Dar Magazine I9 Page 21

Water-conserving irrigation in Saudi Arabia

Figure 3 The team picked low to medium waterdemanding plant species

Figure 6 Irrigation zones

KL method sample result

Figure 4 depicts an example of a parcel's irrigation requirements
(Parcel 2.11) being recalculated according to LEEDrecommended
species, density and microclimate factors. When the landscape
factor KL method is applied, total water use is reduced by 57%.
Furthermore, no potable water is used.

Water-saving technologies

In parallel with waterconserving design, the team effected a
number of efficient irrigation technologies and design practices.

They designed the irrigation system to be fully automatic, and
equipped it with a controller that connected command valves,
flow and soil moisture sensors. The controller and remote control
devices allow the punctual supply of irrigation water to the
landscaped areas (Figure 5).

The team divided the landscaped area into irrigation zones,
based on plant types, waterusage category, and wind and sun
exposure (Figure 6). These zones were controlled by separate
valves delivering the necessary water amount. The valves, all
remotecontrolled, can control one irrigation zone at a time.
What is more, they feature pressureregulating devices that can
lead to water savings of up to 50%.

High-efficiency subsurface drip irrigation systems

The team recommended highefficiency subsurface drip irrigation
systems that supply water slowly and directly to the plant root
bulb. Savings from such subsurface dripline systems can reach
up to 40% over conventional water systems. The special drip
systems have exceptional advantages:

Reduce the evaporation of applied water

Cause less water runoff

Avoid overspray.

Figure 7 shows the dripperline system, which can be either
looped or in an open grid.

All the drip emitters used were of the pressurecompensating type,
a selfpressure compensating feature that minimizes the water's
outflow fluctuations, resulting in a highuniform water distribution.

Shurb or ground
cover bed

Air relief valve at
high point

Flush valve
at low end

PVC drip manifolds
for trees and ground
cover beds on
separate zones

Barbed tee or
elbor or cross

Driplines with PC emitters
in bed or around tress

Tree canopy

Tree or single

shurb

Figure 7 Plan of typical layout of subsurface dripline over mixed planted area

Encouraging results

Adopting these designs and technologies helped Dar's client save substantial amounts of water over conventional systems. The final
LEED calculation forms proved that the design reduced total water use by an average of 59% across the three parcels.

The reduction in total water applications together with the nopotable water use strategy helped the team earn the maximum four points
of the LEED Water Efficient Landscaping WE Credit 1 for all three parcels. The experience cemented our engineers' skills in a field that is fast
becoming essential in today's thirsty cities.

Figure 5 One remote control device for all comand valves and sensors