The 15th Congress of the tAHR was held in Istanbul on September 3-8, 1973. The hydraulic aspects of poiludon control and water conservation were considered at technical session B of the Congress including: a) diffusion and dispersion, effect of turbulence; b) hydraulic structures controlling the water environment; c) full-scale investigations and modeling techniques. At the session 39 reports from 14 countries were presented, including 8 from the USA, 5 each from France and West Germany, 4 each from the USSR and Turkey, 2 each from England, Canada, and the Netherlands, and 1 each from the remaining countries (see list of reports). The general reporters presented summary reports: I. Iwasa (lapan) [1-7, 15-20], A. M. Air-sam (USSR) [8-14], 6. Harm (West Germany) [21-31], J. Abraham (Netherlands) [32-34].* The reports can be combined according to topics into the following groups: determination of the coefficient of diffusion and dispersion, calculation of the passive impurity concentration field in turbulent flows [1, 2, 3, 4, 5, 6, 9, 10, 11]; turbulent diffusion and mixing in tidal reaches of rivers and in estuaries [14, 15, 35]; effect of turbulence on jet mixing [19]; calculation of the distribution of suspended particle concentrations in a turbulent flow and in a settling basin [7, 8, 26]; probabilistic description of the diffusion of impurities in the sea [16]; current and mass exchange in reservoirs as a factor of water quality [12, 13, 28]. calculation of secondary currents [20]; modeling as a means of investigating effects on watercourses and water bodies [30], mathematical models of water quality in watercourses [36, 37, 38], mathematical and physical hydrothermal modeling of thermal pollution of waters [17, 18, 34]; use of laser and infrared techniques in hydraulic and hydrothermal investigations [32, 33]; structures for intensifying mixing upon discharge of wastewaters into a watercourse [24, 27], aeration of the turbulent flow in hydraulic structures [21, 22, 23]; investigations of the operation of individual structures: tailrace channels of thermal power stations [25] and marine intakes [29]. The reports contained extensive information and new data needed for investigating, designing, and operating structures affecting the water environment. The reports of Soviet specialists at this session [1, 2,16,17] were well received by the general reporters and foreign scientists.tOne of the main physical processes determining water quality in rivers and bodies of water affected by industrial and domestic liquid wastes is mixing of the discharged water with that in the watercourse or water body. Mixing calculations are presently made by an analytical or numerical solution of the equation of turbulent diffusion.The methods proposed for calculating the mixing of wastewaters in rivers have been developed with varying degrees of detailed elaboration. Thus in mathematical modeling of water mixing in a river the one-dimensional [2, 3. 5, 6. 10, 36] river model, considering the velocity and concentration averaged over t...
