Interpretive Glossary of Water-related Terms and Expressions - E

ecosystem: A limited and specific micro-community within the environment.

effective permeability: See permeability (2).

effluent: (1) Relative to any form of treatment of liquids, any liquid that flows out. Can be a filtrate. Effluent water, if it can be reclaimed through filtration and chemical means, is reclaimed for reuse and may be recycled a number of times through additional beneficial uses, or returned. Effluent is a downstream product that has been taken from the original renewable water, i.e. the original source of effluent is renewable water. Effluent, in any quantity, has reduced renewable water by that same quantity.

Effluent is an after product of beneficial use. The amount of effluent is dependent on the efficiency or inefficiency of the beneficial use and reclamation processes. No matter what is done to the effluent, it cannot add to or increase the renewable water supply from whence it was taken, but it can minimize waste by reuse and contribute to preservation by downstream replenishment. Reclamation and recycling are important parts of conservation and preservation, but neither is part of the renewal process. Renewable water can be renewed only through the hydrologic cycle of water movement of which precipitation is the key to the renewal and sustainability of our water supply. See hydrologic cycle.

In a hypothetical example, when or if there is a break in the hydrologic cycle and the renewal process ceases, and when stores and pressures are depleted, there will be no more downstream effluent to be reclaimed and reused. Effluent, therefore, depends on the renewal process, but the renewal process does not depend on effluent.

(2) Liquid sewage or other wastewater discharged with or without treatment into the environment.

(3) Relative to a drilling mud, it is the mud filtrate that penetrates the formation during the well-drilling process.

effluent exchange: The practice of exchanging suitable wastewater effluent for other water sources, without causing injury to other water rights, as a replacement source for diversion of water farther upstream that would otherwise have been out of priority. CSU.

elasticity: See under bulk modulus.

end cap: A cap or nose placed at the downhole end of the casing to prevent sediment from entering the casing.

energy: Non specific. (1) Ability to perform work or provide force. Examples, artesian head, pore pressure, water pressure, hydrostatic pressure, heat.

(2) A form of power. Kinetic, gravity, hydraulic, electric, wind, water, solar.

environment: (1) Our natural surroundings of earth, air, water, and other natural resources that sustain life and maintain equilibrium in the quality of life.

(2) The immediate surroundings of the well bore at the depth of interest in a water well.

(3) The natural conditions existing at the time when an event takes place or took place.

environmental concerns: A recognition of the fragile equilibrium provided by our environment, and that without smart and careful management that equilibrium can become unbalanced, natural resources damaged, and the quality of life greatly diminished. Has been explicitly endorsed by the General Assembly as a legitimate concern in land use planning by local governments. Involves preservation and conservation.

eolian: Pertains to material transported by and deposited by wind. See aeolian.

ephemeral stream: Generally a small stream, or upper reach of a stream, that flows only in direct response to precipitation. It receives no protracted water supply from melting snow or other sources and its channel is above the water table at all times. NSSH.

equity: As it applies to ownerships of ground water in the different aquifers. It has been legislated that the ownership of ground water is to be allocated upon the basis of the ownership of the overlying land. But, the reality is that the quality of the aquifers from which the water comes is not all equal and the efficiency that rock releases its hold on water can differ from location to location and from aquifer to aquifer. A true measure of equity is not how much water is in place, but how much water can be recovered or can be produced by employing normal methods. See equity determination.

equity determination: Although it is the intention of legislation to be fair, the de facto result is that fairness does not always follow. Additionally, water knows no political or surface boundaries. As a result, water migrates across surface boundaries, flowing from a region of higher formation pressure to a region at lower formation pressure such as the drainage area of a series of wells, or drainage area of a dominant producing well. When this migration is caused by water production from another well, well-to-well interference can result in decreasing energy or pore pressure at inferior wells. This interference, in the form of pressure depletion, can reduce the producing life of a well, resulting in a decrease in equity and can be recognized by the lowering of the static water level(s)in a nearby monitoring well(s). See Darcy’s equation (3) and water level (1).

The Colorado Supreme Court holds that ground water is a public resource. Technically, the ownership of the waters produced belongs to the owners of land overlying the aquifer in proportion to their predetermined equities. The oil and gas industry recognized this problem of ownership many years ago and devised formulae to determine equities for all owners or leaseholders of land overlying shared reserves or resources. Along with the areal extent of overlying land and aquifer thickness, other factors influencing the length of time and efficiency with which water can be produced, and ultimately controlling the quantity of water that can be recovered are: formation pressure, porosity, permeability, grain size and surface area, clayiness, mineralization, consolidation, connectivity, irreducible water, etc. Only by addressing as many of these factors and their changes, as are necessary and appropriate, can equity and injury be defined. See Darcy’s equation, drainage, deplete, clay, fines, permeability, pore pressure, recovery factor, resistance to flow, Senate Bill 5, withdrawal process.

erosion: A natural process by which soil or ground surface is weathered away by the action of water, wind, freezing or landslides.

eutrophication: The process of surface water nutrient enrichment causing a water body to fill with aquatic plants and algae. CSU.

evaporation: (1) The physical process by which a liquid or solid changes to a gaseous state. A phenomenon that occurs at the surface usually between liquids and gases. Near the surface of liquids, and some solids such as ice, some molecules are continually breaking away from the cohesive forces that bind them. See surface tension. At the same time some of the molecules in the vapor phase created above or outside the surface of the cohesive substance are returning. When the conditions are such that the number of escaping molecules exceeds the number of returning molecules, evaporation will take place and the volume of the cohesive substance will diminish. See also sublimation.

(2) When the number of molecules escaping a liquid's cohesive surface exceeds the number of returning molecules, a vapor pressure is created in the gaseous phase. When an equilibrium is reached between escaping and returning molecules the gaseous phase will be saturated. When the vapor pressure equals the ambient pressure or atmospheric pressure, boiling will occur.

evaporite: A mineral that has been precipitated from a highly concentrated water solution as a result of evaporation.

evapotranspiration: 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. See Consumptive Use.

exchange: Of water. Diverted out of priority at one point of diversion by replacing it with a like amount of water at another point of diversion. Compare effluent exchange.

exempt uses: Any recognized uses that are not subject to administration under the priority system. CSU.

exempt well: Exempt wells do not require an augmentation plan, while most nonexempt wells do require an augmentation plan. Exempt wells are usually limited to 15 gpm and require non- vaporative wastewater systems. See also non-exempt well. CSU.

extrusive: A term that describes igneous rock that has been formed from magma that has cooled and solidified upon reaching the surface or near surface of the ground. Also see magma.


Compiled and Edited by Robert C. Ransom


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