การฟัง TOEFL

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Listen to part of a lecture in an environmental science class. Professor: Today we’re going to discuss the concept of 'peak water,' which is analogous to 'peak oil.' Peak water refers to the point at which the renewable freshwater supply in a region becomes limited, either because of over-extraction or because of changes in climate. One example is the Ogallala Aquifer in the central United States. This underground reservoir supplies water for irrigation across eight states. However, since the 1940s, farmers have been pumping water out much faster than it can be naturally replenished. In some areas, the water table has dropped by more than 150 feet. This has led to increased pumping costs and, in some cases, the abandonment of wells. Unlike surface water, groundwater is often invisible, so the depletion is not immediately obvious to the public. But the long-term consequences are severe, including reduced agricultural productivity and land subsidence. Some scientists argue that we have already crossed the peak water threshold for many aquifers, meaning that we will see a gradual decline in available freshwater in the coming decades.