Matsya Purana — Kailasa
सरस्वती प्रभवति तस्माज्ज्योतिष्मती तु या अवगाढे ह्युभयतः समुद्रौ पूर्वपश्चिमौ //
sarasvatī prabhavati tasmājjyotiṣmatī tu yā avagāḍhe hyubhayataḥ samudrau pūrvapaścimau //
From there the river Sarasvatī arises; and the river Jyotiṣmatī, plunging deep, reaches both seas—the eastern and the western.
It does not describe Pralaya directly; it presents sacred geography, stating the emergence and deep-flowing course of Sarasvatī and Jyotiṣmatī toward the eastern and western seas.
By mapping sacred rivers, it supports tirtha-yātrā, vows, and charitable rites; kings and householders are encouraged in the Purāṇas to protect riverine holy places and to perform purification and dāna connected with such tīrthas.
The ritual takeaway is tīrtha sanctity: rivers and their courses define auspicious sites for स्नान (ritual bathing), śrāddha, and offerings; such river-banks are also preferred zones for temple and ghat placement in later Vāstu-informed practice.