for use in measuring water levels in deep reservoirs. The gage basically is a modified mercury manometer in which the water pressure is transmitted by gas pressure to a recording instrument through a small flexible tube. The gas is fed through the tube and bubbles freely into the water at a fixed elevation. The pressure in the tube at any elevation is essentially equal to the pressure on the bubbler orifice located in the stream or reservoir. Thus water pressure can then be correlated as a function of the head on the orifice. The Corps of Engineers currently is using this type of commercially available bubbler gage at a number of gaging stations. RADIOISOTOPE GAGE FOR MEASURING WATER CONTENT OF SNOW Information concerning the location and water equivalent of deep snowpacks is an essential element in forecasting snow runoff in connection with controlled use of water and operation of reservoirs. In view of the requirement for frequent and accurate reports of snow conditions in remote areas, development of a snow-measuring instrument was initiated under joint sponsorship of the U.S. Weather Bureau and Corps of Engineers. The snow-measuring feature of the instrument was based on the principle of measuring the attenuation of a known intensity of gamma radiation directed through the snowpack. The Upon completion of early experimental work, the Corps of Engineers extended the development of such equipment for practical use. instrument finally developed used a gamma ray source, cobalt 60, enclosed in a lead cylinder set flush with the ground surface (fig. 2). A beam of gamma radiation leaving the source penetrates the snow pack and strikes a Geiger-Muller radiation detector tube suspended 15 feet overhead. Pulses of electricity caused to flow in the GM tube are transmitted by radio to a recorder having a counter mechanism. The rate of pulses are then translated into data representing the water equivalent of the snowpack. Measurement of snow depths up to 50 inches of water content has been found practical by this method. Recent investigations have been undertaken to improve the operating characteristics of this instrument as well as the means of transmitting the data to a central receiving point. This instrument is not yet available commercially. ELECTRONIC FLOOD MODEL OF RIVER BASIN An electronic flood model of the Kansas River Basin has been developed under contract with the University of California. The model will incorporate about 50 inflow units, 12 reservoir storage and release units, and a number of channel units. Runoff for about 50 subdivisions of the basin and scheduled reservoir releases will be plugged in with small pins and hydrographs of stage and discharge (oscilloscope) are then available immediately at any desired downstream location provided for in the design. The equipment will be housed in a console about 6 by 4 by 5 feet in size. The model will be used in scheduling releases from flood control reservoirs and associated flood forecasting in the Kansas River Basin. As data becomes available during a flood, the model will show FIGURE 2.-Typical field installation radioisotope-radiotelemetering snow gage. promptly the effects of reservoir storage on downstream conditions. Results of possible alternative reservoir operations are available immediately for downstream locations as an aid in determining what adjustment, if any, should be made in the reservoir regulation schedules. INSTRUMENT FOR MEASURING WAVE HEIGHTS In connection with a program of investigating winds and waves in inland waters to improve procedures for estimating freeboard allowances for dams and levees, a new type of instrument for measuring the height of relatively short waves was developed. This gage, developed by the Beach Erosion Board, is a step resistance staff gage, consisting of four 5-foot lengths of standard aluminum channels. The channels are coated with neoprene rubber to insulate the internal 85639 062 13 resistances and contacts. The resistors and modified automotive type spark plugs are mounted on the channel at 0.2-foot intervals. The resistance changes caused by waves successively shorting out more and more resistance elements in the wave staff result in changes in the electrical current transmitted to a Brush oscillograph and are recorded by means of a magnetic pen motor. This step-resistance staff gage is economical, easily constructed, and has proven very effective in providing information concerning wave heights. Gages of this type have been used in studies of inland waters as well as in studies involving ocean waves. Various programing devices have been developed for use in connection with these gages to permit selective recording of data needed, and avoidance of unnecessary recordings. EQUIPMENT FOR SEDIMENT MEASUREMENT AND ANALYSIS The Corps of Engineers cooperates in the activities of the Federal interagency sedimentation project, located at the St. Anthony Falls Laboratory at the University of Minnesota, by contributing funds and furnishing project engineers. The principal objective of the project has been to develop improved equipment and methods for securing and analyzing sediment samples. The investigations include (1) the development and testing of instruments for use in obtaining samples of suspended sediment and sediment deposits and (2) development of instruments and methods for laboratory analysis of sediment samples. Parallel investigations include literature reviews and canvasses of educational institutions in search of promising ideas and items of equipment developed by others outside the Government agencies involved in the cooperative project. Progress to date includes development of the following items which are generally accepted as standard equipment: (1) A total of eight models of three different types of suspended sediment samplers for collection of various types of data under different field conditions (fig. 3); (2) two improved bed-material samplers for securing samples of submerged deposits (fig. 4); and (3) laboratory apparatus for rapid analysis of particle size (fig. 5). USE OF CHEMICALS TO INDUCE RAPID SETTLING OF SUSPENDED SEDIMENTS Certain chemicals have been used effectively for inducing rapid settling of fine materials from water used in spreading operations. The chemicals cause fine sediment particles in suspension to gather into mass flocs whose settling rates are much more rapid than those of the individual sediment particles. The practicability of using this method to hasten sedimentation of fine materials behind dikes and in clearing up reservoirs and lakes is being field tested by the Corps of Engineers. Investigations are also being made to study the feasibility of using this principle in dredging operations by concentrating the sediment prior to dumping operations. FIGURE 5.-Visual accumulation tube sand size analyzer, recorder and valve mechanism. RADIOISOTOPE GAGE FOR MEASURING IN-PLACE DENSITIES OF SUBMERGED SEDIMENT DEPOSITS The development of instruments for automatically measuring the densities of underwater deposits, has been accomplished by instrument manufacturing companies, cooperating Government agencies and individual Government agencies working independently. A radioisotope probe, using radium 226, which is now generally accepted as being superior to conventional instruments for measuring densities of marine deposits, was developed through studies and contract arrange |