An evaluation of three management strategies for the mitigation of high salinities in the Coorong

[摘要] EXECUTIVE SUMMARY: A series of possible strategies for alleviating the present high salinities in the Coorongincluding pumping brine from the South Lagoon and increasing the dredging effort at theMouth have been evaluated in recent studies. Here, the hydrodynamic model developed forthese studies is used to investigate the salinity and water level responses in the Coorong forthree additional sets of scenarios. The scenarios examine the impacts of varying the locationof the intake for South Lagoon pumping, of short term modification of Upper SoutheastDrainage (USED) discharges, and of constructing a pipe connection between the SouthLagoon and the sea to facilitate exchange.The intake location considered for pumping brine from the South Lagoon in order to lowersalinities there has been approximately mid-way along the Lagoon. An alternative site closeto the northern end of the South Lagoon has the substantial advantage of requiring arelatively short pipe connecting to the sea. Model simulations of pumping from both locationssuggest that salinities would be reduced about 2/3 as much in the South Lagoon for pumpingfrom the northern site compared to the mid-lagoon site, but water level responses in theLagoon would be little different from one another.Model simulations were undertaken to assess the impacts of increasing inflows to the SouthLagoon from the USED scheme. Inflows through the drought years 2001-2008 haveaveraged ~7 GL/year. Approximately doubling this drought inflow has a modest effect onSouth Lagoon salinities, but increasing the inflow to 60 GL/year causes average salinity inthe Lagoon to reduce from ~150 g/L to less than 90 g/L. The imposition of median barrageflows on top of the enhanced USED inflows causes further major reduction in South Lagoonsalinity.The third scenario type investigated is the potential benefit of a pipe connecting the SouthLagoon with the sea which would be flushed naturally by flows driven by water leveldifferences across the pipe ends. Such differences would arise due to due to wind set-upsand evaporation in the Lagoon and to the tides and other longer term level variation in thesea. The hydrodynamic simulations showed that the effect of a 2-m diameter pipe would beto cause a salinity reduction in the South Lagoon of ~40 g/L which is similar to pumping brinefrom the Lagoon at 250 ML/day. However, it is probable that the benefit of the pipe would bemuch less than this in reality as the model does not properly account for ponding around thepipe outlets and the likelihood that this water would flow back through the pipe when the flowreverses.

[发布日期] 2010-04-01 [发布机构] CSIRO

[学科分类] 地球科学(综合)