Lake Condah Sustainable Development Project

Transcription

1 Lake Condah Sustainable Development

2 Contents Executive Summary 1. Introduction 1.1 The Lake Condah Sustainable Development 1.2 The Vision and Objectives of the Overall 1.3 The Purpose of this Document 1.4 The Principal Water Restoration Objective 1.5 The Aspirational Water Restoration Objectives 2. Lake Condah Description 2.1 The Natural lake 2.2 The Cultural Lake 2.3 The Drained Lake 3. Previous Water Restoration Attempts 4. Key Challenges 4.1 Land Ownership 4.2 Incomplete Data Incomplete Hydrological Knowledge Conflicting Maps Effect of the Drain on the Lake 4.3 Water Levels Need to Avoid unnatural flooding of Private Land Need to Avoid Archaeological Damage Need to Avoid Excessive Seepage Summary on Water Levels 4.4 Water Availability, Environmental and Diversion Flows Current Status Water Modelling for Dry Years Water Modelling for Mean Years Environmental and Diversion Flows Summary on Water Availability 4.5 Managing Stakeholders 5. Implementation 5.1 Risk Assessment and Management 5.2 The Proposed Method of Water Restoration 5.3 The Proposed Water Levels Current Water Levels With an Outlet Water Level Regulator Effect on surrounding Land Land West of Lake Land Upstream Land Downstream 5.4 Delivering Desired Outcomes Management Partnership Trained Personnel Develop and Implement an Adaptive Water Management Regime 5.5 Data Confirmation 5.6 Securing Investment Funds 5.7 Summary of Action Plans Page Lake Condah Sustainable Development Page 1

3 Contents continued 6. Action Plan Tables, Timeframes and Indicative Costs 6.1 Consultation Strategy 6.2 Land Acquisition and Consolidation 6.3 Interim Works Diversion Works Maintenance Channel Filling Removal of Cattle Removal of Fencing Improved Access 6.4 Data Confirmation 6.5 Adaptive Management Joint Venture in Management Personnel Water Regulation Management and Monitoring Archaeological Monitoring and Protection 6.6 Outlet Water Level Regulator 6.7 Possible Associated Works with Applications and Licences 6.9 Management Plan 6.10 Tourism Assessment 6.11 Record Retention 6.12 Funding 7. Concluding Remarks Page Acknowledgements Acronyms References End Page Maps, Tables & Charts Page Photographs Page Locality Map Lake Condah Map Ingram s 1883 Lake Sketches Table 4A- Water Requirements Table 4B- Water Modelling Risk Assessment & Management Table 5.3A- Current Water Levels Table 5.3B- Desired Water Levels Chart 5.3C- Water Level Effect at 52.0 AHD Chart 5.3D- Water Level Effect at 52.5 AHD Summary of Action Plans 5 6 & Water on Lake July aerial Photomontage Dry Lakebed Southern end Water on South end July 2004 First floodwaters April 2004 NW Arm of Lake June 2004 Main drain near OWLR site Diversion Weir Flooded Diversion weir East-west drain and Main Drain Aerial View 2001 Drain to sinkholes Fencing on Lakebed Aerial View July Lake Condah Sustainable Development July 2004 Lake Condah Sustainable Development Page 2

4 Executive Summary This year represents the 50th anniversary of the final draining of Lake Condah and the 40 th anniversary of the first proposal by the former Fisheries and Wildlife Division to restore permanent water to the Lake. The Key Water Restoration Objective is the return of water to Lake Condah in as permanent way as possible, given the constraints of water availability and non-interference with private land holdings above, below and surrounding the lake. Believed to be 8,000 years old and covering some 600 acres, Lake Condah was a superb, environmentally rich wetland; providing a breeding habitat in particular for birds and fish. Testimonies from those who lived and worked alongside the Lake prior to 1954 state that it was a permanent body of water in all but the rare, very dry seasons. As a wetland, the Lake s biodiversity was dependent on the rise and fall of water levels. The cultural Lake was built on this very fact. Fishtraps at the Lake operate over a wide range of water levels. Aboriginals modified the Lake several thousand years ago, to develop a sophisticated and extensive aquaculture system. Whilst the wetlands of Lake Condah will be of State significance, the archaeological sites at Lake Condah are considered to be of world importance because they preserve critical evidence of technological and social developments, which exemplify the transition from a nomadic hunter-gatherer lifestyle into a semi-sedentary society. Almost nowhere else in the world has dry stone heritage sites been preserved on the scale found at Lake Condah. Falsely blamed for flooding the Condah Swamp area in 1946, the Lake was drained of permanent water in Subsequent attempts to restore water to Lake Condah failed with power and position taking precedence over purpose. Only the Northwest arm of the Lakebed is privately owned and acquisition of this land is a key to the project proceeding without compromise. 50 years of not having permanent water on the Lake creates gaps concerning the hydrology of the Lake but still, much is known. Previous research has shown that land above and below the Lake will not be affected by water restoration, nor will groundwater levels be affected south of the Lake. An adaptive water management regime is proposed to avoid unnatural flooding of private land; to avoid archaeological damage and facilitate its further study; to avoid excessive seepage and to maintain water levels high enough to restore the Lake s biodiversity and facilitate the development of sustainable tourism and aquaculture businesses. Water availability, seepage and evaporation modelling indicates water coverage can be maintained all year. Initially, this will require some flood flows. If permanent water restoration had been attempted in 2002 or 2003, it would have failed but would have succeeded in In all probability it will take several years of mean (or greater) rainfall and stream flow to restore permanent water to Lake Condah Sustainable Development Page 3

5 Lake Condah. As was concluded by Rural Water Commission in the 1987, the only real way to prove the accuracy of conceptual modelling is to put water into the Lake and observe what happens. To this end a Learning period is proposed as part of the Adaptive Water Management Regime. The proposed method of water restoration to the Lake is to construct an Outlet Water Level Regulator on the Main Drain. The process of design, consultation, approval and construction will take approximately two years; with the project estimated to cost $335,000. It is not proposed to recommission the Diversion weir, which was a failure. The Outlet Water Level Regulator will give the Lake its best chance of retaining permanent water; will best facilitate re-establishment of the Lake s biodiversity; will allow more of the Lake s archaeology to be operational at various times of the year than any other proposal; and best deals with the restrictions of the Main Drain running through the Lake, without compromising the operation of the Drain. The desired summer autumn average water depths are 1.0 metre in that part of the Lake north of the Lava Ridge and 1.5 metres south of the Lava Ridge. These are seen to be the optimum water levels and most closely resembling the pre 1954 Lake circumstances, which even then was affected by a lesser drain through the Lake. Risks have been assessed and management proposals developed for them. Extensive Action Plans have been designed to deliver the project. This Water Restoration is one of the most significant wetland restoration projects currently being undertaken in Victoria. It will undoubtedly be one of the most significant archeological restoration projects in Australia, attracting keen and warranted international attention. It can be achieved without detriment to the district farmers who historically have opposed it. The further development of the Aspirational Objectives will deliver economic opportunities through aquaculture and tourism developments. The tourism potential of the cultural Lake is of national and international significance. It all begins with the restoration of permanent water to the Lake. Water on the Lake in early July Looking westwards, the Lava Ridge is in the centre of the photo. By the end of July there were more than 50 swans nests on the northern section of the Lake. Hopefully sufficient water will remain to complete the breeding cycle. Lake Condah Sustainable Development Page 4

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8 1. Introduction 1.1 The Lake Condah Sustainable Development The Lake Condah Sustainable Development (LCSDP or ) is an innovative partnership approach to sustainable development based on exciting, visionary, yet achievable concepts. The, based on the restoration of water to Lake Condah, encompasses wide ranging economic, social, cultural and ecological benefits. A broad range of stakeholders and interested parties has linked together to help commence the. Included in this group are the Indigenous community; Federal, State and Local Government bodies and authorities; private enterprise and individuals. The will make a difference at many levels. It is anticipated that it will provide the impetus for engagement, practical reconciliation and healing for Indigenous and non-indigenous communities in the South West of Victoria. Major aspects of the include sustainable job opportunities associated with a significant tourism attraction, environmental management and cultural preservation, together with significant historical, natural and cultural heritage, ecological, economic and educational outcomes. Lake Condah is a nationally significant site showcasing unique and remarkably well preserved archaeology, coupled with historical and environmental aspects of Australia s Indigenous culture. Prior to drainage, Lake Condah was a stunning example of Australian biodiversity. It is hoped to regain this biodiversity. An Executive Committee with broad representation of key stakeholders has been established to oversee and direct the detailed work required to achieve the goals of the. This Committee has been successful in seeking funding from several sources for the first stage of the LCSDP implementation phase. 1.2 The Vision and Objectives of the Overall The vision of the Lake Condah Sustainable Development is the sustainable development of the significant natural and cultural assets of the Lake Condah area through a unique partnership of Aboriginal and non- Aboriginal peoples, corporations and Governments. The Lake Condah is based on an integrated Master Plan. Key components of the development include: Gaining National Heritage listing followed by World Heritage listing for the Lake Condah area; Restoring water to Lake Condah to revitalize the wetlands and reactivate the traditionally constructed aquaculture system; Re-building the old mission Church at Lake Condah; Developing a communications and knowledge network to foster the education and understanding required for long-term sustainable tourism development; Lake Condah Sustainable Development Page 7

9 Developing employment and enterprise activities focused on tourism, aquaculture and related activities. 1.3 The Purpose of this Document The Lake Condah Water Restoration is a major component of the LCSDP and is the subject matter of this Plan. Draining the Lake commenced shortly after 1886 and was concluded by Despite various attempts over a period spanning 40 years, the Lake still remains dry today except for shortterm inundation. The purpose of this document is to establish a detailed Plan for the restoration of water to Lake Condah, after consideration of previous proposals and taking the advice of the Lake Condah Water Restoration Sub- Committee. The LCSDP Leadership Group established the Lake Condah Water Restoration Sub-Committee to scope previous water restoration proposals and to provide advice on the best method to restore water to Lake Condah. The Sub-Committee convened its first meeting on Thursday 5 February The Sub Committee has been an important source of advice and advocacy for the restoration of water to Lake Condah, determining water levels and methodology. This Lake Condah Water Restoration Business Plan has been developed so as to be consistent with the aims and objectives of the larger Lake Condah Sustainable Development, as stated in Section 1.2 above. 1.4 The Principal Water Restoration Objective The Key Water Restoration Objective is the return of water to Lake Condah in as permanent way as possible, given the constraints of water availability and the non-interference with private land holdings above, below and surrounding the lake. 1.5 The Aspirational Water Restoration Objectives The following Aspirational Objectives flow from the restoration of water to the Lake: (1) Preservation and display of the archaeology at the lake, which is of world significance; (2) Restoration of wetlands of State significance; (3) Re-establishment of as much of the original biodiversity of the Lake as is possible; (4) Re-development of an Indigenous aquaculture business, based on eels; and (5) Development of a culturally sensitive tourism industry based on the Lake and it s many natural and cultural heritage values. Lake Condah Sustainable Development Page 8

10 LAKE CONDAH WATER RESTORATION BUSINESS PLAN 2. Lake Condah Description 1947 aerial photomontage of Lake Condah showing significant water coverage and the old drain through the Lake (Obtained from the archives of Glenelg Hopkins Catchment Management Authority). Lake Condah Sustainable Development Page 9

11 2.1 The Natural Lake Whilst current scientific opinion estimates the lake to have formed 8,000 years ago, the first written description of Lake Condah occurs in the Portland Mercury on 11 th January The find was reported by Mr. Edgar of Second River (later named Heywood) and his two companions as follows: a splendid fresh water lake about a mile and a half long and three quarters of a mile wide, and contains almost every variety of fish in abundance, with swans, ducks &c. It is of considerable depth, and receives a river about fifty yards broad; one side is bold and rocky and contains a number of small coves into one of which a beautiful stream empties itself, and the other side is a gently sloping shore surrounded by a fine tract of country. Long-term district residents further attested the natural attributes and biodiversity of the Lake, all of whom had an involvement with the Lake from the 1930 s onwards. The late Mr. James Vaughan stated before the major drainage schemes were implemented, There was generally permanent water over the Lake area. Only during rare and very dry seasons did it go dry. This provided a habitat for regular breeding programs of the main types of wild life, in particular birds and fish. White Ibis had extensive colonies on typical breeding rafts in the Lake. He referred to prolific breeding of ducks. (Source: VFGA Submission on Lake Condah, 1978). The late Mr. W.R. Malseed stated: There was permanent water in the northern end of Lake Condah to a depth of approximately 18 in depth over the period from 1933 until major draining operations in This loss of water caused loss of reed beds and associated aquatic life, which supported large populations of many species of waterfowl. They almost blotted out the sky when they took off. (Source: VFGA Submission on Lake Condah, 1978). Mr. Roy Vaughan and his wife, who lived and farmed alongside the Lake for many years prior to its drainage, described the summer water depth at the northern end of the lake as generally being waist deep, except for the rare dry year (Personal communication June 2004). A different reference point is the most likely reason for the variation in water depth. The late Mr. Hector Field described the Lake as essentially a permanent body of water prior to major drainage activities. The water in places, particularly over the southern section of the lake was so deep that on duck shooting excursions, it was reached only by boat Fish were available in very large quantities especially Toupong and Tench. After drainage the stench from dead fish could be smelt up to a mile away. (Source: VFGA Submission on Lake Condah, 1978) The natural Lake, whilst mostly a permanent body of water had fluctuating water levels. We know this from the different elevations of the fishtraps constructed and used by the Aborigines at the Lake over a period of several thousand years. Wetland Care Australia defines a wetland as areas of land that are either temporarily or permanently covered by water. Wetlands support a large variety of plant and animal species that are adapted to fluctuating water levels. (Source: What, Why & How Wetlands Work, Wetland Care Aust.). Lake Condah Sustainable Development Page 10

12 By this definition Lake Condah is a wetland. It was the rising and falling water levels that allowed the Lake to develop a uniquely diverse ecosystem. Shallow water, deep water, warm water, cool water all simultaneously available together with flood waters spreading out over the shallow sections of the Lakebed followed by receding water and a year round flow of water - created a rich and self-sustaining wetland area. The drying cycle stimulated growth and breeding in food chains, with particular benefit to small native fish species, which in turn provided food for larger fish species and bird life. The Lake offered spawning and breeding sites, nursery sites, protected sites, diverse habitat and was a complete food bowl for fish, birds, animals and insect life. This environment was especially attractive to eels. Lake Condah was a healthy, self-sustaining wetland supporting huge quantities and varieties of birds, fish and insect life. This biodiversity was dependent on the rise and fall of the Lake water levels. 2.2 The Cultural Lake Lake Condah was not only a natural Lake with stunning attributes but it was also a cultural Lake of world significance. Referring to the Mt. Eccles lava flow (of which Lake Condah is a part), Dr. H. C. Builth wrote: The environmental conditions provided unique opportunities for the local Indigenous people. Aboriginal adaptation to this environment had evolved to a highly organised and efficient level prior to European contact. Gunditjmara had evolved a cohesive social and economic system with its foundation firmly interwoven with a spiritual knowledge base. (Source: Builth 2002, The Archaeology and Socioeconomy of the Gunditjmara) Aboriginal people usually do not distinguish between natural and cultural values in environmental resources. In general, Aboriginal people see natural and cultural values of the country as interwoven so that looking after the land, waters, plants and animals means looking after culture; and looking after culture means looking after the land, waters, plants and animals. The practical importance of the interweaving of nature and culture is that many places and features of cultural importance to Aboriginal people also have significant natural heritage values; and equally, many places which have natural heritage values also have cultural importance to Aboriginal people. (Source: SAMLIV 2003). Lake Condah is such a place. Aboriginals modified the Lake environment by building fishtraps, races, stone weirs and walls. The route of each stone race and canal has been carefully chosen to take full advantage of the natural topography, generally following drainage lines. In order to confine fish within a system, stone walls have been constructed to supplement the natural barriers that define the margins of the system. Such walls may also have served as walk-ways, facilitating movement around the system. (Source: Records of the VAS June 1978 Aboriginal Engineers of the Western District, Victoria, Coutts, Frank & Hughes). Lake Condah Sustainable Development Page 11

13 More recent understanding of the archaeology suggests that these very walls may have been used to artificially retain water for longer periods. The overall outcome of these lake modifications was an extensive aquaculture system and related economy. Surveyor A. Ingram s January 1883 sketch of Condah Swamp, Lake Condah and diagram of a section of Fishtrap area No.6, showing channels and fishtraps (Courtesy of the South Australian Museum). Lake Condah Sustainable Development Page 12

14 The archaeological sites at Lake Condah are considered to be of universal importance because they preserve critical evidence of technological and social developments which exemplify the transition from a nomadic huntergatherer lifestyle into a semi-sedentary society and which are characteristics of incipient agrarian peoples. By world standards, the archaeology of the Lake Condah region has received only limited study. Nevertheless, the investigations of this area have revealed a scale and quality of sites which is not found elsewhere. The challenge now is to develop a more complete understanding of the dating, chronology, function and hydrological context of those sites. (Source: VAS Nov 1992, Lake Condah: Review and Assessment, van Waarden & Simmons) Dr. J.W. Rhoads summed up the importance of the Lake Condah archaeology writing: ancient heritage sites infrequently survive and almost nowhere else have they been preserved on a scale of the Lake Condah sites. (Source: The Occurrence of Dry Stone Structures: World-wide Review of Ethnographic Literature, Dr. J.W. Rhoads July 1992). 2.3 The Drained Lake The arrival of Europeans who wanted farmland inevitably meant that fertile wetlands would be drained. This was the case with the Condah Swamp area, encompassing some 6,300 acres to the immediate north of Lake Condah (refer Ingram sketch on previous page). Drainage of this area commenced in January 1886 and by 1908 the Leader Newspaper reported that Lake Condah was being blamed for damming back floodwaters. The article advocated draining the Lake and making the 600 acre Lakebed available for selection. The Lake would appear to have been partially drained at this stage but with no drain maintenance, increasingly less effective with time. The last reported regular Aboriginal fishing of the Lake was in 1909 (Source: VAS Occasional Report No. 35, Penney & Rhodes, Lake Condah, 1990), although this was probably a result of Mission restrictions. After years of not maintaining the drains, the 1946 floods extensively damaged the Condah Swamp area and drainage system. Lake Condah was again blamed. In 1954 the drain through the Lake was deepened (as it was for the whole drainage system, often using explosives) and from then, the Lake has never held permanent water. In addition, further drains were carved into the lakebed to reinforce this status. As V.K. Hand (the drainage surveyor and engineer) wrote in his 1973 Report Coinciding with the re-construction programme commenced in 1954 the water impounded on Lake Condah diminished and finally virtually disappeared. (Source: V.K.Hand, Report on a Proposal to Contain Surface Water on the Area known as Lake Condah, 1973). Since 1954, Lake Condah has only ever been subject to short-term inundation. Fifty years later this still remains the case. Lake Condah Sustainable Development Page 13

15 LAKE CONDAH WATER RESTORATION BUSINESS PLAN The dry Lakebed looking across the southern end from a stone ridge th The same area on 29 July 2004 with water depth averaging 1300mm Lake Condah Sustainable Development Page 14

16 3. Previous Water Restoration Attempts In 1964, just 10 years after the final drainage of the Lake, the then Fisheries and Wildlife Division (FWD) made a submission advocating that Lake Condah become a State Wildlife Reserve. By implication, this meant restoration of some water to Lake Condah. In 1973 the Land Conservation Council supported this view and in 1977 the Victorian State Government gazetted Lake Condah as a State Wildlife Reserve. In 1970, FWD sought permission to build a weir at the lake outlet. This was after the Condah Swamp Drainage Authority had permitted the building of six concrete weirs on the Condah Swamp system to hold water over summer (although by 1973 only three had been built). The 1954 drain was too deep, too efficient and the Condah Swamp land suffered from being too dry. State Rivers & Water Supply Commission (SR&WSC) did not give its permission to the FWD weir proposal. In 1972, FWD commissioned V.K. Hand to write a report (refer section 2.3 above) on water restoration, which suggested the possibility of a weir at the northern end of the Lake to divert water into the Lake. In late 1973, SR&WSC issued a report echoing Hand s report but it was not until 1990 that this weir was actually built and then, only as a trial. In 1977, the FWD Secretary, R.J. Mitchell wrote to the Shire of Portland, proposing a weir near the outlet and said: The main issue is to attempt to restore the original water regime to Lake Condah. With the reconstruction of the Condah Swamp drain and the resultant lowering of the drain water levels, the Division firmly believes that Lake Condah has been denied its normal water regime. (Source: FWD letter to Shire of Portland, 30 th June 1977). This became the line in the sand and commenced a regrettable period where power and position took precedence over purpose. What ensued was a sustained and prolonged attack on the project. In 1986, FWD proposed a trial flooding of Lake Condah over the summer of on just the south end of the Lake. The proposal by this time had been significantly reduced both in terms of area to be covered and the depth of water, such was the pressure placed on the project. The trial flooding eventually commenced on 1 st November The trial was short lived and its demise blamed on vandalism at the weir. In fact the weir did not do the job, with water drying up quickly; compromising the breeding cycle of water birds. So, the project remained dormant until 2002 when the LCSDP Partnership was established at the instigation of the Indigenous community, receiving broad community support. The actual cost of constructing the trial weir and diversion channel is not known (key files have not been kept by relevant organisations). Investigation and design costs were estimated to be $13,800 in During the mid- Lake Condah Sustainable Development Page 15

17 1980 s $300,000 from the State Government was spent on research associated with the water restoration proposal and at the Lake Condah Mission site. None, other than for a new culvert bridge, appears to have been spent on physical works at the Lake. Originally, the $300,000 was to be allocated $70,000 for a Feasibility Study and $230,000 for flooding works, access works, bridge and toilets. There is no record of such a Feasibility Study being done. Since 1964, FWD s total spend on the project is incalculable. The way in which FWD and its successor bodies continued to pursue this project, despite the difficulties and opposition encountered over a period of decades is noteworthy. It is also worth noting that until late 1986, the proposal to restore water to Lake Condah was essentially a wildlife habitat restoration proposal. The first mention of Aboriginal involvement only occurs on 12 th November 1986, when Kerrup Jmara Elders became involved with the Lake Condah Investigatory Committee. This committee was the first time all stakeholders came together on the same committee. It was at this point that water restoration to the Lake started to take on board indigenous cultural values as well. Fifty years after the Lake was finally drained and forty years after the first proposal to restore water, the lakebed is still dry, except for temporary winter and spring flooding in some years is one such year where significant amounts of floodwater have flowed onto the lakebed. First floodwaters in April 2004, immediately attracting Birdlife. Lake Condah Sustainable Development Page 16

18 4. Key Challenges 4.1 Land Ownership The Lake Condah Map (next page) indicates the current ownership status of land surrounding the Lake. With the exception of 400 acres of privately owned stone country on the north east corner of the Lake, all land to the east and south of the Lake is either owned by the Kerrup Jmara Elders Aboriginal Corporation or Parks Victoria. This 400 acre block should be acquired to complete indigenous ownership of the Lake s east side and to remove cattle from the Lake. The Lakebed is generally owned by Parks Victoria with the Department of Sustainability and Environment owning strips of land around the Lake. Land on the west side of the Lake is all privately owned, including the Northwest arm of the Lakebed. This piece of Lakebed has to be acquired (or a suitable permanent agreement reached) before the proposed Outlet Water Level Regulator can be operated. This is a key issue in restoring permanent water to Lake Condah without compromise. A decision needs to be made regarding land on the west side of the Lake regarding its usefulness as a buffer zone. It may be appropriate that this land is progressively acquired as it becomes available for sale. Northwest arm of the Lake partially covered with floodwater 19th June Lake Condah Sustainable Development Page 17

19 Given that Kerrup Jmara Elders Aboriginal Corporation is in liquidation; the likelihood of further land acquisitions, Native Title Claims and the number of different Government departments involved in land ownership at the Lake, there is a need to rationalize the landholdings. Lake Condah Sustainable Development Page 18

20 4.2 Incomplete Data Incomplete Hydrological knowledge on how the Lake operates Whilst State Rivers & Water Supply Commission and its successor body Rural Water Commission, investigated in detail the hydrology at and surrounding the Lake during the 1970 s, 1980 s and the early 1990 s, some information about how the Lake actually operates hydrologically remains unknown. The primary reason for this incomplete knowledge is simply the Lake not having permanent water over the last 50 years. A secondary reason is the loss of files on Lake Condah. What we do know from those investigations is: 1. The SR&WSC Report to FWD titled Lake Condah Water Supply Investigations and dated October 1980 (unpublished) recorded: The following conclusions have been reached from the hydrological investigations: (i) Waters from the Lake Condah Main Drain could be diverted to Lake Condah (both north-west and south-eastern portions included) without adversely affecting the Lake Condah Drainage Scheme and interests of the users of the water downstream. (ii) The flows to Lake Condah would need to be regulated during the four months January to April, in order to give priority to downstream users of water. (iii) In the absence of any firm figures for losses through seepage, no guarantee can be given that the required pondage depth, during the periods requested, will be maintained. 2. In a letter dated 26 May 1987, from J. Oates (Snr. Exec. Engineer) RWC to the Regional, DCF&L it is stated that the effects of filling the lake, on flood discharges downstream or flood levels upstream from the lake will be negligible as the lake volume is too small compared with normal flood volumes. This was specifically in relation to proposed lake level of 50.5AHD. 3. In a RWC internal memorandum from Snr. Geologist F. Cox to the Principal Geologist dated 8 December 1989, titled Lake Condah hydrographic monitoring Notes on Bore Water Levels and Sink Hole Levels South of the Lake; it was concluded: Data to November 1989 indicates that there is no significant effects due to flooding of Lake Condah at distances exceeding 2.75 km from the Lake. Those bores and sink holes monitored were not affected by lake levels. This was confirmed in 1993, when RWC again concluded: no response can be determined as being due to the flooding of Lake Condah in 1991 and (Source: RWC Internal Memorandum from J. Oates to I. Potts, dated 4 th March 1993; titled Lake Condah Groundwater Monitoring Review ). Lake Condah Sustainable Development Page 19

21 What we do not know at this stage about the Lake hydrology includes: 1. What the actual Lake seepage rates are at each half-metre increment in water level. SR&WSC estimated seepage losses of 529 ML/month on the basis of four month s observation to November 1979, when the water level dropped an estimated 1.5m. This assumption appears to be flawed in that seepage/drainage rates would have been accelerated, especially at higher water levels because the Lake had internal drains built in 1954 to speed up the drainage process. Modelling in this document has used both these original seepage rates and some lesser rates (refer Table 4B). 2. What the actual difference between winter-spring and summer-autumn water levels will be. Previous water restoration proposals have assumed it will be only half a metre. This is unsubstantiated. 3. What the critical minimum spring water depth is to retain water all year round on the Lake. The solution remains the same as RWC advised DCF&L in 1987; that Trial flooding of the Lake will provide the most accurate estimates of seepage and provide advice on likely effects (J. Oates, RWC to D. Read, DCF&L, unpublished letter dated 26 May 1987) Conflicting Maps There are two known contour maps of Lake Condah. The first and oldest map is referred to in this document as the 1980 State Rivers and Water Supply Commission (SR&WSC) Contour Map. It was developed from a November 1979 field survey and placed over a 1972 aerial photomontage. It has 0.5m contours. The second map is a Vicmap 1989, Ministry for Planning & Environment / VAS map with 1m contour Intervals and is based on GIS technology. One (or both) of the maps is incorrect in that the AHD reference point used is wrong. Which one is incorrect is not known. In this document, the 1980 SR&WSC AHD datum has been used for the following reasons: It was the datum used for the Condah Swamp drainage system including the Main Drain; It was the datum used for drainage of the Lake; Permanent markers adjacent to the Lake use this datum (although they appear to have been interfered with); It was the datum used to build the Diversion Weir and channel at the north end of the Lake; and It is consistent with previous attempts to restore water to the Lake. The two maps have a range of differences from 1m to 1.9m in the lakebed elevations. Part of the difference is explained by one map picking up an incorrect AHD reference point but it does not explain all of the variations. Lake Condah Sustainable Development Page 20

22 In this context, the outcomes (including a 200mm contour map) from the planned aerial GIS survey are critical for the construction of the planned Outlet Water Level Regulator. This GIS survey will enable accurate modelling of outcomes from the operation of the proposed Outlet Water Level Regulator. Digital elevation models (DEM) will accurately predict the depth and coverage of water in the Lake at various elevations. The data capture is planned for 2004 with the full results becoming progressively available over the following 18 months The Effect of the Drain on the Lake It would appear that no research has been done on whether the substantially deepened Main Drain running through the north and west side of the Lake will have an effect on the lake s ability to retain water. Did deepening the drain break the mud seal over the underlying permeable lava flows, alluvium or limestone? If so, then greater seepage losses can be expected. Should this occur, the solution will be to identify the leaks and reseal the drain floor with spoil from the spoil banks at those points where water is leaking downward through runaway holes. Given three decades of uninterrupted silt build up, this is unlikely to be an issue. The Main Drain as it heads west away from the Lake. The proposed Outlet Water Level Regulator could be upstream or downstream of this bend. Lake Condah Sustainable Development Page 21

23 4.3 Water Levels The key challenges associated with water levels are: Need to avoid unnatural flooding of private land Under the Water Act of 1989, it is an offence to place nuisance water on private land. This must be avoided. The only safe way to control this risk is to acquire all affected land, of which there appears to be only one property. Measures are proposed to ensure no other properties will be affected. In the period leading up to the commissioning of the Outlet Water Level Regulator, any water on privately owned land would be naturally occurring water inundation (Refer photo at page 16 of the NW arm of the Lake in June 2004). However, with an Outlet Water Level Regulator, water can be held permanently and at higher levels (up to 52.0 AHD). This will result in permanent or semi-permanent flooding of the privately owned lakebed Need to avoid Archaeological damage It is improbable that permanent water restoration will cause any archaeological damage; given that various fishtraps appear to operate over a water level range of at least 4.5m. It needs to be acknowledged that Lake Condah s archaeology is far more complex than is presently understood. The Lake archaeology is of world significance and data collection is significantly incomplete, as is our understanding of it. It is therefore best to be cautious in initially restoring water levels. Water levels will also need to be managed to facilitate further study. Once again, the proposed 200mm contour map will be important in understanding how the fishtraps worked. Issues such as rabbit burrows in the vicinity of fishtraps need be considered, and where found, filled in so as to avoid the possibility of collapse Need to avoid excessive seepage There are at least five areas on the Lake where it was drained to an approximate 50.5 AHD level or less, in1954 and reinforced in Some of these will need to be filled in so as to be able to maintain the desired water levels. Careful observation of leakages is required in the initial years of water restoration, and solutions developed. This may involve claying some rock walls but the lake did hold permanent water from 1909 to 1954 without this being done. Once the proposed GIS flyover has been done, digital elevation models of the lake should identify any likely leakage problem areas. Lake Condah Sustainable Development Page 22

24 4.3.4 Summary on Water Levels Treating the first years of permanent water restoration as a Learning period is essential to gaining a body of knowledge regarding the most appropriate water levels for the Lake. In the first years this may mean lower than desired water levels, should the suggested confirmation process not eliminate all concerns. Careful observations and recording of what happens to water levels will form the basis of an appropriate Adaptive Water Management Regime for the Lake. 4.4 Water Availability, Environmental and Diversion Flows Current status We know that pre-1954 the Lake held permanent water. What has changed since 1954 in terms of water availability? A general change in the pattern of rainfall with heavy autumn falls less frequent (lack of a regular cycle); The weirs on the Condah Swamp drains diverting some water over summer and autumn; The influence of the neighbouring bluegum plantation (lowered water table?); There are no active springs directly feeding the Lake, as was the original scenario (probably a direct consequence of drainage); and The Drain itself. The combined effect of these changes is unknown, other than it is a reasonable assumption to say that water availability is less than it was pre It is noted that the Victorian Government s White Paper Securing our Water Future Together (June 2004) proposes a Stream Flow Management Plan for the Darlots Creek within 5 years, the aim of which is to reduce water diversions over summer and autumn. The only water flow data currently collected in the district is at the Homerton Bridge, south of the Lake. Data was collected for 4 years at the Lake Condah Bridge but ceased in There was one year of overlap with the two data collection sites. Whilst that year indicated that water on average at Lake Condah Bridge would be about 80% of that at Homerton Bridge, this is not conclusive. In 1980, SR&WSC estimated the relationship at 86% but by 1987 RWC Engineers had restated the relationship to 35% of Homerton Bridge flows when water was flowing at less than 80ML/day and at 160% where the flow was greater than 250ML/day. They concluded: There is adequate water in the Drain in the winter months, even in the driest year of 1982, to allow a constant flow into the lake, (although the minimum flow required to maintain the lake level will not be known until after the trial filling). (Source: RWC Internal Memorandum from Design Engineer R. Evans, to Executive Engineer, dated 13 April, 1987). Lake Condah Sustainable Development Page 23

25 It is therefore important to fill the Lake to a sufficiently high level in winter - spring so as to achieve the desired summer-autumn level, allowing for seepage and evaporation losses. Floodwaters will be useful in this process, if not necessary. Monitoring of water flows in the Darlots Drain should commence immediately to determine the accuracy of water modelling assumptions Water Modelling for Dry years Using the Homerton Bridge data, there has been 5 years in the 34 year period to 2003 where the annual flow has been less than 20,000 ML. For the purposes of this exercise, a dry year has been defined as 24,400 ML pa or less, against a mean stream flow of 49,904 ML pa. Using the same assumptions made by SR&WSC in their 1980 modelling, the following Table indicates that the Lake will dry up each summer in dry years. It is relevant at this stage to make some comments on these assumptions. Firstly, the relationship between flow rates at Lake Condah and Homerton Bridge cannot be regarded as accurate. Secondly, the evaporation rates are based on Rocklands Dam figures. Of all the assumptions made, this one is likely to be the most accurate. Thirdly, seepage rates for the whole Lake are based on anecdotal evidence that the Lake dropped 1.5m in water height in the four months to November This was calculated to be equivalent to 529 ML / month. This is likely to be inaccurate for several reasons: The rate of water loss would have been exaggerated as the Lake was artificially drained to 50.5 AHD at several locations. The rate of seepage would not have been a constant 529 ML / month, all year round. It would be reasonable to suggest that the seepage rate declines with the decrease in Lake volume. The 1979 observations indicate that the spring water level was at least 52.0 AHD, assuming that by November the Lake was at 50.5 (the level at which the Lake was drained to). It may have been greater. The water on the Lake was from floodwaters only was slightly below the mean year datum recorded at Homerton Bridge. Allowing for the above factors, the modelling was re-worked with lesser seepage rates at different trigger points. The Lake still remained dry. The modelling of water availability is based on a Drain Environmental and Diversion flow below the Diversion Weir of 30 ML/day (when available). Lake Condah Sustainable Development Page 24

26 4.4.3 Water Modelling for Mean Years As defined above, a mean annual stream flow is 49,904 ML. Even at these flow rates, the modelling indicates that the Lake will still dry up, using the SR&WSC assumptions. It is only when the seepage assumptions are reduced and coupled with flood flows increasing the overall Lake volume that water appears to be retained all year. This is the known factual circumstance of the Lake - that it did have permanent water all year round, in all but unusually dry years Environmental and Diversion Flows DCE (now DSE) determined in 1991 an environmental and diversion flow for the Darlots Creek of 30 ML/day, subject to its natural availability. As an operating condition, the Diversion Weir located at the north end of the Lake was only to operate if the flow in the Main drain is greater than 30 ML/day. It is not proposed to change this requirement. The following table indicates that the Lake in a mean stream flow year will only take 12% of available water, before the effects of flooding, whilst maintaining the environmental and diversion flow requirement. Table 4A Water Requirements of the Lake Available Water Allocation Dry % Mean % Mean % Year Year Year(1) 24,400ML 49,900ML 49,900ML Environmental & Diversion Flow 8,200 10,520 10,520 Excess water 11,400 33,461 32,785 Darlots Creek Total flow 19, , , Water into Lake Condah 4, , , Total Water Available 24, , , The above table is based on the same information and assumptions specified in the next table (4B). It is based on the Darlots Drain (at the Lake) having a minimum daily flow of 30 ML/day. (1) Assumes an additional 676 ML of floodwater flows into the Lake. No allowance has been made for water flowing back out of the Lake into the Drain or indeed via springs into Darlots Creek. Both situations will increase the flow in Darlots Creek. Footnote: Technically and historically, the Darlots Creek commences below Lake Condah. Above the Lake, it is a drain. Lake Condah Sustainable Development Page 25

27 Table 4B Water Modelling Estimated Lake Volume in ML Dry Year 24,404ML Dry Year 24,404ML Mean Year 49,904ML Mean Year 49,904ML Mean Year 49,904ML Mean Year 49,904ML Mean Year 49,904ML Mean Year 49,904ML Adjustments & & 3 2 & 4 July August September October November December January February March April May June Lake Dry Lake has water all year Assumptions used: The Lake is empty on 1 st July. Evaporation losses are based on the average monthly losses from Rocklands Reservoir ( ) as calculated by SR&WSC in The figures used seem reasonable when compared to actual evaporation losses (which included seepage) for 1991 and Seepage losses were calculated at 529 ML/month by SR&WSC in Filling of Lake occurs in winter and spring with little or no filling during summer and autumn. Any Lake volume in excess of 1824 Ml is dependent on some combination of Flood flows and water level regulation. The 1963 relationship between water availability at Lake Condah Bridge and Homerton Bridge is appropriate for all years. Environmental & Diversion Flow of 30 ML/day allowed for, unless specified. Adjustments: (1) Seepage Losses of 529 ML/month reduced by 50% where level below 880Ml and by 75% where below 253ML (2) Seepage Losses reduced to 400ML above 880ML, reduced by 50% of original where level below 880Ml and by 75% where below 253ML. (3) Lake filled to 2500ML instead of 1824 ML capacity (1824 ML = 51.5 AHD SR&WSC datum). (4) Environmental & Diversion Flow reduced from 30 ML/day to 20 ML/day Footnotes 1. The data collected from the trial flooding of 1991 and 1992 is irrelevant to the Lake Condah water modeling as the data collected was at Allambie, more than 2 kms north of the Lake on the Main drain. 2. Assuming the Lake has 880ML in it on July 1, the second, third and fourth scenarios above for 49,904 ML flow, retain water all year. Lake Condah Sustainable Development Page 26

28 4.4.5 Summary The only conclusive way to prove the accuracy (or otherwise) of conceptual modelling is to put water into the Lake and record what happens. Actual seepage rates and flood flows will be crucial to the Lake having full year water coverage. We know historically that the Lake did have permanent but fluctuating water levels all year round, therefore it can be presumed (but remains unproven) that the seepage rates used of 529 ML/month are excessive. Modelling indicates that with lesser seepage rates, together with some flood flows, water coverage can be maintained all year. However flood flows are not assured each year and if permanent water restoration had been attempted in either of 2002 or 2003, it would have failed but would have succeeded in In all probability it will take several years of mean or greater stream flow and rainfall to restore permanent water to Lake Condah. Additional modelling based on the Lake having 880ML of water on July 1 indicates that all year round water coverage can be maintained, with all reduced seepage scenarios. It will be important to monitor and record water levels and other observations on a daily basis. Particular attention will need to be paid to repairable leaks. Monitoring of water flows in the Darlots Drain should commence immediately to determine the accuracy of water modelling assumptions. 4.5 Managing Stakeholders There are numerous stakeholders associated with this. These include the Indigenous community, farmers above, below and adjacent to the Lake, the Partners, the three tiers of Government together with their relevant authorities and departments. The wider is formulating a communications strategy involving all stakeholders. However, farmer concerns are of particular relevance in relation to permanent water restoration to Lake Condah. Despite this being the 40 th year since the first water restoration proposal, permanent water is still not held in the Lake. During the 1970 s, 1980 s and into the early 1990 s there was considerable farmer opposition to the water restoration proposals. Although based on groundless fears, the resultant political pressure brought about a substantial winding back of the proposed Lake size and ultimately, the retention of the status quo of no permanent water in the Lake. The solution is to have open and transparent discussions with the farmer groups and to work cooperatively with them in addressing their concerns. Consultation needs to be timely, ongoing, accurate, cooperative and encourage goodwill and reconciliation. Lake Condah Sustainable Development Page 27