Low Flow Database

Glossary

A B C D F G H I M N P R S T W

A

Aquifer – An underground geologic formation capable of holding large quantities of water in the (interstial) spaces between rocks, sand and soil. Aquifers may serve as a source of drinking water.

Aquifer transmissivity – The quantity of water that a given aquifer can transmit. It is the average hydraulic conductivity times the average thickness of the aquifer.

B

Base flow – The flow that a perennially flowing stream reduces to during the dry season. It is supported by groundwater seepage into the channel.

Benthic – Pertaining to the bottom (bed) of a water body.

Biomonitoring – Examining the biological (living) communities in a given body of water (or other habitat) to determine the complexity, diversity, and species composition in the water body. This information helps assess the overall health of the habitat.

C

Cfs – Cubic feet per second. A unit expressing rates of discharge. One cubic foot per second is equal to the discharge of a stream of rectangular cross section, 1 foot wide and 1 foot deep, flowing water an average velocity of 1 foot per second.

Cfsm – Cubic feet per second per square mile.The average number of cubic feet of water per second flowing from each square mile of area drained by a stream, assuming that the runoff is distributed uniformly in time and area.

Class A, B, C water quality standards – Under the Federal Clean Water Act, each state must establish specific water quality classifications with defined water quality criteria. In Massachusetts waters are assigned an A, B or C classification. A waterway's classification reflects the water quality needed for the designated uses of a given water body (the waterways potential) and not the existing water quality.

Clean Water Act (CWA) – A federal law establishing comprehensive national policies for water quality management. The essence of the CWA is to have all US waters "fishable and swim able".

D

Discharge – The rate of flow, especially fluid flow; the volume of fluid passing a point per unit time, commonly expressed as cubic feet per second, million gallons per day, gallons per minute, or cubic meters per second.

F

FERC – The Federal Energy Regulatory Commission is an independent regulatory agency within the Department of Energy that, among other energy-related tasks, licenses and inspects private, municipal and state hydroelectric projects.

First Order Stream – The smallest size class of streams (i.e. a “headwater stream”).. Where two first order streams join the resulting stream is second order.

G

Groundwater – Water that is held in the rocks and soil beneath the surface of the Earth. Ground water feeds wells and springs.

H

Hydropeaking dam –

I

Impervious Surface – A surface that does not allow water to penetrate such as pavement.

Impoundment – A body of water contained by a barrier such as a dam.

Induced infiltration – Movement of water from a surface water feature, such as a river or lake, into the groundwater as a result of groundwater pumping.

Inflow (to a reservoir) – The amount of water flowing into a reservoir from upstream tributaries.

Interbasin transfer – A transfer of water from one basin/watershed into another. These transfers are regulated in Massachusetts under the Interbasin Transfer Act.

M

Macroinvertebrate – Macroinvertabrates are small, but visible with the naked eye, animals without backbones (insects, worms, larvae, etc.). Water bodies have communities of aquatic macroinvertebrates. The species composition, species diversity and abundance of the macroinvertebrates in a given water body can provide valuable information on the relative health and water quality of a waterway.

N

Natural Flow Regime – The magnitude, frequency, timing, duration, and rate of change of stream flow in a particular river under “natural” conditions.

P

Percolation – Movement of water from the surface or surface groundwater into the groundwater table.

Permitted withdrawal – The amount of water that is permitted to be withdrawn at one location under the Massachusetts Water Management Act.

Pump test – A preliminary period of groundwater pumping to determine the capacity, and environmental effects of a well.

R

Registered withdrawal – The amount of water that a given source was withdrawing at the time of the first passage of the Massachusetts Water Management Act. These withdrawals were allowed to be registered, or “grandfathered”, without having to complete the permitting procedure that is now required under the Water Management Act.

Rheophilic – Species that prefer or depend on flowing water conditions.

Riparian zone – The land adjacent to and along a river or stream. When a riparian area has a natural vegetative cover it serves a buffer between the upland and water course.

Run-of-river dam – A hydroelectric generating power plant that operates based only on available streamflow andsome short-term storage (hourly, daily, or weekly).

S

7Q10 – The lowest streamflow for seven consecutive days that occurs on average once every 10 years.

Species richness – The number of different species in a given area; the greater the number, the richer the area.

Stratified drift – Well sorted fluvial sands and gravels deposited from glacial meltwater streams. The permeability of stratified drift is greater than that of till.

Stream reach – A length of stream or river channel that is uniform in its discharge, depth, area, and slope; a relatively homogeneous length of stream having a similar sequence of characteristics.

Stressed basin – A designation created by the MA Office of Water Resources to aid in the implementation of the Water Management Act. Rivers in the “high stress” category have low streamflow for their drainage area as compared to other rivers of the Commonwealth of Massachusetts. Projects within these watersheds that may impact water availability are scrutinized more closely than in other areas.

Substrate – The base or surface on which an organism lives. This includes the material comprising a stream bed or the surfaces which plants or animals may attach or live upon.

T

Target fish community – The number and relative abundance of fish species that have been identified through expert opinion and historic data as a goal for fisheries restoration in a particular river.

Till – Unsorted and unstratified materials ranging in size from clay to large boulders that were transported and spread over the land surface by glaciers.

Turbidity – Defined by the American Public Health Association as the "optical property of a water sample that causes light to be scattered and absorbed rather than transmitted in straight lines through the sample," i.e., the cloudiness or transparency of the water sample.

W

Watershed – The area of land drained by a river or stream system.

Definitions taken from: USGS online glossary, Merriam-Webster dictionary, Nevada Division of Water Planning Water Words Dictionary, USGS Water-Resource Investigations Report 00-4029, Sam Houston State University Hyrogeology online lecture notes, and the South African River Health Program webpage.