Karst is a topography formed from the dissolution of soluble carbonate rocks such as limestone, dolomite, and gypsum. It is characterized by features like poljes above and drainage systems with sinkholes and caves underground. More weathering-resistant rocks, such as quartzite, can also occur, given the right conditions.
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.
Subsidence is a general term for downward vertical movement of the Earth's surface, which can be caused by both natural processes and human activities. Subsidence involves little or no horizontal movement, which distinguishes it from slope movement.
A sinkhole is a depression or hole in the ground caused by some form of collapse of the surface layer. The term is sometimes used to refer to doline, enclosed depressions that are also known as shakeholes, and to openings where surface water enters into underground passages known as ponor, swallow hole or swallet. A cenote is a type of sinkhole that exposes groundwater underneath. Sink and stream sink are more general terms for sites that drain surface water, possibly by infiltration into sediment or crumbled rock.
Water extraction is the process of taking water from any source, either temporarily or permanently, for flood control or to obtain water for, for example, irrigation. The extracted water could also be used as drinking water after suitable treatment.
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 freshwater 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.
Saltwater intrusion is the movement of saline water into freshwater aquifers, which can lead to groundwater quality degradation, including drinking water sources, and other consequences. Saltwater intrusion can naturally occur in coastal aquifers, owing to the hydraulic connection between groundwater and seawater. Because saline water has a higher mineral content than freshwater, it is denser and has a higher water pressure. As a result, saltwater can push inland beneath the freshwater. In other topologies, submarine groundwater discharge can push fresh water into saltwater.
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.
Houston, the most populous city in the Southern United States, is located along the upper Texas Gulf Coast, approximately 50 miles (80 km) northwest of the Gulf of Mexico at Galveston. The city, which is the ninth-largest in the United States by area, covers 601.7 square miles (1,558 km2), of which 579.4 square miles (1,501 km2), or 96.3%, is land and 22.3 square miles (58 km2), or 3.7%, is water.
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 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. Management of aquifer resources is associated with the Santa Clara Valley Water District.
Kissingen Spring was a natural spring formerly flowing in Polk County, Southwest Florida. It was also a venue for recreation until it dried up in 1950. Hundreds of wells drilled into the Floridan Aquifer may have caused the demise of the springs. Its site is located near the northern end of Peace River, approximately 3/4 mile east of U.S. Highway 17 and 4 miles south of Florida SR 60 / south of Bartow.
Groundwater pollution occurs when pollutants are released to the ground and make their way into groundwater. This type of water pollution can also occur naturally due to the presence of a minor and unwanted constituent, contaminant, or impurity in the groundwater, in which case it is more likely referred to as contamination rather than pollution. Groundwater pollution can occur from on-site sanitation systems, landfill leachate, effluent from wastewater treatment plants, leaking sewers, petrol filling stations, hydraulic fracturing (fracking) or from over application of fertilizers in agriculture. Pollution can also occur from naturally occurring contaminants, such as arsenic or fluoride. Using polluted groundwater causes hazards to public health through poisoning or the spread of disease.
The Willamette Lowland basin-fill aquifer is 31,000 km2, 12,000 square mile aquifer underlying the region of Oregon and parts of Washington (state) between the Oregon Coast Range and the Cascade Range. The aquifer shares a name with the local river, the Willamette River, originating from a Clackamas Chinook word. The "mette" of Willamette was used by the Clackamas to mean water or river. The Willamette valley is home to 70% of Oregon's population, with the aquifer supplying water for agricultural, domestic, and industrial purposes. Reported in 2005, the total water use from the aquifer was 1.6 hm3 per day, with 58% going to irrigation, 24% to public supply, and 18% to industrial use. In general, the aquifer withdraw is sufficiently compensated in the long term by recharge through precipitation, however regions of the aquifer have shown long term declines, including that regions underlain by the Columbia River basalt unit. However, during the dry season from June-September, withdrawals from the aquifer result is significant seasonal variations in the ground water table height, changing by more than 60 ft. In the state of Oregon, all water is publicly owned and maintenance and protection of water is done by the Oregon Water Resources Department and the Oregon Water Resources Commission. However, local governments can provide land use permits for aquifer use, notably, use for new rural residences.
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.
In between November 2013 to 2017, more than 200 sinkholes were formed in the Armala area of Pokhara. The sinkholes were formed mostly in the paddy fields in the alluvial fan deposit. The sinkholes terrorised and displaced hundreds of local residents.
A fissure is a long, narrow crack opening along the surface of Earth. The term is derived from the Latin word fissura, which means 'cleft' or 'crack'. Fissures emerge in Earth's crust, on ice sheets and glaciers, and on volcanoes.
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).
