انْخَفَضَ مَنْسُوبُ الْمَاءِ.
The water level fell.
انْقَطَعَ الْمَاءُ.
The supply stopped.
Both are declarative sentences, but they assert different facts. The first concerns degree or quantity; the second concerns cessation. A fall in level does not entail complete interruption. Therefore the subsequent correction is not redundant: it blocks an inference that the listener might otherwise make.
In analyzing such a report, distinguish the subject, the predicate and the qualification that specifies whether the event is diminution or cessation.