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Comparison of variability of particulate (SS, POC) and dissolved (DOC) matter during flood events in two catchments (Basque Country, Northern Spain)

Jon García-García1, Estilita Ruiz-Romera1, Miren Martínez-Santos1, Borja Muñoz-Leoz1, Eider Unamuno1
1 University of Basque Country (UPV/EHU)

P 7.8 in Controls of dissolved organic matter fluxes in ecosystems

Poster Session 1 on Monday, 16:30-18:30

This study was conducted in two catchment of Basque Country, Northern Spain. Oka river catchment is an agro-forestry catchment, and Deba river catchment is an urban and industrial catchment. The aim of the work is to compare the behaviour of Dissolved Organic Carbon (DOC) and Particulate Organic Carbon (POC) in flood events during the hydrological year 2011 – 2012. For this purpose, is necessary (i) to determine the relationship between precipitation, discharge, suspended sediment (SS) and organic carbon yield during flood events for the hydrological year (2011-2012), (ii) to quantify the specific suspended sediment and organic carbon yield, (iii) to study the variability of CQ hysteresis for SS, POC and DOC.

The total export of SS, DOC and POC are 61.86, 3.46 and 1.58 t km-2 year-1, respectively, in Oka catchment, whereas in Deba catchment are higher, 105, 4.6 and 6.2 t km-2 year-1, respectively. Hysteresis behaviour gives information about the source of DOC and POC. Butturini´s methodology is based on the use of two descriptive biogeochemical parameters that synthesizes changes in the solute concentration (∆C) and the general dynamic for each hysteresis loop C-Q (∆R) (Butturini et al., 2006). In the Oka catchment, loops are considered nonlinear which indicate an increase in the SS in the ascending limb of hydrograph. This means that suspended solids arrive prior to discharge peak; corresponding to material sources near the catchment area. In the Deba catchment however, in all cases an increase is observed in the concentration of suspended solids during the descending limb of the hydrograph and anti-clockwise loops mean that the material arrives later than the flow, corresponding to sediment sources far from the catchment. Analyzing the POC in the case of the Oka catchment, does not follow the same trend as the SS above. Clockwise and anti-clockwise loops are shown for different flood events. For Deba catchment, however, the POC follow the same trend as the SS, indicating an increase in the POC during the descending limb of the hydrograph (anti-clockwise loops). Thus, the particulate material arrives later than the discharge peak corresponding to material sources that are far from the catchment. Regarding the DOC, in the case of the Oka catchment, clockwise and anti-clockwise loops are shown. In most cases, clockwise loops correspond to the first parts of the flood event (DOC ​​sources are near to the catchment zone) being anticlockwise second parts (material sources are far from the catchment zone). In the case of the DOC for Deba catchment, again the same trend is repeated as in the cases of SS and POC.

Letzte Änderung 04.04.2014