The Poatina Power Station is fed by water from Great Lake in the Central Highlands, and discharges into Brumbys Creek, which flows into the Macquarie and South Esk rivers quite far downstream in the lower catchment. The primary land-use is agriculture, and on the watercourses downstream of Poatina the land is generally cleared to the stream bank. The riparian zone is highly degraded with willow infestations and widespread stock access, and there are numerous water abstractions for irrigation, aquaculture and town water supply. Brumbys Creek is a popular recreational trout fishery, and an aquaculture facility is situated at its downstream end.
The impacts of power station discharges compound the multitude of land-use issues in this catchment, and Basslink operatinal changes were projected to further exacerbate many of the present issues. Areas of concern related predominantly to impacts on riparian landowners and recreatinal trout fishing. More rapid fluctuations in water level and frequent dewatering periods were anticipated to have environmental and socio-economic implications including bank condition, macrophytes (aquatic plants), macroinvertebrates (aquatic insects), fish and trout recruitment, water abstraction difficulties due to pump locations, increased risk of stock strandings and public safety risks.
The outcome of the downstream Poatina investigations was a commitment by Hydro Tasmania to construct a re-regulation storage immediately downstream of tailrace, accompanied by a monitoring program to assess effectiveness of this measure.
The re-regulation storage would dampen in the order of 60% of downstream flow fluctuations, maintain a higher than present minimum water level in Brumbys Creek weir ponds, and improves both present and Basslink concerns with water quality, bank erosion, stresses on instream biota, and problems for landowners.