The characteristics of climate and hydrology in mountain areas remain poorly understood relative to lowland areas. High spacial and temporal variability in precipitation, runoff and subsurface flow processes, and stream flow, as well as sparse instrumentation networks and limited historical records of climate and hydrology, contribute to limited understanding of the distribution and movement of water in mountain environments. As the editors of this volume note, mountain regions play an extremely important role as "water towers" to the world, perturbing climatic circulation patterns and storing water for gradual release to adjacent lowlands. The papers collected in this book make an important contribution to advancing the understanding of climate and hydrology in mountain areas because they present pioneering work that, in many cases, represents the first application of existing measurement techniques to mountain regions. These applications demonstrate the utility and limitations of existing techniques in mountain areas, at the same time providing detailed information about the specific regions to which they are applied.