Hot Stream, Cold Stream – Measuring the impact of Groundwater on Stream Temperature

Groundwater that drains to surface water through seeps and springs is generally referred to as “discharge.” Groundwater discharge is a primary component of stream base flow, or streamflow that occurs between storms, periods of snowmelt runoff, and periods of quick soil drainage. 

Streams that gain groundwater as they flow are common across glaciated regions such as the Delaware River Basin, and the hydrogeologic mechanisms that control exchanges of surface and groundwater are complex. Because of this complexity, groundwater discharge rates are rarely evenly distributed throughout stream networks, which may instead be dominated by locations of preferential discharge along riparian wetlands, streambanks, and the streambed. 

Groundwater discharge is a crucial component in many model-based forecasts of future water quality and cold-water habitat viability for Salmonids along headwater streams. However, U.S. Geological Survey (USGS) streamgage density is generally low in mountain headwater stream networks, and traditional streamflow measurements may not sufficiently capture groundwater discharge characteristics that are needed to improve predictions. 

By collecting new and varied types of water temperature data related to groundwater discharge at scales from streambank to watershed, the Next Generation Water Observing System (NGWOS) program supports model calibration, water resource-related predictions, and management decisions.

This video demonstrates a range of water temperature monitoring technologies and techniques that allow efficient mapping of groundwater discharge processes.