13 

 Usinger: Introduction 



UPPCR JOHORAN 

 HANSITIONi IOWER SONORAN 



Intro. 



fig. 15. Stylized profile of the Merced River from the crest 

 Sierra to the valley (after Grinnell and Storer, 1924). 



>f the 



classify springs according to topography, whether 

 their waters immediately fall away after leaving the 

 ground or whether they are caught in a pool of varying 

 size (Bornhauser). One could also classify them 

 according to size and temperature; as for the latter, 

 the springs range from icy dullness to boiling point. 

 One might arrange them according to color, which not 

 only differs among different springs, but often in the 

 same spring at different times. Again, one could 

 classify them according to substances in solution, 

 such as carbonates, arsenates, chlorides, silicates, 

 sulphides, etc., or according to substances in sus- 

 pension, such as sulfur, mud, sand, silt, etc." Cali- 

 fornia examples could be cited for each of the above 

 criteria, from the hottest waters of the Lassen region 

 to the saline springs of Death Valley, but the more 

 normal springs are cool and fresh and form seepage 

 areas and bogs in the humid northwest and feed many 

 streams and lakes throughout the state. 



Contingent on the source and also the soil and 

 vegetation in the drainage area, Ricker (1934) recog- 

 nized hard-water streams with a bicarbonate content 

 greater than 100 parts per million (expressed as 

 CaC0 3 ) and hardness more than 150 parts per million. 

 Comparable figures for soft-water streams were: 

 bicarbonate content less than 25 parts per million 

 and hardness less than 50 parts per million. Hydrogen 

 ion concentration has also been used as a basis for 

 classifying streams, the acid streams that drain bogs 

 being much less productive than streams with a pH 

 of 7.0 or above. 



Permanence. — Depending on the source, but also 

 on many other factors, a stream may flow continuously 

 (glacial and most spring-fed streams), may recede to 

 its higher reaches during the dry months of summer 

 and fall, or may dry up completely soon after the 

 rains stop. The first of these is, of course, perennial. 

 The second may be termed a receding intermittent and 

 the third a temporary intermittent. Each of these is 

 characterized by distinctive insects, though the 

 receding intermittent has characteristics of both the 

 perennial and temporary. 



Slope, size, and speed of current. — Much has been 

 made of these three interrelated factors in classifying 

 streams. Slope, for example, was used by Huet (1949) 

 as the basis for a classification of the streams of 

 Western Europe. His so-called "slope-rule" states 



that, "In a given biogeographical urea, rivers of like 

 breadth, depth, and comparable slopes, have identical 

 biological properties and specifically similar fish 

 populations." In California, slope is obviously an 

 important factor and follows a Btylized profile from 

 the highest mountains to the lowland valleys, dese 

 or sea coast (intro. fig. 15). 



Size is a factor in its own right, though obviously 

 related to other things. For example, verj small 

 streams are largely "extrinsic," being influenced to 

 a great extent by their surroundings. Lar<;e rivers, 

 on the other hand, are "intrinsic" in the sense that 

 they determine to a great extent their own course, 

 type of bottom, and productivity and are more or less 

 independent of their immediate environment. 



Arbitrary size limits have been set by various 

 authors to define creeks, rivers, and the like. Ricker 

 (1934) chose a volume of flow less than 10 cubic feet 

 per second (on June 1) and a width of less than 10 feet 

 for his "creek" category. Streams with volume and 

 width above these figures he termed "rivers." Huet 

 (1949) found that slope and breadth had a combined 

 influence on fish populations in Western Europe — the 

 smaller the river, the greater the slope tolerated In 

 a given species. 



////////////////////////////// 



wmiiiiiiiimii/n/nm 



mm^mmm ^\\mm^m m^mmmm^ 





Intro, fig. 16. Grophic representotion of the speed of current in 

 a stream, a, vertical view; b, horizontal view. The dark area 

 represents a stream with half the width o'nd depth (Hoet, 1949). 



