Destouni, G and Jarsjo, J and Persson, K (2011) Diffuse hydrological mass transport through catchments: scenario analysis of coupled physical and biogeochemical uncertainty effects. On the colour and spin of epistemic error(and what we might do about it). Hydrology and Earth System Sciences..

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Abstract

This paper quantifies and maps the effects of cou- pled physical and biogeochemical variability on diffuse hy- drological mass transport through and from catchments. It further develops a scenario analysis approach and investi- gates its applicability for handling uncertainties about both physical and biogeochemical variability and their different possible cross-correlation. The approach enables identifi- cation of conservative assumptions, uncertainty ranges, as well as pollutant/nutrient release locations and situations for which further investigations are most needed in order to re- duce the most important uncertainty effects. The present scenario results provide different statistical and geographic distributions of advective travel times for diffuse hydrolog- ical mass transport. The geographic mapping can be used to identify potential hotspot areas with large mass loading to downstream surface and coastal waters, as well as their op- posite, potential lowest-impact areas within the catchment. Results for alternative travel time distributions show that ne- glect or underestimation of the physical advection variabil- ity, and in particular of those transport pathways with much shorter than average advective solute travel times, can lead to substantial underestimation of pollutant and nutrient loads to downstream surface and coastal waters. This is particu- larly true for relatively high catchment-characteristic prod- uct of average attenuation rate and average advective travel time, for which mass delivery would be near zero under as- sumed transport homogeneity but can be orders of magni- tude higher for variable transport conditions. A scenario of high advection variability, with a significant fraction of rel- atively short travel times, combined with a relevant average.

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