The use of the flashiness index as a possible indicator for nutrient loss prediction in agricultural catchments

A characterisation of the hydrological behaviour of four small agricultural catchments in Estonia and Norway was carried out using a flashiness index (FI). FI reflects the frequency and rapidity of short term changes in runoff values. A comparison of FIs based on hourly and average daily discharge indicated large within-day variations over very short time intervals. Large differences were observed between the Norwegian and Estonian catchments, irrespective of whether average daily discharge or hourly discharge values were used. A comparison of the FI and the base flow index (BFI) showed that high FI values corresponded to low BFI values. Norwegian catchments with high FI or low BFI values showed high nutrient losses, whereas the contrary was observed for the Estonian catchments. Although the FI does not a priori give information about the flow processes within catchments, we believe that the FI, as well as the BFI, might be helpful in explaining differences in nutrient and soil losses between catchments.