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Water glossary



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Water Glossary - S

  • Safe water: Water that does not contain harmful bacteria, toxic materials, or chemicals, and is considered safe for drinking.

  • Safe yield: The annual amount of water that can be taken from a source of supply over a period of years without depleting that source beyond its ability to be naturally refilled.

  • Saline water: Water that contains more than 1,000 milligrams per liter of dissolved solids.

  • Salinity: Amount of dissolved salts in a given volume of water.

  • Saltwater intrusion: The invasion of fresh surface water or groundwater by saltwater.

  • Sand filtration: Sand filtration is a frequently used and very robust method to remove suspended solids from water. The filtration medium consists of a multiple layer of sand with a variety in size and specific gravity. Sand filters can be supplied in different sizes and materials both hand operated and fully automatically.

  • Sanitary landfill: Landfill that is lined with plastic or concrete or located in clay-rich soils to prevent hazardous substances from leaking into the environment.

  • Sanitary sewers: Underground pipes that carry off only domestic or industrial waste, not storm water.

  • Saturated zone: The area below the water table where all open spaces are filled with water.

  • Saturation: The condition of a liquid when it has taken into solution the maximum possible quantity of a given substance at a given temperature and pressure.

  • Scale: The precipitate that forms on surfaces in contact with water as the result of a physical or chemical change.

  • Screening: Use of screens to remove coarse floating and suspended solids from sewage.

  • Seal: The impermeable material, such as cement grout bentonite, or puddling clay placed in the annular space between the borehole wall and the casing of a water well to prevent the downhole movement of surface water or the vertical mixing of artestian waters.

  • Seasonal rate structure: Rate structure that bills all water consumed during the summer or peak season at a higher rate than during the other seasons.

  • Secondary treatment: Second step in most waste treatment systems, in which bacteria break down the organic parts of sewage wastes; usually accomplished by bringing the sewage and bacteria together in trickling filters or in the activated sludge process. Compare primary treatment, tertiary treatment. Compare primary treatment, tertiary treatment.

  • Secondary wastewater treatment plant: A facility that reduces pollutants and suspended solids to a greater level than that achieved by a primary treatment plant; the water goes through additional treatment processes, producing "cleaner" wastewater.

  • Sediment: Fragmented organic or inorganic material derived from the weathering of soil, alluvial, and rock materials; removed by erosion and transported by water, wind, ice, and gravity.

  • Sedimentary cycle: Biogeochemical cycle in which materials primarily are moved from land to sea and back again.

  • Sedimentation: The deposition of sediment from a state of suspension in water or air.

  • Sediments: Soil, sand, and minerals washed from land into water, usually after rain.

  • Seep: A spot where water contained in the ground oozes slowly to the surface and often forms a pool; a small spring.

  • Seiche: A periodic oscillation, or standing wave, in an enclosed water body the physical dimensions of which determine how frequently the water level changes.

  • Self-supplied water: Water withdrawn from a surface- or ground-water source by a user rather than being obtained from a public supply.

  • Semi-confined aquifer: An aquifer partially confined by soil layers of low permeability through which recharge and discharge can still occur.

  • Semipermeable: A medium that allows water to pass through, but rejects dissolved solids, so that it can be used to separate solids from water.

  • Separate sewer: A sewer system that carries only sanitary sewage, not stormwater runoff. When a sewer is constructed this way, wastewater treatment plants can be sized to treat sanitary wastes only and all of the water entering the plant receives complete treatment at all times. Compare combined sewer.

  • Separation: The isolation of the various compounds in a mixture.

  • Septic tank: Tank used to hold domestic wastes when a sewer line is not available to carry them to a treatment plant; part of a rural on-site sewage treatment system.

  • Settleable solids: In sewage, suspended solids that will settle when the sewage is brought to a quiet state for a reasonable length of time, usually two hours.

  • Settling: The process of sinking of a substance sinking in water. This occurs when the substance does not dissolve in water and its density is larger than that of water.

  • Settling pond: A holding pond for wastewater where heavier particles sink to the bottom for removal and disposal.

  • Sewage: The waste and wastewater produced by residential and commercial establishments and discharged into sewers.

  • Sewage contamination: The introduction of untreated sewage into a water body.

  • Sewage sludge: Sludge produced in a public sewer.

  • Sewage system: Pipelines or conduits, pumping stations, force mains, and all other structures, devices, and facilities used for collecting or conducting wastes to a point for treatment or disposal.

  • Sewer: A channel or conduit that carries wastewater and storm water runoff from the source to a treatment plant or receiving stream.

  • Sewerage: The entire system of sewage collection, treatment, and disposal.

  • Silt: Fine particles of sand or rock that can be picked up by the air or water and deposited as sediment.

  • Siltation: The deposition of finely divided soil and rock particles upon the bottom of stream and river beds and reservoirs.

  • Sleet: Precipitation which is a mixture of rain and ice.

  • Slickensides: A smooth striated polished surface produced on rock by movement along a fault.

  • Sludge: A semi-solid residue from any of a number of air or water treatment processes.

  • Snow: Precipitation in the form of branched hexagonal crystals, often mixed with simple ice crystals, which fall more or less continuously from a solid cloud sheet. These crystals may fall either separately or in cohesive clusters forming snowflakes.

  • Soft water: Any water that does not contain large concentrations of the dissolved minerals calcium or magnesium.

  • Softening: The removal of calcium and magnesium from water to reduce hardness.

  • Soil erosion: The processes by which soil is removed from one place by forces such as wind, water, waves, glaciers, and construction activity and eventually deposited at some new place.

  • Solidification: Removal of wastewater from a waste or changing it chemically to make it less permeable and susceptible to transport by water.

  • Solubility: The amount of mass of a compound that will dissolve in a unit volume of water.

  • Solute: Any substance derived from the atmosphere, vegetation, soil, or rock that is dissolved in water.

  • Solvent: Substances (usually liquid) capable of dissolving or dispersing one or more other substances.

  • Source protection: Protection of a water source by a small utility, ranging from simple sanitary surveys of a watershed to the development and implementation of complex land use controls, in an effort to avoid water contamination.

  • Sparger: A device that introduces compressed air into a liquid.

  • Sparging: Injection of air below the water table to strip dissolved volatile organic compounds and to facilitate aerobic biodegradation of organic compounds.

  • Specific conductance: A measure of the ability of a water to conduct an electrical current. Specific conductance is related to the type and concentration of ions in solution and can be used for approximating the dissolved solids concentration in water. In general, for the san antonio river basin, conductivity *.6 approximates tds. People monitoring water quality can measure electrical conductivity quickly in the field and estimate tds without doing any lab tests at all. See tds.

  • Specific heat: The amount of heat required to raise the temperature of a kilogram of a substance (water) by 1 degree Celsius.

  • Spillway: The channel or passageway around or over a dam through which excess water is diverted.

  • Spoils: Dirt or rock that has been removed from its original location, destroying the composition of the soil in the process, as with strip-mining or dredging.

  • Spray irrigation: Application of finely divided water droplets to crops using artificial means.

  • Spring: An area where groundwater flows naturally onto the land surface.

  • Sprinkler irrigation: A pressurized irrigation system where water is distributed through pipes to the field and applied through a variety of sprinkler heads or nozzles. Pressure is used to spread water droplets above the crop canopy to simulate a rainfall.

  • Standard industrial classification (SIC) codes: Four- digit codes established by the Office of Management and Budget and used in the classification of establishments by type of activity in which they are engaged.

  • Standard solution: Any solution in which the concentration is known.

  • Stoke's Law: A method to calculate the rate of fall of particles through a fluid, based on density, viscosity and particle size.

  • Storm sewer: A system of pipes (separate from sanitary sewers) that carry only water runoff from building and land surfaces.

  • Stormwater discharge: Precipitation that does not infiltrate into the ground or evaporate due to impervious land surfaces but instead flows onto adjacent land or water areas and is routed into drain/sewer systems.

  • Stream: Any body of running water moving under gravity flow through clearly defined natural channels to progressively lower levels.

  • Stream segment: Refers to the surface waters of an approved planning area exhibiting common biological, chemical, hydrological, natural, and physical characteristics and processes. Segments will normally exhibit common reactions to external stress such as discharge or pollutants.

  • Streamflow: The discharge that occurs in a natural channel. Although the term "discharge" can be applied to the flow of a canal, the word "streamflow" uniquely describes the discharge in a surface stream. The term "streamflow" is more general than the term "runoff", as streamflow may be applied to discharge whether or not it is affected by diversion or regulation.

  • Sublimation: The transition of water directly from the solid state to the gaseous state, without passing through the liquid state; or vice versa. Compare condensation, evaporation.

  • Submetering: Use of separate meters to indicate individual water use in apartments, condominiums, and trailer homes, while the entire complex of units continues to be metered by the main supplier.

  • Subsidence: Sinking down of part of the earth's crust due to underground excavation, such as removal groundwater.

  • Supply: A schedule that shows the various quantities of things offered for sale at various prices at a point in time. Compare demand.

  • Surface impoundment: An indented area in the land's surface, such a pit, pond, or lagoon.

  • Surface irrigation: Application of water by means other than spraying such that contact between the edible portion of any food crop and the irrigation water is prevented.

  • Surface tension: The elastic-like force in a body, especially a liquid, tending to minimize, or constrict, the area of the surface.

  • Surface water: All water naturally open to the atmosphere (rivers, lakes, reservoirs, streams, impoundments, seas, estuaries, etc.); also refers to springs, wells, or other collectors that are directly influenced by surface water.

  • Surface-water disposal: Refers to the release of reclaimed water or treated effluent directly into a surface water body (including marshes or wetlands). This does not include water discharged into ponds for holding or percolation purposes.

  • Surge irrigation: The intermittent application of water to irrigation pathways. This method pulses water down the furrow and creates more uniform irrigation.

  • Suspended solids (SS): Defined in waste management, these are small particles of solid pollutants that resist separation by conventional methods. Suspended solids (along with biological oxygen demand) are a measurement of water quality and an indicator of treatment plant efficiency.

  • Sustainable development: Development that ensures that the use of resources and the environment today does not restrict their use by future generations.

  • Sustainable management: Method of exploiting a resource that can be carried on indefinitely. Removal of water from an aquifer in excess of recharge is, in the long term, not a sustainable management method.

  • Sustained overdraft: Long term withdrawal from the aquifer of more water than is being recharged.

  • Swamp: A type of wetland that is dominated by woody vegetation and does not accumulate appreciable peat deposits. Swamps may be fresh water or saltwater and tidal or nontidal.

  • Synergism: The combined action of several chemicals, which produces a total effect greater than the effects of the chemicals separately.

Water glossary