Irrigation & Drainage Flashcards
The quantity of water, exclusive of precipitation required to maintain desired soil moisture and salinity level during the crop season
Irrigation Water Requirement
Methods of irrigation water application wherein the soil is moistened in much the same way as rain
Overhead irrigation
Sum of evapotranspiration and percolation losses
Crop Water Requirement
In-line structure with a geometrically specified constriction built in an open channel such that the center line coincides with the center line of the channel in which the flow is to be measured
Flume
A device with individual scales on the rods to provide data to plot furrow depth as a function of the lateral distance where data can then be numerically integrated to develop geometric relationships such as area vs depth, wetted perimeter versus depth and top-width vs depth
Profilometer
Farm turnout requirements plus conveyance losses in the main canal and lateral up to the farm turnout
Diversion requirement
This system is used in rolling topography where drainage is necessary only in small valleys
Natural system
Recommended slope for basin irrigation method
Less than or equal to 0.1%
Recommended slope for border irrigation method
2 - 5 %
Recommended slope for furrow irrigation method
0.05 - 3%
Maximum sprinkler spacing, in rectangular pattern if average wind speed is above 15 kph
30 % between sprinklers, 50% between laterals
An overflow structure built perpendicular to an open channel axis to measure the rate of flow of water
Weir
Application of water by gravity flow to the surface of the field
Surface irrigation
It is the ratio between the gross amount of irrigation water and the net requirement of the crop
Water application efficiency
Structures which raises the water flowing through rivers, creeks or streams to a desired height. The water is then diverted to conveyance canals to supply the requirements of the areas served
Diversion dam
The power theoretically required to lift a given quantity of water each second to specified height
Water horsepower
The soil type largely influences the width of bed to be used. The furrows drain to collection ditches
Bending system
This system is adapted to areas that have depressions which are too deep or too large to fill by land leveling
Random ditch system
Expresses the relationship between speed in rpm, discharge in gpm, and head in feet
Specific speed
These structures are usually constructed or placed along supplementary farm ditch at head of the internal farm ditch to control and regulate water flow serving the farm or group of forms
Off-takes
The ratio of the dry weight of the soil to the volume of soil particles alone
Particle density
This is suitable on flat, poorly drained soils that have numerous shallow depressions, in general, the ditches are 185m to a max. to 370 m apart
Diversion or parallel ditch system
Maximum sprinkler spacing, in square pattern if average wind speed is 13-19 kph
45%
Maximum sprinkler spacing, in rectangular pattern if average wind speed is up to 10 kph
40% between sprinklers, 65% between laterals
