Limnology

Limnology is the study of waters that are not part of the oceans or seas. This includes rivers, lakes, swamps, streams, wetlands, water under the ground, and even bodies of water made by people. Scientists who study this are called "limnologists". Their work includes biology, chemistry, physics, geology, and hydrology.
The "International Society of Limnology" promotes limnology to scientists throughout the world. There are many centres for such research throughout the world. 
Limnology helps to explain why some lakes have lots of plants and animals and some have very few. The Freshwater Biological Association which is based next to Windermere in England did a lot of the early work. Limnologists there worked out why deep lakes have cold water at the bottom in summer-time but not in Winter. The reason was that winds in Autumn mix the waters up.