Karst issues in an hydro-electric power proposal: Iralalaro-Paitchau karst, Timor-Leste
1 Latrobe University Environmental Geoscience, & Victorian Speleological Association 2 Sydney Speleological Society, & Southern Tasmanian Caverneers. 3 Australian Speleological Federation Conservation Commission, & Victorian Speleological Association
The proposed Iralalaro hydro-electric scheme in far eastern Timor-Leste would divert water from the Irasiquero River upstream of the Mainina sinkhole to a tunnel through the Paitchau Mountains leading to a power station on the coast. The Iralalaro-Paitchau Mountains area is a karst region, containing a wide range of karst-related landforms and features. These include a large polje, collapse dolines, sinkholes, blind valleys, karren, caves and springs. A substantial component of the hydrology is underground and the area relies on underground water for almost all of its water supplies. The area has significant surface and underground geodiversity and biodiversity. The proposal, as currently formulated, appears to have a number of significant limitations which, unless adequately addressed, could cause significant cost overruns and/or seriously undermine the scheme's viability. Estimates of the construction costs appear to have underestimated the risks and costs of drilling, tunnelling and de-watering the karstic terrain, and as a result are inadequate. Understanding of the relationship between the lake and the watertable is inadequate, as are stream flow records, with consequent implications for sustainable power generation from the scheme. The karst has not been subjected to a thorough and detailed study by experts in this specialised field, and the implications of the karstic nature of the terrain appear to have been poorly understood. A full investigation of the hydrology, caves and karst features of the region is essential. The proposed hydro scheme is incompatible with the maintenance of many of the natural and cultural values which give the area its special significance and ecotourism potential. It jeopardises proposals to provide protection to the special environmental values of the area and could damage precisely the features most likely to attract adventure tourists, putting at risk the development of tourism in the region. The people living in the environs of the proposed scheme appear ambivalent about the possible benefits. A lowered regional watertable may affect the entire population and agricultural production east of Los Palos. The existing proposal inadequately addresses the problems of the very limited infrastructure in the area. There are serious questions as to the ability of the proposed scheme to provide the claimed electricity output on a continuing basis at the currently estimated costs and with the suggested low levels of environmental impact. Despite the serious inadequacies in the investigations and documentation there are indications that the Timor-Leste Government is likely to approve the scheme.