February 6, 2010 - Water

Not all lake water remains in the lake.  Lakes lose some water from seepage, depending on what kind of rock and sediment lies beneath the lake.  A rocky bottom holds water better than a sandy bottom.  So you can see that some lake bottoms are leakier than others.

Lakes are also subject to evaporation from their surfaces – especially in a dry places – for example, the American West.

So why don’t lakes just dry up?  The answer is that lakes have to be replenished.  There are both natural and man-made lakes. The main way that water gets into reservoirs and man-made lakes is from the rivers and streams that were dammed to create them. Like man-made reservoirs and lakes, natural lakes may also be replenished by rivers and streams.

Natural lakes have another advantage, when it come to holding their water.  They tend to form in the lowest elevations in a given area. So these sorts of lakes may also get underground water that flows in from underneath the lake – the lake floor may be an area of water input, rather than a drain for the lake.

Written by earthsky