Reservoir is the word that identifies a large natural or human-made lake used to supply water.
Reservoir is a large natural or human- made lake used as a source of water supply. Reservoirs are very useful because they supply water when natural water bodies such as rivers, run dry (especially during droughts). Reservoirs help to control flooding and they are also used for fishing and boating. Valley-dammed reservoirs, bank-side reservoirs, and service reservoirs are the three main types of reservoirs.
If you are implying one these choices not needed for survival it would be parents only when you can survive on your own (I'm not that sure but I hope this helped the slightest but)
Energy flow is the amount of energy that moves through a food chain chemical cycling is the flow of elements and compounds between living organisms and the physical environment
