24 BULLETIN 1430, U. S. DEPARTMENT OF AGRICULTURE 
STREAMS OF THE PLATEAU OF CENTRAL TEXAS 
A number of rivers of Texas have their headwaters in the deeply 
fissured limestones of the Edwards Plateau region of the central 
part of the State. These streams are normally clear. They carry, 
however, during periods of flood, an enormous quantity of silt eroded 
from the gorges and channels of the small streams which indent and 
canyon through the plateau region. None of these streams heading 
on the Edwards Plateau are fed by melting snows. They are sub- 
ject to wide fluctuations between minimum and maximum flow. The 
floods at San Antonio and at Cameron, Tex., on September 9 and 
10, 1921, are extreme examples of the maximum flow of streams of 
this character. At Cameron the Little River increased from a nor- 
mal low flow of 177 second-feet to a maximum discharge of 647,000 
second-feet. The Colorado River, on which was erected the ill-fated 
dam at Austin, is another. At the time this dam broke, after 10 
years of service, it was found that its storage capacity had been re- 
duced 56 per cent during the decade as a result of siltings. T. U. 
Taylor reports that the new reservoir, constructed in 1913, had losj 
84 per cent of its capacity through silting by 1922. (PI. 17.) The silt 
burden of the Colorado River (of Texas) is roughly estimated at 
1 per cent of its volume or an average of 18,000 acre-feet a year. 
The Weather Bureau records show a rainfall of 0.9 of an inch 
within five minutes at Taylor and 4.46 inches in one hour at Pales- 
tine. Only a small portion of rains of such intensity can be ab- 
sorbed, since if there is any colloidal content in the soil the surface 
quickly puddles and further absorption takes place slowly. 18 The 
Brazos River above Waco, with a drainage area of 30,000 square 
miles, bears more than 3,200,000 tons of soil a year. 
The streams of this region, notwithstanding their high silt burdens 
and the possibility of poor foundations on which to erect dams on 
certain sites, present many excellent opportunities for water storage 
in their deep canyons, which in places spread out into broad basins; 
and nowhere would the results from water storage be of more benefit. 
Not only might storage result in preventing, or at least in lessening, 
the ravages of such floods as that which visited San Antonio, but 
it would furnish a great deal of power and water for irrigation in a 
section which is subject to long and costly droughts. It might be 
possible through such storage to irrigate a considerable portion of 
the Edwards Plateau region and thus add enormously to the value 
of these lands, the utility of which at present is largely restricted to 
grazing and that itself sometimes uncertain as during the drought 
of 1924. It would probably be necessary to make provision for flush- 
ing the silt from reservoirs by means of water stored in smaller 
reservoirs located above and constructed with this object in view, 
if this procedure should prove feasible. The woodland and her- 
baceous cover of this region is too light, on account of the limited 
rainfall, to protect the surface from erosion, but it is possible by 
adequate regulation of grazing, and by better protection of stream 
banks if not to reduce erosion at least to prevent its further increase. 
Range depletion as well as the maintenance of the protection of the 
cedar brakes requires careful investigation. 
18 See footnote 12 on p. 7. 
