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Modeling chloride transport using travel time distributions at Plynlimon, Wales
Author(s) -
Benettin Paolo,
Kirchner James W.,
Rinaldo Andrea,
Botter Gianluca
Publication year - 2015
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1002/2014wr016600
Subject(s) - environmental science , hydrology (agriculture) , tracer , range (aeronautics) , chloride , deposition (geology) , drainage basin , dispersion (optics) , sampling (signal processing) , residual , water quality , scale (ratio) , geology , mathematics , chemistry , computer science , geography , physics , geomorphology , algorithm , structural basin , materials science , geotechnical engineering , filter (signal processing) , ecology , optics , composite material , biology , nuclear physics , computer vision , cartography , organic chemistry
Here we present a theoretical interpretation of high‐frequency, high‐quality tracer time series from the Hafren catchment at Plynlimon in mid‐Wales. We make use of the formulation of transport by travel time distributions to model chloride transport originating from atmospheric deposition and compute catchment‐scale travel time distributions. The relevance of the approach lies in the explanatory power of the chosen tools, particularly to highlight hydrologic processes otherwise clouded by the integrated nature of the measured outflux signal. The analysis reveals the key role of residual storages that are poorly visible in the hydrological response, but are shown to strongly affect water quality dynamics. A significant accuracy in reproducing data is shown by our calibrated model. A detailed representation of catchment‐scale travel time distributions has been derived, including the time evolution of the overall dispersion processes (which can be expressed in terms of time‐varying storage sampling functions). Mean computed travel times span a broad range of values (from 80 to 800 days) depending on the catchment state. Results also suggest that, in the average, discharge waters are younger than storage water. The model proves able to capture high‐frequency fluctuations in the measured chloride concentrations, which are broadly explained by the sharp transition between groundwaters and faster flows originating from topsoil layers.