Saving a Wheatbelt wetland refuge Unseasonal heavy rainfall earlier this year brought much life to Toolibin Lake, filling it for the first time in more than 20 years. But it also brought some unexpected challenges in managing this fragile Ramsar-listed wetland. by Karla Graham mid the patchwork of agricultural land of Western Australia’s AWheatbelt lies Toolibin Lake, an important refuge for plants and animals, especially waterbirds. For decades, government departments, local community members and stakeholders have worked to ensure this wetland continues to survive and thrive, despite the pressures of altered hydrology and other threats to natural resources. In February 2017, unseasonal rainfall filled the lake for the first time in more than 20 years, causing much celebration, along with some unique and welcome challenges for those working to conserve the lake. Previous page Main The February 2017 rainfall brought WATER RETURNS TO THE LAKE much interest to the lake. Early this year, more than 160 Photo – Deanna Rasmussen/DBCA millimetres of rain was recorded at Toolibin Above The newly filled Toolibin Lake. Lake over three days. Hydrologists Photo – Karla Graham /DBCA calculated that about 4,100 megalitres filled the lake, which rose to two metres ● Toolibin Lake deep. Nearby, Dulbining and Walbyring lakes, and two un-named wetlands, also received the rain. Importantly, the rainwater that filled Toolibin Lake was devoid of the salt that usually threatens this wetland. Early the State’s south-west, and the largest in south-west WA. This is the highest days saw the environment re-awaken in the area that features the threatened number of species recorded at any inland with a chorus of frog calls ready to begin ecological community made up of south-west wetland. the breeding cycle; as whirls appeared sheoak (Casuarina obesa) and paperbark The February rain event presented on the water from tiny invertebrates (Melaleuca strobophylla). Once common a perfect opportunity to carry out a and bejeweled damselflies; and flocks of throughout the Wheatbelt, many waterbird survey at Toolibin Lake. Parks waterbirds revelled in the ideal feeding and examples of this type of community have and Wildlife Service staff spent a day breeding conditions. By late March, the now succumbed to altered hydrology. identifying and counting waterbirds. first sightings of new life could be spotted Due to its biological diversity, Toolibin They counted 800 individuals from 12 on the lake. is listed as a threatened ecological species, including Eurasian coots, grey As a seasonal wetland, Toolibin community with the Australian teals, pink-eared ducks, hoary-headed Lake naturally goes through wet and Government and is internationally grebes, swans and Australasian shovelers, dry phases. This has contributed to the recognised as a Wetland of International and recorded 63 chicks. The next day, formation of wooded wetlands, as dry Importance under the Ramsar Convention. at nearby Walbyring Lake, they counted periods enable trees to regenerate in 592 individuals from 12 species, including an area that receives an annual average WATERBIRDS FLOCK BACK 41 chicks. The abundance of waterbirds rainfall of 300 to 400 millimetres. With more than 90 per cent of the in these areas is comparable to surveys However, in recent years, Toolibin Lake surrounding catchment cleared of native from 1996, but species richness was much has had to withstand the pressures of vegetation, the lake and surrounding nature lower. There were very few large wading changes in climate, human-induced reserves provide a stronghold for native birds (herons, spoonbills and egrets) and impacts on the water table and naturally plants and animals, including waterbirds. no cormorants. Black swans have taken occurring salinity, collectively known as Since 1965, 50 species of waterbird up residence at the lake again and have ‘altered hydrology’. have been recorded at the lake, including been recorded breeding. The surveys will Toolibin is the one of the largest and the freckled duck, which has a very be repeated in spring and summer if water last remaining inland freshwater lakes in small (500 to 1,000) breeding population remains in these wetlands to provide more 20 LANDSCOPE “... the rainwater that filled Toolibin Lake was devoid of the salt that usually threatens this robust wetland... and flocks of waterbirds revelled in the ideal feeding and breeding conditions.” Above Pink-eared ducks are one of the species that occurs at Toolibin Lake. accurate comparisons to those carried out Photo – Roz Barber in 1996. The area surrounding Toolibin Lake Left The desolate Taarblin Lake. also boasts more than 300 native plant Photo – Maria Lee/DBCA species and 10 native mammal species as well as a wide diversity of insects, reptiles, amphibians and terrestrial birds. AN ALTERNATE FATE Just a few kilometres from Toolibin Lake, positioned lower in the landscape, you’ll find Taarblin Lake. This monochrome landscape, with its desolate lake bed of petrified trunks and limbs, lies in stark contrast to the vibrant Toolibin Lake. The heavily salt-affected Taarblin Lake provides hydrologists, private landholders and lower groundwater levels; constructing a sobering glimpse at what Toolibin Lake volunteers, with support from natural a waterway to move highly saline water might have looked like if management resource management groups such as through the catchment and away from intervention hadn’t been undertaken. the South West Catchments Council, other natural resources, and carrying Since 1994, management of Toolibin Wheatbelt NRM and other stakeholders. out broadscale revegetation on private Lake has been guided by the Toolibin Management actions have included property and Crown land to help manage Lake Recovery Plan. Implementing the constructing a channel, feeder drains altered hydrology and benefit agricultural actions outlined in the plan has relied on and sump to move saline surface water productivity and biodiversity. This the tireless work of Parks and Wildlife away from the lake; installing a series of approach was recognised in 2002 when Service staff, members of the community, pumps on the lake bed to remove and the Toolibin Lake recovery team and its LANDSCOPE 21 monitored for its proximity to the lake “A series of removable metal gates installed at the northern bed. If the groundwater rises through end of the channel are closed to direct freshwater into the soil profile, it brings salt to the root Toolibin Lake, and opened to divert water away when zones of plants, causing their death and the collapse of stands of trees, particularly salinity levels become unacceptable. “ the two deep-rooted species after which the threatened ecological community is named – paperbark and sheoak. technical advisory group were awarded direct freshwater into Toolibin Lake, and During the past decade, periodic the Institute of Engineers of Australia opened to divert water away when salinity monitoring on the lake floor and within National Salinity Prize for innovation in levels become unacceptable. The rain the catchment enabled the department to managing salinity. event of February 2017 was the first time monitor groundwater levels. Hydrologists A revised Toolibin Lake Catchment Plan, the channel had been tested against such a will use this data to develop models that which is expected to be released this year, large event. detail how and when water and salt moves will present an opportunity to audit this When the rain fell, Parks and Wildlife through the catchment in order to make approach, and garner continued support Service staff saw a golden opportunity recommendations for on-ground works for managing this remarkable wetland. to allow freshwater into Toolibin. The that will help stall any rising of the water water quality was tested upstream and table that might be happening. DIVERSIONARY TACTICS staff determined it was fresh enough to At the beginning of this year, One of the key infrastructural be let into the lake. They then closed the monitoring the groundwater levels at components in the fight against altered metal gate panels, thereby closing off Toolibin Lake involved driving across the hydrology at Toolibin Lake is a seven- the diversion channel and allowing the dry lake floor, taking measurements from kilometre-long, 20-metre-wide diversion nourishing freshwater to flow directly the top of bores drilled down through channel constructed in 1995 around the into Toolibin Lake. Staff tested the water the surface of the lake to the water table western edge of the lake. This channel quality periodically and opened the gates below. But now, conservation staff make was designed to redirect saline water when the fresh flows ceased. their way around the 300-hectare lake flows from upstream away from the lake via boat, deftly manoeuvring on the calm itself, and into the sacrificial Taarblin Lake, MANAGING GROUNDWATER waters around sheoak and paperbark which had already collapsed. A series of But it’s not just the water above trees, stopping at each of the 19 bores removable metal gates installed at the ground that contributes to the lake’s now partially submerged to record northern end of the channel are closed to health. The groundwater is closely groundwater levels. 22 LANDSCOPE Opposite page Left Diversion gates can be opened and shut depending on the saline levels of the water. Photo – Gary Mills/DBCA Above Pumps are used to remove saline water away from Toolibin. Photo – Karla Graham/DBCA Right All staff from the department’s Narrogin and Merredin offices helped secure a breach of the diversion channel by hand. Photo – Deanna Rasmussen/DBCA Far right Aerial footage showed the extent of the inundation, which had not been seen in more than 20 years. Photo – Peter White/DBCA One method being used to combat landscape-scale approach to conservation news, it also presented some interesting rising groundwater is the use of pumping is the only true method of conserving this challenges to overcome.