The article presents an overview of the main hydrological and water management tasks and problems that have arisen in recent decades on the Lower Volga because of the construction and operation of the VolgaKama cascade of reservoirs, anthropogenic changes in runoff as a result of economic activity, and the consequences of poorly predictable climatic changes. It is shown that the hydrological regime in the lower reaches of the Volga River has undergone significant changes, both as a result of regulation of runoff by reservoirs and due to climatic changes. The observed changes in f low f luctuations have led to serious changes in the aquatic environment and the entire ecosystem of the river. A number of negative consequences were predicted during the development of reservoir cascade projects, and the construction and operation processes were accompanied by the implementation of a set of compensatory measures of a fisheries’ nature. Nevertheless, the functioning of a complex water management system and insufficient attention to environmental problems led to the emergence of new environmental, technical, and scientific problems that required an integrated approach for their solution, and the effectiveness of the planned measures turned out to be insufficient. The study of the consequences of seasonal regulation of runoff by reservoirs, changes in the estimates of water resources, the involvement of new methods of studying the hydrological system, including multi-arm channels, and the analysis of anthropogenic-altered river sections allowed to obtain new results but at the same time to formulate a block of unresolved scientific problems. Among such problems, there is a need to solve such engineering and hydrological tasks as increasing the feasibility of forecasts of inf low to reservoirs, long-term forecasting of long-term f luctuations in runoff under conditions of ongoing climate change, obtaining up-to-date estimates of negative processes—deformation of riverbeds under anthropogenic impact. The latter is very important for the downstream of the Volgograd Hydroelectric Power Station. In terms of predicting the behavior of the ecosystems of the Lower Volga, with an assessment of their stability, further development of methods for assessing permissible impacts, the development of monitoring systems for their condition is required. The management of the Volga-Kama cascade of reservoirs is a complex scientific and technical task. Today, this management is carried out on the basis of dispatching rules dating back more than a dozen years. It is shown that modern management should be based on a coordinated system of priorities, including environmental criteria. The required optimization formulation of the task of finding optimal cascade control can be based, for example, on the search for a compromise solution at the level of agreement of the parties. A set of environmental and water management problems unsolvable for decades has been formed in the northern part of the Volga-Akhtuba f loodplain as well as in the zone of the Western-subtidal ilmens (system of lakes in the Volga River Delta). To solve these problems, new methods of studying ecological systems under severe anthropogenic stress and appropriate engineering approaches that allow a comprehensive approach to achieving sustainable water resources management are considered. The problem of poorly predictable f luctuations in the level of the Caspian Sea and the problem of water resource management in the region in conditions of conf licting interests of users are touched upon. The main measures are discussed, whose implementation will mitigate the consequences of f low regulation for the ecosystem of the Lower Volga. Among the important system principles, the need for a basin approach is noted, which involves, at a minimum, the development of a General Scheme for the Use of Water Resources of the Volga River.