Rashi on Genesis 8:2/רש"י על בראשית ח׳:ב׳

1ויסכרו מעינות AND THE FOUNTAINS … WERE STOPPED –– When they were opened, it was stated that all fountains were opened (7:11), whilst here the word all is omitted: the reason is that such of them as were essential to the world were left unstopped, such as the hot springs of Tiberias and their like (Sanhedrin 108a).

2ויכלא means was restrained. withheld, as (Psalms 40:12) “Thou wilt not withhold (תכלא) thy mercies” and (Genesis 23:6) “None of us will withhold (יכלה) from thee.’’