Belongil Estuary Byron Bay
Estuaries are partly enclosed water bodies near the coast where sea water enters and mixes with fresh water runoff carrying materials from the land as it flows to the sea. Estuaries are places of rich biodiversity and productivity because of this mixing. Birds and fish thrive on the invertebrates and insects of the food chain of the estuary.
The Belongil is a relatively small estuarine water body near Byron Bay in northern New South Wales, where runoff from the surrounding catchment of 3,000 hectares area meets the sea. The estuary entrance is a pleasant walk of about 21/2 kms north of Byron township.
The estuary is the type known as an "ICOLL" - Intermittently Closed and Open Lake or Lagoon. In its natural state the estuary would have been closed for sometimes lengthy periods during dry weather and sand build-up on the beach bar at the entrance, then breaking open when heavy rainfall and runoff filled the catchment. The local area receives the highest average rainfall in NSW at 1,850mm per year.
Over the last 100 years significant development has occurred in the lower lying areas of the catchment and over the decades the estuary has been artificially opened for longer periods both to reduce flood risk and increase terrestrial land uses. Today, much of the commercial district of Byron Bay is at risk of flooding if the estuary is closed under particular weather conditions. A complex management effort to strike a balance between the realities of historical development and the needs of the ecosystem has been underway for several years.
The estuary water area is about 13 hectares. There is no seagrass, but there are about 5 hectares of saltmarsh and a similar area of mangroves. An extensive artificial drain network connects the catchment to the estuary, allowing runoff to drain much faster than in natural conditions. A large proportion of the catchment (about a third to a half) was once wetland, mainly melaleuca wetlands, and this fact has a large bearing on how the estuary functions today.
Many of the wetlands were cleared and drained for agriculture early in the 20th Century, with resulting heavy acid sulfate runoff from the soils down through the artificial drains. When wetland soils are drained and dried out, severe chemical reactions take place. This process continues today. However, the once-regular fish kills have been stopped in recent years through targeted management of the entrance opening by Council under a licence.
Urban development in Byron Bay and surrounds has also extended down into the wetlands in places, with stormwater and other pollutants adding to the acid soils impacts. High bacterial counts, mainly from stormwater, make the estuary unsuitable for swimming. The large West Byron Sewage Treatment Plant also impacts on the estuary, although some 40 hectares of effluent 'polishing' wetlands have been added and water quality is closer to 'natural waters' standard.
Industrial effluent and rural runoff is added to all these pressures, but the largest impacts have been shown in many studies and reports over the years to be acid sulfate runoff.
In spite of the many problems, the estuary has partly recovered in recent times from massive pollution events before 2000 when large fish kills occurred and the entire estuary was often devoid of life. Fish, prawn and crab populations are slowly recovering and can be seen by walking on the mudflats or along the channels. In the last three years a sustained effort led by Belongil Bird Buddies has succeeded in returning good populations of shorebirds to the estuary mudflats and entrance area.
Much more remediation work is needed, and the present estuary opening approach is seen as only a short term strategy. 'De-coupling' of the estuary from the upstream wetland areas by reducing or eliminating artificial drains is a major management goal. A holistic stormwater management system based on the Water Sensitive Urban Design approach, expansion of effluent reuse and wetlands, and the large-scale reinstatement of natural wetlands will restore the estuary to virtually full health.
Several committees exist to deal with these issues and interested people should inquire at Byron Shire Council about adding their voluntary labour to the rehabilitation effort.