Why does the flood season of Sri Lankan rivers occur in the winter half of the year?

Sri Lanka has many rivers, originating from the Mahaweli River in the central part of the island, flowing northeast, and finally flowing into Trincomalee Bay. The rivers meander through canyons and spread across the plains. The river falls down the cliff to form a waterfall, the deep canyon is filled with water vapor, and the landscape is beautiful. Most rivers in Sri Lanka are short and often interrupted by topographic discontinuities. The longest river in Sri Lanka is the Mahaweli River, with a total length of 335 kilometers. The upper reaches of the river are wild, unnavigable rapids, and the lower reaches are prone to seasonal flooding. The importance of this river is evident as it irrigates the eastern part of Sri Lanka when rainfall is insufficient.