当時はきれいな水がこの川にも流れていた。

at that time; in those days

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

pretty; lovely; beautiful; fair; clean; clear; pure; tidy; neat; completely; entirely

water (esp. cool, fresh water, e.g. drinking water); fluid (esp. in an animal tissue); liquid; flood; floodwaters; water offered to wrestlers just prior to a bout; break granted to wrestlers engaged in a prolonged bout

indicates sentence subject (occasionally object); indicates possessive (esp. in literary expressions); but; however; still; and

this (something or someone close to the speaker (including the speaker), or ideas expressed by the speaker)

river; stream; the .... river; (suffix used with the names of rivers)

at (place, time); in; on; during; to (direction, state); toward; into; for (purpose); because of (reason); for; with; by; from; as (i.e. in the role of); per; in; for; a (e.g. "once a month"); and; in addition to; if; although

too; also; in addition; as well; (not) either (in a negative sentence); both A and B; A as well as B; neither A nor B (in a negative sentence); even; as much as; as many as; as far as; as long as; no less than; no fewer than; even if; even though; although; in spite of; further; more; again; another; the other

to stream; to flow (liquid, time, etc.); to run (ink); to be washed away; to be carried; to drift; to float (e.g. clouds); to wander; to stray; to sweep (e.g. rumour, fire); to spread; to circulate; to be heard (e.g. music); to be played; to lapse (e.g. into indolence, despair); to pass; to elapse; to be transmitted; to be called off; to be forfeited; to disappear; to be removed