In what climatic zone and why is the annual flow of rivers the most uniform?

In almost all climatic zones, precipitation is seasonal, for example, there are rainy seasons, droughts, cold winters, when precipitation falls in solid form, etc. And the rivers that receive water from precipitation, depending on the seasons, become full-flowing or high-flowing.
But in the equatorial and subequatorial zones, the rains fall steadily all year round, and the rivers that originate at these latitudes are stable and full of water.