Matsya Purana — Cosmography of Śākadvīpa and Successive Dvīpas: Mountains
अभिगच्छन्ति ता नद्यो यतो वर्षति वासवः इत्येष संनिवेशो वः कुशद्वीपस्य वर्णितः //
abhigacchanti tā nadyo yato varṣati vāsavaḥ ityeṣa saṃniveśo vaḥ kuśadvīpasya varṇitaḥ //
Those rivers flow toward the region where Vāsava (Indra) sends down the rain. Thus the arrangement and disposition of Kuśadvīpa has been described to you.
This verse is not about pralaya; it belongs to cosmographic description, stating that rivers are oriented toward the rain-bearing region governed by Indra (Vāsava).
Indirectly, it models ordered governance in nature—rain (Indra) and river-flow sustaining lands—an ideal a king mirrors through irrigation, water management, and protection of rivers for public welfare.
While not a direct Vāstu rule, it emphasizes orientation and environmental logic (rainfall and drainage). Such principles align with Vāstu planning: siting settlements/temples with attention to water-flow, catchment, and auspicious/functional geography.