River runoff is movement of water in the form of flow through a river bed under the action of gravity. It is one of the essential components of the hydrologic cycle ensuring water movement from the land to oceans or to the areas of internal drainage. The quantitative value of the flow per unit time is called water discharge.

In hydrology, river runoff implies flow quantity, i.e. volume of water (or mineral substances, sediment runoff) passed through a certain section per unit time, most often per year. It includes surface runoff (formed from precipitation and snowmelt) and groundwater flow formed due to underground waters. Annual river runoff is an objective measure used to assess river affluence.

Flow rate is an average value of runoff volume for a long-term period of such duration that its prolongation does not effect considerably on that value. Flow rate can be calculated by averaging annual runoff volume values (annual flow rate), flood runoff value (flow rate during flood time), for certain months or other periods of the year. The flow rate term is often used to abridge the concept of annual flow rate. Flow rate is expressed in unit discharges (specific rate of flow), runoff depth, and long-term average annual flow rate of that period of the year for which it is calculated.

Reassessment of today’s surface and ground water resources taking into consideration currently observed climate changes is one of the relevant problems of hydrology and hydrogeology. Assessment of dry-weather and minimum flow is especially important for the prevention of ecological problems. Study of the spatial-temporal regularity of river runoff formation, features of hydrological regime of rivers makes possible identifying principal relations between water balance components, particularities of recharge of surface and ground waters and formation of their natural resources under current and forecasted climatic conditions.

Monographs and brochures

Mapping the resilience of international river basins to future climate change-induced water variability / L.De Stefano, J.Duncan, S.Dinar, K.Stahl, K.Strzepek, A.T. olf (2010) 

Papers

Schoof J.T. - Scale Issues in the Development of Future Precipitation Scenarios (2012) 

Shahgedanova M., Afzal M., Usmanova Z., Kapitsa V., Mayr E., Hagg W., Severskiy I., Zhumabayev D. - Impacts of Climate Change on river discharge in the Northern Tien Shan: results from long-term observations and modeling (2016)