Explanation:

Surface Irrigation System:

We have two sources of water to be used as irrigation water one is ground water and or is flowing water. Based on source of water used as irrigation water, water irrigation system is mainly divided in to two categories:

1. Lift irrigation – when ground water lifted up to be used as irrigation water ( Eg: Well Irrigation)
2. Flow irrigation – when flowing water is used as irrigation water.

These are furr classified as below – 

Note:

Methods of Irrigation systems:

Irrigation water may be applied to crops by three basic methods:-

1. Surface Irrigation method

2. Sprinkler irrigation method

3. Sub-surface irrigation method

Concept: 

Lacey's scour depth is given by:

$R=1.35{\left(\frac{q^2}{f}\right)}^{\frac{1}{3}}$

Where, q = Discharge per meter width, f = silt factor

Calculations:

Given, q = 3 cumec, f = 1.2

$R=1.35{\left(\frac{3^2}{1.2}\right)}^{\frac{1}{3}}=2.64m$

Important Points

Various formulas deduced by lacey is given below:

1) silt factor ⇒ $\mathrm{f}=1.76\sqrt{{\mathrm{d}}_{\mathrm{m}\mathrm{m}}}$

2) velocity of flow ⇒$V={\left[\frac{Q{f}^2}{140}\right]}^{\frac{1}{6}}$

3) hydraulic mean depth ⇒$R=\frac{5V^2}{2f}$

4) wetted perimeter ⇒ $P=4.75\sqrt{Q}$

Explanation:

Stream load:

• Stream load is a geologic term referring to solid matter carried by a stream.
• Erosion and bed shear stress continuously remove particles which are transported by water eir in suspension or as dissolved.

?It primarily depends on-

• Nature of soil in catchment (as rocks generally don't dissolve, but small earn particles get dissolved)
• Topography of catchment as more slope more velocity of water.
• The intensity of rainfall as more rainfall leads to more runoff, thus increasing sediment carrying capacity of any stream.

Concept:

A cross drainage work is a structure constructed for carrying a canal across a natural drain or river intercepting canal to dispose drainage water without mixing with continuous canal supplies.

Types of Cross - Drainage Works:

(1) Type I (Irrigation canal passes over drainage)

(a) Aqueduct

(b) Siphon aqueduct

(2) Type II (Drainage passes over irrigation canal)

(a) Super passage

(b) Siphon super passage

(3) Type III (Cross drainage works admitting  drain water into  canal)-

In this type of cross drainage works, canal water and drain water are allowed to intermingle with each or. This may be achieved by following two types of cross drainage works:-

(a) Level crossing

(b) Inlet and outlet

Level Crossing

The level crossing is an arrangement provided to regulate flow of water through drainage and canal when y cross each or approximately at same bed level. It consists of 2 regulators and 1 Crest Wall (Weir).

Aqueduct

The aqueduct is just like a bridge where a canal is taken over deck supported by piers instead of a road or railway. The highest flood level of drainage remains lower than level of underside of canal trough. Generally, canal is in shape of a rectangular trough which is constructed with reinforced cement concrete. Sometimes, trough may be of a trapezoidal section.

• The drain water flow under canal such that re is sufficient headway available between HFL of drain and underside of canal trough.
• The drain water flows at atmospheric pressure.

• An inspection road is provided along side of trough.

Siphon Aqueduct

In siphon aqueduct,  bed of drainage is depressed below bottom level of canal trough by providing a sloping apron on both sides of crossing. It is constructed where water surface level of drain at high flood is higher than canal bed. The streambed is locally depressed where it passes under trough of canal and barrels discharge flow under pressure.

• The sloping apron may be constructed by stone pitching or cement concrete.
• The section of drainage below canal trough is constructed with cement concrete in form of a tunnel. This tunnel acts like a siphon.

Super Passage

The super passage is just opposite aqueduct. In this case, bed level of drainage is above full supply level of canal. The drainage is taken through a rectangular or trapezoidal trough of channel which is constructed on deck supported by piers.

• A super passage is constructed where bed level of drain is well above canal FSL. In this case, drain water is taken across canal in a trough supported on piers.
• The canal flows at atmospheric pressure under work.

Siphon Super Passage

It is just opposite of siphon aqueduct with difference that in this case, canal water is carried through barrels under drain. The barrels in this case also act as inverted siphons through which water flows under pressure. The section of trough is designed according to high flood discharge. The bed of canal is depressed below bottom level of drainage trough by providing a sloping apron on both sides of crossing.

• The sloping apron may be constructed with stone pitching or concrete slabs.
• The section of canal below trough is constructed with cement concrete in form of a tunnel which acts as a siphon.

Concept:

Meandering River:

• The formation of successive bends of reverse order may lead to formation of a complete S curve called Meanders.
• When consecutive curves of reverse order connected with short straight reaches called crossings are developed in a river reach, river is stated to be a Meandering river.

Meandering of a river is due to erodibility of bed and banks of streams.

Causes:

1. Extra turbulence generated by excess of river sediment during floods. When silt charge is in excess of quantity required for stability, river starts building up its slope by depositing silt on its bed.

2. The increase in bed slope tends to increase width of channel, if banks are not resistant. The banks are attacked by river water and in process one bank is likely to be attacked slightly more than or, causing a slight deviation in flow. This slight deviation from uniform axial flow, helps in improving more and more flow towards one bank than towards or. This process continues causing once bank convex and anor concave. Hence, increasing slope is also a reason for meandering.

Important Points

Meander parameters:

Meander Length: It is axial length of one mender, i.e. tangential distance between corresponding points of meander.

Meander Belt: It is distance between outer edges of clockwise and anticlockwise loops.

Meander Ratio: It is ratio of meander belt to meander length.

Tortuosity: It is ratio of length along channel (actual length) to direct axial length.

Crossings or cross-over: It is shortest reaches of river, connecting two consecutive clockwise and anticlockwise loops.

Explanation:

Sprinkler irrigation:- In this method, irrigation water is applied to land in form of a spray, somewhat as in ordinary rain through a network of pipes and pumps.

• It can be used for all crops except rice and jute and for almost all soil except very heavy soils with very low infiltration rates.
• Best suitable for very light soils as deep percolation losses are avoided.
• It is suitable for undulating topography and hence land leveling is not necessary.

Limitations of sprinkler irrigation:- Under strong wind conditions and high temperatures, water distribution and water application efficiencies are low.

• This system is costly to install, operate, and maintain.
• Continuous supply of power is required.
• Corner remain under irrigated
• Saline water may cause leaf burns in many crops.

Advantages of sprinkler irrigation:- By use of this method, erosion of soil can be controlled.

• Uniform application of water is possible.
• Labor cost is reduced as no land preparation is required.
• It is specially adapted to more humid regions.
• Evaporation and percolation losses are less.

Hence option A and B is limitation of sprinkler irrigation and option C is advantage of sprinkler irrigation.

Concept:

Weir or notch is a physical structure of masonry constructed across channel width to calculate  discharge of channel section.

Rectangular (suppressed) Notch:

The discharge through a rectangular notch weir is,

$Q=\frac{2}{3}{C}_{d}L\sqrt{2g}{H}^{3/2}$

$L=\frac{3Q}{2C_d\sqrt{2g}{H}^{3/2}}$

Where, Q = discharge of fluid, Cd = Coefficient of discharge and H = height of water above notch

Additional Information

Triangular Notch: 

A V-notch weir is also called triangular notch or weir. The discharge over a triangular weir or notch is given by :

$Q=\frac{8}{15}{C}_{d}tan\frac{\theta }{2}\sqrt{2g}{H}^{5/2}$

Where, Q = discharge of fluid, Cd = Coefficient of discharge, θ = Notch angle and H = height of water above notch

Trapezoidal weir (or) Notch:

$Q=\frac{2}{3}{C}_{d_1}\sqrt{2g}L{H}^{\frac{3}{2}}+\frac{8}{15}{C}_{d_2}\sqrt{2g}.\tan ?\frac{\theta }{2}.H^{\frac{5}{2}}$

Where, $\left(\frac{\theta }{2}\right)$ = weir angle of inclination with vertical.

$C_{d_1}$ = Coefficient of discharge for rectangular portion.

$C_{d_2}$ = Coefficient of discharge for triangular portion.

Duty: It is number of hectares of land irrigated for full growth of a given crop by a supply of 1 cumec of water continuously during entire base period of that crop.

Duty of water changes from place to place, it will be maximum at field and minimum at head of main canal.

Duty is area that can be irrigated by discharge of 1 cumec of water.

At head of canal, re are numerous losses to occur later which requires more amount of water to irrigate a particular field. However, if considered on field, all losses have already occurred and a lesser amount of water is required to irrigate same considered area.

Concept-

According to Hydraulic design, dams are classified as 

• Overflow dam or overfall dam -
  • It is constructed with a crest to permit overflow of extra water that cannot be retained in reservoir.
  • Generally dams are not designed as overflow dams for ir entire length.
  • Diversion weirs of small height may be designed to permit overflow over ir entire length.
• Non-overflow dam - it is constructed such that water is not allowed to overflow over its crest.