Freshwater Lakes and Reservoirs

Abstract

Lakes, ponds, and lacustrine environments are characterized by standing water in depressions ofthe landscape left by glacier scouring or impoundments along river networks. Depending on their origin and climatic conditions, lakes can be ancient (e.g., African rift lakes) or very young (e.g., recent landslides). The age ofmost of today’s lakes are in the range of tens of thousands of years old as they were created during the glacier recession of the last ice age (e.g., lakes on or near the Canadian Shield). A handful of largest lakes contain a major proportion of the world’s lake water volume whereas small lakes are more numerous and account for most of lakes surface area. Over time, the natural evolution of lakes is to gradually fill from autochthonous and allochthonous material and sediments. Freshwater lakes, like other surface water ecosystems, offer a wide array of benefits for people, such as water provision, fisheries, flood attenuation, and recreational purposes, and play an important role in global biogeochemical cycles, including water, carbon, and nutrient balances. Overexploitation of fresh- water resources threatens the capacity of these ecosystems to provide these benefits in the future.