Anthropogenic impacts on the water and salt budgets of St Lucia estuarine lake in South Africa
Anthropogenic impacts on the water and salt budgets of St Lucia estuarine lake in South Africa
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DOI：
10.1016/j.ecss.2011.04.005
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发表时间：
2011-05
影响因子：
2.8
通讯作者：
Robynne A. Lawrie;D. Stretch
中科院分区：
文献类型：
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作者：
Robynne A. Lawrie;D. Stretch
南非的圣卢西亚湖是联合国教科文组织世界遗产的一部分，也是具有国际重要性的拉姆萨尔湿地。像世界各地的许多沿海湿地，人类活动，包括集水区土地利用的变化，水改道/提取，并操纵口状态显着影响其功能在过去的世纪。有关其可持续性的问题促使人们重新评价过去作出的管理决定和今后的备选办法。因此，水和盐的预算模型已被用来调查“如果”的情况下，在过去的人为干预。特别是，模拟使我们能够评估从圣卢西亚转移Mfolozi河对系统功能和驱动生态系统生物功能的各种水位/盐度状态的发生的影响。在过去，当圣卢西亚河口和Mfolozi河有一个联合入口时，河口主要是开放的。该湖的水位相对稳定，但盐度变化不定，在干燥条件下，由于蒸发损失和海水流入，盐度会增加。如果河口关闭，Mfolozi流被转移到湖中，从而降低盐度并保持或增加水位。模拟表明，如果没有与Mfolozi的联系，湖泊系统自然会有一个主要封闭的入口，平均盐度较低，但水位变化较大。在干旱条件下，水位会下降，导致湖泊大面积干涸，最近发生了这种情况。我们的结论是，圣卢西亚和Mfolozi入口的人工分离是对湖泊水盐预算的最重要影响的基础，其逆转是系统可持续性的关键。
Lake St Lucia in South Africa is part of a UNESCO World Heritage site and a Ramsar wetland of international importance. Like many coastal wetlands worldwide, anthropogenic activities including catchment land-use changes, water diversions/abstractions, and manipulation of the mouth state have significantly affected its functioning over the past century. Questions concerning its sustainability have motivated a re-evaluation of management decisions made in the past and of options for the future. A model for the water and salt budgets has therefore been used to investigate “what if” scenarios in terms of past anthropogenic interventions. In particular, simulations allow us to evaluate the effects of diverting the Mfolozi river from St Lucia on the functioning of the system and on the occurrence of various water level/salinity states that drive the biological functioning of the ecosystem. In the past, when the St Lucia estuary and the Mfolozi river had a combined inlet, the mouth was predominantly open. The lake had relatively stable water levels but variable salinities that increased during dry conditions due to evaporative losses and saltwater inflows from the sea. If the mouth closed, the Mfolozi flow was diverted into the lake which reduced salinities and maintained or increased water levels. Simulations indicate that without a link to the Mfolozi the lake system would naturally have a mainly closed inlet with lower average salinities but more variable water levels. During dry conditions water levels would reduce and result in desiccation of large areas of the lake as has recently occurred. We conclude that the artificial separation of the St Lucia and Mfolozi inlets underpins the most significant impacts on the water & salt budget of the lake and that its reversal is key to the sustainability of the system.