In the field of hydrogeology, storage properties are physical properties that characterize the capacity of an aquifer to release groundwater. These properties are storativity (S), specific storage (Ss) and specific yield (Sy). According to Groundwater, by Freeze and Cherry (1979), specific storage, [m−1], of a saturated aquifer is defined as the volume of water that a unit volume of the aquifer releases from storage under a unit decline in hydraulic head.
The Floridan aquifer system, composed of the Upper and Lower Floridan aquifers, is a sequence of Paleogene carbonate rock which spans an area of about 100,000 square miles (260,000 km2) in the southeastern United States. It underlies the entire state of Florida and parts of Alabama, Georgia, Mississippi, and South Carolina.
The Santa Ynez River is one of the largest rivers on the Central Coast of California. It is 92 miles (148 km) long, flowing from east to west through the Santa Ynez Valley, reaching the Pacific Ocean at Surf, near Vandenberg Space Force Base and the city of Lompoc.
Santa Maria River on the Central Coast of California, is formed at the confluence of the Sisquoc River and Cuyama River, just east of the city of Santa Maria, and flows 24.4 miles (39.3 km) to its delta at the Pacific Ocean.
The Cuyama River is a 118-mile-long (190 km) river in southern San Luis Obispo County, northern Santa Barbara County, and northern Ventura County, in the U.S. state of California. It joins the Sisquoc River forming the Santa Maria River. The river's name comes from an Indian village named for the Chumash word kuyam, meaning "clam" or "freshwater mollusk".
Overdrafting is the process of extracting groundwater beyond the equilibrium yield of an aquifer. Groundwater is one of the largest sources of fresh water and is found underground. The primary cause of groundwater depletion is the excessive pumping of groundwater up from underground aquifers. Insufficient recharge can lead to depletion, reducing the usefulness of the aquifer for humans. Depletion can also have impacts on the environment around the aquifer, such as soil compression and land subsidence, local climatic change, soil chemistry changes, and other deterioration of the local environment.
The Los Gatos Creek runs 24 miles (39 km) in California through Santa Clara Valley Water District's Guadalupe Watershed from the Santa Cruz Mountains northward through the Santa Clara Valley until its confluence with the Guadalupe River in downtown San Jose. The Guadalupe River then continues onward into San Francisco Bay.
The Santa Clara Valley Water District provides stream stewardship, wholesale water supply and flood protection for Santa Clara County, California, in the southern San Francisco Bay Area.
Groundwater-related subsidence is the subsidence of land resulting from unsustainable groundwater extraction. It is a growing problem in the developing world as cities increase in population and water use, without adequate pumping regulation and enforcement. One estimate has 80% of serious U.S. land subsidence problems associated with the excessive extraction of groundwater.
The Central Valley in California subsides when groundwater is pumped faster than underground aquifers can be recharged. The Central Valley has been sinking (subsiding) at differing rates since the 1920s and is estimated to have sunk up to 28 feet. During drought years, the valley is prone to accelerated subsidence due to groundwater extraction. California periodically experiences droughts of varying lengths and severity.
Borrego Valley Groundwater Basin, located in the very southern region of California, is one of the driest basins in the state. With climate change predicted to have strong effects into foreseeable future, the region is viewed with a skepticism in the sustainable use of water at current rates of consumption. Both natural and man-made geographic divisions within this basin allow for a closer inspection of the various management techniques implemented throughout the years, and provide a basis for what may be pursued for an uncertain future.
Joseph Fairfield Poland (1908–1991) was the founding expert in the hydrogeologic field of land subsidence. He committed 50 years of his life to understanding and bringing awareness to the issue. Land subsidence results from over pumping groundwater that leads to compaction of unconsolidated aquifer systems and is the leading cause of land subsidence. He pioneered invaluable research on the subject throughout his career at United States Geological Survey (USGS).
Principal aquifers of California are those principal aquifers of the United States that lie within the California state boundaries. Per the Oxford Dictionary of Environment and Conservation, an aquifer is a "body of permeable and/or porous rock that is underlain by impermeable rock and through which groundwater is able to flow."
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