G4 



DATA OF GEOCHEMISTRY 



N 



Fiodke 1.— Mean daily supply of chloride and sulfate plus nitrate in relation to wind 

 direction. The inner and outer circles delimit 50 and 100 meq/100 m*, respectively. 

 High chloride is characteristic of winds from a southwesterly direction, that is, 

 from the sea, whereas sulfate and nitrate are high in winds blowing from the in- 

 dustrial regions lying cast and southeast of the station in the English Lake district 

 where the rain was collected. After Gorham (1958). Reprinted by permission 

 of the Eoyal Society, London. 



and mineral soil, is usually much more concentrated 

 than surface runoff, the more so because it is usually in 



contact with the mineral material of the soil under 

 conditions of oxygen and carbon dioxide tension that 

 are particularly favorable to the solution of many 

 mineral components. As a result, the concentration 

 of dissolved matter of river water usually bears an in- 

 verse relation to discharge, although the relation is 

 seldom simple. The water of heavy rains has less 

 opportunity to be concentrated by evaporation and is 

 usually less concentrated to begin with than the water 

 of light showers. These combined effects cause rivers 

 at high stage to be less concentrated than rivers at low 

 stage. Although it is usually difficult to separate the 

 various concentration processes, their net effects are 

 usually greatest in arid lands. For example, the 

 Moreau River, S. Dak., with an annual discharge of 2 

 inches over the 1,570 square miles of its drainage 

 basin, has a total ion content that ranges from 160 to 

 3,400 ppm (parts per million) during a single year. 

 Monthly analyses for the principal elements are given 

 in table 4. This may be contrasted with a range from 

 36 to 57 ppm for Mayo River, N.C. (table 5), from a 

 humid region with an annual discharge of 17 inches 

 over the 260 square miles of its drainage basin. 



It is impossible to appreciate the full extent of the de- 

 pendence of river chemistry on discharge from the 

 comparison of monthly means, which smooth out the 

 more dramatic fluctuations. Complete data do not 

 appear to be available for any stream showing violent 



Table 4. — Moreau River at Bixby, S. Dak., showing changes in chemical composition of a stream in a semiarid region 



[The drainage area above the sampling station is 1,670 square miles and the data, which cover the water year October 1949-September 1950, have been recalculated from U.S. 



Geol. Survey (1955b)] 



Date of Sample 



1949 



Oct. 1-3 



Oct. 4-12 



Oct. 13-28 



Oct. 27-31 



Nov. 1-30 



Dec. 1-21 



1950 



Mar. 6-9 



Mar. 10 



Mar. 14-Apr. 1... 



Apr. 3 



Apr. 4-6 



Apr. 7. 



Apr. 11-14 



Apr. 15-17 



Apr. 18-20 



Apr. 21 



Apr. 22-26 



Apr. 27 



Apr. 28-May 15— 



May 16-31 



June 1-30 



July 1-31 



Aug. 1-6 



Aug. 6-8 



Aug. 9-31 



Sept. 1-19 



Sept. 20-24 



Sept. 25-30 



Mean 



discharge 



(cfs) 



3.2 

 16 

 7.0 

 8.0 

 4.1 

 3.2 



123 



100 



126 



2,900 



2,800 



6,690 



1.260 



7,600 



1,350 



363 



280 



160 



470 



45 



30 



14 



4.1 



76 



6.7 



4.6 



34 



6.2 



pH 



8.9 

 8.9 

 8.5 

 8.3 

 8.4 

 8.4 



8.4 

 7.3 

 7.2 

 7.2 

 7.1 

 7.4 

 7.2 

 7.4 

 7.5 

 7.1 

 7.3 

 7.5 

 7.6 

 8.0 

 7.9 

 7.9 

 7.9 

 7.9 

 8.3 

 8.3 

 7.8 



Percent 



SiOi 



0.2 

 .3 

 1.3 

 1.0 



3.0 

 1.5 

 3 2 

 8.1 

 6.4 

 5.4 

 5.0 

 5.6 

 3.1 

 2.1 

 2.1 

 1.5 

 2.0 

 1.6 

 .6 



2.1 

 .7 



1.9 

 .7 



Fe 



0.002 

 .002 

 .010 

 .005 

 .005 

 .002 



.003 

 .004 

 .009 



.015 

 .027 

 .011 

 .014 

 .005 

 .007 

 .003 

 .004 

 .002 

 .001 

 .002 

 .002 

 .002 

 .024 

 .004 

 .003 

 .054 

 .004 



Ca 



0.5 

 .6 

 1.7 

 1.9 

 2.3 

 1.3 



3.0 

 4.4 

 4.9 

 7.5 

 9.2 

 10.1 

 9.1 

 8.2 

 9.1 

 8.6 

 6.7 

 7.3 

 7.2 

 6.6 

 3.8 

 4.6 

 2.1 

 3.1 

 1.8 

 1.4 

 2.1 

 1.8 



Mg 



1.0 

 .6 

 .5 

 .2 

 .6 

 .9 



1.4 

 1.4 

 1.4 

 2.8 

 2.6 

 2.5 

 2.1 

 2.5 

 3.2 

 2.5 

 2.5 

 2.8 

 2.6 

 4.6 

 2.6 

 1.6 

 .7 

 .8 

 1.1 

 .4 



Na 



0.3 



.2 

 .5 

 .4 



.9 

 .8 

 1.1 

 3.2 

 1.6 

 1.3 

 1.2 

 1.2 

 1.1 

 .9 

 .8 

 .6 

 .7 

 .6 

 .5 

 .5 

 .5 

 .9 

 .5 

 .4 

 .7 

 .6 



COj 



2.6 

 3.2 

 1.7 

 1.7 

 1.2 

 1.2 



HC0 3 



SOt 



CI 



0.9 

 .7 

 .6 

 .6 

 .6 

 .6 



.7 

 1.9 

 .7 

 .3 

 1.2 

 .7 

 .7 

 .9 

 .6 

 .6 

 .7 

 .6 

 .6 



.6 

 .9 

 1.1 

 .7 



0.02 

 .02 

 .03 

 .02 

 .02 

 .01 



NOj 



0.05 

 .08 

 .22 

 .09 

 .06 

 .02 



.39 

 .40 

 .64 

 2.73 

 .80 

 .64 

 .61 

 .37 

 .66 

 .26 

 .28 

 .14 

 .18 

 .14 

 .07 

 .06 

 .07 

 .63 

 .15 

 .08 

 .26 

 .08 



0.02 

 .02 

 .02 

 .02 

 .02 

 .02 



.02 

 .01 

 .02 

 .06 

 .04 

 .03 

 .03 

 .04 

 .03 

 .04 

 .02 

 .02 

 .01 

 .01 

 .01 

 .01 

 .02 

 .06 

 .03 

 .03 

 .04 

 .00 



Total 



ions 



(ppm) 



3,400 

 2,430 

 1.200 

 1,450 

 1,740 

 3,810 



540 



890 



410 



160 



250 



300 



340 



270 



390 



540 



610 



810 



800 



1,170 



2,000 



1,800 



1,890 



660 



1,430 



1,760 



920 



1,440 



