Aquifers
; Flow of water
; Groundwater
; Groundwater geochemistry
; Groundwater pollution
; Groundwater resources
; Hydrogeology
; Land use
; Rain
; Rivers
; Runoff
; Stream flow
; Sulfur compounds
; Water resources
; Headwater catchment
; Hydraulic properties
; Lumped parameter models
; Major ion geochemistries
; Mean transit time
; Shallow groundwater
; South-eastern Australia
; Sulfate concentrations
; Catchments
; catchment
; concentration (composition)
; drainage basin
; drainage network
; headwater
; hydrogeochemistry
; rainfall
; streamflow
; sulfate
; tritium
; water quality
; Australia
; Otway Range
; Victoria [Australia]
英文摘要:
Understanding the timescales of water flow through catchments and the sources of stream water at different flow conditions is critical for understanding catchment behaviour and managing water resources. Here, tritium (3H) activities, major ion geochemistry and streamflow data were used in conjunction with lumped parameter models (LPMs) to investigate mean transit times (MTTs) and the stores of water in six headwater catchments in the Otway Ranges of southeastern Australia. 3H activities of stream water ranged from 0.20 to 2.14TU, which are significantly lower than the annual average 3H activity of modern local rainfall, which is between 2.4 and 3.2TU. The 3H activities of the stream water are lowest during low summer flows and increase with increasing streamflow. The concentrations of most major ions vary little with streamflow, which together with the low 3H activities imply that there is no significant direct input of recent rainfall at the streamflows sampled in this study. Instead, shallow younger water stores in the soils and regolith are most likely mobilised during the wetter months.
MTTs vary from approximately 7 to 230 years. Despite uncertainties of several years in the MTTs that arise from having to assume an appropriate LPM, macroscopic mixing, and uncertainties in the 3H activities of rainfall, the conclusion that they range from years to decades is robust. Additionally, the relative differences in MTTs at different streamflows in the same catchment are estimated with more certainty. The MTTs in these and similar headwater catchments in southeastern Australia are longer than in many catchments globally. These differences may reflect the relatively low rainfall and high evapotranspiration rates in southeastern Australia compared with headwater catchments elsewhere.
Howcroft, W., School of Earth, Atmosphere and Environment, Monash University, 9 Rainforest Walk, Clayton, VIC 3800, Australia; Cartwright, I., School of Earth, Atmosphere and Environment, Monash University, 9 Rainforest Walk, Clayton, VIC 3800, Australia, National Centre for Groundwater Research and Training, Flinders University, G.P.O. Box 2100, Adelaide, SA 5001, Australia; Morgenstern, U., GNS Science, 1 Fairway Drive, Avalon, P.O. Box 368, Lower Hutt, 5040, New Zealand
Recommended Citation:
Howcroft W.,Cartwright I.,Morgenstern U.. Mean transit times in headwater catchments: Insights from the Otway Ranges; Australia[J]. Hydrology and Earth System Sciences,2018-01-01,22(1)