Interactions of Stream Water with Atmospheric Water and Groundwater in Herring Run, Baltimore, Maryland

Herring Run is a significant 17.9 km tributary of Back River in Baltimore, Maryland, encompassing a 36.7 km² watershed above Sinclaire Lane Bridge. Originating in Towson, Maryland, it traverses Baltimore County and City before returning to the county and eventually discharging into Back River, which flows into the Chesapeake Bay. Herring Run usually cuts to bedrock with or without side alluvium aquifers. This study characterizes the Herring Run watershed as a monthly-variable linear urban geohydroclimatic system for each same month's trend-outflow. We identify 12 headwater trend-flow linear equations correlated with monthly precipitation for each month, spanning January to December. These equations are based on gauged stream flow data at Idlewylde Bridge based on stream flow and precipitation data from 1958 to 2019. Additionally, we find 12 trend-outflow linear equations for the segment between Idlewylde bridge and Sinclaire Land Bridge, utilizing stream flow data from 1991 to 2020. This set of 24 equations enables the estimation of interactions between stream water, atmospheric water, and groundwater in the Herring Run watershed above Sinclaire Lane Bridge under average monthly precipitation. Within the 5.5 km² headwater watershed area, annual surface water production totals 447 mm (39%), including 163 mm (14%) from groundwater, sourced from 1142 mm of precipitation. Concurrently, evapotranspiration accounts for 695 mm (61%) of the total precipitation. For the broader watershed above Sinclaire Lane Bridge, surface water production is 927 mm (81%), comprising 462 mm (44%) from groundwater. An additional 480 mm (42%) over the total 1142 mm of precipitation, with groundwater contributing 30%, is discharged to the Montebello lakes. This outflow originates from the Montebello Water Treatment plant, which receives water through a 12 km conduit (with diameter of 3.7 m) from Loch Raven Dam outside the watershed. This analysis sheds light on the intricate dynamics of water interactions within the Herring Run watershed, facilitating a more comprehensive understanding of its hydrological processes.