Climate Reporting Terms and Conditions

acre-foot (acre-ft)–the volume of water required to cover 1 acre of land (43,560 square feet) to a depth of 1 foot. Equal to 325,851 gallons or 1,233 cubic meters.

adaptation: The Intergovernmental Panel on Climate Change uses adaptation to refer to measures taken ahead of time to reduce vulnerability to climate change. Taking measures ahead of time to reduce vulnerability is what the NDMC means by mitigation. See also mitigation.

alluvium–deposits of clay, silt, sand, gravel, or other particulate material that has been deposited by a stream or other body of running water in a streambed, on a flood plain, on a delta, or at the base of a mountain.

aquifer–a geologic formation(s) that is water bearing. A geological formation or structure that stores and/or transmits water, such as to wells and springs. Use of the term is usually restricted to those water-bearing formations capable of yielding water in sufficient quantity to constitute a usable supply for people’s uses.

aquifer (confined)–soil or rock below the land surface that is saturated with water. There are layers of impermeable material both above and below it and it is under pressure so that when the aquifer is penetrated by a well, the water will rise above the top of the aquifer.

aquifer (unconfined)–an aquifer whose upper water surface (water table) is at atmospheric pressure, and thus is able to rise and fall.

artesian water–groundwater that is under pressure when tapped by a well and is able to rise above the level at which it is first encountered. It may or may not flow out at ground level. The pressure in such an aquifer commonly is called artesian pressure, and the formation containing artesian water is an artesian aquifer or confined aquifer. See flowing well

artificial recharge–an process where water is put back into groundwater storage from surface-water supplies such as irrigation, or induced infiltration from streams or wells.

Annual streamflow-Mean annual flow is the average flow for the individual year or multi-year period of interest. When working with hydrologic data it is customary to view the data by water years (October-September) rather than by calendar years (January-December).

Baseflow:sustained flow of a stream in the absence of direct runoff. It includes natural and human-induced streamflows. Natural base flow is sustained largely by groundwater discharges.

climate: long terms patterns of weather. Climatology is the study of climate.

climograph: a graph that shows monthly average temperature and precipitation for some location.

conveyance loss–water that is lost in transit from a pipe, canal, or ditch by leakage or evaporation. Generally, the water is not available for further use; however, leakage from an irrigation ditch, for example, may percolate to a groundwater source and be available for further use.

cubic feet per second (cfs)–a rate of the flow, in streams and rivers, for example. It is equal to a volume of water one foot high and one foot wide flowing a distance of one foot in one second. One “cfs” is equal to 7.48 gallons of water flowing each second. As an example, if your car’s gas tank is 2 feet by 1 foot by 1 foot (2 cubic feet), then gas flowing at a rate of 1 cubic foot/second would fill the tank in two seconds.

desalination: the process of removing salts and other minerals from seawater so that it can be used for drinking water.

drought: less rainfall than is expected over an extended period of time, usually several months or longer.

drip irrigation–a common irrigation method where pipes or tubes filled with water slowly drip onto crops. Drip irrigation is a low-pressure method of irrigation and less water is lost to evaporation than high-pressure spray irrigation.

drawdown–a lowering of the groundwater surface caused by pumping.

drought index: a numerical scale that scientists use to describe the severity of a drought. Scientists take many kinds of data (like streamflow, rainfall, temperature, and snowpack) and “blend” it into a single number, called a drought index value, to make it easier to understand the drought conditions of a particular area. Drought indices are one type of drought indicator.

drought indicator: a way to look at one or more variables, such as precipitation, to describe available water in soil or hydrologic systems. It may be a record of a single measurement, such as rainfall at a particular rain gauge. It may also be a complex index. Drought indices (indexes) are a subset of drought indicators.

Dust Bowl: an area of the U.S. Plains that included parts of Kansas, Colorado, Oklahoma, Texas, and New Mexico. The term was coined in the 1930s, when dry weather and high winds caused many dust storms throughout the United States, but particularly in this area.

effluent–water that flows from a sewage treatment plant after it has been treated.

El Niño: a weather phenomenon that occurs in the eastern and central equatorial Pacific Ocean. During an El Niño, the affected area’s winds weaken and sea temperatures become warmer.

erosion: a process that wears the earth’s surface away, causing soil to move from one place to another. It’s a natural process, but human activities can make it worse.

Evaporation: the process of turning from liquid into vapor

evapotranspiration:the sum of evaporation and transpiration and is driven by water availability, solar radiation, and plant type, but also affected by wind and vapor pressure.

flood stage–The elevation at which overflow of the natural banks of a stream or body of water begins in the reach or area in which the elevation is measured.

flowing well/spring–a well or spring that taps groundwater under pressure so that water rises without pumping. If the water rises above the surface, it is known as a flowing well.

groundwater–(1) water that flows or seeps downward and saturates soil or rock, supplying springs and wells. The upper surface of the saturate zone is called the water table. (2) Water stored underground in rock crevices and in the pores of geologic materials that make up the Earth’s crust.

groundwater, confined–groundwater under pressure significantly greater than atmospheric, with its upper limit the bottom of a bed with hydraulic conductivity distinctly lower than that of the material in which the confined water occurs.

groundwater recharge–inflow of water to a groundwater reservoir from the surface. Infiltration of precipitation and its movement to the water table is one form of natural recharge. Also, the volume of water added by this process.

groundwater, unconfined–water in an aquifer that has a water table that is exposed to the atmosphere.

hydroelectricity: electricity created by channeling water through turbines in power stations located below dams.

Hydrograph:a plot of the variation of discharge with respect to time (it can also be the variation of stage or other water property with respect to time).


Hydrologic cycle: also known as the water cycle. the continuous circulation of water in the Earth-atmosphere system. Of the many processes involved in the water cycle, the most important are evaporation, transpiration, condensation, precipitation, and runoff. Although the total amount of water within the cycle remains essentially constant, its distribution among the various processes is continually changing.

Hydrology:the branch of science concerned with the properties of the earth’s water, especially its movement in relation to land.


injection well–refers to a well constructed for the purpose of injecting treated wastewater directly into the ground. Wastewater is generally forced (pumped) into the well for dispersal or storage into a designated aquifer. Injection wells are generally drilled into aquifers that don’t deliver drinking water, unused aquifers, or below freshwater levels.

irrigation–the controlled application of water for agricultural purposes through manmade systems to supply water requirements not satisfied by rainfall. Here’s a quick look at some types of irrigation systems.

Indices- an indicator, sign, or measure of something. For example, the results from the indices are a measure of drought conditions.a value that identifies and is used to locate a particular element within a data array or table.


jet stream: strong wind currents at high altitudes in the earth’s atmosphere. They are thousands of miles long and hundreds of miles wide, and they move weather patterns around the earth.

La Niña: a weather phenomenon that involves unusually cold ocean temperatures in the equatorial Pacific Ocean. La Niña events don’t occur as often as El Niño events.

lentic waters–ponds or lakes (standing water).

levee–a natural or manmade earthen barrier along the edge of a stream, lake, or river. Land alongside rivers can be protected from flooding by levees.

lotic waters–flowing waters, as in streams and rivers.

maximum contaminant level (MCL)–the designation given by the U.S. Environmental Protection Agency (EPA) to water-quality standards promulgated under the Safe Drinking Water Act. The MCL is the greatest amount of a contaminant that can be present in drinking water without causing a risk to human health.

mitigation: actions that we can take before, or at the beginning of, drought to help reduce the impacts of drought. Mitigation includes actions as diverse as drought planning, implementing land use practices that increase the organic content and water-holding capacity of soil, and designing agricultural policy that doesn’t encourage short-term economic gains at the expense of long-term productive capacity. The Intergovernmental Panel on Climate Change uses mitigation to mean reducing emissions of greenhouse gasses.

nephelometric turbidity unit (NTU)–unit of measure for the turbidity of water. Essentially, a measure of the cloudiness of water as measured by a nephelometer. Turbidity is based on the amount of light that is reflected off particles in the water.

NGVD–National Geodetic Vertical Datum. (1) As corrected in 1929, a vertical control measure used as a reference for establishing varying elevations. (2) Elevation datum plane previously used by the Federal Emergency Management Agency (FEMA) for the determination of flood elevations. FEMA current uses the North American Vertical Datum Plane.

NGVD of 1929–National Geodetic Vertical Datum of 1929. A geodetic datum derived from a general adjustment of the first order level nets of the United States and Canada. It was formerly called “Sea Level Datum of 1929” or “mean sea level” in the USGS series of reports. Although the datum was derived from the average sea level over a period of many years at 26 tide stations along the Atlantic, Gulf of Mexico, and Pacific Coasts, it does not necessarily represent local mean sea level at any particular place.

non-point source (NPS) pollution–pollution discharged over a wide land area, not from one specific location. These are forms of diffuse pollution caused by sediment, nutrients, organic and toxic substances originating from land-use activities, which are carried to lakes and streams by surface runoff. Non-point source pollution is contamination that occurs when rainwater, snowmelt, or irrigation washes off plowed fields, city streets, or suburban backyards. As this runoff moves across the land surface, it picks up soil particles and pollutants, such as nutrients and pesticides.

operational definition of drought: how agencies, communities, or individuals will recognize a drought in its early stages. Do they have their own rain gauge, river flow meter, or water level meter? Do they rely on state or national climatological data? Do they have a unique way to measure soil moisture, such as the appearance of certain plants or other environmental features?

outfall–the place where a sewer, drain, or stream discharges; the outlet or structure through which reclaimed water or treated effluent is finally discharged to a receiving water body.

Pacific Decadal Oscillation (PDO):often described as a long-lived El Niño-like pattern of Pacific climate variability. Learn more about it here.

peak flow–the maximum instantaneous discharge of a stream or river at a given location. It usually occurs at or near the time of maximum stage.

per capita use–the average amount of water used per person during a standard time period, generally per day.

point-source pollution–water pollution coming from a single point, such as a sewage-outflow pipe.

polychlorinated biphenyls (PCBs)–a group of synthetic, toxic industrial chemical compounds once used in making paint and electrical transformers, which are chemically inert and not biodegradable. PCBs were frequently found in industrial wastes, and subsequently found their way into surface and groundwaters. As a result of their persistence, they tend to accumulate in the environment. In terms of streams and rivers, PCBs are drawn to sediment, to which they attach and can remain virtually indefinitely. Although virtually banned in 1979 with the passage of the Toxic Substances Control Act, they continue to appear in the flesh of fish and other animals.

porosity–a measure of the water-bearing capacity of subsurface rock. With respect to water movement, it is not just the total magnitude of porosity that is important, but the size of the voids and the extent to which they are interconnected, as the pores in a formation may be open, or interconnected, or closed and isolated. For example, clay may have a very high porosity with respect to potential water content, but it constitutes a poor medium as an aquifer because the pores are usually so small.

potable water–water of a quality suitable for drinking.

potentiometric surface/piezometric surface–the imaginary line where a given reservoir of fluid will “equalize out to” if allowed to flow; a potentiometric surface is based on hydraulic principles.

primary wastewater treatment–the first stage of the wastewater-treatment process where mechanical methods, such as filters and scrapers, are used to remove pollutants. Solid material in sewage also settles out in this process.

prior appropriation doctrine–the system for allocating water to private individuals used in most Western states. The doctrine of Prior Appropriation was in common use throughout the arid West as early settlers and miners began to develop the land. The prior appropriation doctrine is based on the concept of “First in Time, First in Right.” The first person to take a quantity of water and put it to beneficial use has a higher priority of right than a subsequent user. The rights can be lost through nonuse; they can also be sold or transferred apart from the land. Contrasts with riparian water rights.

rating curve–A drawn curve showing the relation between gage height and discharge of a stream at a given gaging station.

recharge–water added to an aquifer. For instance, rainfall that seeps into the ground.

reclaimed wastewater–wastewater-treatment plant effluent that has been diverted for beneficial uses such as irrigation, industry, or thermoelectric cooling instead of being released to a natural waterway or aquifer.

recycled water–water that is used more than one time before it passes back into the natural hydrologic system.

Resilience- the capacity to recover quickly from difficulties; toughness.

return flow–(1) That part of a diverted flow that is not consumptively used and returned to its original source or another body of water. (2) (Irrigation) Drainage water from irrigated farmlands that re-enters the water system to be used further downstream.

return flow (irrigation)–irrigation water that is applied to an area and which is not consumed in evaporation or transpiration and returns to a surface stream or aquifer.

riparian water rights–the rights of an owner whose land abuts water. They differ from state to state and often depend on whether the water is a river, lake, or ocean. The doctrine of riparian rights is an old one, having its origins in English common law. Specifically, persons who own land adjacent to a stream have the right to make reasonable use of the stream. Riparian users of a stream share the streamflow among themselves, and the concept of priority of use (Prior Appropriation Doctrine) is not applicable. Riparian rights cannot be sold or transferred for use on nonriparian land.

Radiation: the emission of energy as electromagnetic waves or as moving subatomic particles, especially high-energy particles that cause ionization.

reservoirs: water that’s collected and stored in natural or manmade lakes.


Runoff: the draining away of water (or substances carried in it) from the surface of an area of land, a building or structure, etc.


secondary wastewater treatment–treatment (following primary wastewater treatment) involving the biological process of reducing suspended, colloidal, and dissolved organic matter in effluent from primary treatment systems and which generally removes 80 to 95 percent of the Biochemical Oxygen Demand (BOD) and suspended matter. Secondary wastewater treatment may be accomplished by biological or chemical-physical methods. Activated sludge and trickling filters are two of the most common means of secondary treatment. It is accomplished by bringing together waste, bacteria, and oxygen in trickling filters or in the activated sludge process. This treatment removes floating and settleable solids and about 90 percent of the oxygen-demanding substances and suspended solids. Disinfection is the final stage

settling pond (water quality)–an open lagoon into which wastewater contaminated with solid pollutants is placed and allowed to stand. The solid pollutants suspended in the water sink to the bottom of the lagoon and the liquid is allowed to overflow out of the enclosure.

submarginal farmland: lands with nutrient-poor soils and/or soils that have been damaged by poor cultivation practices.

specific conductance–a measure of the ability of water to conduct an electrical current as measured using a 1-cm cell and expressed in units of electrical conductance, i.e., Siemens per centimeter at 25 degrees Celsius. Specific conductance can be used for approximating the total dissolved solids content of water by testing its capacity to carry an electrical current. In water quality, specific conductance is used in groundwater monitoring as an indication of the presence of ions of chemical substances that may have been released by a leaking landfill or other waste storage or disposal facility. A higher specific conductance in water drawn from downgradient wells when compared to upgradient wells indicates possible contamination from the facility.

sprain–an archaic term (1600’s) referring to a spring or branch of a river. Spelling was “sprayne”.

spray irrigation–an common irrigation method where water is shot from high-pressure sprayers onto crops. Because water is shot high into the air onto crops, some water is lost to evaporation.

spring–a water body formed when the side of a hill, a valley bottom or other excavation intersects a flowing body of groundwater at or below the local water table, below which the subsurface material is saturated with water.

subsidence–a dropping of the land surface as a result of groundwater being pumped. Cracks and fissures can appear in the land. Subsidence is virtually an irreversible process.

supernatum –the top level of a fluid at rest; important in many applications of water and wastewater treatment. In particular, it is of concern and often measured in settling tanks and skimmers.

surface tension–the attraction of molecules to each other on a liquid’s surface. Thus, a barrier is created between the air and the liquid.

Soil moisture:Water contained in the upper regions near the earth’s surface.

Streamflow: the amount of water flowing in a the body of water.

tertiary wastewater treatment–selected biological, physical, and chemical separation processes to remove organic and inorganic substances that resist conventional treatment practices; the additional treatment of effluent beyond that of primary and secondary treatment methods to obtain a very high quality of effluent. The complete wastewater treatment process typically involves a three-phase process: (1) First, in the primary wastewater treatment process, which incorporates physical aspects, untreated water is passed through a series of screens to remove solid wastes; (2) Second, in the secondary wastewater treatment process, typically involving biological and chemical processes, screened wastewater is then passed a series of holding and aeration tanks and ponds; and (3) Third, the tertiary wastewater treatment process consists of flocculation basins, clarifiers, filters, and chlorine basins or ozone or ultraviolet radiation processes.

thermal pollution–a reduction in water quality caused by increasing its temperature, often due to disposal of waste heat from industrial or power generation processes. Thermally polluted water can harm the environment because plants and animals can have a hard time adapting to it.

transmissibility (groundwater)–the capacity of a rock to transmit water under pressure. The coefficient of transmissibility is the rate of flow of water, at the prevailing water temperature, in gallons per day, through a vertical strip of the aquifer one foot wide, extending the full saturated height of the aquifer under a hydraulic gradient of 100-percent. A hydraulic gradient of 100-percent means a one foot drop in head in one foot of flow distance.

transpiration–process by which water that is absorbed by plants, usually through the roots, is evaporated into the atmosphere from the plant surface, such as leaf pores. See evapotranspiration.

teleconnection: a relationship between two distant weather events. The weather phenomenon El Niño, for example, has been linked to a wide variety of events, including wildfires in the Australian Outback, flooding in the Peruvian Andes, and above-normal rainfall in the Greater Horn of Africa.

unsaturated zone–the zone immediately below the land surface where the pores contain both water and air, but are not totally saturated with water. These zones differ from an aquifer, where the pores are saturated with water

water banking: a water management strategy that temporarily transfers water from those who are willing to lease it to those who are willing to pay to use it.

water recycling (water reclamation, water reuse): reusing treated wastewater for purposes like agricultural and landscape irrigation.

water year–s continuous 12-month period selected to present data relative to hydrologic or meteorological phenomena during which a complete annual hydrologic cycle normally occurs. The water year used by the U.S. Geological Survey runs from October 1 through September 30, and is designated by the year in which it ends.

weather: the condition of the earth’s atmosphere over a brief period of time, like a day or a week.

Watershed– area of land where all water that falls and drains off of goes into a common outlet (USGS Water Science School)

xeriscaping–a method of landscaping that uses plants that are well adapted to the local area and are drought-resistant. Xeriscaping is becoming more popular as a way of saving water at home. More on xeriscaping: Colorado WaterWise Council


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