9415862 Chiu The flow in rivers and streams is a major component of the hydrologic cycle on earth. To study and forecast the flow and various processes such as the transport of sediment and pollutants in rivers and streams, an essential hydrologic variable that must be measured or estimated is the discharge. To determine the discharge, conventional methods require a great amount of velocity measurement and are, therefore, too time-consuming, inefficient and costly for applications in many situations of critical importance. The proposed project will develop an efficient method of discharge measurements, which will have a sound, theoretical basis, and will require only a small amount of velocity measurement. The method can also enchance a modern, velocity-profile measuring device, such as an Acoustic Doppler Current Profiler (ADCP) which,for technical reasons, misses velocity data near the bed and water surface. The method to be developed can fill the missed data and quickly translate a velocity profile measured by the device into the cross-sectional mean velocity and, hence, the discharge. Therefore, it should be applicable even to flows in rivers and streams that change rapidly with time, such as flows under the effects of ice, wind, and tides. It is also applicable to rivers connecting two lakes, in which even the flow direction changes periodically. Another important application of the method is to determine the discharge for (Kalman) filtering schemes, that can be designed to sequentially update the flow resistance by using the monitored discharge and water level, to reduce the uncertainty in flow forecasting. The method will be based on a velocity distribution model capable of representing various velocity distribution patterns, from the channel bed to the water surface, regardless of whether the maximum velocity occurs on or below the water surface. The model is based on the probability and entropy concepts, coupled with a geometrical technique using a curvilinear coordinate s ystem.
