Testing a conceptual model of conservative tracer transport in a watershed

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Date
2015-05-08
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Johns Hopkins University
Abstract
Rain falls on a catchment, infiltrates into soils and mix with subsurface water, and finally becomes stream water. We could observe the rain and the infiltration. However, we can't directly observe how water flows through catchment or measure the water storage. What happens underground has been studied for decades but is still not well understand. Different models have been are proposed for flow paths, runoff generation and water history underground. This study explore theory exploration and data analysis for water age history, flow generation and stream chemistry. Transit time distribution have been used to predict natural tracers concentration in the stream. Catchment sensitivity functions provide a mode of how discharge response to water storage in a catchment. A way to combine catchment sensitivity function with transit time distribution is examined here. The combination of these two theories is used to predict stream chloride concentration with precipitation, discharge and water quality series. The data used were collected or measured at the Upper Hafren Catchment at Plynlimon, Wales. The data series includes long-term weekly and short-term 7hourly water quality along with other regular hydrology data. However, the prediction of the combination doesn't work so well, indicating combining catchment sensitivity function with transit time distribution in this naive way is not conform to reality.
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Keywords
sensitivity function, transit time distribution, stream natural tracer
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