Rivers
The Hawkesbury and its Tributaries
The Upper Hawkesbury River flows through the LGA, from Wisemans Ferry to Yarramundi, a total length of around 76km. The tidal limit of the Hawkesbury River occurs at Yarramundi, approximately 140km upstream of the river mouth.
There are a number of major tributaries flowing into the Upper Hawkesbury River including the Colo, Nepean, Macdonald and Grose Rivers and other tributaries like South Creek, Redbank Creek, Rickabys Creek, Webbs Creek and Cattai Creek.
The catchment has a distinct appearance. From the Grose River junction to Lower Portland the channel is sandy. Around Windsor the channel has large meanders and wide floodplains. There are also lagoons and floodplain wetlands like Pitt Town Lagoon and Long Neck Lagoon which provide significant bird habitat and are listed on the register of the National Estate. From Windsor to Sackville the river is wide and deep and the flat banks are cleared and cultivated.
From Sackville to Wisemans Ferry the river remains wide and deep with steep sandstone cliffs that are characterised by native vegetation, similar in appearance to the conditions 200 years ago.
The Upper Hawkesbury River is utilised for a range of activities. There is water skiing and wakeboarding particularly between Windsor and Wisemans Ferry. Kayaking is popular in the natural areas of the Colo River and Webbs Creek. Commercial fishers and prawn trawlers operate in the river, particularly downstream of Sackville.
Water Quality
Water Quality
Hawkesbury City Council carries out a water quality monitoring program across five distinct locations along the Hawkesbury river. The aims of the monitoring program are to assess the ecological health of Upper Hawkesbury River, from Windsor to Wiseman’s Ferry, using methods that are scientifically valid and standardised, and to report the information generated in an accessible way to the community in a report card style format.
What is the water tested for?
The water is tested to assess long-term ecosystem health and analyse factors that influence water quality such as turbidity and chlorophyll.
At each site a portable probe is used to measure:
- Dissolved Oxygen (DO% sat and DO mg/L)
- Electrical Conductivity (EC ms/cm and ECµs/cm)
- pH
- Salinity (ppt)
- Temperature (ºC)
- Turbidity (NTU)
A sample is also collected from each site and analysed for:
- Nutrients (nitrogen and phosphorus) (mg/L)
- Suspended Solids (mg/L)
- Chlorophyll-a (µg/L)
Results
To assess the health of the river, we compare the monitoring results with the guideline values from the Australian and New Zealand Guidelines for Fresh and Marine Water Quality.
Grades for water quality are then determined by calculating how often, and to what extent, the values for turbidity and chlorophyll-a exceed the statewide 80th percentile trigger value.
Chlorophyll-a
Nutrients such as nitrogen and phosphorous are usually present in aquatic habitats, but extra nutrients can contaminate a system. This can cause some plants and microalgae to grow out of control (algal blooms), whereas other plants and animals can decline.
The level of chlorophyll a, a green pigment found in plants, in water samples indicates the amount of microalgae and can indicate an excess of nutrients.
Excess nutrients can reduce:
- light, which has a negative effect on aquatic vegetation and reduces food and shelter available for aquatic animals
- oxygen levels, caused when the microalgae die and are broken down by oxygen-consuming bacteria
- biodiversity.
Turbidity
Turbidity is a measure of how clear water is and is related to the amount of material suspended in water. We measure turbidity in the field and collect water samples to assess for total suspended solids (TSS) back in the lab.
High turbidity or TSS can:
- restrict the amount of light available for plant growth
- increase water temperatures
- decrease dissolved oxygen levels
- have a negative impact on aquatic ecosystems
- indicate potential sedimentation (smothering) rates
- indicate the extent of catchment erosion or other potential contamination sources, such as sewage outfalls or stormwater drains
- result from urbanisation, clearing of vegetation and agriculture, which can expose soil and increase the amount of material that is washed into our waterways
Rainfall also plays a major role and can influence water quality by increasing stormwater flows, bringing with it higher turbidity and suspended solids, washing rubbish and contaminants into streams and creeks and increasing the likelihood of overflows from sewerage systems into waterways in developed areas.
The Upper Hawkesbury Water Quality Monitoring Program report cards can be found below;
Boat ramps and Jetties
Council has a formal boat ramp at Governor Phillip Park, Windsor, to give boating access to the Hawkesbury River. Ample trailer parking is available and there are amenities and a fish-cleaning table on site. The ramp is open to the public 24hrs except during major boating events like the Bridge to Bridge. The dates of these closures are advertised prior to the events.
Informal boat ramps are also located at Holmes Drive Reserve, Cumberland Reach and Skeleton Rocks Reserve, Lower Portland. These ramps have no additional facilities, limited parking and are not suitable for large watercraft.
Council has three canoe access jetties located at: Macquarie Park, Freemans Reach; Hanna Park, North Richmond and Colo Park, Colo. These give access to the Hawkesbury and Colo Rivers.
Informal canoe access to the Hawkesbury river can be achieved at: Yarramundi Reserve, Yarramundi; Navua Reserve, Grose Wold and Skeleton Rocks Reserve, Lower Portland.
Informal canoe access to the Colo River can be achieved at Upper Colo Reserve, Upper Colo and Skeleton Rocks Reserve, Lower Portland.
Informal canoe access to the Macdonald River can be achieved at St Albans Park, St Albans, depending on river levels.
Coastal Zone Management Plan
To better manage all the pressures on the river a Coastal Zone Management Plan (CZMP) has been prepared. As part of the preparation of the CZMP there was extensive consultation with landowers and key river users. The CZMP also looked in detail at some of the areas of erosion and structures (like jetties and seawalls) that have been built along the river and also areas of weed infestation, particularly the species Arundo donax, the Giant Weed.
The CZMP is a document which identifies how Council plans to manage the Upper Hawkesbury River over the next 5-10 years. Thirty nine Action Plans have been developed which will provide the greatest benefit to estuary health and environmental sustainability.
The supporting documents which were important in the preparation of the CZMP include the Synthesis Report which is a summary of available literature about the River and the Bank Erosion, Foreshore Structure and Weed Mapping Report and the Community Consulation Report which is a summary of the outcomes of the consultation which took place during the preparation of the CZMP
Wetlands of the Hawkesbury
There are many common names for wetlands; swamps, saltmarshes, billabongs, lagoons, fens and peat lands to name a few. Wetlands can be permanently or seasonally inundated with water and have unique soil conditions that support characteristic wetland vegetation.
Wetlands are important for many environmental, social and economic reasons and they play a key role in how our environment functions. They help purify incoming flows of water by removing nutrients and other pollutants, act as natural sinks and reduce flooding, and support life during times of drought.
The Hawkesbury-Nepean catchment contains many significant wetlands occurring from the floodplains of the rivers to the upland swamps of the Blue Mountains. For further information on wetlands see the links below.
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