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RANGE MANAGEMENT IN NEW MEXICO. on 
be found where a small earth dam and a proper spillway will make 
a tank that will catch and hold a large quantity of water. (PI. IX, 
fig. 1.) These tanks are usually not very expensive, and, notwith- 
standing the high rate of evaporation, water is often maintained in 
such tanks throughout the year. The deeper the tank in proportion 
to its area the smaller the relative amount of loss by evaporation. 
Even in the plains country there is always sufficient run-off to collect 
large quantities of water in tanks properly located. (Pl. IX, fig. 2.) 
A little judgment in the selection of a site and the use of some plows 
and scrapers are all that is necessary to develop a valuable supply. 
In the mountainous country it is frequently very easy to make 
lakes of considerable size by deflecting the flow of the smaller streams 
into natural basins, where a small dam will make a lake several acres 
in extent. The construction of such lakes is one of the best things 
that can be done upon a ranch, since all such bodies of water help to 
regulate the run-off. They always afford a supply of water for stock, 
and they frequently change intermittent streams into permanent 
ones, thus distributing the water so that the stock do not need to 
congregate. They thus reduce the run-off and tend to remove the 
main cause of trail making, both of which factors are very potent in 
reducing erosion. 
No other one factor is so important as the abundance of good, clean 
water, well distributed over the ranch, and there are relatively few 
ranches that now have the water so well distributed that the range 
may be uniformly grazed. Stock mostly have to go too far for water, 
with the result that much grass is trampled out around the watering 
places, and the range is apt to be cut up by trails that ultimately 
become arroyos. And it is equally true that much more water could 
be developed upon most ranges, a procedure that would materially 
help the business. But under the present uncertainty of tenure of 
the range lands such expenditures are not warranted. 
Reducing the effects of erosion.—There are two ways by which the 
effects of erosion may be reduced. Attention has already been called 
to the regulation of the run-off and the making of trails. What is 
necessary on many ranches to-day is the repair of arroyos already 
made. The aggregate area of land that now produces no forage as 
the result of the erosive action of water is large. More or less intri- 
cate systems of drainage channels have been established where for- 
merly there was but gently rolling country with no definite channels. 
The original condition existed because the plant cover of the soil pre- 
vented the water from collecting into streams. The run-off occurred 
mostly as a thin sheet of water gently moving over all slopes, the 
motion being so slow as to allow most of it to soak into the soil. 
This is the best possible condition for the conservation of both the 
