Issued JULY 1936 TECHNICAL BULLETIN NO. 524 Revised August 1939 SILTING OF RESE] ^fiEAk ^ NOVi OF 0193Í By HENRY M. EAKIN Head, Sedimentation Studies Division of Research Soil Ck>nseryation Service Revised by CARL B. BROWN Project Supervisor Reservoir Investigations Soil Ck>n8ervation Service UNITED STATES DEPARTMENT OF AGRICULTURE, WASHINGTON, D. C. For sale by the Superintendent of Documents, Washington, DéCi -• -------••-•-- Price ?1.00 JULY 1936 TECHNICAL BULLETIN NO. 524 REVISED AUGUST 1939 UNITED STATES DEPARTMENT OF AGRICULTURE WASHINGTON, D. C. SILTING OF RESERVOIRS ' By HENEY M. EAKIN^ Head, Sedimentation Studies, Division of Research, Soil Conservation Service Revised by CABL B. BROWN Project Supervisor, Reservoir Investigations CONTENTS Page Page Introduction 2 Reservoir surveys—Continued. The project.- _ — 2 Upper Crystal Springs Reservoir 114 Economic aspects of the problem . 3 Upper San Leandro Reservón: 116 Physical aspects of the problem 4 Original capacity survey of Lake Mead... 117 Processes of reeervoir silting 6 General summary of results of the 1934-38 Previous investigations— 8 surveys 119 Basin reservoirs -.- 9 Reservoir reconnaissance investigations, 1934- Basin reservoirs resurveyed in 1935-36- 37 126 White Rock Reservoir Sediment measurements in other south- Elephant Butte Reservoir eastern reservoirs 126 Roosevelt Reservoir Emporia Reservoir, Emporia, Va 125 Lake Michie__ Wateree Reservoir, near Cam den, S. C. 127 Gibraltar Reservoir ._ Lake Murray, Saluda River, above Basin reservoirs with earlier records Columbia, S. C 128 only Appalachie Reservoir, Greer, S. C 128 Lake Worth Stevens Creek Reservoir, Augusta, Ga_ 130 Lake McMillan Warwick Reservoir, near Cordele, Ga_ 131 Zuni Reservoir Flint River and Muckafoone Reser- Sweet water Reservoir _ voirs, Albany, Ga 135 Lake Chabot Lake Martin, Dadeville, Ala 136 Guernsey Reservoir Completely filled Piedmont reservoirs 139 Cheoah Reservoir._. Silting of southern Appalachian Mountain Ocoee No. 1 Reservoir reservoirs.. 140 O'Shaughnessy Reservoir Little River Reservoir, near Brevard, Pine Lake N. C 140 Mujskingum College Reservoir Green River Reservoir, near Tuxedo, Channel and other reservoirs of small ca- N. C... 141 pacity-inflow ratio. Bridgewater Reservoir or Lake James, Reservoir surveys by the Soil Conservation upper Catawba River, west of Mor- Service in 1934-36 ganton, N. C . 141 Field work Burton, Rabun, Nacoochee, and Tal- Methods of survey lulah Reservoirs, upper Tugaloo Surveys in southeastern United States. _. River Basin, near Tallulah Falls, LakeMichie Ga 142 University Lake Sediment measurements in other south- Greensboro Reservoir central reservoirs 143 High Point Reservoir Lake Dallas, near Dentón, Tex 143 Lake Concord Lake Worth, Fort Worth, Tex_ 145 Spartanburg Reservoir Lake Penick, near Lueders, Tex. 146 Lloyd Shoals Reservoir Lake Henryetta, Henryetta, Okla 147 High Rock Reservoir Lake Okmulgee, Okmulgee, Okla 147 Lay Reservoir Lake McAlester, McAlester, Okla 147 Surveys in south-central United States.._ Sediment measurements in reservoirs of Rogers Municipal Reservoir the Pacific Southwest 147 Lake Waco Santiago Creek Reservoir, Santa Ana, White Rock Reservoir Calif 147 Guthrie Reservoir Harding Reservoir, near Santa Ana, Boomer Lake Calif 148 Lakes Crook and Gibbons Barrett Reservoir, 26 miles east of San Surveys in southwestern United States... Diego, Calif 149 Elephant Butte Reservoir Summary 160 San Carlos Reservoir 99 Literature cited.. 152 Hodges Reservoir. 111 Appendix. 153 Morena Reservoir 112 Instructions for reservoir sedimentation Gibraltar Reservoir 113 surveys. 153 1 Progress report on reservoir surveys and investigations by the Soil Conservation Service in 1934-36 with notes on previous investigations of reservoir silting made by other agencies. Revised to bring up to date Information on reservoirs described in first edition. The author of the revision acknowledges the valuable assistance received from F. F Barnes and G. A. Zwerner of the Section of Sedimentation Studies. a Deceased, October 20, 1936.. 80832°—39- 1 1 2 TECHNICAL BULLETIN 524, U. S. DEPT. OF AGRICULTURE INTRODUCTION THE PROJECT The inherent relation of silting of reservoirs to problems of erosion control led the Soil Conservation Service to institute in July 1934 the first attempt at a general Nation-wide investigation of the condition of American reservoirs with respect to reduction of storage by silting. The ultimate objective of these studies is to accumulate information on the factors involved in the silting of reservoirs, including rates of silting, and to correlate the results with soil, slope, and climatic con- ditions and land use in watershed areas. It seems obvious that such a broad factual basis is necessary for sound determination of policy and practice of reservoir development and sediment control in the various sections of the country. The work accomplished through 1936 under the project consisted of detailed surveys of sediment accumulation in representative reservoirs in the southeastern, south-central, and southwestern type areas, along with reconnaissance examinations of other reservoirs in the same regions incident to selection of more broadly significant cases for special study. The direct objective of each detailed survey has been to determine the volume and distribution of sediment deposits acciunulated in the reservoir during a known period of time, either the entire period of the reservoir's existence or a shorter period between an earlier survey and the current resurvey. From these data and those on tributary drainage basins the average annual rate of silting per unit of drainage area is derived as an important practical index to dif- ferences and changes in regional erosional conditions and expectancy of useful life of existing or contemplated reservoirs. These studies have been continued over a period of 5 years, and at the date of revision of this bulletin (June 1939) a total of 76 surveys have been completed, of which 67 are original sedimentation surveys, 3 are sedimentation resurveys, and 6 are surveys of reservoir basins made prior to initial flooding to establish permanent range systems for future sediment measurements. In addition, reconnaissance investiga- tions have been made on some 500 other reservoirs out of an estimated total of nearly 10,000 in the United States. This bulletin was originally prepared with a view to giving a pre- liminary outline of the more important aspects of the problem of reservoir silting, to summarize the results of the more important in- vestigations in this field previously made by other agencies, and to present the findings of the Soil Conservation Service studies during the fiscal year ended June 30,1935. This revised edition does not attempt to present, even in summary, most of the data collected during the succeeding 3 years. To accomplish this would require a bulletin several times the present size. This revision is devoted mainly to bringing information up to date on reservoirs described in the original edition. Detailed surveys! have been made on six reservoirs previously described under recon- naissance investigations and a very; brief discussion of these and a few others has been included in the appropriate place under detailed surveys. Further reconnaissance studies have been made on other reservoirs, and the results are given herein. Additional information on watershed characteristics has been added where available, and SILTING OF RESERVOIRS 3 errors in fact and figures discovered since original publication have been corrected. Table 13 includes not only the results of the surveys described in this bulletin but also pertinent data on all reservoirs surveyed through June 30, 1938. Advance reports on many of these additional reser- voirs, containing information on the reservoir, its drainage basin, and sedimentation, have been mimeographed for circulation to cooperating technical workers for their information and criticism prior to final publication. Table 13 is inserted so that the summary data may be made more widely available for analysis and use by conservationists and engineers. Advance reports on most of the reservoirs not de- scribed in this bulletin can be furnished by the Soil Conservation Service on request. ECONOMIC ASPECTS OF THE PROBLEM The economic values involved in present and proposed reservoir developments are very large. They include not only investments in dams and basin lands of the reservoir properties themselves, but also the much larger values of appurtenant water supply and power facilities, industrial establishments, and irrigated-land resources and improvements. A comprehensive inventory of the Nation's resources dependent upon water storage has never been made, but even rough calculations of Federal, State, municipal, and corporate expenditures for reservoir and auxiliary facilities and similar estimates of the aggregate value of dependent private holdings easily run to several billion dollars. All of these interests are bound together under the common menace of depletion of reservoir capacity by silting wherever accelerated erosion occurs. It is true, of course, that some of these resources are less critically impaired by loss of reservoir storage than others. Powder reservoirs, even when completely silted, still afford operating head for ordinary stream flow. Where stream flow is equable through the seasons, either naturally or by reason of regulation by other reservoirs in the same watershed, the injury from local reservoir silting may be