Modeling Chlorophyll a with Use of the SWAT Tool for the Nielba River (West-Central Poland) as an Example of an Unmonitored Watercourse

The majority of eutrophication studies focuses on lacustrine processes, thus riverine systems remain less recognized in this context. Moreover, since the availability of data related to parameters affecting this phenomenon is quite limited, modeling efforts should be considered. The current study verifies the SWAT model’s capability to simulate chlorophyll a loads for unmonitored watercourse. The analyses of the relationships between individual parameters, directly involved in the eutrophication process, help in the exploration of its dominant trends in SWAT modeling. The results obtained for the Nielba River pilot catchment (west-central Poland) showed a strong correlation of chlorophyll a with flow and surface runoff, but no relationship with temperature or solar radiation. Moreover, an impact of local conditions (hydrological features) on chlorophyll a load simulation could be traced in detail. The research specified the limitations and impact of generalization in the SWAT model on the results. Furthermore, intricacies related to the dataset statistical treatment (e.g., outliers) have been presented.