Informational Encyclopedia

Case A: for full flowing Pipe

Case B : for Partial FLowing Pipe

1: Discharge

It is measurement of volume of water in flowing condition. Unit of discharge are and brief description are following
(a) Cusec.
If one cubic foot volume of water is passing in one second from a certain point, then the discharge of the water is equal to 1 cusec. 1 cusec is equal to ft³/sec.
(b) Musecs/Cumec.
It is metric unit of discharge. If one cubic meter volume of water is passing in one second from a certain point then the discharge is called 1 musecs or cumec. (m³/sec.)
(c) Liter per second
If one liter of volume of water is passing in one second from a certain point discharge is called 1 L.P.S. or liter per second.
(d) Gallon per minute
If one gallon of water is passing in one minute from a certain point the volume or discharge is called G.P.M.
(e) Acre Foot
Area of one acre is completed full with the volume of water to the depth one foot, then volume of water is called acre foot (A.F.)

2: Inlet

It is the point of a hydraulic structure when water is enter in that structure.

3: Outlet

It is the point of a hydraulic structure where water is going out from that structure.

4: Upstream

The side of the flume or hydraulic structure from where water is entering in the flume or structure. In waterworks/dams side of the reservoir of water is the upstream.

5: Downstream

The side of the flume or hydraulic structure where water is going out from the flume or structure.

6: Water Allowance

It is the quantity of irrigation water allowed for 1000 acres of cultivable land.

7: Perimeter

Length of cross section or the length of a section of canal/dis tributary/watercourse which is contact with water.

8: X-Section

Cross section or x-section of channel is from which water flows. It is the distance of section i.e depth and width of flow.

9: Free Flow

When water passes through a hydraulic structure and downstream water level does not affect the water level of the upstream, flow is called free flow.

10: Submerged Flow

When water passes through a hydraulic structure and downstream water level affect on the upstream water level, flow is called submerged flow.

11: Delta of water

It is the total requirement of water of a crop from sowing time till maturity.
some Delta of water required for crops

Wheat = 16 inches                        Cotton = 28 inches                  Sugar Canes = 70 inches

Maize = 13 inches                         Rice    = 55 inches                  Potato           = 18 inches

Flow Measurement

The branch of engineering science deals with discharge measurement. Basic definition of flow measurement is " The measurement or assessment of volume of water passing per unit time from any point".

Needs of flow measurement 

Distribution of water from head works to main canals

Then main canals have specific design and discharge carrying capacity. To meet the designed water levels of water levels of canals off taking from head works,fixed discharge is diverted to these canals to irrigate their command areas. Discharge indicating gauges are fixed at several places in each canal and are monitored continuously to maintain designed discharge.

Maintaining designed depth of water in canals

To meet the designed discharges of outlets according to their command areas it is essential to operate/run canals at designed fully supply level. For maintaining full supply levels of distributaries and minors, measured discharge is provided/allowed from their parent canals, through regulatory gates.

 Equity in water distribution among end users (Farmers)

Equal distribution of water among farmers is of great concern, Evaluation of equity in water distribution among farmers can be made possible through regular flow measurement in watercourses or at farm levels.

Measured irrigation to crops

Saving of precious water is dire need of current drought situations. At farm level different techniques are adopted for saving of water.Thus it is very important to irrigate crops according to their water requirements and to avoid over or under irrigation by applying measured quantities of water.
Planning and Designing of Irrigation and Drainage structures
Different types of hydraulic structures are constructed on irrigation channels and on surplus water carrying drains. All such structures are designed for passing of a limited quantity of discharge.

Pre and Post improvement of irrigation system

For evaluating the performance of water management or irrigation projects, flow measurement in canals or watercourses before improvement is taken as base line. After completing such projects flow of these water channel is again measured for evaluation.

Water Management

The importance of flow measurement at different stages of irrigation system it can be said that without flow measurement , proper water management is not possible.