What is a gaining stream?

A gaining stream is defined as one that receives water from the groundwater, resulting in an increase in its flow during the dry season or periods of low precipitation. This happens when the water table is higher than the surface of the stream, allowing groundwater to seep into the stream, effectively replenishing it and maintaining its flow. This characteristic is essential for understanding the hydrological cycle, as gaining streams often play a critical role in sustaining aquatic ecosystems, especially in arid regions or during droughts when surface water is limited.

In contrast, a stream that loses water to groundwater represents a losing stream, which can lead to a decrease in flow, particularly in dry conditions. Streams that have no connection to groundwater and those that flow evenly throughout the year do not accurately describe gaining streams, as they do not involve the significant exchange of water between the stream and the groundwater system typical of gaining streams.