The effect of severe drought on the dissolved organic carbon (DOC) concentration and flux from British rivers

SummaryThe effect of severe drought on the biogeochemistry of dissolved organic carbon (DOC) production has been proposed as a possible explanation of the widespread observed increase in the flux and concentration of DOC in sub-boreal catchments across the northern hemisphere. It compares the pattern and extent of DOC increases to the pattern and extent of severe droughts. It also considers the effect of the two most severe droughts during the period of the available DOC records and includes DOC records from 97 sites. This study derives five different drought severity indices and compares these to the observed increase in DOC over the 4-year period after each severe drought. The results show no visual correlation between drought indices and trends in either DOC concentration or flux. Decreasing DOC fluxes and concentrations were observed in the areas that had experienced severe droughts, even in peat-covered catchments. Using analysis of variance (ANOVA) and multiple linear regressions, no consistent or significant pattern of DOC increase after severe drought could be distinguished. This study does not exclude a role for drought in causing the observed DOC increases, but it suggests that the role of drought in DOC is limited to some individual catchments or some peat-covered headwaters.