Runoff accounting at hydroelectric stations of Tadzhikistan

On streams with a sequence arrangement of hydroelectric stations it is necessary to have at least two stream-gauging stations of the hydrometeorological service: upstream of the first reach of the sequence (inflow station) and downstream of the last reach (outlet station).

Operation of turbine flowmeters under conditions of the mountain rivers of Tadzhikistan, the water of which contains a large amount of suspended silty sediment, showed that they are rapidly put out of operation owing to clogging of the impulse tubes with silt and entry of air into them. Under such conditions it is apparently best to use pneumohydraulic apparatus.

The discrepancy in the mean monthly discharges past hydrostations on the Vakhsh River, determined by the data from operation and the gauging stations of UGMS, reaches 20–30%; the causes of the discrepancies are, on the one hand, the inaccuracy of flow measurement at the gauging stations of UGMS and, on the other, the noncorrespondence of the calculated discharge capacity of individual discharge structures to the actual.

To reduce the discrepancies it is necessary to increase the accuracy of hydrologic measurements and observations at gauging stations of UGMS; at hydroelectric stations it is necessary to carry out full-scale rating of the turbines and conduits and to check these characteristics periodically (once every five years), and also to refine the curves of the dynamic relations of the storage capacity of reservoirs to their water levels.