Matsya Purana — Kailasa
तासां नद्युपनद्यो ऽन्याः शतशो ऽथ सहस्रशः उपगच्छन्ति ता नद्यो यतो वर्षति वासवः //
tāsāṃ nadyupanadyo 'nyāḥ śataśo 'tha sahasraśaḥ upagacchanti tā nadyo yato varṣati vāsavaḥ //
Into those rivers flow other rivers and tributaries—by the hundreds and even by the thousands—for from there Vāsava (Indra) sends down the rains.
It does not describe Pralaya directly; it presents a sustaining cosmic order where Indra’s rains nourish river-systems through countless tributaries.
Indirectly, it supports dharma through water-sustenance: rulers and householders are expected to protect water sources, maintain tanks/canals, and honor rain and river deities as the basis of prosperity.
The verse implies the primacy of water in settlement and ritual life—useful for Matsya Purana Vastu Shastra tips such as siting habitations/temples near reliable watercourses and performing rain-and-river related rites.