Irrigation & Hydrology (General Engineering) (SSC JE)

Advantages of the sprinkler irrigation method–
• Fertilizers can be uniformly applied, because they are mixed with irrigation water itself.
• This method leaches down salts and prevents waterlogging or salinity.
• It is less labour oriented and hence useful where labour is costly and scarce.
• It is easily operated (Automated).

Drip irrigation–
• In drip irrigation water is discharged as drops at the root zone of plants. Iirrigation is done at frequent time intervals. Plastic pipes are used for conveyance.
• Water advances on the soil around a dripper only after the amount of water applied exceeds the infiltration rate at a point.
• Typically, a dripper wets a diameter from 20 to 120 cm depending upon the soil type.
• The depth of wetting for any specific soil primarily depends on the time of operation of the dripper.

Run-off–The amount of water which flows over the surface of the earth after all the losses have taken place is called run-off.

Mass curve–The mass curve of a rainfall of a storm is a plot of accumulative rainfall v/s time in chronological order.
• Hyetograph - Rainfall intensity v/s time
• Hydrograph - Discharge/Runoff vs time

Consumptive use–Depth of water consumed by plant during growth in the process of transpiration, evaporation and interception is called as consumptive use of crop.

Lacey's stated that a channel may not be in regime condition if it is flowing with non-scouring and non-silting velocity.
• Therefore, three regime condition as following–
(i) True regime (ii) Initial regime (iii) Final regime
• Lacey specified that regime theory is valid for final regime condition only. The shape of regime channel as per Lacey is semi-ellipse.

Mobile boundary flow–A channel composed of loose sedimentary particles in which particles moves under the action of flowing water is called as mobile boundary channel. Upper regime of mobile boundary flow is known as antidunes or sand waves and lower regime is termed as dunes and ripples.
1. Waves grow steeper and break
2. Occurs in super critical flow
3. High-sediment transport rate
4. Low resistance to flow

As per Bligh's creep theory, percolation of upstream water flows along the outline of the base of the foundation of the dam.

Super passage–When a canal flowing under pressure is carried below a natural drainage such that is FSL does not touch the underside of the supporting structure the provided structure is called as super passage.

Aqueduct–A structure in which natural drain flows below the canal is called as aqueduct.

A deficit of sediments in flowing water may cause a degrading type river that means erosion of river bed takes place.

Aggrading–When depth of river decrease due to accumulation of sediments is known as aggrading.