Calls for implementation of environmental flows have been growing over the past 20 years, and their implementation is now being recognized. The need for such assessments to occur in conjunction with maintenance of environmental water temperatures has also been emphasized. When the costs of departures from natural thermal regimes are considered, this moves from being an academic exercise to a tangible management imperative. Pest outbreaks of aquatic macroinvertebrates typically occur when environmental conditions disproportionately and overwhelmingly favor a particular species. This has been the case for at least three major river systems of economic importance in South Africa, namely, the Orange River and its major tributary (Vaal River) as well as the Great Fish River. In these rivers, two species of pest blackfly, Simulium chutteri and S. damnosum (Diptera: Simuliidae), have become problematic following on from changes in natural flows through either impoundment or interbasin transfers. In this study, a statistically robust reference thermal condition was defined and exceedances assessed (based on a 2°C increase in water temperatures). The implications of these assessments were then applied to future possible pest blackfly outbreaks, factoring in changes in flows in response to global climate change. Results show that the current seasonal variation in the likelihood of pest outbreaks is replaced by high perpetual outbreak probabilities. Interactions between major environmental variables become synergistic, with major cost implications to regional economies. Lessons from this study can be generalized and used as a means of predicting similar synergistic effects in other aquatic macroinvertebrate disease vectors (such as bilharzia vector snails and mosquitoes) in response to global climate change.

中文翻译：

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与气候相关的淡水生境变化将产生成本影响：两条相连的南非河流中的害虫黑蝇病暴发

在过去的20年中，要求执行环境流量的呼声越来越高，现在人们已经意识到执行环境流量的呼声。还强调了需要与维持环境水温一起进行这种评估。考虑到偏离自然热能系统的成本时，这已从学术活动转变为切实的管理势在必行。当环境条件不成比例且压倒性地有利于特定物种时，通常会发生水生大型无脊椎动物的害虫暴发。在南非至少三个具有重要经济意义的主要河流系统就是这种情况，即奥兰治河及其主要支流（瓦尔河）以及大鱼河。在这些河流中，有两种有害生物的粉虱，ul菜和S. damnosum（Diptera：Simuliidae），由于蓄水或流域间转移引起的自然流量变化而成为问题。在这项研究中，定义了统计上稳健的参考温度条件，并评估了超出的水平（基于水温2°C的升高）。然后将这些评估的含义应用于未来可能发生的害虫粉虱暴发，将应对全球气候变化的流量变化考虑在内。结果表明，目前有害生物暴发可能性的季节性变化被高持久性暴发概率所取代。主要环境变量之间的相互作用变得协同作用，对区域经济造成重大成本影响。