Demonstration sites

Artificial wetland: the wetland constructed on the Marshall's property is designed to reduce nutrient transport from a small agricultural catchment area. The wetland has two connected ponds. Catchment runoff flows into the first pond, and slows enough for suspended sediment to drop out. The accumulated sediment will be removed every few years. Water then flows through a perforated rock bund into the second pond, planted with 17,000 sedge plants.

This pond forms the wetland nutrient filter. Sedges are fantastic at taking up nitrogen and phosphorus from the water and sediment. A "bio-film" of bacteria covering the sedges will utilise nitrogen in the water.

It will take two to three years before the nutrient uptake function of the plants in the wetland is optimum. From time to time the sedges will be harvested, so that new plant growth will continue to take out the nutrients entering the wetland.

Marbelup drain: rehabilitation work has been carried out along half a kilometre of eroding stream on the Martin's property. The work was designed to promote waterways best management practices.

The watercourse has been fenced to exclude stock; stock crossing and rock riffles constructed; spraying, ripping and mounding carried out; and 2,250 local native fringing wetland species planted.

Grassmere drain: re-contouring of the drain took place in 2001. The design slows the water flow enough for sediment to settle out. The rock riffle placed in the channel bed roughens the surface so that flowing water is re-oxygenated.

Land Management Students from Great Southern TAFE carry out monthly aquatic invertebrate monitoring at this site. The students have also planted the bank with 400 plants, including 11 local native fringing wetland species.

Ribbons of Blue sites

Ribbons of Blue is an environmental education network aimed at increasing community awareness and understanding about local water quality, and taking action for a better environment. Ribbons of Blue programs involve school students and community groups in monitoring water quality.

Both the artificial wetland and the Marbelup drain restoration, shown as demonstration sites, are also Ribbons of Blue study sites.

Foreshore condition

Marbelup Brook (in 2000) and Seven and Five Mile Creeks (in 2001) have been assessed to determine the quality of the fringing vegetation and the erosion of the banks. The scoring method follows a procedure used on other waterways in the region. The condition of sections of the waterways is allocated to one of four categories on the basis of weed infestation, soil exposure and erosion. The classification system takes account of sections which had been highly modified, sometimes including constructed drains.

The results are used to identify threats to the waterways, set priorities and plan remedial action.

CSIRO Cyanobacterial Study

Cyanobacterial blooms and chlorophytes in Lake Powell and Marbelup Brook have caused concern to residents and affected tourist potential. The situation has been so severe that at times Torbay Inlet has been closed to fishing and swimming for several months because of toxic algal blooms.

This study examined phytoplankton species in the waterways and the associated drainage system. It also looked at the physical characteristics of the water, and measured the nutrients in the system. Sediment deposits were also sampled.

Marbelup Brook studies

Several research projects focussing on Marbelup Brook, and supported by the Water Authority, have been carried out recently by university students. James Mackintosh of the University of Western Australia investigated the fate of simazine in soils in the Marbelup Brook catchment. Kate Gole of the Department of Soil Science and Nutrition at the University of Western Australia looked at the estimation and control of erosion in the catchment

In addition, CALM carried out a Marbelup Brook Water Quality Study in October 2000