There has been a noted reduction in winter rainfall throughout much of the south west of Western Australia (Indian Ocean Climate Initiative; 2004); which may impact hydrological regimes.
Although these are not confirmed climate change events; they have affected hydrological regimes.
This has altered the perceptions of regional climate even though a similar; albeit less severe; dry sequence was experienced earlier in the century The recent rainfall decrease was only observed in early winter (May July) rainfall late winter (August October) rainfall has actually increased; although by a smaller amount The winter rainfall sharply and suddenly decreased in the mid 1970s by about 15 20 .
Hardy Head (Leptatherina wallacei) and the Swan River Gobi (Pseudogobius olorum) have been recorded in the lower Dalyup River where it terminates at Lake Gore Aquatic invertebrates Low richness due to high salinities Species composition has been variable Vegetation Lake Gore has fringing vegetation consisting of Melaleuca cuticularis High water mark of Lake Gore consists of Schoenus brevifolius and Gahnia trifida; samphire species (Suaeda australis and Sarcocornia quinqueflora) and the grass species Sporobolus virginicus and herb Samolus repens Melaleuca cuticularis is replaced by Acacia sp. as the elevation increases on the northerly side of Lake Gore The majority of the riparian vegetation of the Lake Gore catchment is dead or declining due to an altered hydrological regime Critical ecosystem benefits and services Provisioning Services Genetic resource Human health Regulating Services Pollution control and detoxification Cultural Services Recreation Science and education Cultural heritage and identity Spiritual and inspirational Aesthetic amenity Supporting Services Hydrological processes Nutrient cycling Biodiversity Physical habitat Priority wetland species Ecological connectivity Threats to the ecological character Agricultural activities in the Dalyup and Altered hydrology Coobidge Creek catchments Pollution Altered fire regimes XVII Ecological Character Description of the Lake Gore Ramsar Site Category Summary Acid sulfate soils .
Actual or likely Potential and or actual Likelihood Timing of threat threat or threatening impact(s) to wetland activities components; processes; benefits and services Agricultural activities Altered hydrological regime Certain high Immediate long in the Dalyup and timing; frequency and extent term Coobidge Creek of inundation catchments have Introduction and resulted in establishment of weeds Increased sedimentation Increased salinisation Clearing of native vegetation (secondary salinisation) Livestock grazing through changed hydrology (Comer et al.; 2001) General cropping and Nutrient enrichment and agricultural activities subsequent algal blooms Pollution; nutrient; sediment and salinity (Comer et al.; 2001) Reduction in waterbird habitat area and condition Reduction in extent of native vegetation Altered fire regimes Changes to water and sediment chemistry Disturbance of potential acid sulfate soils Increasing fragmentation; loss of remnants and lack of . . . . . .
Potential and or actual impact(s) to wetland components; processes; benefits and services recruitment (Comer et al.; 2001) Reduction in the capacity for the site to provide provisioning; regulating; cultural and supporting services Competition with native flora and fauna reducing habitat area and condition Loss of native species Reduction in the capacity for the site to provide provisioning; regulating; cultural and supporting services Altered catchment hydrological regimes timing; magnitude and frequency of flows into Lake Gore Altered hydrological regime of Lake Gore timing; frequency and extent of inundation Changes to flora and fauna distribution and condition Increased non native flora and fauna species Increases in sedimentation Reduction in the capacity for the site to provide provisioning; regulating; cultural and supporting services Introduction and establishment of weeds Spread of alien species such as Phytophthora cinnamomi Destruction of flora and fauna habitat Increased fire risk Direct impacts on flora and fauna (e.g. by vehicles; trampling; disturbing mating and nesting sites) Reduction in the capacity for the site to provide provisioning; regulating; cultural and supporting services .
The impact of these blooms on waterbird populations is unknown. 4.1.3 ALTERED FIRE REGIMES Due to the surrounding land use fire and fire suppression are a potential threat to the ecological character of the site.
However; this is also dependant upon other factors such as fire frequency and timing (Morrison; 2002).
Fire can also cause hydrological changes through the removal of vegetation.
Other threats resulting from fire include the attraction of feral animals to an area to feed on new growth that results post fire (Nikki Cowcher; Fire Operations Officer; DEC; pers. comm.; 2008).
For example; post fire there is often a concentration and abundance of rabbits which causes erosion and changes vegetation structure more rabbits attracts more foxes which may also feed on native species (Nikki Cowcher; Fire Operations Officer; DEC; pers. comm.; 2008). 4.1.4 ACID SULFATE SOILS As the soils of the Gore system have a high probability of having PASS (Massenbauer; 2007); the agricultural activities in the surrounding catchment may disturb and expose these PASS.
Hydrology The Dalyup River has now become more perennial; with increased annual discharge and flood peaks (Callow; 2007) Estimated peak discharges are significantly higher and flow has increased from 20 to 80 of the year since clearing (Callow; 2007) Since catchment clearing; bankful discharge rates are now occurring 2 4 times a year depending on catchment location (Callow; 2007) An increase in the groundwater levels in the Dalyup catchment of between 0 cm and 35 cm per year since listing (George et al.; 2008) with many groundwater aquifers close to full capacity (John Simons; Regional Hydrologist DAFWA; pers. comm.; 2008) An altered hydrological regime has caused increases in the extent and duration of water inundation at Lake Gore and has not dried out since listing The most recent monthly water depth data (i.e. from 2006 2008) indicates that Lake Gore is remaining inundated throughout the year with an average depth of 1.5 m (n 36) The current hydrological regime has resulted in the establishment of a new high water mark ( 17.5 m AHD) The minimum and maximum exposed shore zone areas at Lake Gore has been reduced from 45 ha 200 ha (optimum) to 0 ha 90 ha (Massenbauer; 2008b Robertson Massenbauer; 2005).
In extreme flood events; overflow from the Lake Gore and Coobidge Creek catchments merge westward via an ill defined watercourse; from the Overflow Swamp to Barkers Inlet approximately 12 km away and then to the Southern Ocean.
These flood events and the changes in the catchment have contributed to the altered hydrological regime of the Lake Gore Ramsar Site.
Due to hydrological changes the flow in the Dalyup River has now become more perennial; with increased annual discharge and flood peaks (Callow; 2007).

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