The Zwalm catchment, a subcatchment of the the Schelde River basin, is situated in the province of East-Flanders, Belgium at approximately 50.84oN and 3.78o E, (see Figure) with the outlet of the basin south of Gent near the village Nederzwalm.
The Sassegem subcatchment, with a drainage area of 2.49km2 and a total channel length of 2.92km, is situated in the extreme south of the Zwalm catchment.
The stations are (see Table 1): 100 (located in the middle of the catchment), 104 (in the Passemere), 105 (between the Peerdestok and the Zwalm in the northern part), 106 (in the central-eastern part) and 107 (in the southwestern part).