What effect does seasonality have on non-perennial water sources?

Non-perennial water sources are characterized by their reliance on seasonal conditions, typically flowing only during certain times of the year. Thus, the correct answer highlights that these sources only contain water during specific seasons.

This seasonality arises from factors such as rainfall patterns, temperature changes, and snowmelt, which affect the water availability in these sources. In contrast to perennial sources, which maintain a continuous flow throughout the year, non-perennial sources can vary widely in their water levels based on seasonal fluctuations. Consequently, understanding this aspect of non-perennial sources is crucial in the context of water management and planning in regions where these sources are significant.

The other choices do not reflect the true characteristics of non-perennial sources. They are not dependable year-round, do not increase in flow during droughts (as droughts typically decrease water availability), and do have seasonal variations, which also makes the notion of "no seasonal variations" incorrect.