Using isotopes to understand the evolution of water ages in disturbed mixed land‐use catchments

Katya Dimitrova Petrova*, Josie Geris, Mark E Wilkinson, Allan Lilly, Christopher Soulsby

*Corresponding author for this work

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Tracer studies have been key to unravelling catchment hydrological processes, yet most insights have been gained in environments with relatively low human impact. We investigated the spatial variability of stream isotopes and water ages to infer dominant flow paths in a ~10 km2 nested catchment in a disturbed, predominantly agricultural environment in Scotland. We collected long‐term (>5 years) stable isotope data of precipitation, artificial drainage, and four streams with varying soil and land use types in their catchment areas. Using a gamma model, Mean Transit Times (MTTs) were then estimated in order to understand the spatial variability of controls on water ages. Despite contrasting catchment characteristics, we found that MTTs in the streams were generally very similar and short (<1 year). MTTs of water in artificial drains were even shorter, ranging between 1 to 10 months for a typical field drain and <0.5 to 1 month for a country road drain. At the catchment scale, lack of heterogeneity in the response could be explained by the extensive artificial surface and subsurface drainage, “short‐circuiting” younger water to the streams during storms. Under such conditions, additional intense disturbance associated with highway construction during the study period had no major effect on the stream isotope dynamics. Supplementary short term (~ 14 months) sampling of mobile soil water in dominant soil‐land use units also revealed that agricultural practices (ploughing of poorly draining soils and soil compaction due to grazing on freely draining soils) resulted in subtle MTT variations in soil water in the upper profile. Overall, the isotope dynamics and inferred MTTs suggest that the evolution of stream water ages in such a complex human‐influenced environment are largely related to near‐surface soil processes and the dominant soil management practices. This has direct implications for understanding and managing flood risk and contaminant transport in such environments.
Original languageEnglish
Pages (from-to)972-990
Number of pages19
JournalHydrological Processes
Volume34
Issue number4
Early online date10 Jan 2020
DOIs
Publication statusPublished - 15 Feb 2020

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Keywords

  • transit times
  • water isotopes
  • soil water isotopes
  • gamma model
  • anthropocene hydrology
  • artificial drainage
  • agricultural catchment
  • land use management
  • Anthropocene hydrology
  • STORAGE
  • RESIDENCE TIME
  • DISTRIBUTIONS
  • STABLE-ISOTOPES
  • MEAN TRANSIT TIMES
  • ENVIRONMENTAL SYSTEMS
  • DYNAMICS
  • SPATIOTEMPORAL VARIABILITY
  • HYDROLOGY
  • STREAM WATER

ASJC Scopus subject areas

  • Water Science and Technology

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