Introduction Climate and Hydrology in Mountain Areas

Undoubtedly, the mountain regions of our world are the main hydrological and climatological triggers or pertubators of the water cycle as well as of complex meteorological patterns including phenomena such as the production or inhibition of rainfall. In terms of their role as water towers, mountain regions form an important supply of snow and/or rain-fed water to the lowlands. In terms of climate, mountain systems develop a considerably complex system of their own, influenced by the often characteristically narrow, deeply incised valleys. It is rare though, to find comprehensive work that combines both the hydrological and climatological aspects of mountain catchments. The purpose of this book is therefore to bring together a very diverse group of scientists from all over the world to present their multidisciplinary research in contrasting mountain environments. This effort was developed by Carmen de Jong in cooperation with Roberto Ranzi and David Collins during the International Year of the Mountains 2002 and is based on cross-disciplinary mountain sessions at EGS/EGU meetings, a diverse team of supportive meeting participants and invited scientists. The ultimate goal was, firstly, to provide a platform for discussion amongst highly motivated and trendsetting mountain groups from different origins and secondly, to combine two hitherto separately treated subject matters - that of hydrology and climatology in mountain areas. Although hydrology and climatology appertain to two separate disciplines, it is important to acknowledge the fact that in nature they are inseparable and that enough crosscutting areas exist that cannot ignore their mutuality. It is not always easy to bring together the different disciplines, but as long as scientists are cooperating strongly in the way observed in this group of authors, such endeavours are possible.

This book covers a wide range of mountain chains including the Alps, Black Forest, Himalayas, Tien Shan, Giant mountains, Norwegian mountains, Laurentian highlands, Appalachian mountains, Rockies, Andes, and

Cascade mountains (see Figure 1). From the distribution of study areas covered, it is obvious that several African mountain ranges and other mountains of the southern hemisphere are missing in this volume. It is hoped to incorporate these in future editions.

The graph below (Figure 2) illustrates the correlation between study-area size and elevation. There is a clear lack of studies carried out in the higher altitudes and only six study sites have an average catchment elevation above 4000 m. Amongst these, all except one have catchment areas below 100 km2. In future, it may be favourable to concentrate research on larger catchments at higher altitudes.

The book is divided essentially into five parts: (1) snow and ice melt, (2) soil water and permafrost, (3) evapotranspiration and water balance, (4) coupling meteorology and hydrology, and (5) climate change impact and mountain hydrology.

Roger Barry introduces the book with a review on alpine climate change and cryospheric responses. In the first section, Rijan Kayastha and his co-authors deal with methods for calculating snow and ice melt in the Himalayas and Pratap Singh and Lars Bengtsson assess methods for interpolation and extrapolation of snow-covered areas using air temperatures in the same region. In contrast, Javier Corripio and Ross Purves introduce a particularly intriguing study on snow and ice penitentes in the central Andes. Uli Strasser then shows how sub-grid parameterization and a forest canopy model can serve to improve snowmelt runoff modelling in the humid, French Alps.

In the second section, Christain Hauck and his coauthors present a coupled geophysical and meteorological approach for monitoring permafrost in the Swiss Alps, while Daniel Bayard and Manfred Stahli monitor the effects of frozen soil on groundwater recharge in the same mountain ranges. A study on the water balance in surface soil is presented by Marilena Menziani and her

Cascade Mountains (11)

Laurentian Highlands (15)

[3 Appalachian Mountains (20)

4 Chilean Andes (3)

[5 Alps

French Alps (4) N. Swiss Alps (6,10,12,17,19) S. Swiss Alps (7) Italien Alps (8,9,14) Austrian Alps (17,19)

[7 Giant Mountains (12) [8 Oppland Mountains (13)

Himalaya

West Himalayas (India) (5) Nepalese Himalayas (2)

101 Tien Shan, Pamir (18)

Figure 1 Location of catchments and experimental sites presented in this book. Chapter numbers associated with mountain ranges are indicated in brackets

8000 7000 6000 5000 4000

2000 1000 0

Figure 1 Location of catchments and experimental sites presented in this book. Chapter numbers associated with mountain ranges are indicated in brackets

8000 7000 6000 5000 4000

2000 1000 0

10,000

100,000

100 1000 Catchment area (km2)

Figure 2 Relation between catchment size and mean catchment altitude for the study sites presented in this volume co-authors with a combined analytical and measurement approach for an alpine valley in Italy, whereas Stefano Barontini and his co-authors describe saturated hydraulic conductivity and water retention relationships for mountain soils in the same mountain chain.

Gerald Eder introduces the third section with a relatively new approach of water balance modelling using fuzzy parameterization in the Austrian Alps. There is a jump then to Cascade mountains in Washington, USA, where Timothy Link and his co-authors monitor the water relations in an intensively instrumentized old growth douglas fir stand. This is followed by another field-based study by Carmen de Jong and her co-authors, where measurements of condensation and evapotranspiration are compared for the Giant Mountains in Poland and the Swiss Alps. Jorg Löffler and Ole Roßler describe an integrated approach for measuring and modelling the hydrology and ecology of mountain basins in Central Norway.

The fourth section is introduced by an overview from Baldassare Bacchi and Vigilio Villi on runoff and floods in the Alps, emphasizing precipitation and runoff formation in addition to flood frequency analysis. In this section, Charles Lin and his co-authors use an interesting coupled meteorological and hydrological modelling approach based on geomorphological principals for flood simulation in the mountainous Sageunay basin in eastern Canada. Stefan Uhlenbrook and Doerthe Tetzlaff assess convective precipitation using operational weather radar as a tool for flood modelling in the Black Forest, Germany. Geomorphological zoning as a tool for improving the coupling of hydrology and meteorology is proposed by Carmen de Jong and her co-authors for the Austrian and Swiss Alps.

In the final section, Wilfried Hagg and Ludwig Braun analyse the influence of glacier retreat on water yield in the high mountain basins of the Alps and Tien Shan. Staying in the Swiss Alps, Franziska Keller and Stephane Goyette model snowmelt under different climate change scenarios. Finally, Osman Yildiz and Ana Barros model water and energy budgets in the Appalachian mountains under climate variability and hydrological extremes.

In summary, it can be said that the studies integrate an interesting combination of field-based and modelling approaches, with several studies concentrating on the coupling ofhydrology and meteorology. The large variety of approaches necessary for well-to-low-instrumented catchments are highlighted and with this comes a general appeal for more long-term monitoring programmes and field-based studies to validate model results. Since mountain regions are remote and difficult environments, a good field-based approach cannot be taken for granted. Thus, the sophistication of field and remote-sensing techniques should keep in pace with the development of modelling concepts, in particular for mountain ranges in developing countries and in arid environments.

Although this comprehensive book has seen a long way from its conception to its production, it is important to state that all chapters were sent to two international reviewers that, with few exceptions, were not authors of the book. We are very grateful to the many hours invested by these voluntary reviewers. It can be imagined that this was not always easy since the subject area is not that widespread.

Our particular thanks go to Martina Knop and Heike Kemmerling of the Geography Department of the University of Bonn for their invaluable administrative support as well as to Martin Gref for his cartographic help and to the family of Carmen de Jong for supporting the long extra hours involved with the reviewing and editing this book. Stefan Taschner of the Department of Civil Engineering at the University of Brescia and Keily Larkins from Wiley are acknowledged for their help in the editorial process.

Carmen de Jong Roberto Ranzi David Collins

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