What is groundwater discharge and its significance for river regimes?

• A. Precipitation infiltrating into soil.
• B. Upward capillary rise from groundwater.
• C. Groundwater discharge is the flow of groundwater into streams, contributing to baseflow and sustaining rivers during dry periods.
• D. Evaporation from groundwater.

Answer: (C)

Groundwater discharge is the flow of groundwater into streams, contributing to baseflow and sustaining rivers during dry periods. This means a steady portion of river flow comes from groundwater seeping into the stream, keeping it flowing even when rainfall is scarce. This baseflow shapes the river regime by providing a relatively constant, long-lasting input that buffers against droughts and governs the shape of the hydrograph, especially during the dry season. It also influences water quality and temperature, since groundwater often has different characteristics than surface runoff and mixes with the stream over time.

Infiltration describes water entering the ground to recharge aquifers, not the water feeding streams. Upward capillary rise can occur locally from groundwater into the near-surface zone but is not the primary mechanism for sustaining streamflow. Evaporation from groundwater reduces water reserves rather than delivering water to streams.