The Hydrology of Switzerland Selected aspects and results M. Spreafi co and R. Weingartner Berichte des BWG, Serie Wasser – Rapports de l’OFEG, Série Eaux – Rapporti dell’UFAEG, Serie Acque – Reports of the FOWG, Water Series No. 7 – Berne 2005 Eidgenössisches Departement für Umwelt, Verkehr, Energie und Kommunikation Département fédéral de l’environnement, des transports, de l’énergie et de la communication Dipartamento federale dell’ambiente, dei trasporti, dell’energia e delle comunicazioni Federal Department of Environment, Transport, Energy and Communications The Hydrology of Switzerland Selected aspects and results M. Spreafi co and R. Weingartner Berichte des BWG, Serie Wasser – Rapports de l’OFEG, Série Eaux – Rapporti dell’UFAEG, Serie Acque – Reports of the FOWG, Water Series No. 7 – Berne 2005 With contributions from: M. Auer, Ch. Graf, A. Grasso, Ch. Hegg, A. Jakob, A. Kääb, Ch. Könitzer, Ch. Lehmann, R. Lukes, M. Maisch, R. Meister, F. Paul, T. Reist, B. Schädler, M. Spreafi co, J.-P. Tripet, R. Weingartner Editors Reviewers M. Spreafico, FOWG M. Barben, FOWG R. Weingartner, GIUB N. Bischof, SLF Ch. Bonnard, EPFL Coordinator A. Gautschi, Nagra N. Goldscheider, CHYN T. Reist, GIUB D. Grebner, IACETH J. Gurtz, IACETH Authors D. Hartmann, SAEFL F. Hauser, GIUB Chapter 1 Ch. Hegg, WSL M. Spreafico, FOWG; R. Weingartner, GIUB P. Heitzmann, FOWG T. Herold, FOWG Chapter 2 A. Jakob, FOWG T. Reist, GIUB; R. Weingartner, GIUB R. Kozel, FOWG Ch. Lehmann, H – W Chapter 3 Ch. Lienhard, MHNG M. Auer, SLF; A. Kääb, GIUZ; Ch. Könitzer, GIUB; M. Maisch, GIUZ; M. Maisch, GIUZ R. Meister, SLF; F. Paul, GIUZ Ch. Marty, SLF B. Meylan, SAEFL Chapter 4 P. Moeschler, MHNG T. Reist, GIUB; R. Weingartner, GIUB A. Pochon, CHYN B. Schädler, FOWG Chapter 5 M. Schürch, FOWG T. Reist, GIUB; M. Spreafico, FOWG D. Streit, FOWG L. Tacher, EPFL Chapter 6 S. Vogt, FOWG Ch. Könitzer, GIUB F. Vuataz, CHYN J. Wessels, SLF Chapter 7 J.-P. Tripet, Bevaix Abbreviations Chapter 8 SAEFL Swiss Agency for the Environment, Forests and Land- Ch. Graf, WSL; A. Grasso, FOWG; Ch. Hegg, WSL; A. Jakob, FOWG; scape, Ittigen-Berne Ch. Lehmann, H – W; M. Spreafico, FOWG FOWG Federal Office for Water and Geology, Ittigen-Berne CHYN Centre of Hydrogeology, University of Neuchâtel Chapter 9 EPFL Lausanne Federal Institute of Technology A. Jakob, FOWG; R. Lukes, FOWG ETHZ Zurich Federal Institute of Technology GIUB Geographical Institute, University of Berne Chapter 10 GIUZ Geographical Institute, University of Zurich T. Reist, GIUB; B. Schädler, FOWG; J.-P. Tripet, Bevaix; H – W Hydrologie – Wasserbau, Urtenen-Schönbühl R. Weingartner, GIUB IACETH Institute for Atmospheric and Climate Science, ETHZ MHNG Museum of Natural History, Geneva Translation Nagra National Cooperative for the Disposal of Radioactive Waste, Wettingen R. Bandi-Tebbutt SLF Swiss Federal Institute for Snow and Avalanche with contributions from M. Auer, A. Clifton, J.-P. Tripet and S. Zach Research, Davos WSL Swiss Federal Institute for Forest, Snow and Landscape Research, Birmensdorf Published by: Federal Office for Water and Geology Cover photo credits: top: Aletsch Glacier. S. Crameri, GIUB middle: River Aare. B. Sigrist, FOWG ISSN: 1660-0746 bottom: Bossy spring (canton of Neuchâtel). NAQUA, FOWG No. of copies: 500 Cover design: H.-P. Hauser, avd Suggested text Spreafico, M. & Weingartner, R. (2005): for quotations: The Hydrology of Switzerland – Selected Address for orders: BBL, Vertrieb Publikationen, CH-3003 Bern aspects and results, FOWG Reports, Water Order no. 804.507 e Series no. 7, Berne. Internet: www.bbl.admin.ch/bundespublikationen Cartographical data: © swisstopo (BA046528) Copyright: © FOWG, October 2005 2 Preface Water is Life Knowledge of the quality and quantity as well as the spatial and temporal aspects of surface and subterra- nean water reserves is essential for the sustainable, ecologically optimal and economically feasible exploita- tion of water as a resource. Obtaining this knowledge, namely through measuring discharge and reserves, as well as analysing and researching the processes that govern them, is the task of hydrologists. For more than 150 years this basic hydrological information has been provided in Switzerland by the Swiss National Hydro- logical Survey, which involves federal offices, cantonal authorities, research institutions and private business as well as individuals. The present publication covers selected aspects and results concerning current knowledge of surface water and groundwater in Switzerland. It focuses on the basic aspects of hydrology in Switzerland and provides an easy-to-read overview. It is a monograph drawn up by several scientists under the guidance of the Swiss National Hydrological Survey and the Hydrology Group of the Geographical Institute at the University of Berne. It is aimed at the general public, for which reason not every scientific detail is explained. I should like to thank everyone who has helped to pro- duce this work. Federal Office for Water and Geology The Director Dr Ch. Furrer 3 4 Contents Preface ....................................................3 3.7 Glaciers ....................................................... 37 3.7.1 Measuring networks.................................... 37 Contents .................................................5 3.7.2 Methods of investigation............................. 37 3.7.3 Glacial processes ......................................... 38 1 Introduction............................................7 3.7.4 Results......................................................... 39 3.7.5 Glaciers as water reservoirs.......................... 40 2 Precipitation............................................9 2.1 Measuring precipitation.................................9 4 Evaporation .......................................... 41 2.1.1 Development of the measuring networks.......9 4.1 Evaporation – The Earth’s natural cooling 2.1.2 Precipitation measuring networks operated system......................................................... 41 by MeteoSwiss...............................................9 4.1.1 Energy balance............................................ 41 2.1.3 Measuring apparatus and errors ..................11 4.1.2 Evaporation – Evapotranspiration ................ 41 2.2 From a point to an area ...............................12 4.1.3 Potential and actual evaporation ................. 42 2.2.1 Reduction factors.........................................12 4.2 Measuring evaporation................................ 42 2.2.2 Interpolation................................................13 4.2.1 Measuring potential evaporation................. 42 2.2.3 Water balance method ................................14 4.2.2 Measuring actual evaporation ..................... 43 2.2.4 Precipitation maps .......................................14 4.3 Calculating evaporation............................... 43 2.3 Precipitation conditions ...............................15 4.3.1 Calculating potential evaporation ................ 43 2.3.1 Annual precipitation ....................................15 4.3.2 Calculating actual evaporation .................... 44 2.3.2 Seasonal precipitation pattern .....................17 4.4 Evaporation conditions................................ 44 2.4 Extreme values.............................................18 4.4.1 Annual evaporation..................................... 44 2.4.1 Heavy precipitation ......................................18 4.4.2 Seasonal variation in evaporation ................ 46 2.4.2 Drought.......................................................19 4.4.3 Trend over the 20th century ......................... 46 2.5 Detailed aspects...........................................20 2.5.1 Net precipitation..........................................20 5 Discharge.............................................. 47 2.5.2 Condensation from fog................................20 5.1 Discharge measurement .............................. 47 2.5.3 Hail..............................................................21 5.1.1 Water levels and discharge .......................... 47 2.6 Precipitation: Switzerland – Europe – 5.1.2 Measuring the water level ........................... 47 Worldwide...................................................22 5.1.3 Measuring discharge ................................... 49 2.7 Trends and prospects...................................23 5.1.4 Measuring stations...................................... 50 5.1.5 Measuring networks.................................... 52 3 Snow and ice ........................................25 5.1.6 Measurement error...................................... 52 3.1 The significance of snow..............................25 5.2 Estimating discharge ................................... 54 3.2 The development of measuring networks ....25 5.2.1 Estimating long-term mean monthly 3.3 Basic conditions for collecting snow data.....26 discharge .................................................... 54 3.3.1 The basic station – time – parameter 5.2.2 Estimating flood discharge .......................... 54 triangle........................................................26 5.2.3 Estimating low-water discharge................... 57 3.3.2 Measuring instruments and methods...........28 5.3 Discharge conditions in Switzerland ............ 59 3.4 Models ........................................................30 5.3.1 Annual discharge ........................................ 59 3.4.1 SNOWPACK – A snow-cover model..............30 5.3.2 Seasonal variation in