Detection of dominant nitrate processes in ecohydrological modeling with temporal parameter sensitivity analysis

•First application of temporal dynamics of parameter sensitivity for nitrate.•High temporal variations in dominance of modeled nitrate parameters and processes.•Temporal variation is related to nitrate transport and plant uptake processes.•Dominant parameters are combined with modeled runoff components and nitrate pathways.•Improved understanding of nitrate process dynamic in model and reality.

River systems are impacted by nutrient inputs from the landscape. The transport of nitrate from agricultural areas into the river systems is related to numerous processes, which occur simultaneously and influence each other permanently. Ecohydrological models aim to represent these complex nitrate processes. For reliable model results, it is essential to better understand the nitrate process dynamics in models.This study aims to improve the understanding of nitrate process dynamics by using a temporal diagnostic model analysis. As diagnostic tool, a temporal parameter sensitivity analysis is applied on an ecohydrological model. With this method, phases of dominant model parameters are detected.The results show that the sensitivity of different nitrate parameters varies temporally. These temporal dynamics in dominant parameters can be explained by temporal variations in nitrate transport and plant uptake processes. A better view on the dynamics of the temporal parameter sensitivity is obtained by analyzing different modeled runoff components and nitrate pathways. Thus, a temporal parameter sensitivity analysis assists the interpretation of seasonal variations in dominant nitrate pathways.