The subsequent scenarios describe a selection of nationally, regionally significant wetlands and other important wetland habitats which may be included for watering as part of the annual watering plan under various climate scenarios. Climate scenarios are hyper-drought, drought, dry, average and wet. Recognition of the inflows to the catchment in the preceding water year are also taken into account. The “wetness” or “dryness” of the catchment gives an indication of the likelihood of wetlands receiving water under predevelopment conditions. The Water Resource Assessment (2005) indicates predevelopment flows for the Lachlan River at Forbes, with maximum annual total flows of 4500 GL, average annual total flows of 1100 GL and minimum annual total flows of <150 GL. Therefore, it is likely that maximum flows would have resulted in floodplain flooding of the lower Lachlan and minimum flows resulting in little, if any, wetland inundation.
Decisions pertaining to when wetlands will receive water are based on:
- time since last watering;
- volumes available for watering, i.e. is there sufficient water available to achieve environmental objectives;
- efficiency of delivery, i.e. can the water reach the target and/or whether other operational flows are also being delivered to the same target; and
- environmental need, i.e. bird breeding completion or averting fish kills may take precedence over other environmental needs.
Climate Scenarios: Hyper-drought | Drought | Dry | Average | Wet
The order in which scenarios are presented within the tables below does not reflect priority.
Hyper-drought
Hyper-drought scenario: applicable at estimated available licenced environmental water <1733 ML (HS)
(likely under minimum flows at the Lachlan River at Forbes i.e. <150 GL/year)
| Target | Volume Required | Delivery Option | Duration of Inundation | Outcomes |
| Burrawang West Lagoon | Up to 420 ML | Bumbuggan Creek | Semi-permanent | To protect relocated Purple-spotted Gudgeons; riparian vegetation and resident Brolgas |
| Curlew Waters | ~500 ML | Lake Cargelligo inlet | Permanent | Provide drought refuge for wetland species |
| Brewster weir pool | ~1000 ML | Lachlan River | Permanent | Provide drought refuge for Olive Perchlet and other native fish species |
Drought
Drought scenario: applicable at available licenced environmental water 1733 ML to 19,000 ML
(likely at approximately 60%of average flows for the Lachlan River at Forbes i.e. <660 GL/year)
| Target | Volume Required | Delivery Option | Duration of Inundation | Outcomes |
| Brewster weir pool | ~1000 ML | Lachlan River | Permanent | To protect resident Olive Perchlet |
| Yarnel Lagoon | Up to 360 ML (volume required will be greater if not supplemented by replenishment flows) | Wallaroi Creek | 4–6 months | Water River Red Gums; frog breeding; protect resident Brolgas |
| Burrawang West Lagoon | Up to 420 ML | Bumbuggan Creek | Semi-permanent | To protect relocated Purple-spotted Gudgeon; riparian vegetation and resident Brolgas |
| Curlew Waters (Lake Cargelligo) | ~500 ML (volume dependent on existing volume: used as storage for town water supply) | Lake Cargelligo inlet | Permanent | Provide drought refuge for wetlands species |
| Lake Brewster inlet wetland | 1500 ML (to fill and maintenance flows: Brewster water savings to be used for this purpose | Lake Brewster inlet channel | >8 months | Stimulate wetland plant growth; provide refuge for Olive Perchlet and other wetland species |
| Lake Cargelligo main lake | Up to 5000 ML (fill to 30% capacity dependent on volume of existing dead storage) | Lake Cargelligo inlet channel | 6–12 months | Provide drought refuge for waterbirds and native fish |
| Eagle Nest Swamp: near Booligal | <200 ML | Merrimajeel/Muggabah creeks | 4–6 months | Provide wetland habitat and support bird breeding: note while not listed as regionally significant this wetland has been included due to land management and location considerations |
| Reed Bed: Great Cumbung Swamp | 5000–15 000 ML (greater volume may be required if not piggy-backed on operational or unregulated flows) | Lachlan River | 4–8 months | Maintain reed bed currently in good condition |
Dry
Dry scenario: applicable at available licenced environmental water ~20,000 ML to 69,000 ML
(drought and hyper-drought options also considered under the dry scenario)
(likely under less than average flows for the Lachlan River at Forbes i.e. <1100 GL/year)
| Target | Volume Required | Delivery Option | Duration of Inundation | Outcomes |
| Lake Merrimajeel/Murrumbidgil Swamp | 500–3500 ML (volume required will be greater if not piggy-backed on 9 GL replenishment flows) | Merrimajeel Creek | >6 months | Water River Red Gums; stimulate bird breeding |
| Lake Cargelligo back wetland area (Management Unit 4: see Lake Cargelligo Community Management Plan) | ~10 000 ML (dependent on Lake Cargelligo dead storage being filled previously) | Lake Cargelligo inlet | >6 months | Stimulate bird breeding; support a variety of wetland types |
| Lake Cargelligo Sheet of Water (Management Unit 2: see Lake Cargelligo Community Management Plan) | 4000 ML (dependent on flows being diverted into Lake Cargelligo main lake for other purposes) | Lake Cargelligo inlet channel | 4–6 months | Provide habitat for migratory waders |
| Lake Ita | 6000–14 400 ML VTF (volume required may be greater to reach required CTF) | Lachlan River | 4–6 months | Support River Red Gum forest; Black Box; Lignum and associated habitat within the Kalyarr Conservation Area |
| Upper Merrowie Creek | 6000 ML (volume required will be greater if not piggy-backed on 9 GL replenishment flows) | Merrowie Creek | 4–6 months | Support wetland habitats and colonial bird breeding |
| Cuba Dam | 4000 ML (volume required will be greater if not piggy-backed on 12 GL replenishment flows) | Merrowie Creek | 4–6 months | Support Lignum and bird breeding |
| Moon Moon Swamp | 2520 ML VTF (up to 25 000 ML may be required to fill if not piggy-backed on unregulated or operational flows) | Lachlan River | 3–6 months | River Red Gum watering and to support bird breeding |
| Willandra Creek | 3000 ML (volume required will be greater if not piggy-backed on 12 GL replenishment flows) | via Willandra Weir regulator | 4–6 months | Support a variety of wetland habitats within the National Park |
| Baconian Swamp | 4800 ML VTF (up to 35 000 ML may be required to fill if not piggy-backed on unregulated or operational flows) | Lachlan River | 4–6 months | To support River Red Gum; Black Box; bird and frog breeding |
| Lake Brewster outflow wetlands | 5000–15 000 ML (Brewster water savings to be used for this purpose) | Lake Brewster inlet channel | 4–6 months | Establishing/maintaining wetland vegetation for improved water quality |
| Water to complete bird breeding events | 2–4 months | Successful bird breeding event | ||
| Mid Lachlan Billabongs | Provide diverse floodplain habitat | |||
Average
Average scenario:applicable at available licenced environmental water ~70,000 ML to 119,000 ML
(previous scenario options also considered)
(likely at average or above flows for the Lachlan River at Forbes i.e. >1100 GL/year)
| Target | Volume Required | Delivery Option | Duration of Inundation | Outcomes | |
| Great Cumbung Swamp | 25 000–50 000 ML (dependent on antecedent conditions) | End of system flow | 6–12 months | Watering River Red Gum community; Reed Bed inundation; bird breeding | |
| Booligal Wetlands | 12 000–57 000 ML (dependent on antecedent conditions) | Merrimajeel/Muggabah creeks | 4–6 months | Bird breeding and Lignum support | |
| Lachlan Swamps | 20 000 ML | Lachlan River | 4–12 months | Watering semi-permanent wetland vegetation and open lagoons;including watering Lake Ita | |
| Merrowie Creek (Cuba Dam to Chillichil Swamp) | 6000 ML (volume required will be greater if not piggy-backed on 9 GL replenishment flows) | Merrowie Creek | 4–6 months | To support River Red Gums; Black Box; Lignum; bird breeding | |
Wet
Wet scenario:applicable at available licenced environmental water >120 000 ML
(previous scenario options also considered)
(likely at greater than average flows for the Lachlan River at Forbes i.e. >2700 to 4500 GL/year)
* Volumes required are outside the scope of discretionary water and would require translucent flows from Wyangala
| Target | Volume Required | Delivery Option | Duration of Inundation | Outcomes | |
| Great Cumbung Swamp | >50 000 ML* (dependent on antecedent conditions) | End of system flow | 12 months | Watering River Red Gum and Black Box community; Reed Bed inundation; bird breeding | |
| Booligal Wetlands | >50 000 ML* (dependent on antecedent conditions) | Merrimajeel/Muggabah creeks | >6 months | Bird breeding and Lignum support | |
| Lachlan Swamps | >20 000 ML* | Lachlan River | 12 months | Watering semi-permanent wetland vegetation and open lagoons;including watering Lake Ita | |
| Merrowie Creek (Cuba Dam to Chillichil Swamp) | 6000 ML (volume required will be less if supplementing replenishment flows) | Merrowie Creek | 4–6 months | To support River Red Gums; Black Box; Lignum; bird breeding | |
| Lake Brewster outflow wetland | 15 000 ML (850 ML = cell 1; 1200 ML = cell 1 & 2; 1200 ML = cell 3); requires maintenance flows | Lake Brewster main storage | 3–4 months | Stimulate plant growth; provide waterbird habitat | |
