Baltimore Ecosystem Study Institute of Ecosystem Studies

2014 BES Annual Meeting Presentation and Poster Abstracts

Use of water isotopes to characterize groundwater-surface water interactions in BES watersheds
Welty, Claire
Co-Authors: Claire Welty and John Kemper

Abstract: Isotopic analysis of local precipitation samples collected since January 2013 reveals significant seasonal and inter-storm variability in d18O and d2H content. Analysis of weekly grab samples from the main BES stream stations shows that the stream isotopic signatures are dampened and lagged compared to the precipitation signal. The observed temporal patterns in precipitation and stream isotopic contents provide an opportunity to evaluate mean watershed transit times. An initial analysis yields mean transit times of the BES watersheds ranging from 15 to 40 days, ordered by watershed area. This relation does not hold where there are significant localized anthropogenic inputs to the stream system other than precipitation, such as leaky infrastructure. For example, a 6-km synoptic (with samples collected every 50 m) conducted over a period of 5 hours during base flow conditions in Dead Run after an extended dry period illustrates the significant spatial variability in isotopic content in this highly urbanized watershed. Anthropogenic inputs such as leaking potable water sources can be detected, superimposed on focused areas of groundwater discharge.