Fluvial-Sediment Discharge to the Oceans from the Conterminous United States .. GEOLOGICAL SURVEY CIRCULAR 67 Fluvial-Sediment Discharge to the Oceans from the Conterminous United States By W. F. Curtis, J. K. Culbertson, and E. B. Chase G E 0 L 0 G I C A L S U R V E Y C I R C U l A R 670 A contribution to the International Hydrologic Decade Washington J973 Department of the Interior WILLIAM P. CLARK, Secretary U.S. Geological Survey Dallas L. Peck, Director First printing 1973 Second printing 1984 Free on application to Distribution Branch, Text Products Section, U. S. Geological Survey, 604 South Pickett Street, Alexandria, VA 22304 CONTENTS Page Abstract 1 Introduction -----------------------------------------·- ------------------- 1 Explanation of data ----------------------------------------------------- 1 Drainage area and water discharge ----------------------------------- 1 Period of record ----------------------------------------------------- 4 Suspended-sediment discharge ----------------------------------------- 4 Suspended-sediment yield --------------------------------------------- 4 Suspended-sediment concentration ------------------------------------- 5 Sediment discharge to the Atlantic Ocean ---------------------------------- 5 Sediment discharge to the Gulf of Mexico ---------------------------------- 6 Gulf of Mexico drainage area ---------------------------------------- 6 Mississippi River drainage basin -------------------------------------- 6 Sediment discharge to the Pacific Ocean ----------------------------------- 8 Pacific Ocean drainage area ------------------------------------------- 8 Colorado River drainage basin ----------------------------------------- 8 Comparison of present and previous estimates of suspended-sediment discharge_ 9 Summary --------------------------------------------------------------- 10 References cited ___ -----_----------------------------------------------- 11 ILLUSTRATIONS COVER. Space photograph of the Colorado River Delta, Baja California, showing fluvial sediment entering the Gulf of California. Flight of Apollo 9, March 1969. From NASA color infrared photograph AS9-26D-3781. Page FIGURE 1. Map of the conterminous United States delineating drainage areas and location of sed~ment stations -------------------------------------------------------------------------- 2 2. Section of river showing zones of sampled and unsampled sediment ------------------------ 5 3. Sketch map of the lower Mississippi River drainage basin showing location of stations u~ed to compute sediment discharge for the Mississippi River --------------------------------- 7 4. Hydrographs of water discharge and suspended-sediment discharge for the Colorado Rber at Yuma, Ariz., 1911-67 _________________________ ----_ _ _ ___ __ _ __ __ __ _ _ _ __ _ _ __ __ _ _ _ __ _ __ 9 TABLES Page TABLE 1. Historical suspended-sediment discharge data for the lower Mississippi River --------------- 8 2. Comparison between present and past estimates of sediment yields for selected rive1·s dis- charging to the oceans from the conterminous United States ------------------------- 10 3. Summary of suspended-sediment discharge to the oceans from the conterminous United rtates_ 11 4. Suspended-sediment discharge from the conterminous United States to the Atlantic Ocean, Gulf of Mexico, and the Pacific Ocean -------------------------------------------- 14 5. Identification of river stations used to compute sediment data ----------------------------- 16 III Fluvial-Sediment Discharge to the Oceans from the Conterminous United States By W. F. Curtis, J. K. Culbertson, and E. B. Chase ABSTRACT even an approximate world rate of e.rosion (Hol­ This report is a contribution to the UNESCO­ eman, 1968). This report, which i~· a contribu­ sponsored project of the International Hydrological tion to the UNESCO-sponsored project of the Decade called the World Water Balance. Annual International Hydrological Decade called the fluvial-sediment discharge from the conterminous World Water Balance, summarizes the quantity United States averages 491,449,600 short tons, of which 14,204,000 is discharged to the Atlantic Ocean, of fluvial sediment discharged to the Atlantic 378,179,000 to the Gulf of Mexico, and 99,066,600 to and Pacific Oceans and the Gulf of Mexico from the Pacific Ocean. Data from 27 drainage areas were the conterminous United States. Tl'e data given used to estimate the average annual discharge, yield, here may be useful to obtain the present total and concentration of fluvial sediment. The data may of world sediment yield to the marine environ­ be used to extrapolate part of the total world sediment yield to the marine environment. ment. The average annual amounts of suspended INTRODUCTION sediment discharged into the ocrans from 27 major drainage areas were computed from sus­ Sediment is defined as fragmental material pended-sediment records from the files of the derived primarily from the physical and chemi­ U.S. Geological Survey, the International cal disintegration of rocks from the earth's Boundary and Water Commission. and the U.S. crust. Once the sediment particles are detached, Army Corps of Engineers. These crainage areas they may be transported either by gravity, and the location of selected sediment stations wind, or water, or by a combination of these within the areas are shown in figure 1. The data agents. When the transporting agent is water, for these areas are given in table 4 in the back the sediment is termed "fluvial sediment." The of the report, and an explanation of the data is terms "fluvial sediment" and "suspended sedi­ given below. ment" are used synonymously in this report to mean inorganic material that is transported in EXPLANATION OF DATA suspension by streams and rivers. DRAINAGE AREA AND WATER DISCHARGE Knowledge of the amount of sediment trans­ ported by the various rivers of the world is im­ The names, total drainage areas, and water portant for many reasons. For example, reser­ discharges for the 27 drainage areas used in voirs should be designed with enough space to this report were taken from Wilson and Iseri store the sediment expected to accumulate in (1967). Some of the data used in that report them and yet retain full effectiveness during have since been revised (Alfonso Wilson and K. their design life, and sediment yield can be an T. Iseri, oral commun., 1971) and the revised indication of the rate of erosion in the drainage data are identified in table 4. vYater and sedi­ basin. A summation of sediment yields by ment discharged into the Great Lakes from the basins may indicate a regional, continental, and United States are not included in this report. 1 •I 0 a• -Daily sedi•ent station 'V -Miscellaneous concentrations ~-Noncontributing area (closed basin) ts]-Souris, Red, Rainy, Great Lakes, and St. Lawrence drainage not included in this report 20-Drainage area nu•ber (See fable 4) -··--Drainage divide FIGURE 1 (above and right) .-Drainage areas and location of sediment stations. 2 FIGUREl .-Continued. 3 PERIOD OF RECORD streambed. Most of the sedhnent moved by rivers and streams is held in suspension and is To keep this report as up to date as possible, transported at about the mean velocity of flow. and yet provide a sufficient period of record for The remainder of the sediment moves more a meaningful average, the 1950-69 period was slowly on or near the streambe':l in the unsam­ chosen. Although a longer period of record may pled zone and generally is referred to as bed­ be desirable, a 20-year period can be expected load plus saltation load, or simply unmeasured to span one or more extreme events, dry and load. Computations of bedload or unmeasured wet years, and is a reasonable base for statisti­ load may be made using var~0u~ thMretical cal summary. formulas; however, for long-term estimates, an All sediment stations ( 43) selected for this unmeasured sediment discharg~ of 10 percent study did not have records covering the full 20- of the suspended-sediment discr arge frequently year period; however, all records available with­ is used. Unmeasured load is not included in this in this period were used. For those stations report. Figure 2 shows the sampled and unsam­ with relatively short periods of record that in­ pled zones in sediment samplin~. cluded one or more extreme floods, the average Daily sediment discharge, in ton.s per day, is annual suspended-sediment discharge was re­ determined by multiplying water discharge, in vised downward to reflect conditions rr•ore com­ cubic feet per second, by the concentration of patible with the long-term discharge. For suspended sediment, in milligrams per liter, example, in 1969, three stations in California times a coefficient and assuming a specific experienced a flood of approximately the 100- gravity of 2.65 for sediment. Tl'e daily records year recurrence interval; thus, the 1969 sedi­ are then summed to give the annual sediment ment records for those stations were not used. discharge. To determine the average annual Also, two other stations, Rouge River at Ray­ suspended-sediment discharge at a station, the gold, Oreg. (25c), and Skagit River near Mt. authors summed the annual sediment dis­ Vernon, Wash. (27d), each had only 1 year of charges and divided that sum by the number record, 1912 and 1910, respectively (Van of years of record. When there were no long­ Winkle, 1914a, b) ; these records were used al­ term records (see "Period of Record") the though they were outside the period f)f record average annual suspended-sedinent