Glossary
Acre-feet (AF) – The volume of water necessary to cover one acre to a depth of one foot. Conversion to gallons- 1 acre-foot = 325,851 gallons.
Alluvial — (1) Pertaining to processes or materials associated with transportation or deposition by running water. (2)Pertaining to or composed of alluvium, or deposited by a stream or running water. (3) An adjective referring to soil or earth material which has been deposited by running water, as in a riverbed, flood plain, or delta.
Aquifer – A geologic formation, group of formations, or part of a formation that contains sufficient saturated permeable material to yield significant quantities of water to wells and springs.
Base Flow — (1) The flow that a perennially flowing stream reduces to during the dry season. It is supported by groundwater seepage into the channel. (2) The fair-weather or sustained flow of streams; that part of stream discharge not attributable to direct runoff from precipitation, snowmelt, or a spring. Discharge entering streams channels as effluent from the groundwater reservoir. (3) The volume of flow in a stream channel that is not derived from surface run-off. Base flow is characterized by flow regime (frequency, magnitude, and duration daily, seasonally, and yearly), by minimum low flow events and in context of the size and complexity of the stream and its channel.
Compact, Water — An agreement between states, ratified by Congress, providing for the division and apportionment of waters of an interstate river or other body of water.
Environmental Impact Statement (EIS) — A report required by Section 102(2) (c) of Public Law 91–190, National Environmental Policy Act (NEPA), for all major projects which significantly impact on the quality of the human environment or are environmentally controversial. The EIS is a detailed and formal evaluation of the favorable and adverse environmental and social impacts of a proposed project and its alternatives. A tool for decision making, the EIS describes the positive and negative effects of an undertaking and cites possible, less environmentally disruptive alternative actions.
Evapotranspiration (ET) — (1) The process by which plants take in water through their roots and then give it off through the leaves as a by-product of respiration; the loss of water to the atmosphere from the earth’s surface by evaporation and by transpiration through plants. (2) The quantity of water transpired (given off), retained in plant tissues, and evaporated from plant tissues and surrounding soil surfaces. (3) The sum of Evaporation and Transpiration from a unit land area. (4) The combined processes by which water is transferred from the earth surface to the atmosphere; evaporation of liquid or solid water plus transpiration from plants. (5) The combined evaporative-type processes, including evaporation, interception, and transpiration, usually applied to biological systems. Evapotranspiration occurs through evaporation of water from the surface, evaporation from the capillary fringe of the groundwater table, and the transpiration of groundwater by plants (Phreatophytes) whose roots tap the capillary fringe of the groundwater table. The sum of evaporation plus transpiration.
Groundwater – Water below the surface of the earth.
Groundwater Model - A groundwater model is a computer model of groundwater flow systems, used by hydrogeologists. Groundwater models are used to simulate and predict aquifer conditions. Groundwater modeling is also referred to as hydrologic modeling. For more information on groundwater modeling visit: http://www.ksda.gov/subbasin/content/317
Hydraulic Conductivity (Ê) — Simply, a coefficient of proportionality describing the rate at which water can move through an aquifer or other permeable medium. The density and kinematic viscosity of the water must be considered in determining hydraulic conductivity. More specifically, the volume of water at the existing kinematic viscosity that will move, in unit time, under a unit Hydraulic Gradient through a unit area measured at right angles to the direction of flow, assuming the medium is isotropic and the fluid is homogeneous. In the Standard International System, the units are cubic meters per day per square meter of medium (m3/day/m2) or m/day (for unit measures).
Hydrologic — Of or pertaining to hydrology, that is the science dealing with water, its properties, phenomena, and distribution over the earth’s surface.
Interstate Water Compact — (1) Broadly, an agreement between two or more states regarding competing demands for a water resource which are beyond the legal authority of one state alone to solve. (2) States administer water rights within their own political boundaries; however, the process becomes more complicated when involving an interstate body of water (Interstate Water). Under these conditions there are three possible ways to achieve an interstate allocation of water: (1) A suit for equitable apportionment brought by the states in the U.S. Supreme Court; (2) a Congressional act; and (3) an interstate compact. An interstate compact is an agreement negotiated between states, adopted by their state legislatures, and then approved by Congress. Once an allocation of interstate water is determined by such a means, the individual states may then issue water rights to its share of the water through their normal administrative process. Interstate compacts have been traditionally used in making water allocations in the western states.
Phreatophyte — (1) Literally, a water-loving plant, one that thrives in wet sites and/or has the ability to tap deep saturation zones. (2) A deep rooted plant that obtains its water from the water table. (3) A plant that habitually obtains its water supply from the Zone of Saturation, either directly or through the Capillary Fringe.
Recharge (Hydrologic) — (1) The downward movement of water through soil to groundwater. (2) The process by which water is added to the Zone of Saturation. (3) The introduction of surface or ground water to groundwater storage such as an aquifer. Recharge or replenishment of groundwater supplies consists of three (3) types: [1] Natural Recharge which consists of precipitation or other natural surface flows making their way into groundwater supplies; [2] Artificial or Induced Recharge which includes actions by man specifically designed to increase supplies in a groundwater reservoirs through various methods such as water spreading (flooding), ditches, and pumping techniques; and [3] Incidental Recharge which consists of actions, such as irrigation and water diversion, which add to groundwater supplies but are intended for other purposes.
Saturated Thickness (Aquifer) — The thickness of the portion of the aquifer in which all pores, or voids, are filled with water. In a Confined Aquifer, this is generally the aquifer thickness. In an Unconfined Aquifer, this is the distance between the water table and the base of the aquifer.
Specific Yield (Ground Water) — The ratio of the volume of water that a rock will yield by gravity, after being saturated, to its own volume, expressed as a percentage.
Transmissivity, also Coefficient of Transmissivity (ô) — The ability of an aquifer to transmit water. The rate at which water of the prevailing kinematic viscosity is transmitted through a unit width of the aquifer under a unit Hydraulic Gradient. It is equal to an integration of the hydraulic conductivities across the saturated part of the aquifer perpendicular to the flow paths. Also, the rate at which water is transmitted through a unit width of an aquifer under a unit hydraulic gradient. Transmissivity values are given in gallons per minute through a vertical section of an aquifer 1 foot wide and extending the full saturated height of an aquifer under a hydraulic gradient of one in the English Engineering System; in the Standard International System, transmissivity is given in cubic meters per day through a vertical section of an aquifer 1 meter wide and extending the full saturated height of an aquifer under hydraulic gradient of one. It is a function of properties of the liquid, the porous media, and the thickness of the porous media.
Tributary — (1) A stream which joins another stream or body of water. (2) A stream or other body of water, surface or underground, which contributes its water, even though intermittently and in small quantities, to another and larger stream or body of water.
Water Budget — (Hydrology) An accounting of the inflows to, the outflows from, and the storage changes of water in a hydrologic unit or system.