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Soil salinity and dryland salinity are two problems degrading the environment of Australia. Salinity is a concern in most states, but especially in the south-west of Western Australia.〔(Monitoring the white death – soil salinity ). Australian Academy of Science.〕 The Eastern Mallee and the Western Mallee of Western Australia are areas that are prone to salinity with little remedial action being undertaken to rectify the problem. Lands surrounding Lake Bryde-East Lake Bryde and Dumbleyung Lake have also been affected. In the Murray River valley irrigation has caused salinity problems. Land surrounding the town of Werrimull in the northwest of Victoria have been affected by salinity due to land clearing. ==Process== The soil in Australia naturally contains salt, having accumulated over thousands of years. This salt may come from prevailing winds carrying ocean salt, the evaporation of inland seas, and from weathered parent rocks.〔 Rainfall absorbs this salt on the surface, and carries it down into the subsoil where it is stored in unsaturated soil profiles, until it is once again mobilised by ground water and rising water tables.〔Bell, David (1999). (Australian Trees for the Rehabilitation of Waterlogged and Salinity Damaged Landscapes ). ''Australian Journal of Botany'', 47: 697–716.〕 When this ground water comes closer to the surface, this salt is also brought up. As the water eventually evaporates, it leaves behind all this concentrated salt, resulting in soil salinity. This can be caused by an imbalance in the hydrological cycle, or by irrigation. Prior to British settlement in 1788, groundwater levels were in equilibrium. Seasonal recharge, and year round utilisation of ground water by deep rooted native vegetation resulted in ground water levels remaining static.〔C.J. Clarke, R.J. George, R.W. Bell, T.J. Hatton (January 2002). (Dryland salinity in south-western Australia: its origins, remedies, and future research directions ), ''Australian Journal of Soil Research'', 40(1): 93–113.〕 Land clearing in Australia has resulted in a loss of this native vegetation, replaced largely by agriculture and pasture crops. These are often annual plants and shallow rooted, and thus, unable to intercept, and adequately absorb stored, and rising ground water. This creates an imbalance in the hydrological cycle, and results in dryland salinity. Salinity is classified as a dissolved salt content of a substance like soil or water. Salinity can prevent crops and other vegetation from growing leaving land empty. Irrigation is also a contributor to salinity. Firstly, the addition of irrigation acts to simulate rainfall, and if not applied at appropriate levels, can result in the recharge of water tables, and promotes rises in the water table.〔Pels, S. 1978. Waterlogging and Salinization in Irrigated Semi-arid Regions of NSW. ''Search'' Volume 9, pp 273-276.〕 Secondly, irrigation water itself can contain salts, which are deposited into the soil with its use. This level of salt can range from 0.5 - 2 tonne per hectare per year, and can greatly increase natural salt levels. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Salinity in Australia」の詳細全文を読む スポンサード リンク
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