Nutrient mass balance at the catchment scale

The objective of the “Nutrient mass balance at the catchment scale” work package is be to calculate a N and a P mass balance at the watershed scale for the Adda and the Ticino river basins, and to identify the main sources that generate the nutrient surplus. The comparison of this excess with the nutrient loads exported by rivers at the basin closing section will permit to quantify the amounts retained in the basin (by biotic or physical processes) permanently or temporarily (e.g. storage in groundwater).

(Photo credits: M. Bartoli)

This calculation consent to estimate the balance between all the potential sources and sinks of N and P within the agricultural surface of a river basin and provides an immediate evaluation of the risk of water pollution/eutrophication. As the data are collected at the municipality level, the spatial resolution of the calculation is high, allowing site-specific insights and remedial actions. Nutrient mass balances will be calculated in two river watersheds, one of which (the Adda river) is the fourth in length among the Italian rivers. In addition, the Ticino and the Adda rivers are the second and third contributors to the Po river in terms of discharge. The comparison with the results available for the Oglio river will provide a detailed picture of the nutrient contamination of groundwater across multiple gradients of fertilization, land use, soil type, denitrification potential, irrigation, nutrient surplus and export. Finally, the assessment of the P budget including groundwater as a potential sink is a remarkable novelty.