Presentation on theme: "South West Waterways Values, Condition & Impacts A context for water issues in the West RFA Dr. Tim Fletcher."— Presentation transcript:
South West Waterways Values, Condition & Impacts A context for water issues in the West RFA Dr. Tim Fletcher
Introduction l General presentation - sets the context for more specific presentations which follow l The information presented is not “new” — it is a broad summary of the state of knowledge of regional waterways l Presents the big picture of waterways in the region - both the condition & impacts — puts RFA water issues in regional context
Outline l Waterways in the West RFA region l Values & uses (demands) of waterways l Impacts on waterways l Condition of regional waterways l Methods to protect waterway values
Waterways within the West RFA Covers part of 16 river basins GoulburnCampaspe LoddonAvoca YarraMaribyrnong WerribeeWimmera-Avon MooraboolBarwon Otway CoastLake Corangamite HopkinsPortland Coast Glenelg Millicent
Waterways in the Corangamite region (Barwon, Moorabool, Lake Corangamite & Otway Coast Basins)
Waterway Values & Uses l Environmental l Economic l Social Many competing demands...
Economic & Social Values l Water supply — drinking & domestic (e.g. garden watering), industrial, agriculture (stock & irrigation) l Extraction — fish, gravel, sand, soil (floodplain) l Tourism & recreation — walking, sightseeing, fishing, boating, swimming l Aesthetics — rural landscape, parkland, urban design l Waste discharge — sewerage, industry, stormwater
Environmental Values l Instream — habitat for fish, macroinvertebrates (“bugs”), macrophytes (“plants”) l Riparian (streamside) zone — habitat corridor, unique landscape element (ecotone) l Floodplain — intermittent habitat (billabongs), nutrient transfer, sediment deposition l Dynamic, variability, diversity
Impacts on Waterways l Urbanisation l Agriculture l Forestry l Others (e.g. mining)
Impacts of Urbanisation (e.g Geelong, Ballarat) l Hydrology — increased impervious area, decreased vegetation cover Õ “flashy catchments” - rapid flows over short time Õ leads to downstream erosion & scouring — river isolated from its floodplain — extraction of flows for water supply l Water quality — increased sediment transport — increased nutrients (N, P) - sewerage, fertilisers, etc — reduced dissolved oxygen (DO) — pathogens, heavy metals, hydrocarbons, litter l Channel & riparian zone — gross modification — channelisation, clearing of vegetation - loss of diversity — barriers to fish passage (weirs, culverts, etc)
Impacts of Agriculture l Hydrology — Vegetation removal ( runoff, erosion, groundwater, salinity) — Diversion & storage of stream water Õ impacts on aquatic communities (flora & fauna) — Flood control (levees, etc) Õ river isolated from floodplain, flow concentration, erosion l Water Quality — sediment & nutrients (fertiliser use, stock access & cropping, soil erosion) — pathogens (stock access) — potential chemical contamination (herbicide/pesticide) — changed organic inputs, dissolved oxygen levels
Impacts of Agriculture (cont.) l Channel & Riparian Zone — vegetation removal (changed shade, temperature, etc) — de-snagging, channel “cleaning” & “straightening” Õ loss of habitat — channel deepening & erosion (from increased runoff) — fish barriers (storages, weirs, poorly designed crossings) — reduced physical and biological diversity Õ smaller range of habitats (suits less species)
Impacts of Forestry l Hydrology — short and long-term changes to water yield — presentation by Dr. Rob Vertessy l Water quality — sediment mobilisation & transport — presentation by Dr. Jacky Croke l Channel & riparian zone — short or long-term changes to vegetation structure Õ depending on proximity of harvesting — generally less than urbanisation or agriculture
Condition of Waterways in SW Vic l Two comprehensive assessments of environmental condition: — Mitchell (1990) Õ 96 sites — Index of Stream Condition (ISC) (1999) Õ 217 sites
Condition Assessment - ISC l Hydrology — deviation from natural flows l Physical form — bed & bank stability — barriers to fish passage — instream habitat (snags, etc) l Streamside zone — vegetation cover & condition, weeds, regeneration l Water quality — total phosphorus, turbidity, EC, pH l Aquatic life — macroinvertebrate population diversity Five sub-indices Index of Stream Condition
Results Excellent 13% Good 25% Moderate 26% Poor 29% Very Poor 7% l Excellent — Generally in forested areas: Õ Otways (e.g. Gellibrand, Barham, Ford Rivers) Õ Moorabool River (e.g. below Lal Lal Reservoir) l Very Poor — Generally in/near urban areas, or where intensive agriculture is present: Õ Naringhil & Kuruc-a-Ruc Cks Õ Yarrowee River & Winter Ck (near Ballarat ) Mitchell, 1990
How can we best protect our waterways? l Considering that — there are many different values/uses of land and water …. ….
Protecting waterway values... l Initial assessment of capability/impacts of the particular use l Best practice land use — urbanisation — agriculture — forestry BUT all of the above depend on l Long-term environmental monitoring — both broad scale/background & specific
Some references Mitchell (1990). The environmental condition of Victorian streams Ladson & White (1999). An index of stream condition: reference manual Commissioner for the Environment (1988). State of the environment report 1988 - Victoria’s inland waters Corangamite CaLP (1997). Corangamite Regional Catchment Strategy Fletcher & Bren (1999). Cumulative effects analysis; grasping the big picture of environmental change in rivers. In Proceedings of 2nd Australian Stream Management Conference
Scales - Spatial & Temporal l Environmental data — variable — in space and time l Analysis needs to consider this l Must consider “cumulative effects” — the accumulation* of effects resulting from a number of individual actions on the environment, distributed through space and/or time Õ * many types (not necessarily linear) Õ recovery, threshold, multiplicative, etc….
Condition Assessment - Mitchell l 10 factors important to aquatic organisms Õ bed composition, pools & riffles Õ bank & verge vegetation Õ cover for fish (snags, boulders, undercut banks) Õ flow depth & velocity Õ submerged vegetation, instream organic matter Õ sedimentation or erosion — Environmental rating Õ very poor - poor - moderate - good - excellent
l Excellent — Generally in forested areas Õ Otways (e.g. Gellibrand, Barham, Ford Rivers) Õ Moorabool River (below Lal Lal Reservoir) l Very Poor — Generally in/near urban areas, or where intensive agriculture Õ Naringhil & Kuruc-a-Ruc Cks Õ Yarrowee River, Winter Ck (near Ballarat), e.g. e.g.