New England WSC Seminar series Barclay 20190724

Date/Time: Wednesday, July 24, 2016, 12:00 pm 
 

Title: Where rivers run cold: spatial patterns of groundwater discharge and groundwater nitrogen loading in a regional river network

Presented by: Janet Barclay, Hydrologist, New England WSC, U.S. Geological Survey

Location: USGS, Massachusetts Office, Northborough, MA

Abstract: 

Groundwater discharge zones supply baseflow, provide critical thermal refugia for aquatic organisms, and serve as point sources of nutrients and contaminants to aquatic ecosystems. Despite their importance, the spatial distribution and the water quality effects of groundwater discharge zones across river networks are seldom predicted at regional scales due to the highly spatially heterogeneous distribution. Regional groundwater flow models are often used to predict net groundwater discharge at larger scales, but finer-scale (e.g., 200 m grid) spatial patterns of discharge from watershed-scale models are largely unevaluated. Advances in remote sensing technology, in particular, thermal infrared imagery (TIR), that allow us to efficiently map seepage zones across space are improving our understanding of groundwater discharge at the watershed scale. We integrated a groundwater flow model, extensive TIR surveys, and groundwater seep chemical analysis to identify spatial patterns of groundwater discharge, nitrogen (N) loading and N removal in a 1570 km², 5^th order watershed (Farmington River, CT and MA). We highlight the influence of model conceptualization on spatial patterns of groundwater discharge, demonstrate the use of TIR for evaluating modeling patterns of groundwater discharge, and quantify rates of N loading and removal across the river network. Our results highlight (1) advances and areas for improvement in modeling groundwater discharge zones and (2) heterogeneity and dominant patterns in N loading and removal at the watershed scale.