divide A ridge that separates one water basin from another. Each water basin will be
drained by streams into a different ocean.
estuary An area where saltwater from the sea mixes with freshwater from a stream or
river. Estuaries often have high biodiversity.
floodplain A flat area covered by a stream or river when it floods. Often rich in nutrients
and thus good places to farm.
intermittent lake A lake that appears and disappears seasonally, as water levels rise and
fall.
lake A larger body of freshwater, usually drained by a stream. May be naturally occurring
or humanmade.
levee A raised structure designed to hold back the waters of a stream or river in the case
of a flood.
limnology The study of all freshwater bodies and the organisms that live in them.
littoral zone The region in a freshwater body closest to shore. Usually contains the most
life in the body of water.
marsh A type of wetland around lakes, streams, or the ocean where grasses and reeds are
common, but there are no trees. May be freshwater, saltwater, or brackish. Water is
generally shallow.
mouth The point where a stream enters a larger body of water like a lake or an ocean.
photic zone The region in a freshwater body where sunlight is abundant. Also called the
open-water zone or limnetic zone.
pond A small body of freshwater, with no stream draining it. Often fed by an underground
spring.
pool A deep, slow-moving part of the stream. The stream is usually wider at the point
where a pool is found.
source The place where a stream starts.