Why do Columbia River water levels rise in late spring and early summer?

The water levels of the Columbia River rise during late spring and early summer primarily due to the melting of snow within its mountainous watershed.1

This seasonal increase in flow is a natural hydrological cycle for the river, contrasting with the low flows typically experienced during the autumn and winter months. These low-flow periods often result in water shortages for the region's hydroelectric power plants, which are a critical component of the river's economic development.12