The water resources of Central Asia are formed primarily in mountainous regions, which account for more than 20% of the Aral Sea basin area (350,000 square kilometers). Approximately 90% of the region's surface runoff originates there, with an average annual water volume of about 115 billion cubic meters in a normal-water year. These resources are mainly concentrated within the two major river systems of the Amu Darya and the Syr Darya. Lakes are important sources of water resources, organic matter, and mineral raw materials. They are used for water supply, irrigation, livestock watering, and fisheries development. Some saline lakes contain valuable mineral resources of importance to the chemical, food-processing, and other industries, including sodium chloride, magnesium chloride, and sodium sulfate. In addition, most highly mineralized lakes contain large quantities of therapeutic mud (mineral mud) with significant value for health and spa treatment. Some lakes also possess considerable recreational value. Lakes are unique aquatic complexes and constitute one of the most important elements of natural landscapes. They differ from the surrounding terrestrial natural complexes. Tens of thousands of lakes of various sizes are distributed throughout Central Asia and northwestern China, occurring in both plains and mountainous areas. Central Asia contains more than 51,000 lakes with a total area of 14,571 square kilometers. These lakes are distributed across the basins of the Amu Darya, Syr Darya, Chu River, and Talas River, as well as in the Issyk-Kul region, the Eastern Pamirs, the Tianshan Mountains, and the endorheic areas of Turkmenistan. In the arid region of northwestern China, there are about 700 lakes, of which 29 have an area exceeding 10 square kilometers. Limnology is an independent interdisciplinary science concerned with continental water bodies characterized by slow water exchange, such as lakes, reservoirs, and ponds. It belongs to the field of geography. This comprehensive discipline studies the interactions among physical, chemical, and biological processes occurring within water bodies, as well as the history and evolution of lakes. At present, the comprehensive study of lakes is becoming increasingly important. An appropriate approach to this issue is the investigation of lakes in Central Asia and the arid regions of northwestern China. Due to intensified human impacts, Lop Nur has already dried up, and similar conditions have appeared in the Aral Sea basin. The basin has reached a critical stage and has become an area of environmental disaster. Rapid economic development requires the full utilization of all natural resources. The primary objective of this book is to conduct a comprehensive study of the development of lake systems and water bodies in the countries of Central Asia, as well as the impacts of climate change on water resources. The book provides information on the origins of lake basins, the physical and chemical properties of lake waters, and hydrological conditions, including water balance and water-level fluctuations, in Central Asia and the arid regions of northwestern China. Against the backdrop of climate change and sustainable development, research on lake systems is of great importance and necessity. Studying the potential effects of climate change on water resources is particularly relevant because the role of lakes in human life depends first and foremost on their vast reserves of freshwater. Lakes are highly sensitive to both climate change and human activities, as lake sediments serve as major indicators and records of climatic and anthropogenic influences. Furthermore, lakes are natural regulators of runoff and form the core of specially protected areas such as national parks and nature reserves of various categories. Under modern conditions, the significance of lakes has increased considerably because, despite continuing human pressures, they remain guardians of clean freshwater resources. This book is intended primarily for scientists and researchers engaged in lake studies, natural-resource utilization, irrigation, hydropower, and water supply, as well as for students and planners. We believe that our contribution to the study of lakes in Central Asia and the arid regions of northwestern China will serve as a valuable source of information and knowledge for all readers concerned with the sustainable utilization and development of natural resources such as lakes.