# Irrigation engineering

## Irrigation engineering

Irrigation engineering : in agriculture, artificial watering of the land. Although used chiefly in regions with annual rainfall of less than 20 in. (51 cm), it is also used in wetter areas to grow certain crops, e.g., rice. Estimates of total irrigated land in the world range from 543 to 618 million acres (220 to 250 million hectares), almost half of them in India, Pakistan, and China. The United States had almost 60 million acres (23.8 million hectares) of irrigated farmland in 1991.

In Irrigation engineering Methods of applying water include free-flooding of entire areas from canals and ditches; check-flooding, in which water flows over strips or checks of land between levees, or ridges; the furrow method, in which water runs between crop or tree rows, penetrating laterally to the roots; the surface-pipe method, in which water flows in movable slip-joint pipes; sprinklers, including large-scale center-pivot and other self-propelled systems; and a variety of water-conserving drip and trickle systems. In many cases irrigation is correlated with drainage

to avoid soil salinity, leaching, and waterlogging. Irrigation may also involve preliminary clearing, smoothing, and grading of land. Especially in areas of high evaporation rates, intensive irrigation can result in excessive quantities of salts accumulating in the upper layers of the soil as water evaporates from the surface, rendering the soil unfit for crop production.

Since prehistoric times water has been diverted from waterways to fields by ditching. Early improvements for raising water included counterbalanced poles with attached water vessels, and adaptations of the wheel and of a pump called the Archimedes’ screw. The use of canals, dams, weirs, and reservoirs for the distribution, control, and storage of water was probably initiated in ancient Egypt. A system of gently sloping underground tunnels (qanats) to deliver water from a subterranean source to distant areas where it is accessed through shafts was developed in ancient Persia and has been widely used elsewhere. In modern times pumps have facilitated the use of underground as well as surface water, but overuse of water in aquifers can exhaust their usable water. Large-scale 20th-century irrigation projects commonly also include water supply, hydroelectric power, and flood control.

## Meter and non meter fall

METER AND NON-METER FALLS The falls may be divided into following two types: 1. Meter falls 2. Non-meter falls. 1. Meter Falls. The falls which can be used to measure the discharge flowing over them, are known as meter falls. Such falls must have broad crest so that the discharge coefficient remains constant under variable …

## Canal Regulation Works

INTRODUCTION To exercise control on discharge, full supply level, velocity of flow, silting etc. various masonry or concrete structures have to be constructed over the canals. All these structures are know Canal Regulation Works. Main Regulation works may be listed as follows: 1. Canal falls 2. Head regulator 3. Cross regulator 4. Metres and Flumes …

## CANAL FALLS

CANAL FALLS Why Falls are Provided When natural slope of the country is steeper than the designed longitudinal slope of the irrigation canal. The falls have to be provided. If falls are not provided, the canals run so much in filling. That it will be almost impossible to even construct the canals. If canal is …

## Classification of falls

CLASSIFICATION OF FALLS The falls can be classified into the following four categories according to the approach conditions. 1. Falls which maintain relation between depth and discharge. 2. Falls which maintain level of U/S water constant. 3. Combination of fall and regulator. 4. Miscellaneous falls. 1. Falls in which D-Q relationship is maintained. In such …

## Type Membrane Lining

Buried and Protected type Membrane Lining These linings are such lining in which a waterproof thin membrane is place on the prepare subgrade. Thereafter it is covered by a protective layer of earth or gravel. The protective layer provides protection to the lining against damage due to outside effects. Membrane itself provides imperviousness. The commonly …

## Lined Canals and Their Design

INTRODUCTION Canal lining is a treatment given to the canal bed and banks, so as to render the canal section impervious. Since imperviousness of the canal section is achieved mostly by making canal section pucca. Either by cement concrete or bricks, the lined canals are also sometimes know pucca canals. Lined canals are mostly referred …

## Essential properties of a good lining

ESSENTIAL PROPERTIES OF A GOOD LINING Following are the essential properties of a good lining: The lining should be completely water tight. The rugosity coefficient of the lining material should be low, so as to make the section more efficient, hydraulically. The lining should be strong and durable. Initial cost of lining and its subsequent …

## Design of lined canal

DESIGN OF LINED CANAL The design of line canals is always done by Kennedy’s Theory.. Following equations given by Kennedy are used in the design. $V0= 0.54mD^{0.64}$ $V= \frac{R^{2/3}S^{1/2}}{N}$ The value of N for protected type of linings is taken same as for natural soil. The value of N of natural soil varies from 0.02 …

## Standards of canal cross section

STANDARDS OF CANAL CROSS-SECTION Usual dimensions of canal cross-section elements have been given here and there inappropriate articles. The standards as suggest by CWPC are given as follows.   1. General. A trapezoidal section is recommended for the canal. The longitudinal slope of the canal is determined depending upon the average slope. The natural ground …