, ▁but ▁this ▁is ▁not ▁always ▁the ▁case , ▁due ▁to ▁v ag uen ess ▁in ▁the ▁language . ▁A ▁river ▁is ▁part ▁of ▁the ▁hydro log ical ▁cycle . ▁Water ▁within ▁a ▁river ▁is ▁generally ▁collected ▁from ▁precip itation ▁through ▁surface ▁run off , ▁ground water ▁re charge , ▁spr ings , ▁and ▁the ▁release ▁of ▁stored ▁water ▁in ▁natural ▁ice ▁and ▁snow pack s ▁( i . e ., ▁from ▁gla ci ers ). ▁ ▁Stream s ▁ ▁A ▁stream ▁is ▁a ▁flow ing ▁body ▁of ▁water ▁with ▁a ▁current , ▁conf ined ▁within ▁a ▁bed ▁and ▁stream ▁banks . ▁In ▁the ▁United ▁States , ▁a ▁stream ▁is ▁class ified ▁as ▁a ▁water course ▁less ▁than ▁ ▁wide . ▁Stream s ▁are ▁important ▁as ▁condu its ▁in ▁the ▁water ▁cycle , ▁instruments ▁in ▁ground water ▁re charge , ▁and ▁they ▁serve ▁as ▁cor rid ors ▁for ▁fish ▁and ▁wild life ▁migration . ▁The ▁bi ological ▁habitat ▁in ▁the ▁immediate ▁vic inity ▁of ▁a ▁stream ▁is ▁called ▁a ▁rip arian ▁zone . ▁Given ▁the ▁status ▁of ▁the ▁on going ▁Hol oc ene ▁ext inction , ▁streams ▁play ▁an ▁important ▁cor rid or ▁role ▁in ▁connecting ▁fragment ed ▁habit ats ▁and ▁thus ▁in ▁conser ving ▁b iod iversity . ▁The ▁study ▁of ▁streams ▁and ▁water ways ▁in ▁general ▁involves ▁many ▁branches ▁of ▁inter - dis cipl inary ▁natural ▁science ▁and ▁engineering , ▁including ▁hydro log y , ▁fl uv ial ▁ge omorph ology , ▁aqu atic ▁e col ogy , ▁fish ▁bi ology