10 



THE IRRIGATION AGE. 



Surface Water Supply of the Lower Miss- 

 issippi Basin* 



By W. B. Freeman and R. H. Bo'ster. 



These investigations of stream flow are not complete 

 nor do they include all the river systems or parts thereof 

 that might purposefully be studied. The scope of the 

 work is limited by the appropriations available. The field 

 covered is the widest and the character of the work is 

 believed to be the best possible under the controlling 

 conditions. The work would undoubtedly have greater 

 scientific importance and ultimately be of more practical 

 value if the money now expended for wide areas were 

 concentrated on a few small drainage basins; but such a 

 course is impossible because general appropriations made 

 by Congress are applicable to all parts of the country. 

 Each part demands its proportionate share of the benefits. 



It is essential that records of stream flow shall be 

 kept during a period of years long enough to determine 

 within reasonable limits the entire range of flow from 

 the absolute maximum to the absolute minimum. The 

 length of such a period manifestly differs from different 

 streams. Experience has shown that the records for 

 some streams should cover from five to ten years, and 

 for other streams twenty years or even more, the limit 

 being determined by the relative importance of the stream 

 and the interdependence of the results with other long- 

 time records on adjacent streams. 



In the performance -of this work an effort is made to 

 reach the highest degree of precision possible with a 

 rational expenditure of time and a judicious expenditure 

 of a small amount of money. In all engineering work 

 there is a point beyond which refinement is needless and 

 vasteful, and this statement applies with especial force to 

 streamflow measurements. Jt is confidently believed 

 that the stream-flow data presented in the publications 

 of the Survey are in general sufficiently accurate for all 

 practical purposes. Many of the records are, however, 

 of insufficient length, owing to the unforseen reduction 

 of appropriations and consequent abandonment of sta- 

 tions. All persons are cautioned to exercise the greatest 

 care in using such incomplete records. 



Records have been obtained at more than 1,550 dif- 

 ferent points in the United States, and in addition the 

 surface water supply of small areas in Seward Peninsula 

 and the Yukon-Tanana region, Alaska, have been inves- 

 tigatea. During 1909 regular gaging stations were main- 

 tained by the Survey and cooperating organizations at 

 about 850 points in the United States, and many miscel- 

 laneous measurements were made at other points. Data 

 were also obtained in regard to precipitation, evaporation, 

 storage, reservoirs, river profiles, and water power in 

 many sections of the conntry and will be made available 

 in the regular surface water-supply papers and in special 

 papers from time to time. 



The results contained in this volume are requisite 

 to meet the immediate demands of many public interests, 

 including navigation, irrigation, domestic water supply, 

 water power, swamp and overflow land drainage, and 

 flood prevention. 



Navigation. The Federal Government has expended 

 more than $250,000,000 for the improvement of inland 

 navigation, and prospective expenditures will approxi- 

 mate several times this amount. It is obvious that the 

 determination of stream flow is necessary to the intelli- 

 gent solution of the many problems involved. 



Irrigation. The United States is now expending $51,- 

 000,000 on federal irrigation systems, and this amount is 

 far exceeded by the private expenditure of this nature in 

 the arid West. The integrity of any iirigation system 

 depends absolutely on the amount of water available. 

 Therefore investigations of stream flow in that portion 

 of the country are not only of first importance in the 

 redemption of the lands, but constitute an insurance of 

 federal and private investments. 



Domestic Water Supply. The highest use of water 



Abstract of Water Supply Paper 276, U. S. Geological Sur- 

 vey, 1909. 



i? for domestic supply, and although this branch of the 

 subject is of less direct federal interest than the branches 

 already named, it nevertheless has so broad a significance 

 with respect to the general welfare that the Federal Gov- 

 ernment is ultimately and intimately concerned. 



Water Power. The development of the water power 

 of the country is an economic necessity. Our stock of 

 coal is being rapidly depleted and the cost of steam 

 power is increasing accordingly. Industrial growth, and 

 as a consequence the progress of the United States as a 

 nation, will cease if cheap power is not available. Water 

 power affords the only avenue now open. When the 

 electric transmission of power was accomplished the re- 

 lation of our water powers to national economy changed 

 entirely. Before the day of electric transmission water 

 power was important only at the locality at which it was 

 generated, but it has now become a public utility in which 

 the individual citizen is vitally interested. Inasmuch as 

 the amount of water power that may be made available 

 depends on the flow of rivers, the investigation of flow 

 becomes a prerequisite in the judicious management of 

 this source of energy. 



Drainage of Swamp and Overflowed Lands. More 

 than 70,000,000 acres of the richest land in this country are 

 now practically worthless or of precarious value by reason 

 of overflow and swamp conditions. When this land is 

 drained it becomes exceedingly productive and its value 

 increases many fold. Such reclamation would add to the 

 national assets at least $700,000,000. The study of run-off 

 i? the first consideration in connection with drainage 

 projects. If by the drainage of a large area into any par- 

 ticular channel that channel becomes so gorged with 

 water which it had not hitherto been called upon to con- 

 vey that overflow conditions are created in places where 

 previously the land was not subject to inundation, then 

 drainage results merely in an exchange of land values. 

 This is not the purpose of drainage improvement. 



Flood Prevention. The damage from floods in the 

 United States probably exceeds on the average $100,000,- 

 000 annually, and in the year 1908, according to estimates 

 based on reliable data, the aggregate damage approxi- 

 mated $250,000,000. Such an annual tax on the property 

 of great regions should be reduced in the orderly progress 

 of government. It goes without saying that any consider- 

 ation of flood prevention must be based on a thorough 

 knowledge of stream flow, both in the contributing areas 

 which furnish the water and along the great lowland 

 rivers. 



The order of treatment of stations in any basin in 

 these papers is downstream. The main stem of any river 

 is determined on the basis of drainage area, local changes 

 in name and lake surface being disregarded. After all 

 stations from the source to the mouth of the main stem 

 of the river have been given, the tributaries are taken up 

 in regular order from source to mouth. The tributaries 

 are treated the same as the main stream, all stations in 

 each tributary basin being given before taking up the next 

 one below. 



The exceptions to this rule occur in the records for 

 Mississippi River, which are given in four parts, as indi- 

 cated above, and in the records for large lakes, where it is 

 often clearer to take up the streams in regular order 

 around the rim of the lake than to cross back and forth 

 over the lake surface. 



Definition of Terms. 



The volume of water flowing in a stream the "run- 

 off" or "discharge" is expressed in various terms, each of 

 which has become associated with a certain class of work. 

 These terms may be divided into two groups: (1) Those 

 which represent a rate of flow, as second-feet, gallons per 

 minute, miner's inches, and run-off in second-feet per 

 square mile, and (2) those which represent the actual 

 quantity of water, as run-off in depth in inches and acre- 

 feet. They may be defined as follows: 



"Second-foot" is an abbreviation for cubic foot per 

 second and is the rate of discharge of water flowing in a 

 stream 1 foot wide, 1 foot deep, at a rate of 1 foot per 

 second. It is generally used as a fundamental unit from 

 which others are computed by the use of the factors given 

 in tables of equivalents. 



"Gallons per minute" is generally used in connection 

 with pumping and city water supply. 



