Hydrologic Calculations

a division of engineering hydrology dealing with methods of calculating quantities characterizing a hydrologic regimen. The results of a calculation are usually given in the form of average values and various probabilities of their repetition.

The problems that are solved in the process of hydrologic calculations may be divided into the following main groups: (1) calculations of the stream flow of water, including normal annual stream flow, maximum high-water and flood discharges, distribution of stream flow within a year, minimum discharges of water, length of flowless period (freezing over and drying up of rivers), and hydrographs of high waters and floods; (2) hydrometeorological calculations of bodies of water, including evaporation from water and land surfaces and atmospheric precipitation; (3) calculations of the water balance of individual bodies of water; (4) calculations of sediment runoff, re-formation of banks, and silting of reservoirs; (5) calculations of the dynamics of water masses, including elements of wind motion, changes in water level caused by offshore and onshore winds, and currents; (6) calculations of characteristics of the thermal regimen, including the freezing and breakup of bodies of water, the thickness of ice and snow, and water temperature; and (7) calculations of hydrochemical characteristics, specifically the mineralization of bodies of water and the components of the water. All these problems are solved by several methods, primarily with the balance method and the mathematical-statistics method.