Ye have seen, i.e. observed or considered, as this word is used, Exodus 32:9, and elsewhere, in order to the reparation of them, and to fortify the city, as the next words manifest. Ye gathered together the waters of the lower pool, that you might both deprive the enemy of water, and supply the city with it; of which see on 2 Chronicles 32:4,5.
Related Commentaries of Isaiah 22:9
Isaiah 22:9
9 Ye have seen also the breaches of the city of David, that they are many: and ye gathered together the waters of the lower pool.