Furrow
Irrigation with Siphon Tubes
| This was one of the earliest forms of irrigation used in the Great
Plains of the United States. The water was carried from a well or
river through an open ditch or canal. The earliest ditches were not
lined. Water was lost from seepage through the canal walls, and from
evaporation from the water surface.
The water is being pumped from a well through the pipe into the ditch.
The outlet has been lined in plastic to protect the ditch from erosion
(the ditch could wash out) and to limit some seepage. |
 |
Later, permanent ditches were lined with concrete to eliminate one source
of water loss and increase the conveyance efficiency of the water (the
efficiency of the water delivery system). Water losses from open,
unlined ditches may be as high as 60% from seepage, evaporation, and water
use by weeds in or along the ditches.
The application efficiency (amount of water applied relative to amount
of water stored in the root zone) and distribution efficiency (even depth
of wetting from top to bottom of field) were usually less than 60% for
these systems. Combined with the low conveyance efficiency, the overall
efficiency of these systems is usually less than 50%, meaning less than
half the water pumped or diverted was actually applied to the field in
the plant root zone.
Furrow irrigation systems require some amount of runoff from the bottom
of the field to get water to be stored deeper in the soil at that end of
the field. This "tailwater" contributes to the low application efficiency.
Though initially lost, it is often captured and recycled, slightly improving
the application efficiency.
Siphon tubes were used to move water from the canal to the furrows
in this cotton field, as you see in the diagrams.
Click on the images to see larger images
of that type of irrigation.
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