Agriculture Reference
In-Depth Information
Box 2.3
(continued)
Figure B2.3.1
Drippers in action in a vine row. Tensiometers are in place to measure soil
water suction.
Calculation of peak supply rate is illustrated by an example for midsummer
(January) for the Riverland region, South Australia. The vine density is 2020 vines
per ha, with two drippers per vine delivering 2 L/hr each. Thus the pump and pipe
system needs to deliver
L/ha/hr L/ha/hr
Suppose the water required per vine, based on evaporative demand, is 16 L/
day. To deliver this quantity of water, the irrigation system should run for 4 hr/day
and the total daily water requirement would be
222020
××
=
8080
×=
≅
, L/ha/day 32,000 L/ha/day
To keep the vines fully supplied with water in midsummer, the water required
per ha for one week would be
8080
4 2 320
×=
L
This figure could be rounded to 250,000 L/ha to allow for leakages and
unforeseen circumstances. Irrigation water volumes in Australia are expressed
in megaliters (i.e., 1 million liters [ML]) so 250,000 L/ha is equivalent to 0.25 ML/ha.
Note also that 1 ML/ha is equivalent to a water depth of 100 mm (compare with rainfall
units).
32 000
,
7
224 000
,
(continued)
