In order to plan effectively for the future of our waterways we need to understand what has occurred in the past.
The waterways of the Peel-Harvey have been formed over extensive geological time-frames.
In recent times, human activity has had a rapid and dramatic impact on the health of the system, bringing it to the brink of collapse.
Now a new chapter is being written in the history of the Peel-Harvey waterways, with a renewed commitment from government, industry and the community to ensure the sustainability of the natural systems which make this region unique.
A system in decline
The natural landscape and catchment area of the Peel-Harvey that evolved over long geological time-frames, was being radically altered by human influence in a comparatively short period of time.
The river and estuarine system could not cope with such rapid and dramatic change and significant environmental problems began to emerge.
The Peel-Harvey Estuary is a large but very shallow body of water, more than half of which is less than 0.5 metres deep. It was previously connected to the ocean only by a narrow inlet channel at Mandurah which did not allow effective flushing of the basin to rid the inland water of the increasing nutrient build-up.
The build-up of nutrients can lead to eutrophication of the water and excessive growth of algae and other aquatic weeds and phytoplankton, and an overall deterioration of water quality. Scientists say the natural design of the estuary, coupled with Western Australia's long, hot summers, makes it predisposed to becoming eutrophic.
The added pressures of nutrient run-off from agriculture and the rapid increase in the local population led to a situation where the natural system was on the verge of collapse.
By the 1960s, a pink algae had developed in the estuary and was being blamed for a decline in the fishing catch. By the late 1960s, a green algae, known locally as 'goat weed', was prevalent and rotting algae piled up on beaches was posing a serious health issue for local residents.
Algal blooms became more common as the estuary's health continued to decline. In the late 1970s, a massive bloom of the potentially toxic phytoplankton Nodularia covered the whole of the Harvey Estuary with a green scum and drifted out into Peel Inlet.
As oxygen levels were depleted by on-going cycles of algal blooms and collapse, localised fish kills and crab deaths became more frequent.
Throughout the 1970s, the weed was harvested using mechanical water-based harvesters and front end loaders, and trucked away, but this did not address the cause of the problems.
In 1980, a study into the problems of the Peel-Harvey concluded that the main cause of the weed problem was the excess of phosphorous in the estuary water and that superphosphate, a fertiliser used in farming, was the principal source.
More research followed but other large green algae became common in the estuary through the 1980s.
Impact of settlement
Prior to European settlement, the Peel-Harvey coastal catchment was a wet landscape subject to seasonal inundation.
The area was occupied by the Nyungar people of the south west of Western Australia with a strong spiritual connection with and between the water, the land and all living creatures.
From around 1830, European settlement began to significantly alter the region's landscape and natural systems. Agriculture began to affect the land through clearing, the introduction of cattle stock and the draining of land for crops, while forestry became a major industry during the 1890s. A thriving fishing industry began in the 1870s but, by the 1890s, had begun to decline for various reasons.
Agriculture continued to expand as an industry throughout the region with large areas of sandy soils cleared, drained and developed from the 1950s.
With the building of better roads linking Mandurah, the main urban centre of the region, with Perth, the local population continued to grow, imposing additional pressures through land development.
Origins of the system
The Peel-Harvey catchment covers almost 12 000 square kilometres and is located directly south of Perth.
The Peel Inlet and the Harvey Estuary as we know them today were most probably formed about 6000 years ago.
The catchment is made up of three distinctive areas - the Swan coastal plain, the Darling Scarp and the eastern Wheatbelt.
Waterways are an iconic part of the catchment, with more than one-third of the coastal plain within 100 metres of a readily, identifiable water course.
The main river systems are the Serpentine, Murray and Harvey which drain into the extensive Peel-Harvey estuarine system. This area forms part of the Peel-Yalgorup system, which is included in the Ramsar list of internationally significant wetlands.
Other info
Department of Environment and Conservation
Environment Protection Authority
Peel Development Commission
Peel-Harvey Catchment Council
South West Catchment Council
Ribbons of Blue
Greening Australia
Shire of Boddington
Shire of Harvey
City of Mandurah
Shire of Murray
Shire of Serpentine-Jarrahdale