The paper discusses an exploratory laboratory study concerning the evaluation of the cavitation potential of various types of roughened concrete surfaces. Methods of evaluating the data determined by the laboratory study, and means of presenting the results for use by design and field engineers, are presented.

This paper presents a brief history and the current status of channel treatment projects in the San Gabriel Mountains of Los Angeles County which are being constructed to lessen the financial burden of flood protection and for the conservation of water.

The need for solving complex hydrologic problems rapidly has led Bureau of Reclamation engineers to the utilization of electronic computers for such studies. Applications have been made to problems in water resources, water requirements, water utilization, flood hydrology, and sedimentation. Optimum solutions of high accuracy are obtained quickly and economically.

Digital computing equipment is now being used by the U.S. Geological Survey to analyze published streamflow data and to process data obtained in connection with water-loss studies. Basic streamflow data are to be recorded in the field on punched paper tape.

The paper discusses model studies in the Bureau of Reclamation's Hydraulic Laboratory in which both the direct weighing method and the pressure area computation method were used to determine hydraulic downpull on two high head gates, and one model study in which the pressure area computation method alone was employed. Also described are the methods used and results obtained in the field measurements of the prototype installations.

For free discharge conditions the hollow-jet valve has proved to be a satisfactory control device for flows through large conduits operating under high heads. Results of field tests with a 96-inch hollow-jet valve have revealed close agreement with hydraulic characteristics predicted from model studies. Piezometric measurements, thrust determinations on the valve needle, and rates of discharge were included in both field and laboratory tests. The prototype valve can be used as a metering device by the employment of model calibration results provided accurate position indicators are used. The only cavitation erosion evident in the prototype valve was caused by local irregularities in the body casting, which have been alleviated in subsequent valves by careful foundry practice and inspection.

The proposed discharge formula contains a discharge coefficient and exponents for hydraulic radius and slope. Both the coefficient and the velocities are given as functions of bed forms and bed material. Velocities computed by the formula check closely with those obtained in the laboratory.

The change from laminar flow to turbulent flow, in the case of water flowing through sand, occurs over a wide transition zone beginning with a Reynolds number of about 10. A method for estimating the exponent of the velocity term for head loss calculations involving flow into wells is presented. Typical calculations show that head losses due to aquifer turbulence may have been over-estimated in previously published material.