<p>This book is dedicated to the International Year of Mountains and the 120th anniversary of the birth of Karamordo Orozov. In recent years, Kyrgyzstan has paid increasing attention to formulating plans for the protection and rational use of natural resources, including water resources. These plans take into account the interests of various areas of the national economy, such as industry, agriculture, public and domestic water supply, hydropower, etc. However, specific information and knowledge needed for regional planning and rational natural use are still lacking, especially when studying large-scale projects. Hydrological and ecological problems are far from being solved. We believe the reason is that traditionally the main focus has been on growing season runoff. This work is dedicated to analyzing the formation conditions of runoff during the dry season and the spatial distribution of the minimum runoff probability of rivers in Kyrgyzstan. Existing and new methods for determining the basic calculation characteristics of minimum runoff are described. These methods can reliably determine the parameters required for rivers that lack or do not fully have hydrological observation data. Considering the importance of the research issues, this work analyzes the current situation of water resources utilization during the dry season and the prospect of using hydrological characteristics to fill reservoirs. Hydrological characteristics with different assurance rates are given for all studied rivers, which are necessary for water-users throughout the year (especially for the uninterrupted operation of ecologically safe small hydropower stations). </p>