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Show Present knowledge of stream-pollution conditions is highly inadequate. Except in a few States, data on streams polluted by industrial wastes need to be aug- mented. Experience indicates that multiple sampling stations are usually required for each source of pollution. The participation by industry in programs for obtaining industrial-waste pollution data is one solution for this problem. Wide gaps in our present knowledge of pollution con- ditions will be reflected in interim comprehensive pro- grams for controlling pollution in the Nation's streams. The Public Health Service proposes to complete these interim programs by January 1, 1951. These programs will list the sources of pollution, the effects of this pollution on water uses, including Federal, State, munic- ipal, and private uses, and the corrective measures re- quired for each major stream in the Nation. However, these purposes will be served only to the degree that available data permit. Since comprehensive programs will not be static, but, instead, will represent the best knowledge available at any time, additional data will be utilized to develop more precise and complete plans. In order that the needs of other Federal agencies and of the general public may be served directly, it is recom- mended that (1) sampling stations be established to provide sanitary water-quality data at locations of Federal development projects and at selected stations which would produce useful and significant data, and (2) that such useful and significant data be published. The selection of sampling stations should be based on the recommenda- tions of the interested Federal agencies. It is not feasible to show graphically the status of adequacy of the data described. Sediment Load Data All streams transport some sediment. The quantity and quality varies tremendously from one part of the country to another, and, in every stream, from season to season. In the Plains States and in the Western and Southwestern States, the amount of sediment transported by streams is causing increasingly serious problems. Examples are the Rio Grande, Missouri, and Colorado Rivers and their tributaries. Streams in other parts of the country also carry large quantities of sediment. Sediment loads of streams include not only important losses of soil from accelerated erosion of agricultural and range lands, from cutting of stream banks, and from erosion of stream beds, but also adversely affect the con- struction and operation of dams and other hydraulic structures. In addition, sediment in streams interferes with irrigation, navigation, highway and railroad con- struction and maintenance, recreation, the utilization of stream waters for industrial and municipal supplies, and is detrimental to fish and wildlife. In order to evaluate the effects of sediment in streams, to take remedial measures for controlling or retarding various forms of erosion, and to make proper allowance for control and use for sediment in the development of river basins, it is essential that reliable and comprehensive information be available about the quantities and qualities of sediment transported by streams throughout the country. Primary and immediate emphasis should be placed on those river basins where the rate of sediment production is highest or where the need for information is greatest. Basic information about the sediment load of streams is being obtained from samples collected at stations lo- cated at selected points on streams. In most instances sediment sampling stations are located at or near stream flow gaging stations since concurrent water discharge measurements are necessary to compute the sediment load. Most sediment stations must be operated for a least 10 or more years to provide adequate records. The fre- quency of sample collection varies from stream to stream but should be sufficient to make possible the calculation of daily, monthly, and annual sediment loads. Figure 30 shows the present status of available sediment load data for different areas in percentage of adequate coverage. In order to evaluate the adequacy of available information, consideration was given to past records as well as to records being collected currently. The present adequacy is the ratio of existing information to the total requirements. The map shows the relatively low coverage of sediment load data on a Nation-wide basis and indicates the need for a large amount of additional information. This method of portrayal does not, however, indicate the areas where sediment production is highest nor the priority of need for additional data. There is much greater need for additional sediment records in such river basins as the Missouri, Colorado, Delaware, and Savannah than, for example, in the Penobscot River Basin. On the other hand, the order of importance for activating sediment measuring stations will probably shift from one area to another as time goes on, depending on changes due to development and the variety of problems that are bound to arise. No part of the country can be completely ig- nored, therefore, in regard to the amount of sediment transported in its streams. An important phase of the sediment load problem is the analysis and interpretation of data. In the past, insuffi- cient emphasis has been placed on analytical and inter- pretive studies of available records. Future programs for measurements of sediment loads of streams should provide for more thorough studies of these basic data in order that they may be of greatest value in the solution of specific problems. At the present time there are about 300 daily sampling stations in operation. To overcome the deficiencies indi- cated, it will be necessary to establish an additional 1,300 daily sampling stations within the next 10 years. Reservoir Sedimentation Surveys Approximately 10,000 storage reservoirs larger than farm pond size have been constructed in the United States for power, irrigation, flood control, municipal and industrial water supply, navigation, recreation, and other purposes. About 10 percent of these reservoirs have capacities of more than 5,000 acre-feet. All reservoirs are subject to loss of storage capacity resulting from deposi- tion of stream-borne sediment. The rate of storage loss in individual major reservoirs ranges from a negligible fraction of 1 percent to as high as 2 or 3 percent annually. At present the average annual loss of storage in the Nation's reservoirs is approximately 350,000 acre-feet. With the accelerated program of reservoir construction 347 |