Thus it is clear that there is a greater contribution of nitrate load from the headwaters of the Thur and Necker in SC2 compared to SC1, accompanied by a nitrate concentration increase in the upper Thur (at T1 and T2) as discussed in Section 4.1 (Table 2, Fig. 6). This is attributed to manure application in spring leading to leaching of nitrate from soil especially during rains in addition to direct contribution from precipitation. Although the headwaters of the Thur and Necker have low population density owing to less urban areas, there is substantial agriculture and pasture land in this area as shown in Fig. 1.