Drainage and irrigation strategy
Drainage
There are two systems proposed for the handling of natural water run off on the site.
The first is a ‘closed' system, that is, water is reticulated within the system. Collection points are within the central zone and also include run off from hard surfaces such as car parks and roads. These areas shed the largest amount of water and consequently impose the highest levels of silt, nutrients and pollutants. The water is directed via a stem of channels to small ponds within vegetated swales. At this point the water is recycled to supplement the irrigation system providing for such areas as car parks, ovals and the University square. Following these recycling processes excess water is not allowed off site until the desired level of nutrients, sediment and pollutants is achieved. This natural filtration will be effected by movement through and storage within bodies of water which will dilute and settle suspended particles.
The second system is an open ended system involving the wider landscape of the campus. Although the run off water from these areas is comparatively `cleaner' than the water run off from areas more built up, it will be directed to the swale system for settling in ponds. This system, therefore, acts as a protective interface between the University site and the sensitive ecological system of the Mooloolah River National Park.
The swales and ponds, which are a part of both of these systems, physically resemble and operate as a natural creek and pond system. Techniques to achieve this include the use of soft elements to re-contour and reconstruct the landscape to produce an economical low maintenance system. The use of geofabrics, logs and plant material may also serve to reduce the velocity of water run off and thereby minimise the potential for erosion, a problem inherent in the site's friable soil.
Irrigation
A major goal of the landscape strategy is to minimise irrigation. For this reason artificially created irrigation zones are limited in both location and area. Filters between the irrigated and non-irrigated areas are created with intermediate planting. In principle, high activity use zones and exotic landscapes are sustained by intensive irrigation via an automatic irrigation system; low use areas and passive zones, planted with predominantly native and endemic vegetation, rely on a combination of the site's existing hydrological cycle, water harvesting from the site and recycling of stored run off in holding ponds.
This approach aligns with a plant palette which has the capacity to be self sustaining and in accord with rainfall levels in the Sippy Downs area. The techniques for achieving the irrigation strategy range from fully automatic pop up sprinkler systems and dripper systems to large mobile field sprinklers.
A key element of the irrigation strategy is water harvesting, where run-off is collected and recycled for irrigation. This aims to prevent any excess nutrient load entering the National Park and consequently disturbing the equilibrium of the ecosystem.
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