I heard the word 水脈 sung as みなすじ in a song, and I wouldn't have known what word was actually being said if I hadn't had the lyrics present. My dictionary doesn't show that as a possible reading, so I checked the individual kanji readings, and while すじ is indeed the kun-yomi for 脈, みな was only listed for 水 as nanori. I wanted to ask if this reading has any precedent--that is, if someone heard this and did not have printed lyrics handy, would they know what word this is? Is this a reading that has been used before or regularly enough to be associated with the word?
脈 as すじ is probably rare, but the same meaning is suggested by compound words that use it such as 山脈, where it means a line of something.
As for みなすじ, it seems to be a word invented by the person who wrote the lyrics as far as I can tell from google results. However it follows the rules for old words that use 水 as a prefix: 水面｛みなも｝, 港｛みなと}, 源｛みなもと｝ 水底｛みなそこ｝.
It's not a piece of standard vocabulary, but I'd say it's definitely "wordy" enough to use as an author.