SOUTHERN GRAMPIANS WETLANDS INFORMATION DAY Sunday 23 rd November 2014

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1 SOUTHERN GRAMPIANS WETLANDS INFORMATION DAY Sunday 23 rd November 2014 Progress of wetland restoration trials at Walker, Gooseneck and Brady Swamps Mark Bachmann, Nature Glenelg Trust (NGT) The Walker, Gooseneck and Brady Swamp complex of wetlands straddle public and private land at the far southeastern corner of the Grampians National Park (see below), near Dunkeld in Victoria s South West. The swamps are associated with a low-gradient reach of the Wannon River, after it exits the valley between the Serra and Mt William Ranges within the Grampians. The construction of artificial drains in what is now known as the Bunnugal Rural Drainage Area, from around 1900, created an additional catchment for these swamps (see image over page). While this was initially limited to the extensive Heifer Swamp system to the east, with time additional private drains were connected into this catchment from as far away as Glenthompson (linked to the Bunnugal drain inflow into Brady Swamp) and also from further afield to the north-east (linked to the second drain inflow via Walker Swamp). Grampians National Park Walker Swamp Lake Reserve Brady Swamp Wildlife Reserve Brady Swamp Gooseneck Swamp Walker Swamp Oblique image looking over the project area towards the Grampians, with Parks Victoria Reserves marked and named as indicated. Gooseneck Swamp falls within the Grampians National Park, and the northern portion of Brady Swamp is a Wildlife Reserve. 1

2 GOOSENECK SWAMP Image from the late 1940s: showing Wannon River flows (blue arrows) and Heifer Swamp drainage inflows (red arrows) into Walker Swamp and Brady Swamp from s After a 50 year period of increased inflows due to discharges from the new Bunnugal Drainage Area catchment, the comprehensive drainage of Walker, Gooseneck and Brady Swamps was attempted in the 1950s. At that time all three swamps were privately owned and managed as grazing enterprises, during a period when private wetland drainage was occurring across the region at an increased rate. Image from the present day: showing the additional drains (red lines and additional arrows) constructed to more comprehensively drain Walker, Gooseneck and Brady Swamps, as it operated from the 1950s

3 However, due to the size and reliability of the catchments that feed these swamps and the low-gradient in this section of the Wannon River, they all continued to effectively function as wetlands during periods with sufficient inflow. In fact, as a result of the environmental values they retained, and thanks to the efforts of people like Gavin Cerini (an officer with the Department of Fisheries and Wildlife at the time), all of Gooseneck Swamp and the northern portion of Brady Swamp were purchased by the government in the mid-1980s, for inclusion in Parks Victoria reserves (Grampians National Park and Brady Swamp Wildlife Reserve respectively). However it still remained the case that, in all but the wettest periods, drainage had altered the depth and duration of inundation, with the sill level (natural retention height) of all three wetlands having been breached. In each case, the drains were cut to the bed level of the swamp, meaning that as soon as inflows ceased (or downstream constrictions in Wannon River flow eased), these wetlands could freely and more rapidly drain to near empty than would occur under natural conditions. Local interest in restoring Gooseneck Swamp and Brady Swamp has been maintained by landholders and the local community since the land was purchased by the government in the 1980s. Eventually in 2013, after many years of work, modelling studies and biological investigations by a range of organisations, Nature Glenelg Trust began working towards a staged process of restoration at the site in partnership with the Glenelg Hopkins CMA, Parks Victoria and local landholders starting with a proposal to construct a low cost and low risk trial sandbag weir structure in the Gooseneck Swamp artificial outlet drain (August 2013 top right). The initial restoration trial was funded by a Victorian Department of Environment and Primary Industries, Communities for Nature Grant. The success of the first trial in 2013 was the subject of an information day held on the 14 th December 2013 (please get in touch if you would like to see the information day summary for last year), and led to the construction of a further two trial structures on private land in 2014, at Brady Swamp (March 2014 middle right) and Walker Swamp (August 2014 bottom right). These subsequent restoration trials were funded by Nature Glenelg Trust s Wetland Restoration Program on Private Land, with grant funding provided by the Australian Government. IMAGES: The Volunteer Sandbagging Crews Top Gooseneck Swamp (August 2013) Middle Brady Swamp (March 2014) Bottom Walker Swamp (August 2014) 3

4 With the three trial structures in place, we had high hopes for the 2014 winter and spring, and the early indications were encouraging. After reasonable early winter rainfall, by the last week of July the first water has just started trickling in from the floodplain delta tributaries of the Wannon River into Brady and Gooseneck Swamps. By that time, the lowest parts of Brady Swamp had already started to hold water from local rainfall (supplemented by early inflows from the Bunnugal Drain), while Gooseneck Swamp was still largely dry. Within a couple of weeks however, not only was water starting to back up against the new structure at Brady Swamp (below left), but Gooseneck Swamp was also covered by a sheet of water (see time sequence at bottom of page) and the natural floodplain flowpath from the swamp was starting to spill, as a result of the second year of successful operation of the trial structure installed in 2013 (below right). The operational trial structures in 2014 at the drains cuttings from Brady Swamp (left - looking downstream away from Brady Swamp) and Gooseneck Swamp (right looking upstream towards Gooseneck Swamp) 21 st July 6 th August 10 th September Gooseneck Swamp in

5 Thanks to Macquarie Plantations giving their support to the trial concept, the installation of the Walker Swamp trial structure was completed by NGT with community volunteer help on the 8 th of August 2014, and as it turns out just in a nick of time! We managed to catch the tail end of a waning drainage inflow that resulted from the rains in late July, and as we all know, there has been very little decent winter or spring rainfall since. Before (left) and after (right) the construction of the trial structure - looking upstream towards Walker Swamp As a result, the structure has done a highly effective job of retaining water in the swamp, when in previous years it would have rapidly emptied (draining close to its bed level) once inflows ceased. It is also worth pointing out that the Walker Swamp structure has been designed to allow water to continue to pass through the site down the existing drainage channel, spilling over the structure at the conservatively set trial height. This initial retention height will be reviewed in future years of the trial in consultation with the land owner. The direction of flow through Walker Swamp, showing the location of the restoration trial structure Walker Swamp in 2014 with the restoration trial structure operational and set at the initially conservative spillway height, looking north along the property boundary between private land (left) & the Parks Victoria Lake Reserve (right) 5

6 In contrast to the operation of the Walker Swamp outlet drain, natural alternative flowpaths still exist for flows exiting Brady Swamp and Gooseneck Swamp, hence the structures at these locations have been operating as blocks rather than spillways, except for a temporary trickle over the Gooseneck structure in The natural direction of flow from Gooseneck to Brady Swamp (blue arrows), artificial drain (red arrow) and location of the restoration trial structure The natural flow from Brady Swamp down the Wannon River (blue arrow), artificial drain (red arrow) and the location of the restoration trial structure 6

7 To illustrate this point, the image below shows the outlet drain from Brady Swamp, with the restoration trial structure operating effectively as a block (as it appeared in August and September 2014), and the Wannon River (the reeds behind the spoil bank in the distance) flowing at about 10cm deep the maximum level it reached under the prevailing flow conditions in The Brady Swamp artificial outlet drain, with operating restoration trial structure & natural watercourse in the background In early October 2014, the Wannon River stopped flowing into Gooseneck and Brady Swamps, in sharp contrast to last year when, with a wetter spring and early summer rains, the Wannon continued to flow until around Christmas time. Hence it was not long after this time that the natural outlets from both Brady and Gooseneck Swamp ceased to flow and the impact of the restoration trial structures this year really kicked in. While a lack of flows was not fantastic news for these wetlands this year, it has provided us with another useful scenario to test the effect of restoration in a below average rainfall year in the Southern Grampians. Given a backdrop of 60% of wetlands having been lost to drainage in the South West since European settlement, extending the period of inundation for wetland plants and animals, enabling them to complete their life cycles and providing additional habitat in the landscape in drier years, is a key benefit of the restorations trials we are witnessing again in At Gooseneck Swamp in November 2014, the structure is still holding back some water and has clearly extended the season for this wetland once again. However the lack of rainfall and warm spring means that the swamp is likely to dry out over the next few weeks. In contrast, Gooseneck Swamp was still full at this time last year, demonstrating just how much variability wetlands can experience from one year to the next due to climate. Over the lunette, and much like Gooseneck Swamp, in an average year Brady Swamp would typically be a lot fuller at this time of year. However, in spite of the below average rainfall and inflows, the trial structure at this site is doing a particularly effective job of retaining water in the deepest parts of the swamp, as this area directly linked to the artificial outlet drain. 7

8 Brady Swamp in November 2014 with the trial restoration structure operational and maintaining wetland levels The success of the restoration trials so far has enabled Nature Glenelg Trust, with the support of our partners, to attract additional grant funding from the Victorian Government that will enable the breached earthen banks at Brady and Gooseneck Swamps to be permanently reinstated in 2015, at the trial structure locations indicated below with yellow dots. The restoration trial at Walker Swamp (red dot below) will continue as a temporary experimental measure over the next couple of years thanks to the support of Macquarie Forestry. Oblique image looking north west towards the Grampians: Wannon River flow direction is marked with arrows, and artificial drain cutting locations where restoration trial structures are now operating are indicated with red / yellow dots. Our hydrological and ecological monitoring of the wetlands will also continue over the next 12 months. On that note, we are grateful for the dedicated efforts of the Hamilton Field Naturalists Club (co-ordinated by Rod Bird) in continuing monthly bird surveys that are helping us to document the value of these wetlands. For more information on the progress of the Southern Grampians Wetland Restoration Projects or our other work, please visit the NGT website: or contact us by ing info@natureglenelg.org.au. 8

9 Wishes to especially thank: Landholders: Roger and Todd Burger Doug Craig Vanne and Judy Trompf Macquarie Bank (Darren Shelden) Parks Victoria (Dave Roberts and Ryan Duffy) Partner organisations: 9