Separating physical and meteorological controls of variable transit times in zero-order catchments

Ingo Heidbüchel, Peter A. Troch, Steve W. Lyon

Research output: Contribution to journalArticle

65 Scopus citations

Abstract

We observed water fluxes and isotopic compositions within the subsurface of six small nested zero-order catchments over the course of three North American monsoon seasons and found that mean transit times (mTTs) were variable between seasons and different spatial patterns of mTTs emerged each year. For each monsoon season, it was possible to correlate mTTs with a different physical catchment property. In 2007, mTTs correlated best with mean soil depth, in 2008 soil hydraulic conductivity gained importance in explaining the variability and in 2009 planform curvature showed the best correlation. Differences in meteorological forcing between the three monsoon seasons explained the temporal variability of mTTs. In 2007, a series of precipitation events caused the storage capacity of the soils of some of the zero-order catchments to be exceeded. As a result those catchments started producing quick runoff (overland and macropore flow). In 2008, precipitation events were more evenly distributed throughout the season, soils did not saturate, runoff coefficients decreased because more water left the catchment via evapotranspiration and soil hydraulic conductivity became a stronger control since matrix flow dominated. The 2009 monsoon was unusually dry, the soil storage became depleted and water flowed mainly through bedrock pathways. Therefore, topographic parameters gained importance in determining how quickly water arrived at the catchment outlet. In order to improve our understanding of what controls mTTs we suggest a dimensionless number that helps identifying partitioning thresholds and sorts precipitation events into one of the three response modes that were observed in our zero-order catchments. Key Points Inherent catchment properties and external forcings control transit times External forcings sort precipitation events into specific response domains Inherent catchment properties control transit times within these domains

Original languageEnglish (US)
Pages (from-to)7644-7657
Number of pages14
JournalWater Resources Research
Volume49
Issue number11
DOIs
StatePublished - Nov 1 2013

Keywords

  • flow paths
  • hydrologic catchment response
  • meteorological controls
  • physical controls
  • storage state
  • transit time

ASJC Scopus subject areas

  • Water Science and Technology

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