A spreading ground is a

water conservation Water conservation includes all the policies, strategies and activities to sustainably manage the natural resource of fresh water, to protect the hydrosphere, and to meet the current and future human demand (thus avoiding water scarcity). Populati ...

facility that retains

surface water Surface water is water located on top of land forming terrestrial (inland) waterbodies, and may also be referred to as ''blue water'', opposed to the seawater and waterbodies like the ocean. The vast majority of surface water is produced by pr ...

long enough for it to percolate into the

soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former ...

. Spreading grounds must be located where underlying soils are permeable and connected to a target

aquifer An aquifer is an underground layer of water-bearing, permeable rock, rock fractures, or unconsolidated materials ( gravel, sand, or silt). Groundwater from aquifers can be extracted using a water well. Aquifers vary greatly in their characteri ...

. Locating them above silt or clay would prevent the surface water from reaching formations that store water. When natural percolation of precipitation is insufficient to replenish groundwater withdrawn for human use, artificial recharge helps prevent aquifer depletion, subsidence and

saltwater intrusion 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, ...

. Spreading grounds are one of several available technologies, and are useful to harness

storm water runoff Surface runoff (also known as overland flow) is the flow of water occurring on the ground surface when excess rainwater, stormwater, meltwater, or other sources, can no longer sufficiently rapidly infiltrate in the soil. This can occur when the s ...

in populated areas with low annual precipitation. For example,

Los Angeles County, California Los Angeles County, officially the County of Los Angeles, and sometimes abbreviated as L.A. County, is the most populous county in the United States and in the U.S. state of California, with 9,861,224 residents estimated as of 2022. It is th ...

has 27 such facilities, and four more operated in conjunction with the department, many of which date to the 1930s. While managed aquifer recharge (MAR) projects utilizing storm water and diverted surface water runoff augment groundwater recharge, data suggests that the infiltration capacity of spreading grounds in drought-prone regions is underused due to the seasonality of

rainfall Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water ...

. In response, interest is being generated around MAR projects that utilize recycled water to supplement other water sources. Orange County's Groundwater Replenishment System serves as an example of one such system that is combining recycled water and storm water to recharge groundwater through spreading grounds to meet the municipality's annual water needs. Today, many spreading grounds, which were once considered single-purpose facilities, are being converted to combine municipalities' goals for groundwater recharge with demands for additional recreational opportunities, green space and wildlife habitat. The Dominguez Gap Wetlands in

Long Beach, California Long Beach is a city in Los Angeles County, California. It is the 42nd-most populous city in the United States, with a population of 466,742 as of 2020. A charter city, Long Beach is the seventh-most populous city in California. Incorporate ...

, which consists of two spreading grounds, is an example of one of these multi-purpose facilities. While the facility's east basin was converted into constructed wetlands, the west basin remains a spreading ground that recharges the local aquifer by an estimated 450-acre feet annually.Landers J. Constructed Wetlands to Improve Los Angeles River's Water Quality. ''Civil Engineering (08857024)'' erial online July 2008;78(7):31-33. Available from: GreenFILE, Ipswich, MA. Accessed June 1, 2018.

References

{{Reflist Water resources management