b6 -171 I I 

UNITED STATES DEPARTMENT OF THE 

INTERIOR J. A. Krug, Secretary. 

GEOLOGICAL SURVEY W. E. Wrather, Director. 

:RCULAR 36 October 1948 

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ANNUAL RUNOFF IN COLUMBIA RIVER · BASIN 

IN PERCENT OF THE MEAN, 192~5 

By 

C. C. McDonald and H. C. Riggs 

WASHINGTON, D. C. 

ANNUAL RUNOFF IN COLUMBIA RIVER BASIN 

IN PERCENT OF THE MEAN, 192845 

By 

C. C. McDonald and H. C. Riggs 

The design or hydraulic projects or the planning or a program or water resource development in a basin requires an adequate knowledge 

or the stream flow. Because or the wide variation in the amount or runorr rrom year to year 

in many basins, many years or stream-rlow rec- ords are.necessary to determine adequately the 

amount and distribution or the discharge and 

the probable dependable yield or the watersh~d. 

Adequate data on stream rlow are rarely a- vailable, and some method or estimation or the 

stream characteristics rrom the data must be 

used. Ir no actual record or discharge rrom an area is available, it 1R dirficult if not 

impossible to determine the runoff with any 

degree of reliability from other data. Having a nischarge record of short duration, however, 

it is often possible to arrive at reasonably reliable estima t:es of discharge ·for a longer 

period. Several methods are available, including rainfall-runoff studies and correlation 

with the rlow of nearby streams. Studies of 

this kind should be made if it is necessary to 

utilize a record or very short duration for 

the design of a water project. 

Estimates of annual mean discharge are often 

possible where the data do not permit reliable 

estimates of monthly means. Although the an- nual mean discharge does not provide information as to the seasonal distribution of runoff, 

it has considerable hydrologic significance. 

It rerlects roughly the runoff characteristics 

during the year. An annual mean discharge below normal strongly indicates a probability 

that the flood activity was below normal,and 

also indicates that the discharge during the 

low-water period was probably below normal. An 

examination of precipitation records with relation ~o normal will assist in making reliable 

deduct;ions. 

This report presents a method of making 

graphical comparisons between the annual mean discharge of one or more years, and the aver- age for the period 1928-45 in Columbia River 

Basin. The period 1928-45 has no particular 

hydrologic significance, but merely represents the period during which a sufficient number or 

gaging stations were operated to provide fairly satisfactory coverage of the basin. The 25-

year period 1921-45 is used in the Water Resources Review !/ as a base period, and the 

median or mid-value is used as a normal. 

Because of the general diminution of runoff 

during the past 50 years, the average runoff 

during the period 1928-45 is slightly leas than 

the average for the period 1921-45. The differences are fairly consistent, and average 

about 3 percent greater ror the period 1921-45. 

The 18-year averages used in this report are, 

therefore, not identical with the 25-year nor- mals used in the Water Resources Review. 

Although the magnitude of the annual runoff 

from various parts of the Columbia Basin varies 

greatly owing to the distribution or precipitation, deviations from the 18-year average are quite consistent. This consistency makes it 

possible to compare the discharge for corre- sponding years on different streams in terms 

of their respective normals. With surficient 

coverage by gaging-station records for the en- tire 18-year period, it is possible to define 

with a fair degree of accuracy the relative 

variation with respect to normal throughout 

the basin. 

A map of the Columbia River Basin was prepared for each year from 1928 to 1946 and laograms of percent of mean runoff were plotted. 

All available discharge records that were re- presentative of natural or fairly consistent 

condi tiona vrere used to define the isograms. 

Such records are not ideally distributed and are inadequate to derine the position of the 

isograms with great accuracy. 

In order to assita in the definition, similar maps were prepared for precipitation, inasmuch as. precipitation stations are more uniformly distributed and provide point definition as compared to the large areas represented by 

gaging stations on the larger streams. The 

iaograms of percent of normal precipitation were particularly useful in ungaged areas. Although most of the precipitation stations were located at a comparatively low elevation, the 

1/Water Resources Review--United States and 

Canada; a monthly inventory of water supplies, distributed as a news release by the Geological 

Survey, Department of the Interior, Wash. 25, 

D. c. and the Dominion Water and Power Bureau, 

Department of Mines and Resources, Ottawa, Ont. 

1 
2 

ratio of each year to the 18-year average is 

believed representative. '{'he~·e is no evidence 

that the ratio to the normal is affected by elevation. 

Complete agreement between precipitation and 

runoff patterns would require a better correlation between rainfall and rUnoff than actually 

exists. One of the factors that affect the 

relation is the time distribution of precipi- tation during the year. In an arid basin a large number of light storms throughout the summer might increase the yearly precipitation 

to above normal, while producing little or no runoff. Conversely, a heavy winter precipitation or a rapid spring snow melt may produce a greater runoff than would normally be ex- pected from the precipitation record. Groundwater storage in a basin may cause a lag between precipitation and the resultant runoff 

that makes a direct correlation impossible. 

Runoff from small areas should correlate 

with precipitation better than that from large areas because the characteristics of a small 

basin are likely to be more uniform. Likewise, 

the precipitation recorded at one point in the 

basin will be more representative of that for a small surrounding area than for a large one. Correlation in areas of heavy precipitation will be better than that in arid ones, other 

things being equal, because of the greater areal 

uniformity. There appear to be no areas over which the pr.ecipi ta tion or runoff pattern is 

similar from year to year. 

Before using the runoff maps to determine 

the mean flow of a stream with a short-term 

record, the drainage basin in question should 

be compared with nearby basins for which rec- ords are available, as regards size, topography, vegetal cover, storm exposure, and ca- pacity for ground-water storage. The relation 

between percent of mean runoff from two similar, proximate basins may be expected to vary 

according to the lines on the runoff maps. 

The history of all basins used in the study 

should be reviewed to determine whether there 

have been any changes during the period 1928-

45, such as diversions, re~oval of vegetal 

cover, irrigation of basin lands, or changes 

in natural or artificial storage. These changes 

should be given weight in computing the mean flow. 

If there are several years of record on the 

stream in question, a determination of the mean flow should be made for each year of rec- ord and the results averaged to obtain the 

ratio between the period of record and the 18-

year average. It is believed that estimates 

made by this method will compare favorably with those obtained by other means. By preparing these maps for the Whole Columbia River 

Basin, the work necessa~ to make a reliable 

estimate of the average flow of a stream with one or more years of record is much simplified, 

and duplication of work is avoided. 

Following the series of maps for each year 

is a map showing average annual runoff in inches for the basin,· based on the 18-year period 

1928-45. '!'his map is intended to show in a general way the distribution of annual runoff 

from the Columbia River Basin. No attempt was made at precise definition of the lines of 

equal runoff to reflect the runoff from very small areas. Records of discharge from areas less than 100 square miles were collected at 

only a few places in the basin during the 18-

year period, and even the smaller of the gaged areas usually include a considerable range in 

elevation. The precise definition of the aver- age runoff for small areas would require a much greater density of gaging stations than 

exists today. Records used in the definition 

of the lines of equal runoff usually represent 

substantially natural conditions. In a few areas where irrigation is practiced, diversions were nearly constant and represent a fairly small percentage of the total annual discharge. 

GP0-8-FSO 1-26-49 500 
GEOLOGICAL SURVEY 

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CIRCULAR 36 PLATE 

li 110 

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COLUMBIA RIVER BASIN 

RUNOFF IN I 9 2 8 IN PERCENT OF MEAN 

Sea •• « 1111 las 

!0 40 !0 !) 

Note: Nu111be,. lncllcole meosuNd l'llnoff ol tat IRQ statioRs 

IR perceRiota of 18-yeor a-ate for period 1928-45. 

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110 

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GEOLOGICAL SURVEY _ 

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CIRCULAR 36 PLAT£ 2 

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COLUMBIA RIVER BASIN 

RUNOFF IN I 929 IN PERCENT OF MEAN 

Scale of Illites 

!0401Pp 

Mote: Nu111bers indicate meCIIUred runoff ot goolao otoliOM 

In percentooe ot 18-,..., overooe tor periocl IS28-45. 

--~---·--·-

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110 
GEOLOGICAL SURVEY 

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CIRCULAR 36 PLATE 3 

110 

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COLUMBIA RIVER BASIN 

RUNOFF IN 1930 IN PERCENT OF MEAN 

Scale of mites 

104080P 

Note: Numbers Indicate measured runoff at gaging stations 

In percentage of 18-yeor o .. rage for period 1928-45. 

122 

... •• ••• l "•·... QANADA -- ----------------

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110 
GEOLOGICAL SURVEY CIRCULAR 36 PLATE 4 

110 

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COLUMBIA RIVER BASIN 

RUNOFF IN 1931 IN PERCENT OF MEAN 

Scale of miles 

10 40 10 , 

Nola: Numbers Indicate measu,.d runoff at gaging llations 

In percentage of 18-yoor average for period 1928-45. 
GEOLOGICAL SURVEY 

'i 

••LCIRCULAR 36 PLATE 5 

COLUMBIA RIVER BASIN 

RUNOFF IN 1932 IN PERCENT OF MEAN 

Scale of mites 

ao •o ao !D 

Note: Numbers indicate measured runoff at g~ging stations 

In percentage of IS.yaor overage for period 1928-45. 

I 

110 
GEOLOGICAL SURVEY 

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CIRCULAR 36 

110 

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COLUMBIA RIVER BASIN 

PLATE 6 

RUNOFF IN 1933 IN PERCENT OF MEAN 

Seale of miles 

to4010P 

Nate: Numbers ind1cate measured runoff at gaging stations 

In percentage of 18-year overage far period 1928-45. 

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110 
GEOLOGICAL SURVEY 

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CIRCULAR 36 PLATE 7 

"f 

COLlJ.MBIA RIVER BASIN 

RUNOFF IN 1934 IN PERCENT OF MEAN 

Scale of miles 

10 40 10 ., 

Note: Numbers indicate measured runoff at gaging stations 

In percentage of 18-yeor overage for period 1928-45 . 

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010 
GEOLOGICAL SURVEY 

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114 

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CIRCULAR 36 PLATE 8 

COLUMBIA RIVER BASIN 

RUNOFF IN 1935 IN PERCENT OF MEAN 

Sccle of mites 

R04080!Q 

Note~ Numbers indicate measured runoff at gogino staticms 

in percentage of 18-yeo< overage for period 1928-45. 

·--t----

1 
GEOLOGICAL SURVEY 

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CIRCULAR 36 

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PLATE 9 

COLUMBIA RIVER BASIN 

RUNOFF IN 1936 IN PERCENT OF MEAN 

Scale of miles 

to 40 !9 11 

Nole: Numbers lndicole measured runoff ar gaging Slalions 

In percenlage of 18-yaor overage far period 1928-45. 

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GEOLOGICAL SURVEY 

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CIRCULAR 36 PLATE 10 

COLUMBIA RIVER BASIN 

RUNOFF IN 1937 IN PERCENT OF MEAN 

Scale of miles 

20 40 eo F 

Note: Numbers indicate measured runoff ol gaging stations 

In percentage of 18-y'aor overage for period 1928-45. 
GEOLOGICAL SURVEY 

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CIRCULAR 36 PLATE II 

COLUMBIA RIVER BASIN 

RUNOFF IN 19 38 IN PERCENT OF MEAN 

Scale of miles 

to 19 !0 10 

Note: Numbers Indicate measured runoff at gaging stations 

In percentage of 18· year average for period 1928-45. 
GEOLOGICAL SURVEY 

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44 __ _ 

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124 122 

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CIRCULAR 36 

110 

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COLUMBIA RIVER BASIN 

PLATE 12 

RUNOFF IN 1939 IN PERCENT OF MEAN 

Scale of miles 

ao~eoe 

Note: Numbers il\dicate measured runoff at ooolng stations 

in percentooe of 18-- overooe for period 1928-45. 

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110 
GEOLOGICAL SURVEY CIRCULAR 36 PLATE 13 

COLUMBIA RIVER BASIN 

RUNOFF IN 1940 IN PERCENT OF MEAN 

Scale of mileo 

to 40 eo p 100 

Note: Numbers Indicate measured runoff at VOIJing statlqns 

In percentage of 18-year overage for period 1928-45. 

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110 
GEOLOGICAL SURVEY 

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CIRCULAR 36 

110 

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COLUMBIA RIVER 

PLATE 14 

BASIN 

RUNOFF IN 1941 IN PERCENT OF MEAN 

Scale of miles 

1040f01) 

Note: Numbers indicate meo\ured runoff at !IGOino stations 

· In percentooe of 18-yeor averaoe for period 1928-45. 

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GEOLOGICAL SURVEY 

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CIRCULAR 36 PLATE 15 

COLUMBIA RIVER BASIN 

RUNOFF IN 1942 IN PERCENT OF MEAN 

Scale of miles 

to 40 so 80 

Note: Numbers indicate measured runoff at g~glng stations 

in percentage of 18-yaar overoQe for period 1928-45. 
GEOLOGICAL SURVEY 

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116 

CIRCULAR 36 PLATE 16 

COLUMBIA RIVER BASIN 

RUNOFF IN 1943 IN PERCENT OF MEAN 

Scale of miles 

1!04060!) 

Note: Numbers indicate measured runoff at gaging stoHons 

in percentage of 18-yeor average for period 1928-45. 

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GEOLOGICAL SURVEY 

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CIRCULAR 36 PLATE 17 

COLUMBIA RIVER BASIN 

RUNOFF IN 1944 IN PERCENT OF MEAN 

Scale of miles 

10 40 so !J 

Note: Numbers Indicate measured runaff at vovtnv stationS 

In percentave of 18· year overave for per lad 1928· 45 · 
GEOLOGICAL $URVEY 

Ill 

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CIRCULAR 36 

110 

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COLUMBIA RIVER 

PLATE 18 

BASIN 

RUNOFF IN 1945 IN PERCENT OF MEAN 

Scale of miles 

1040!0ft 

Note: Numbers Indicate measured runoff at gaging stations 

In percentage of 18-yeor average for period 1928-45. 

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·-=.. .. I · i · 

•••• • ._\__ G AN ADA_ -----~- ----------------_:. 

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110 
GEOLOGICAL SURVEY 

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CIRCULAR 36 PLATE 19 

110 

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COLUMBIA RIVER BASIN 

RUNOFF IN 1946 IN PERCENT OF MEAN 

Seale of miles 

20 40 10 !0 

Note: Numbers Indicate measured runoff at gaging stations 

In percentage of 18-yaor overage for period 1928-45 . 

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l ' ~ .... ..... \\1 \ -/ ········\\··= · ... / \ 
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PLATE 20 

A RIVER BASIN 

COLUMBI IN INCHES 

ANNUAL RUNOFF AVERAGE 1928-45 

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