What type of stream flows intermittently between rain events?

The correct choice is ephemeral streams, which are characterized by their intermittent flow. These streams only carry water during and immediately after rainfall events, meaning they can dry up completely during dry periods. This type of stream is typically found in regions that experience seasonal rainfall or have significant variations in climate, where water is not consistently available.

In contrast, permanently flowing streams maintain a continuous flow throughout the year, regardless of precipitation. Perennial streams also exhibit a stable flow pattern, fed by groundwater or consistent rainfall, and are typically found in areas with regular water supply. The term "perwashed streams" is not commonly used in hydrology and does not accurately describe any recognized category of stream flow. Hence, ephemeral streams aptly describe those waterways that only run intermittently due to the timing and amount of rainfall.