On the Northern Donets--Donbas canal, as on other large hydraulic structures, on-site observations are constantly carried out in which the hydrologic, englneerlng-geologlc, hydraulic, seepage, and other characteristics of the structure are recorded. Every year the control laboratory records the flows and velocity regime, seepage losses, overall water balance, and siltation in the canal. As a result of 20 years of observations it was established that the considerable changes in the hydrogeologlcal conditions and physical and mechanical properties of the soils in the cana~ zone, thatwere caused by copious seepage and a rise in the groundwater level in the surrounding territory during the first years of operation, have now stabilized. Ice phenomena on the canal were also observed for many years, as a result of which new methods and technical means of controlling ice jams were developed and partly put into practice.All these tests were and still are being carried out under normal operating conditions of the structures. However, even long years of systematic observations of a structure do not make it possible to record its operation in the most serious, emergency situations. On a canal such situations can be the simultaneous emergency stopping of several pumps, breaching of the canal embankment, icing of trash racks, rupture of pipelines, etc. Additional hydraulic tests under artificially created emergency situations could yield valuable data for judging the operating reliability of both individual structures and equipment on the canal and of the system as a whole.Simulation of an emergency also contains an element of risk for operation of the structure. Obviously, this risk can be justified where emergency situations have, however, a comparatively frequent occurrence and, therefore, should be considered design situations. Emergency stopping of pumping stations should be considered among these, but not isolated emergencies such as breaching of the embankment or rupture of a pipeline. Experiments with simulation of emergencies should be very thoroughly prepared. Their inclusion as mandatory in start-up tests would simplify organizational problems of such preparation.On the Northern Donets--Donbas canal the matter most acutely confronting us is the damage which can arise in the case of emergency stopping of the lower pumping station of the second rise, the canal from which has quite long open stretches. The length of the canal between pumping stations No. 2 and No. 3 is 58 km, and in this stretch are located two cross regulators and five inverted siphons with a length of 189-1097 m; the canal gradient in this stretch is 0.0001, bottom width 3.14 m, side slopes 1:2, and maximum flow depth 4.7 m.The canal is provided with a system of measures for preventing overflow of the stretch of the second rise in the case of emergency stopping of pumping station No. 3. If necessary, this stretch can be separated into six reaches by lowering the gates on the two cross regulators and three inverted siphons. However, the reliability of...
