Watercourse


Mean monthly discharge or flow

Updated on 26/10/2022
Définition
Sens technique
Arithmetic mean of the monthly flow rates in a given month, calculated over a period long enough to be representative. It can characterize the mean flow in a given month.
Source
According to the Ministry for the Environment and OFB

Monthly discharge

Updated on 26/10/2022
Définition
Sens technique

Average flow rate during a month: it is most often obtained by adding the average daily rates of the month and by dividing the result by the number of days in the month.

Source
According to the Ministry for the Environment and OFB

Useful flood flow

Updated on 26/10/2022
Définition
Sens technique
Flood flows essential to the life of the watercourse and its water dependent areas, and having no unacceptable effects (especially on living settlements). Small floods have a fundamental role in the dynamics of environmental recovery, they should not be removed nor the environments be protected from them.
Source
According to the Ministry for the Environment and OFB

Critical low flow

Updated on 26/10/2022
Définition
Sens technique

Low flow value below which the supply of drinking water for essential needs for human and animal life, and for the survival of the species found in the environment, are endangered. At this low-flow level, all possible measures to restrict consumption and

Source
According to the Ministry for the Environment and OFB

Warning level (or threshold) flow

Updated on 26/10/2022
Définition
Sens technique

"Threshold" value of the flow that triggers the first restrictions for some activities. These measures are taken at the initiative of the prefectural authority in connection with a crisis cell and in accordance with a crisis plan. Below this threshold, one of the functions (or activities) is compromised. To partially restore this function, it is necessary to limit temporarily another: withdrawal or discharge (first restriction measures)…

Source
According to the Ministry for the Environment and OFB

Low water flow

Updated on 26/10/2022
Définition
Sens technique
Minimum stream flow calculated in a given time step during low water periods. For a given year, we will talk about: daily low water flow, low water flow on n consecutive days, monthly low flow - average daily flow in a low-flow month (QMNA). With several years of observation, the statistical processing of series of low flows allows calculating a low- flow frequency. For example, the five-year low water flow (or QMNA 5) is a monthly flow that occurs on average once every five years. The QMNA 5 is the reference low water flow for the implementation of the water policy.
Source
according to the Ministry of the Environment and OFB

Reference or basic low water flow

Updated on 26/10/2022
Définition
Sens technique

Legal reference flow, defined as the monthly low-flow recurring every five years (or frequency of 1/5, i.e. occurring one year in five), known by the acronym QMNA 5 (frequency 1/5).

Source
According to the Ministry for the Environment and OFB

Annual flow

Updated on 26/10/2022
Définition
Sens technique
Average flow over a year: it is most often obtained by adding the average daily water flows of the year and by dividing the result by the number of days in the year.
Source
According to the Ministry for the Environment and OFB

Assigned flow

Updated on 26/10/2022
Définition
Sens technique

According to the Water Act of 1992, "when hydraulic development works, other than those conceded or authorized and intended or resulting in the regulation of the flow of a non-State owned watercourse or for increasing its flow during low-flow periods, all or part of the artificial

Source
According to the Ministry for the Environment and OFB

Reserved watercourse

Updated on 26/10/2022
Définition
Sens réglementaire
A watercourse for which, under the Act of 16 October 1919, amended by the Act of July 1980 on energy savings and the use of heat and the law of June 1984 on freshwater fishing, no authorization or concession is given for new…
Source
According to the Ministry for the Environment and OFB