14 Transactions Texas Academy op Science. [ 46 ] 
I do not know of any > attempts in this country to remove silt once 
deposited in large storage reservoirs, though for small ones it is some- 
times sluiced out through pipes at the bottom, as in water supply res- 
ervoirs. Considerable manual labor is required at the same time to 
make the process effective. Wherever a good head of water can be 
obtained it would seem possible to move the sediment by means of a 
jet from a nozzle, as in hydraulic mining, but in the case of an irriga- 
tion reservoir such a source of water pressure is not available, at least 
not in any cases with which I am familiar. As far as experience has 
so far shown us the best plan seems to be to keep the silt from being 
deposited, whenever possible, or if the filling is inevitable to so plan the 
whole system that within the life of the reservoir the returns will more 
than compensate for the first cost. Otherwise, abandon the project. 
The deposit of silt in irrigation canals is a source of much annoyance 
and expense. Sometimes sand gates are used to remove a portion of it 
near the upper end where the cross section of the ditch should be great 
enough to allow the bulk of the sediment to be there deposited, in case 
it is not possible to give sufficient fall to maintain a velocity thaf will 
prevent deposition. Moss grows rapidly in canals kept constantly full 
of water, and as this retards the flow very much, it is necessary to 
remove it. If the water cannot be cut off this involves considerable 
expense, but when the canal can be allowed to dry out for a few days 
the moss will wither and die and the attendant expense will be quite 
small. 
I should like to have been able to give you some of the results of the 
chemical analyses of the waters of the Brazos, the Wichita and other 
rivers, but this paper is now long enough. For the former rivers, I will 
say, however, that both the sediment and the water at times of red 
rises carry considerable available plant food, and that at times of low 
water there is considerable alkali in the water, but very much less than 
that carried in the Pecos water, which is now being successfully used 
for irrigation in ISTew Mexico and Texas. 
