According to our findings, the concentration pattern of nutrients in the river Kleine Aa depends on the relative contribution of the four components "ground water", "interflow" (including water from drainage pipe systems), "discharge from impermeable surfaces" and "surface runoff from soils" to the total discharge. It is further modified by seasonal effects, likely due to varying frequencies of manure application throughout the seasons. The loss of PO4 from the soil to the water exceeds the tolerable PO4 load of the receiving Lake Sempach by 20 to 60 %. In order to lower the P load of the lake, the content of the soil in mobile P has to decrease. This can be achieved by transiently spreading less manure (< 2,3 cattle equivalents / ha yr) or by decreasing the mobility of P by other measures.