Spatiotemporal decomposition of solute dispersion in watersheds
2015 (English)In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 51, no 4, 2377-2392 p.Article in journal (Refereed) Published
Information about the effect of different dispersion mechanisms on the solute response in watersheds is crucial for understanding the temporal dynamics of many water quality problems. However, to quantify these processes from stream water quality time series may be difficult because the governing mechanisms responsible for the concentration fluctuations span a wide range of temporal and spatial scales. In an attempt to address the quantification problem, we propose a novel methodology that includes a spectral decomposition of the watershed solute response using a distributed solute transport model for the network of transport pathways in surface and subsurface water. Closed form solutions of the transport problem in both the Laplace and Fourier domains are used to derive formal expressions of (i) the central temporal moments of a solute pulse response and (ii) the power spectral response of a solute concentration time series. By evaluating high-frequency hydrochemical data from the Upper Hafren Watershed, Wales, we linked the watershed dispersion mechanisms to the damping of the concentration fluctuations in different frequency intervals reflecting various environments responsible for the damping. The evaluation of the frequency-dependent model parameters indicate that the contribution of the different environments to the concentration fluctuations at the watershed effluent varies with period. For the longest periods (predominantly groundwater transport pathways) we found that the frequency typical transport time of chloride was 100 times longer and that sodium had a 2.5 times greater retardation factor compared with the shortest periods (predominantly shallow groundwater and surface water transport pathways).
Place, publisher, year, edition, pages
2015. Vol. 51, no 4, 2377-2392 p.
solute transport, watershed dispersion, transport network, modeling, spectral analysis, central temporal moments
Oceanography, Hydrology, Water Resources
Research subject Land and Water Resources Engineering
IdentifiersURN: urn:nbn:se:kth:diva-149531DOI: 10.1002/2014WR016385ISI: 000354733500029ScopusID: 2-s2.0-84929624256OAI: oai:DiVA.org:kth-149531DiVA: diva2:739896
QC 20150615. Updated from manuscript to article in journal.2014-08-222014-08-222015-06-15Bibliographically approved