Environmental Engineering Reference
In-Depth Information
installation is incorrect and should be avoided. As can be seen in Fig. 7.6, to
supply the minimum irrigation needed by the edges of a turf area, a central
sprinkler head must substantially overirrigate the central part of the turf.
On sandy soil, this overwatering can cause rapid water percolation that
results in substantial nutrient leaching, and on heavier soil, it may result in
increased soil compaction from foot and vehicular traffic. In all cases,
overirrigated areas are more susceptible to diseases, and their soil has
less favourable physical properties, which negatively influence turf
growth and use of the turf area. Because the single row of sprinkler heads
does not assure uniformity of irrigation, the sprinkler heads should instead
be placed to cover overlapping half circles from opposite edges of the turf
area (Fig. 7.7). The savings associated with installation of half as many
underground water lines and sprinkler heads often tempts managers into
incorrect decisions with lasting negative consequences.
Rotating sprinklers produce the desired wedge-shaped pattern of
irrigation when they are operated within the proper range of water
pressure. Excessive high pressure causes the water to form a fine spray
instead of droplets. Wind can then divert a large portion of it and cause
irregular and unpredictable irrigation patterns. Insufficient water pres-
sure results in streams of water that do not disperse sufficiently and
irrigate only a narrow band at some distance from the sprinkler head.
When water pressure fluctuates, irrigation can be excessive in some areas
and insufficient in others (Fig. 7.8). Wind strongly influences irrigation
patterns and water efficiency; often more than do water pressure,
sprinkler-head design or sprinkler spacing. Its influence should be min-
imized as much as possible. The largest sprinkler heads should operate
around sunrise, when wind velocity is usually lowest.
Fig. 7.7. Sprinklers on the edge overlap with sprinklers in the centre.
