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DOI	10.5194/hess-22-635-2018
	Mean transit times in headwater catchments: Insights from the Otway Ranges; Australia
	Howcroft W.; Cartwright I.; Morgenstern U.
发表日期	2018
ISSN	1027-5606
起始页码	635
结束页码	653
卷号	22 期号:1
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. The long MTTs imply that there is a long-lived store of water in these catchments that can sustain the streams over drought periods lasting several years. However, the catchments are likely to be vulnerable to decadal changes in land use or climate. Additionally, there may be considerable delay in contaminants reaching the stream. An increase in nitrate and sulfate concentrations in several catchments at high streamflows may represent the input of contaminants through the shallow groundwater that contributes to streamflow during the wetter months. Poor correlations between 3H activities and catchment area, drainage density, land use, and average slope imply that the MTTs are not controlled by a single parameter but a variety of factors, including catchment geomorphology and the hydraulic properties of the soils and aquifers. © Author(s) 2018.
语种	英语
scopus关键词	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]
来源期刊	Hydrology and Earth System Sciences
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/160178
作者单位	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
推荐引用方式 GB/T 7714	Howcroft W.,Cartwright I.,Morgenstern U.. Mean transit times in headwater catchments: Insights from the Otway Ranges; Australia[J],2018,22(1).
APA	Howcroft W.,Cartwright I.,&Morgenstern U..(2018).Mean transit times in headwater catchments: Insights from the Otway Ranges; Australia.Hydrology and Earth System Sciences,22(1).
MLA	Howcroft W.,et al."Mean transit times in headwater catchments: Insights from the Otway Ranges; Australia".Hydrology and Earth System Sciences 22.1(2018).