لِمَنْ لَا يَعْلَمُ: انْخَفَضَ مَنْسُوبُ الْمَاءِ.
To someone uninformed: The water level has fallen.
لِمَنْ يُنْكِرُ: إِنَّ مَنْسُوبَ الْمَاءِ قَدِ انْخَفَضَ.
To someone denying it: The water level has indeed fallen.
لِمَنْ يَتَّهِمُ: مَا أَوْقَفْنَا السَّحْبَ لِحِرْمَانِكُمْ، بَلْ لِلْفَحْصِ.
To an accuser: We suspended pumping for inspection, not to deprive you.
These utterances do different jobs: initial reporting, strengthened assertion and specific rebuttal. The change is not mere ornament; it preserves what the discourse situation actually calls upon the speaker to establish.