Irrigation Engineering (civil engineering)

 * Syllabus *

• 1. Water Requirement of crops, Method of Irrigation, Lift Irrigation.
• 2. Water Logging, Dams, Spillways.
• 3. Energy Dissipation, Diversion head works, Canal & Canal Structures.
• 4. Cross Drainage works, River Training works.

-----------------------*---------------------*---------------------*-----------------

*Irrigation :- Process A artificial application of Water to the soil or land for the growth of crops.

*Advantages :-

1) Increase in crop yield.

2) Protection against famines.

3) Revenue Generation.

4) Avoidance of mixed cropping.

5) Navigation:- Irrigation canals may be used for inland navigation, useful for communication and transportation.

6) Hydroelectric power generation.

7) Generation of employment opportunities.

* Disadvantages :-

1) Wastage AIrrigation water.

2) formation of marshy land :- Excessive Seepage of water from irrigation canals.

3) Dampness of weather :- Dampness in the area lead to occurance of diseases originating from dampness.

4) Loss in valuable Land:- valuable land gets submerged when storage reservoirs are formed on account of construction of weirs, Barrages or dams.

* System of Irrigation*

* Surface & Subsurface Irrigation *

I) Surface Irrigation :-

--> water distributed through Small channels.

--> water is applied and distributed either by gravity or by pumping.

--> good for soils with low to moderate irrigation Capacities and lands with uniform terrain.

i) Flow Irrigation :-water Supplied by the action of gravity.

ii) Lift Irrigation:-water lifted by mechanical means and then Supplied (eg. Pumps etc.). Mostly Tubewells are used for this purpose.

II) Subsurface Irrigation :-

--> water flows undergrounds and nourishes plant roots by capillarity.

--> water applied by underground network of pipes which consists main pipe, submain pipe and Lateral perforated pipes.

--> Suitables for Soils which are highly permeable.

i) Natural Sub-Irrigation :- leakage water from channels during its passage through subsoil irrigates crops suon on lower lands.

ii) Artificial Sub-Irrigation :- A system of open jointed drain is artificially laid below the soil. Costly process.

* Method of Irrigation*

1) surface Irrigation

a. uncontrolled or wild or free flooding method

b. Border Strip method

c. Check method

d. Basin method

e. Furrow Method

2) Subsurface Irrigation

3) Sprinkler Irrigation

4) Trickle (Drip) Irrigation

* Choice of Method of Irrigation *

-->It depends on following factors.

1. Size, Shape & Slope of field.

2. Soil Characteristics.

3. Nature & availability of water System.

4. Type of crops being grown.

5. Initial development cost and availibility of funds.

6. Preferences and Past experiance of farmer.

* uncontrolled flooding *

-->Ditches are excavated in field.

--> water from these ditches are allowded to flow across the field without any restriction by opening the field regulators.

--> Cost of land preperation is low.

--> water application efficiency is low.

--> Series of field channels connected to the main supply Channel.

* Border flooding *

-->Time required by water to irrigate an area.

f = Infiltration capacity

y = Average depth of water flowing over the strip.

Q = discharge through supply ditch.

--> maximum area of field which can be irrigated with given discharge and for given type of soil.

Amax. Condition

1. Losses = 0 (zero)

2. Rate of application of water should be maximum.

** ALWAYS REMEMBER **