IRRIGATION WATERS AND THEIR EFFECTS. 15 
stored and have become heavily laden with salts by seepage or 
solution carry comparatively little of either the potash or nitrogen 
that is needed by onr soils. 
Nothing has been said about this latter element, concerning 
which it is customary to say a great deal. The reason for this is 
that neither the irrigation, nor ground, nor drain waters showed a 
content of nitrogen which justified any special notice. There is 
still another point frequently mentioned in connection with irri¬ 
gation waters which we will notice a little more fully, i. e., that 
they fertilize the soil by means of suspended matter which they 
carry. This point is not in the least applicable to stored 
waters which remain stored from one to twelve months and some¬ 
times still longer, during which time they would deposit their 
suspended matter if they ever carried any. This suspended mat¬ 
ter tends to silt up the reservoirs which process is evidently proceed¬ 
ing very slowly. The question relative to the value of the suspended 
matter applies then to water used for direct irrigation and to flood 
waters. This question, too, is of varying importance according as 
the streams had in view are mountain streams, whose courses are 
through massive and metamorphic rocks, as is the case with the 
upper portions of our rivers, or whether they are plains streams, 
having their courses through sections of sedimentary material 
which is easily torn loose by heavy rains and currents. If the 
section of country through which the rivers run is subject to visi¬ 
tations by torrential rains, the river waters may at such times car¬ 
ry very large amounts of suspended matter. Such conditions do 
not prevail in this section of Colorado. We occasionally have 
torrential rains and the river waters mav be black or red with 
mud, according to the character of the country in which the rains 
fall. But such conditions are of short duration. The period of 
high water is due to the melting of snow in the high mountains. 
The water of this season is, it is true, more turbid than during 
times of low water, times of heavy rain or flood excepted. The 
amount of suspended matter during this time of high water is in¬ 
significant in quantity. I have made observations to establish 
the amount and found it to be only 0.0016 per cent, of the weight 
of the water, or about forty-four pounds per acre-foot of water If 
this sediment were never so rich it would amount to but little as 
a means of fertilizing our soils. It is no more important from 
the standpoint of its quality than it is from that of its quantity. 
It contains just about the same percentage of potash that the soil 
itself contains and it is even less available if there is any differ¬ 
ence at all. The value of this suspended matter is less than I ex¬ 
pected to find it. 
It is seldom that our waters carry large amounts of suspend¬ 
ed matter due to heavy rains, but occasionally thev do. On an 
