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Investigating the consequences of flow barriers on water flows and nutrient export in the Peel Main Drain, Western Australia

Fardin, Gianni (2013) Investigating the consequences of flow barriers on water flows and nutrient export in the Peel Main Drain, Western Australia. Masters by Coursework thesis, Murdoch University.

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Water is a valuable resource in south-western Australia due to its relative scarcity. In the Peel-Harvey Region, water quality and declining groundwater are two issues that impact on the sustainability of water resources. Rainfall and streamflow are forecast to decline further by 2030. High nutrient levels in drains and rivers, and declining groundwater levels can be mitigated by controlled drainage, through reductions in baseflow, and nutrient efflux.

The Peel Main Drain, located in the Peel Region of Western Australia extends from Jandakot to near Warnbro where it joins the Serpentine River. The Peel Main Drain is a large source of nitrate (N) and phosphorus (P) efflux into the Peel-Harvey Estuary, contributing more than 26t N and 4.5t P per year or 2.2% and 2.4% of total contribution to the estuary respectively. Using a simple nutrient load model, baseflow which is derived from groundwater, accounts for approximately half of PO4 efflux in the Peel Main Drain, during the later period of the year, from August to December.

This thesis examines the effectiveness of using controlled drainage in the Peel Main Drain, through an investigation of the literature on nutrient movement in the Peel Region, and an assessment of the hydrology of the Peel Main Drain and surrounding area. Water levels in the Peel Main Drain were modeled using hydrograph data, and the HECRAS river analysis model.

Flooding and cost are two issues relating to controlled drainage. Modelling of flow and groundwater level in the Peel Main Drain area highlighted the interaction of groundwater and flow, and the large number of former and present wetlands in the study area. This thesis argues that flooding risk can be managed through the use of variable height weirs or other adjustable flow barriers, with associated costs. Cost limits areas where controlled drainage would provide significant benefits.

Item Type: Thesis (Masters by Coursework)
Murdoch Affiliation(s): School of Veterinary and Life Sciences
Supervisor(s): Harper, Richard
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