Table 1 Geology of the four regional catchments (Fig. 1)

Mellichbach

Mainly in the ZS ophiolite nappe, 6 km at NE of Zermatt

55% of watershed area of 25 km² is covered by several glaciers

Leiterspitzen, Kinhorn, Täschhorn, Alphubel, Allalinhorn, Rimpfischorn, Pfulwe

From 2200 m at Mellichbach to 4490 m Täschhorn

Spread several streams joining the main river Mellichbach

Eclogite, blueschist, serpentinite

Rotbach subcatchment: paragneiss

Findelbach

ZSO on the N side; Monte Rosa on the S side, 6–11 km east of Zermatt

40% of watershed area of 37 km² is covered by Findelngletscher and other glaciers

Oberrothorn, Adlerhorn, Schwarzberghorn, Cima di Jazzi, Stockhorn and Gornergrat

From 2000 m at Findelnbach to 3803 m Cima di Jazzi

Spread small lakes and streams; one main river Findelbach

N side: metabasalt, serpentinite, calcareous micaschist, marbles,

S side: granite, gneiss,

Trockener Steg

Mainly ZSO, 5 km at SW of Zermatt

50% of watershed area of 18 km² is covered by Theodulgletscher

Hirli, Matterhorn, Furgghorn, Theodulhorn

From 2200 m at Furggbach to 4477 m Matterhorn

Spread small lakes; one stream, Furggbach

E side: serpentinite

W side: metabasalt, micaschist, marbles

Gornera

Monte Rosa and ZSO, 5 km south of Zermatt

80% of watershed area of 82 km² is covered by several glaciers which are tributary to Gornergletscher

Breithorn, Liskamm, Dufourspitze, Cima di Jazzi, Gornergrat

From 2005 m at the Gornera water intake to 4634 m Dufourspitze

Spread small streams; only one river, the Gornera

Granite, gneiss in MR nappe, serpentinite (Breithorn), metabasalt, calcareous micaschist and marble in lower part