托福TPO24阅读真题及答案Lake Water.doc

以下,是这次环球托福为正在进行托福备考的考友们整理了托福 TPO24 阅读真题及答案 Lake Water 。我们建议考友们, 先做真题, 后看答案进行验证自己的正确率。之后, 环球托福还会进一步推出托福 TPO24 阅读真题的做题思路讲解分析,做完真题后,更便于提高托福阅读能力。托福 TPO24 阅读真题 Lake Water Lake Water Where does the water ina e from, and how does water leave it? Water enters a lake from inflowing rivers, from underwater seeps and springs, from overland flow off the surrounding land, and from rain falling directly on the lake surface. Water leaves a lake via outflowing rivers, by soaking into the bed of the lake, and by evaporation. So much is obvious. The questions e plicated when actual volumes of water are considered: how much water enters and leaves by each route? Discovering the inputs and outputs of rivers isa matter of measuring the discharges of every inflowing and outflowing stream and river. Then exchanges with the atmosphere are calculated by finding the difference between the gains from rain, as measured (rather roughly) by rain gauges and the losses by evaporation, measured with models that correct for the other sources of water loss. For the majority of lakes, certainly those surrounded by forests, input from overland flow is too small to have a noticeable effect. Changes in lake level not explained by river flows plus exchanges with the atmosphere must be due to difference between what seeps into the lake from the groundwater and what leaks into the groundwater. Note the word "net": mea