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Article (Scientific journals)
How long should we measure? An exploration of factors controlling the inter-annual variation of catchment sediment yield
Vanmaercke, Matthias  ; Poesen, J.; Radoane, M. et al.
2012 • In Journal of Soils and Sediments, 12 (4), p. 603-619
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Keywords :
Measuring period; Monte Carlo simulations; Runoff; Scale dependency; Temporal variability; Uncertainty; Monte Carlo analysis; Romania
Abstract :
[en] Purpose: Although it is well-known that catchment suspended sediment yields (SY; tons per square kilometre per year) can vary significantly from year to year, little information exists on the magnitude and factors controlling this variability. This is crucial to assess the reliability of average SY values for a given measuring period (MP) and is of great geomorphic significance. This paper aims to bridge this research gap. Materials and methods: A worldwide database was compiled with time series of measured SY values. Data from 726 rivers (mostly located in Europe, the Middle East and the USA) were collected, covering 15,025 annual SY observations. The MPs ranged between 7 and 58 years, while catchment areas (A) ranged between 0.07 and 1.84 × 106 km2. For 558 catchments, the annual runoff depths corresponding to the SY observations were also available. Based on this database, inter-annual variability was assessed for each catchment, and relationships with factors potentially explaining this variability were explored. Results and discussion: Coefficients of variation of SY varied between 6% and 313% (median 75%). Annual SY data were generally not normally distributed but positively skewed. Inter-annual variability generally increased with increasing average SY. No significant relationship was found between the inter-annual variability of SY and A, while weak but significant relationships were noted with the variability in annual runoff and rainfall depths. Detailed analyses of a sub-dataset corresponding to 63 catchments in Romania revealed no clear relationships between inter-annual variability of SY and land-use or topographic characteristics. Nevertheless, indications were found that variability was larger for catchments with erosion-prone land-use conditions. Using a Monte Carlo simulation approach, the effect of inter-annual variability on the reliability of average SY data was assessed. Results indicate that uncertainties are very large when the MP is short, with median relative errors ranging between -60% and 83% after 5 years of monitoring. Furthermore, average SY values based on short MPs have a large probability to underestimate, rather than to overestimate, the long-term mean. For instance, the SY value of a median catchment after a 1-year MP has a 50% probability of underestimating the long-term mean by about 22%. Uncertainties quickly decrease after the first few years of measurement but can remain considerable, even after 50 years of monitoring. Conclusions: It is important to consider uncertainties associated with average SY values due to inter-annual variability, for example when attempting to predict long-term average SY values using a steady-state model, as such uncertainties put fundamental limits to the predictive capabilities of such models. © 2012 Springer-Verlag.
Disciplines :
Earth sciences & physical geography
Author, co-author :
Vanmaercke, Matthias ;  Université de Liège > Département de géographie > Géographie physique et du quaternaire
Poesen, J.;  Department of Earth and Environmental Sciences, K.U. Leuven, Celestijnenlaan 200 E, 3001 Heverlee, Belgium
Radoane, M.;  University of Suceava, Suceava, Romania
Govers, G.;  Department of Earth and Environmental Sciences, K.U. Leuven, Celestijnenlaan 200 E, 3001 Heverlee, Belgium
Ocakoglu, F.;  Department of Geological Engineering, Eskisehir Osmangazi University, Eskisehir, Turkey
Arabkhedri, M.;  Soil Conservation and Watershed Management Research Institute, Tehran, Iran
Language :
English
Title :
How long should we measure? An exploration of factors controlling the inter-annual variation of catchment sediment yield
Publication date :
2012
Journal title :
Journal of Soils and Sediments
ISSN :
1439-0108
eISSN :
1614-7480
Publisher :
Springer
Volume :
12
Issue :
4
Pages :
603-619
Peer reviewed :
Peer Reviewed verified by ORBi

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