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Water resources on the south coast | April 2001 |
The term water resources is used to describe all groundwater and surface waters along the coastal area, but does not include marine waters. Wetlands, estuaries, rivers and creeks are all water resources that are in part managed by the Department of Environment, along with other agencies. The department has a general duty to protect potable (drinking water) supplies.
Residents of the south coast appreciate the beauty of these areas, and also understand the economic value of these resources. But residents are also aware these resources are under threat, from increased development, inappropriate land uses and land clearing. Sedimentation, algae blooms, fish kills, increased salinity, pollution events, destruction of foreshore vegetation, infilling of wetlands and reclamation of estuaries are very visual examples of the pressure being placed on water resources in the region.
Our knowledge of water resources is far from perfect. While some estuaries or groundwater areas receive much research and are well understood, others have little information available. Establishing priorities for action across the south coast needs to recognise this shortfall in information.
Potable surface water supplies are limited away from the coast, as water quality is generally too saline or of insufficient supply. The exception is Bolganup Creek which has been dammed to provide water for Porongurup and Mt Barker. The creek's water quality is maintained due to its catchment being entirely within the Porongurup National Park.
The Albany-Denmark region has various rivers and creeks that offer possibilities for future potable water supplies. They include the Kent and Denmark rivers, which are included as Water Resource Recovery Catchments in the Government's Salinity Action Plan. The plan hopes to reduce salinity in these catchments so that they can be used for drinking water purposes by the years 2030 and 2020, respectively. Other options for future potable water include a number of small coastal creeks, such as the Goodga river. The Water Corporation is presently assessing the suitability of using Marbellup Creek as a future water supply. The Marbellup catchment is already declared a water reserve under the Country Areas Water Supply Act.
The utilisation of coastal creeks for potable water could have a number of environmental impacts, caused by the reduction in downstream flows and through the construction of dams or pipeheads. The protection of these water supplies also has important impacts on the suitability of development in these catchments.
The consideration of present and future potable surface water supplies is covered in more detail in the Albany-Denmark Region and Esperance Region Water Resources Reviews and Development Plans, both prepared by the Water and Rivers Commission in 1997. See the bibliography for more details.
A regional classification of wetlands has been recently completed that identifies significant wetland suites and their potential threats. Seventeen outstanding wetland systems have been identified that are of national or international significance. These include the Ramsar listed Warden System and the potential Ramsar site of Lake Gore (list pending). There are also another 77 wetland systems that have been identified as of state or regional significance. The identification and classification of these wetlands provides the basis for improved management and understanding of these important systems.
| Name | Significance | Conservation category | Fringing vegetation | Hydrological regime | Salinity |
|---|---|---|---|---|---|
| Balicup Lake System | N | C | A | Modified | Hypersaline |
| Lake Gore System | R | C | B | Significantly altered | Saline |
| Lake Warden System | R | C | C | Significantly altered | Hypersaline |
| Howick Lake | W | C | B | Modified | |
| Monjingup Lake | W | C | B | Modified | Fresh |
| Benje Benjenup Lake | W | C | C | Modified | Hypersaline |
| Mortijinup Lake System | N | C | A | Modified | Saline |
| Pink Lake | N | C | C | Modified | Hypersaline |
| Coomalbidgup Swamp | W | C | B | Significantly altered | Fresh |
| Roberts Swamp | W | C | B | Modified | Brackish |
| Coujinup Swamp | W | C | B | ||
| Lake Chidnup | W | C | B | Modified | Brackish |
| Yellilup Yate Swamp System (Pabelup, Cordinup and Marendiup suites) | N | C | B | Significantly altered | Brackish |
| Lake Muir (Muir-Unicup Suite) | N | C | B | Significantly altered | Marginal |
| Lake Pleasant View System (Corimup Suite) | N | C | B | Modified | Fresh |
| Stokes Inlet System | W | C | A | Modified | Saline |
| Peak Charles System | W | C | A | Modified | Saline |
| Owingup Swamp Suite | N | C | A | Modified | Fresh |
| Kojaneerup Suite | W | C | A | Natural | Saline |
| Manypeaks Suite | W | C | B | Modified | Fresh |
| Lake Saide Suite | W | R | C | Modified | Fresh |
| Frenchman Bay Suite | W | C | B | Natural | Fresh |
| Lake Seppings Suite | W | R | C | Modified | Fresh |
| Jerdacuttup Lakes System | W | C | B | Modified | |
| Lake Shaster System | W | C | A | Natural | |
| Kent Lakes (Unicup Suite) | W | C-R | B | Modified | Fresh-Saline |
| Lake Matilda | W | R | C | Significantly altered | Saline |
| Pardelup Lagoon | W | C | B | Modified | Fresh |
| Mills Lake System | W | R | D | Significantly altered | Marginal |
| Goode Beach Suite | W | C | A | Natural | Fresh |
| Gull Rock Suite | W | C | A | Natural | Fresh |
| Gardner Lake Suite | W | C | A | Natural | Fresh |
| Moates Lake Suite | N | C | A | Natural | Fresh |
| Fringing vegetation |
A: Wetland in national park, nature reserve or State Forest. B: Wetland in small reserve or large block of remnant vegetation. C: Some remnant vegetation connected to the wetland. D: Wetland surrounded by cleared land |
| Hydrological regime |
Natural: Natural hydrological regime, wetland fully functioning. Modified: (for example due to stormwater or rural drainage discharge, clearing, abstraction of groundwater or surface water etc). Generally wetland remains healthy. Significantly altered: Wetland hydrology significantly altered, resulting in impacts upon wetland health (tree deaths, changes in vegetation composition, loss of habitat) |
| Significance |
R: Wetland of international importance nominated for inclusion under the Ramsar Convention N: Wetland included in "A Directory of Important Wetlands in Australia" (Australian Nature Conservation Agency, 1996) W: Regionally significant wetland, as identified in a regional study |
| Conservation category |
C: Conservation wetlands: Wetlands recognised at the international, national or regional levels; High Conservation and Conservation wetlands identified using Bulletin 374 assessment; wetlands 95-100% undisturbed, vegetated sections of extensive wetlands. R: Resource Enhancement: Wetlands 20-94% vegetated and Bulleting 374 Resource Enhancement and Open Space wetlands not defined as Classification C. |
Many of the more valuable wetlands are located just inland of the region's coastal dunal system. These wetlands receive higher levels of rainfall and are often protected through inclusion in national parks or reserves. These wetlands are less modified by development or by changed water levels or salinity. Further inland wetlands have been affected by land clearing, rising groundwater levels and salinity. Some wetlands have also been modified by drainage.
Nutrient enrichment of wetlands is also common on the south coast, and this may create increased problems with midges and harmful algae blooms. Modified wetlands may still have a valuable conservation function, as is the case with Lake Powell located between Albany and Denmark. This lake is a nature reserve and an important habitat for wading birds, but its also suffering from blue-green algae blooms caused by changes in flows through drainage works and in past discharges of treated effluent.
Further details of south coast wetland types, location and management issues can be found in reports undertaken by V. and C. Semeniuk Research Group (see bibliography).
A survey of major rivers using remote sensing shows that there are reaches that have riparian vegetation in good condition although many of these reaches occur in parks and reserves. Several rivers and tributaries have now been surveyed in detail to examine foreshore and channel condition and to provide management recommendations. While considerable work has already been undertaken, fencing and revegetation of riparian zones continues to be a priority for most waterways in agricultural areas.
Several river systems in the south coast suffer from increased nutrient levels. The Wilson Inlet catchment, drained by the Denmark, Hay and Sleeman rivers, is one of four national Focal Catchments under the National Eutrophication Management Program.
| River | Nutrients | Erosion/sedimentation | Fringing vegetation | Salinity | Flood risk |
|---|---|---|---|---|---|
| Tributaries to Lake Warden | Very High | Poor | Poor | Saline | Medium |
| Lort and Young River | Moderate | Poor | Moderate | Saline | Low |
| Oldfield River | High | Moderate | Moderate | Saline | Low |
| Phillips River | Moderate | Poor | Moderate | Saline | Low |
| Hamersley River | Excellent | Saline | Low | ||
| Fitzgerald River | Low | Excellent | Saline | Low | |
| Gairdner River | Very High | Poor | Moderate | Saline | Low |
| Bremer River | Moderate | Poor | Moderate | Brackish | Low |
| Pallinup River | Moderate | Poor | Poor | Saline | Low |
| Kalgan River | Low | Moderate | Moderate | Brackish | Medium |
| King River | Moderate | Moderate | Moderate | Fresh | Medium |
| Torbay Drainage System | High | Poor | Poor | Marginal | Medium |
| Sleeman Cuppup Drainage System | High | Poor | Poor | Marginal | Medium |
| Hay River | Low | Poor | Moderate | Brackish | Medium |
| Denmark River | Low | Moderate | Moderate | Marginal | Medium |
| Scotsdale Brook | Low | Moderate | Moderate | Fresh | Low |
| Mitchell River | Low | Excellent | Excellent | Fresh | Low |
| Kent River | Moderate | Poor | Moderate | Brackish | Low |
| Bow River | Very High | Moderate | Moderate | Fresh | Low |
| Gordon River | Very High | Poor | Poor | Saline | Medium |
| Frankland River | Low | Moderate | Moderate | Brackish | Low |
| Deep River | Low | Excellent | Excellent | Fresh | Low |
| Salinity |
Fresh: 0 - 500 mg/litre Marginal: 500 - 1000 mg/litre Brackish: 1000 - 5000 mg/litre Saline: 5000 - 35000 mg/litre Hypersaline: >35000 mg/litre |
| Nutrients ( Total N or Total P) |
Extreme: > 4.0 mg/litre or > 0.5 mg/litre Very High: 3 - 4 mg/litre or 0.3 - 0.5 mg/litre High: 2 - 3 mg/litre or 0.2 - 0.3 mg/litre Moderate: 1 - 2 mg/litre or 0.1 - .02 mg/litre Low: <1 mg/litre or < 0.1 mg/litre |
| Fringing vegetation |
Excellent:Riparian corridor is largely intact, with possibly some small areas of degradation Moderate: Balance between intact riparian vegetation and moderately affected areas Poor: Largely cleared with land in private ownership for full length |
| Erosion/sedimentation |
Excellent:No evidence of sedimentation Moderate: Some evidence of increased sedimentation Poor: River pools largely filled with sediment or significantly enhanced sedimentation in estuary |
| Flood risk |
High:High probability with high consequences Medium: Low probability with high consequences or high probability with low consequences Low: Low probability with low consequences |
Despite these problems the region's rivers provide important economic and environmental functions. The tidal reaches of major rivers such as the Denmark, King and Kalgan provide varied recreational opportunities and are important fish nurseries. The small coastal creeks are mainly fresh and provide habitat for fish species often not found elsewhere, and even the more occasional flowing rivers in the east of the region leave permanent ponds which provide year round aquatic habitats.
In general, estuaries along the south coast are suffering from nutrient enrichment and sedimentation. Estuaries are the receiving bodies for water, nutrients and pollutants from the catchments and so ensuring their good health relies on good catchment management throughout the whole of the south coast region.
| Estuary | Nutrients | Erosion/sedimentation | Fringing vegetation |
|---|---|---|---|
| Stokes Inlet | Moderate | Excellent | Excellent |
| Oldfield Estuary | Moderate | Excellent | Excellent |
| Culham Inlet | Moderate | Poor | Moderate |
| Hamersley Inlet | High | Excellent | Excellent |
| Dempster Inlet | Excellent | ||
| Fitzgerald Inlet | Excellent | ||
| Saint Mary | Very High | Excellent | Excellent |
| Gordon Inlet | High | Excellent | Moderate |
| Wellstead | High | Moderate | |
| Beaufort Inlet | High | Poor | Excellent |
| Cheyne Inlet | Moderate | Moderate | |
| Cordinup and other minor estuaries east of Albany | Moderate | Moderate | |
| Waychinicup | Excellent | Excellent | |
| Norman's | Low | Excellent | Moderate |
| Taylor Inlet | Low | Moderate | |
| Oyster Harbour | Low | Moderate | Moderate |
| Princess Royal Harbour | Low | Excellent | Poor |
| King George Sound | Low | Excellent | Excellent |
| Torbay Inlet | Moderate | Poor | Moderate |
| Wilson Inlet | Low | Poor | Moderate |
| Parry Inlet | Moderate | Excellent | |
| Irwin Inlet | Low | Excellent | |
| Nornalup-Walpole Inlet | Low | Excellent | Excellent |
In the recently prepared National Land and Water Resources Audit only two estuaries on the south coast are considered 'near pristine', these being the Oldfield Estuary and Broke Inlet. Other estuaries or inlets have valuable and sometimes unique characteristics. For example, Waychinicup Inlet is unique in being the only river gorge flooded by the ocean along the south west coast. Oyster Harbour is permanently open to the sea and provides a regionally significant fish nursery. Princess Royal Harbour and King George Sound provide safe anchorage for the port of Albany. Nornalup Inlet has near pristine karri and tingle forrest heath and sedgelands extending to the edge of the inlet, and is located within the Walpole-Nornalup Park. All the estuaries and inlets on the south coast offer recreational opportunities, often of a wilderness type experience.
Albany-Denmark Region Water Resources Review and Development Plan April 1997. Vol 1 of 11. WRC Report WRAP2 1997.Esperance Region Water Resources Review and Development Plan February 1997 Water and Rivers Commission Report WRAP5 1997.
Hydrogeology of the Mt Barker-Albany 1:250 000 sheet. Water and Rivers Commission Report HM1 1997
Hydrogeology of the Esperance-Mondrain Island 1:250 000 sheet. Water and Rivers Commission Report HM2 1998
Hydrogeology of the Ravensthorpe 1:250 000 sheet. Water and Rivers Commission Report HM4 1998
Preliminary delineation of consanguineous wetland suites between Walpole and Fitgerald Inlet, South Western Australia. V and C Semeniuk Research Group. Water and Rivers Commission June 1998.A preliminary evaluation of wetlands in the Esperance Water Resource Region Ecologia Water and River Commission Nov 1999 (Draft)
Estuaries and coastal lagoons of South Western Australia. Environmental Protection Authority Perth W.A.Estuaries of the Denmark Shire. Estuarine Studies Series Number 3 August 1988.
Estuaries of the Jerramungup Shire. Estuarine Studies Series Number 4 November 1988.
Estuaries of the Shire of Manjimup. Estuarine Studies Series Number 6 September 1989.
Estuaries of the Shire of Albany. Estuarine Studies Series Number 8 November 1990.
