Let thy fountains be dispersed abroad, and rivers of waters in the streets. The figurative language is still continued, and under the terms "fountains" and "rivers of waters," are to be understood children, the legitimate issue of lawful marriage.
So Aben Ezra and the majority of modern commentators, Schultens, Doderlein, Holden, Muenscher, Noyes, Wardlaw, etc. The meaning appears to be, "Let thy marriage be blessed with many children, who may go forth abroad for the public good."
Other interpretations have been adopted.