Assessment of the Jabiluka Project : report of the Supervising Scientist to the World Heritage Committee
Johnston, A.; Prendergast, J. B.; Bridgewater, Peter
E-Publications; E-Books; PublicationNT; Supervising Scientist Report; 138
Alligator Rivers Region
Main report--Appendix 2 of the Main Report. Submission to the Mission of the World Heritage Committee by some Australian Scientists ... --Attachment A. Johnston A. and Needham S. 1999. Protection of the environment near the Ranger uranium mine--Attachment B. Bureau of Meteorology 1999. Hydrometeorological analysis relevant to Jabiluka--Attachment C. Jones, R.N., Hennessy, K.J. and Abbs, D.J. 1999. Climate change analysis relevant to Jabiluka--Attachment D. Chiew, F and Wang, Q.J. 1999. Hydrological anaysis relevant to surface water storage at Jabiluka--Attachment E. Kalf, F. and Dudgeon, C. 1999. Analysis of long term groundwater dispersal of contaminants from proposed Jabiluka mine tailings repositories--Appendix 2 of Attachment E. Simulation of leaching on non-reactive and radionuclide contaminants from proposed Jabiluka silo banks.
Uranium mill tailings - Environmental aspects - Northern Territory - Alligator Rivers Region; Environmental impact analysis - Northern Territory - Jabiluka; Uranium mines and mining - Environmental aspects - Northern Territory - Jabiluka; Jabiluka - Environmental aspects
Supervising Scientist Report; 138
1 volume (various pagings) : illustrations, maps
https://hdl.handle.net/10070/462403; https://hdl.handle.net/10070/462400; https://hdl.handle.net/10070/462405; https://hdl.handle.net/10070/462406; https://hdl.handle.net/10070/462408; https://hdl.handle.net/10070/462409; https://hdl.handle.net/10070/462411
55 The predictions for change in the Wet season rainfall in the region range from +1% to - 6%. The intensity of extreme storm events is likely to increase despite the fact that there is likely to be an overall decrease in the annual rainfall. It was also found that decadal scale variability was significant and that there exists in the historical record a small long-term upwards trend in the mean annual rainfall but it was concluded that both of these effects are included in the stochastic rainfall model used to assess the required water storage capacity at Jabiluka and need not be considered further. The minimum predicted temperature increase is the extreme scenario for water balance modelling since this would minimise evaporation and hence maximise the required storage volume. The minimum predicted increase of 0.35C over the next 30 years is insufficient to have any significant impact on evaporation. There is no need, therefore, to adjust the hydrological model to take the effect of temperature change into account. The maximum predicted change in annual rainfall from global warming over the next 30 years is 1%. There is, therefore no need to repeat the simulation of the water management system presented in section 5.2.3 to take this effect into account. The effect of climate change will be negligible. The climate change model DARLAM predicts (Jones et al 1999) that storm intensity will increase over the next 30 years. DARLAM simulates little change in annual rainfall over Jabiluka by the year 2030, but extreme rainfall becomes about 10% stronger and the present 1-in-10 year event becomes a 1-in-7 year event. Even in the main months of the Wet season (December until February) when average rainfall is predicted to decrease by about 3%, extreme rainfall is predicted to increase by about 5%. The largest changes are predicted to occur at the junction of the Wet and the Dry seasons (March until May) when it becomes about 30% wetter on average, extreme rainfall intensities rise by up to 24% and extreme events double in frequency. It should be noted, however, that of the six models used to assess climate change (see table 4.3.3), DARLAM is the model that predicts the highest positive changes in mean rainfall in both the Wet and Dry seasons. The effect of the predicted change in storm intensity can be assessed by examining the results obtained in section 5.2.4 in which the results of a sensitivity analysis were presented. The difference in required storage volume between the use of a daily time step in the model and that obtained from the use of a monthly time step was 1.4%. This result was obtained for the same total rainfall in each month. The predicted increases in storm intensity arising from global warming would have the effect of increasing the rainfall on a daily basis but decreasing the overall monthly figure. The results of the sensitivity analysis, therefore, indicate that the increase in storm intensity predicted by the global warming model would not have any significant impact on the required storage capacity of the water management system at Jabiluka. 5.3 Risk assessment for the ERA proposal In principle, the information derived in the previous section on the probability of exceeding the capacity of any specified water retention pond at Jabiluka could be combined with research results on the environmental impact of the constituents of mine waters to determine the pond capacity required to meet specified environmental protection objectives. These objectives would include ensuring that the radiation exposure of people who consume foods collected from downstream waterbodies would be below the recommended international limits on radiation dose. They would also include specifications on the upper limits for
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