Environmental Engineering Reference
In-Depth Information
specific pressure. When pumps are arranged in series, nominal water
pressure is equal to the sum of the capacities of the individual pumps;
flow rate remains equal to that of a single pump. When pumps are
arranged in parallel, water pressure remains equal to that of a single
pump, but flow rate equals the sum of the capacities of the individual
pumps (Fig. 7.11).
A well-designed sprinkler system should deliver water evenly to all
areas. Sprinkler heads must also be selected and adjusted so they do not
spray water beyond turf areas onto streets, buildings or people using
parks or playgrounds. Sprinklers should also not be permitted to spray
directly onto the trunks of trees or into shrubs and flowerbeds. The sheer
force of the water pressure can score tree bark, and perpetual wetting
may weaken it, making it more susceptible to pests and diseases. Direc-
ted water spray can also blast leaves and flowers and should be avoided.
Installation of an automated sprinkler system requires considerable
investment, careful planning, ground excavation, trenching, etc. If the
turf area is larger than a small home lawn, the design and groundwork
should be done by experienced professionals. Selecting the correct
sprinklers, pipes, valves, pumps and control systems requires a compe-
tent irrigation designer. Installation of the irrigation system should also
be left to a professional who understands the capabilities and limitations
of all the system's components. Errors in design or installation result in
poor operation, water leaks, damage to sprinkler heads during mowing,
etc. and are costly to correct.
Wetting Agents
Sometimes water applied during irrigation cannot readily penetrate and
wet the soil. Wetting agents (surfactants, surface active agents) are com-
pounds able to change water-repellent soils and other surfaces and make
Pressure
X + Y + Z
Pressure X
Pressure Y
Pressure Z
Flow rate X
Flow rate
X + Y + Z
Flow rate Y
Flow rate Z
Fig. 7.11. Arrangement of water pumps in series influences water pressure, whereas
arrangement of pumps in parallel influences the rate of water flow.
