SEEPAGE OR RETURN WATERS PROM IRRIGATION. 
49 
§ 43. On the Muzza canal, in Italy, the loss is equivalent to a 
layer 1.7 feet deep per 24 hours. The canal runs through an 
exceedingly pervious soil, and has a great fall. 
The Naviglio Grande, of Italy, loses a layer of water ten inches 
deep. The Canale Martesana, a layer 1.5 feet deep daily. The 
three canals above mentioned have been built for some 700 years. 
The Centreville and Kingsburg canal, in California, from data 
given by C. E. Grunsky, of San Francisco, loses an average of five 
feet in depth, for six miles, in twenty^four hours. In one particular 
mile, where the loss is excessive, because of porous soil as well as from 
the location of the canal, near the edge of a bluff, the daily loss 
amounts to a layer fifteen feet in depth. This is an extreme case. * 
Another case of a great loss occurred in the Cavour canal, of Italy, at 
the crossing of the Dora river. This was by an artificial embank¬ 
ment. At first the loss amounted to a layer nearly twenty feet in 
depth. This was afterward very much reduced by using muddy 
water and allowing the silt to settle, and fill and cover the surface. 
If we consider that in each of these cases the water occupies 
one-third of the volume of the sand, the distance it flows in twenty- 
four hours would be three times the thickness of the layers noted 
above, or from 2.5 feet on the Naviglio Grande to 60 feet in the 
Cavour instance. 
It may be said, in passing, that the amount of loss from the 
canals may be much reduced by the settlement of fine clay or sedi¬ 
ment. In one case, in the Cache a la Poudre Canal No. 2, where 
the seepage had made a considerable area so wet as to be impassa¬ 
ble with teams, a check built for other purposes, by causing the 
deposition of silt, was sufficient in a few years to lessen the seepage 
so that the land became passable. 
Another instance, illustrating the same effect, was shown in a 
canal near Greeley. When first built, considerable damage was 
done from the raising of the ground water and flooding cellars in 
some parts of town. After a few years the cause of complaint dis¬ 
appeared, silt sealing the bottom of the canal. In 1895 sand was 
obtained from the bottom of the ditch, where the ditch crossed a 
ravine, and where there was a good deposit of sand suitable for 
building purposes. The top layers of the sand were partially 
cemented. Within a few months after water was turned in com¬ 
plaint arose regarding the influx of water into the cellars. Ten 
days after the water was turned out of the canal, the water began to 
* Since the above was in type, additional data, obtained through the cour¬ 
tesy of Mr. Grunsky, indicate losses of depths of 1.5, 1.7, and .6 feet, from 
stretches of the Kings River and Fresno canal; of 2.8, .25, and .4 from portions 
of the Fresno canal, and 1.2,1.9, 3, 7 and 6.4 feet from certain laterals, the veloc¬ 
ity through the soil being about three times as great. 
