Thegoa Lagoon Management Plan (Draft)
  
1.0 BACKGROUND
1.1 Introduction
Thegoa Lagoon is a natural lagoon, immediately west of Wentworth at the junction of the Murray and Darling Rivers (Figure 1). The floodplain bordered by the lagoon and the Murray River covers approximately 445 hectares. Much of this land (approximately 400 hectares) forms the Thegoa Lagoon Reserve (Reserve No. R78909 as of 16th August 2002, Parish of Wentworth, County of Wentworth) which is classified as community land for public recreation and plantation. It is Crown Land with the Shire of Wentworth as Trustee. Several small private lease-holdings occupy the remaining land in this area.
The lagoon has a surface area of almost 80 hectares and a capacity of approximately 770 megalitres.
1.2 History
During and following floods, the lagoon would have provided abundant wildlife and plant material for use by local Aboriginal people. It would also have been highly significant due to its strategic location at the junction of the Murray and Darling Rivers. The lagoon remained a well known meeting place for large groups of Aboriginal people into the second half of the nineteenth century.
Figure 1: Location and features of Thegoa Lagoon
European settlement of the area occurred from the 1860s and the area of the current reserve was known as Wentworth Common from the late 1800s. A large camp was established in the reserve possibly near the existing cemetery during the construction of Weir and Lock 10 in the 1920s. Three agricultural leases were established in the floodplain bounded by the lagoon in the early 1950s, and the remaining floodplain area was gazetted as a reserve in 1956 for use as "community land for public recreation and plantation".
Prior to the construction of the Wentworth Weir in 1928, water would have only entered Thegoa Lagoon during substantial floods in the Murray or Darling Rivers.
Following the 1956 flood, a 300mm-diameter pipe was installed by Wentworth Shire Council in the depression upstream of the weir when Cadell Street was reformed. It was reported in 1969 that a 600mm diameter pipe had been laid parallel to and adjoining the existing 300mm pipe, but with an invert level 600mm lower and 1200mm below pool level of the Murray River. It was ascertained that the Wentworth Shire Council also installed the 600mm pipe. These works allowed regulated flows in the Murray River to enter Thegoa Lagoon.
A license was issued to Wentworth Shire Council in May 1970 authorising a 600mm-diversion pipe with the purpose of augmenting the supply of water in Thegoa Lagoon for recreational purposes. The fate of the 300mm-diversion pipe has not been recorded, however it is no longer operative.
This artificial inlet has been operated since the 1970s; until recently, to maintain unnaturally high and constant water levels in the lagoon by allowing water from the weir pool to replenish the lagoon water level. This occurred despite the lagoon's classification as an unregulated watercourse. This conversion of the lagoon to a permanent waterbody provided visual amenity and a water supply to water users around the lagoon.
With the introduction of the Volumetric Allocation Scheme on the Murray River it was determined that all water which entered the lagoon, other than at times of surplus flows in either the Murray or Darling Rivers, would be considered to be a debit against water allocated from the rivers to NSW. Upon investigation, it was concluded that the continued inflow of regulated water from the Murray River into the lagoon was causing an unreasonable loss of regulated water.
When the diversion license was renewed in 1975 the following conditions were added to the license to address the above concerns.
· The licensee was to install a stop valve or other control device in the diversion pipe near its point of off-take to the satisfaction of the then Water Resources Commission (now DIPNR).
· The authorised work was only to be used for the purpose of augmenting the supply of water in Thegoa Lagoon when the Water Resources Commission (now DIPNR) announced off-allocation supplies were available in the Murray River at the point of off-take. At all other times the diversion pipe was to be effectively closed.
A metal slide control device was installed on the upstream end of the diversion pipe in 1980. Refurbishment and upgrading of the eastern regulator was undertaken by Wentworth Shire Council in 2002.
1.3 Wetland Ecology
Prior to river regulation, the lagoon was a temporary wetland, which filled with floodwaters from either the Murray or Darling Rivers. The natural cycle of periodic filling and drying maintained the natural processes and productive environments within the lagoon.
The ecology of wetlands along the floodplains of most inland Australian rivers is adapted to periodic cycles of flooding and drying. Such cycles are a critical driving force for the ecological productivity and diversity of these wetlands. Along the Murray River, regulation of flows has resulted in near-permanent inundation of many wetlands and the loss of their natural water level variation and periodic drying. The long history of regulation, combined with the relatively high frequency of floods and high river flows in the last 25 years, has also created a perception that wetlands such as Thegoa Lagoon require permanent and stable water levels. However, such conditions have caused serious degradation to wetlands throughout the river system.
1.4 Significance of the Lagoon and its Environs
Previous studies have highlighted the significance of the wetland and floodplain environments (refer Appendix).
1.4.1 Aboriginal Heritage
The area contains numerous archaeological sites including burials, scar trees, boundary trees and middens. All but one of these sites have been assessed as moderate to high scientific significance due to their representativeness and preservation. All of the sites remain significant to Barkindji Elders and the Barkindji community. Several sites are of special significance.
1.4.2 Non Aboriginal Heritage
Although a thorough assessment of the historic heritage of the reserve has not been completed, general observations have identified several significant sites throughout the area. Lagoon and surrounds have history of use as a major travelling stock route, stock reserve and town common, the town sewerage system was also located on the floodplain. Source of soil for town levee banks.
1.4.3 Environmental Significance
The lagoon and surrounding floodplain is an unusually healthy and diverse example of the riverine environment of the region. In particular, the area includes a high diversity of habitats within a relatively small area. The three vegetation communities of River Red Gum, River Cooba/Black Box and Chenopod Shrubland, occurring around the lagoon are ecologically significant and include one species that occurs only over a restricted range. Four native fauna species occurring at the lagoon are listed as threatened and 14 species are listed as vulnerable and rare.
1.4.4 Eco-cultural Tourism Potential
The area offers considerable opportunities for the development of eco-cultural tourism facilities due to its proximity to Wentworth, its accessibility and the variety and integrity of its natural and cultural features.
1.4.5 Other Values
The lagoon provides several other values. The wetland environment provides a natural setting enjoyed by local residents and visitors, as well as a recreational resource for camping, fishing and picnicking. The lagoon also provides a source of water to surrounding properties for irrigation, recreation and stock and domestic use.
1.5 The Need for a Management Plan
No integrated management of the lagoon and its environs has been undertaken to date. This has resulted in ad hoc management decisions in the past, which have not fully considered the implications for, and the long-term protection of, the diverse features and values of the area. In addition, several activities have been allowed to occur which have damaged the natural environment and culturally significant sites. Given its documented significance, the lagoon requires a more integrated and long term approach to the management of its land, water, vegetation and cultural heritage values.
This plan has been developed to identify broadly accepted management goals and actions to ensure the natural and cultural features of the area are recognised and protected. It aims to achieve long term rehabilitation and conservation of the natural environments and cultural features of the lagoon and floodplain. In particular, it integrates the management of all aspects of the lagoon and its environs including:
· hydrologic rehabilitation of the wetland,
· recognition and protection of the Aboriginal and non Aboriginal cultural heritage associated with the area,
· development of appropriate access and interpretation facilities.
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