Appendix to the Journals of the Senate and Assembly of the ..session of the Legislature of the State of California . s stirred so as to produce a nuilch three inches deep the evapora-tion was three-fourths of an inch, or 12J per cent of the water applied,and when the mulch was nine inches in depth the loss from evaporationamounted to only four-tenths of an inch of water or less than 7 per centof that applied. The conclusions deduced from the experiments are: 1. A dry, granular mulch three inches deep will save, otherconditions being equal, at least one-half of the loss from anunmulched surface
Appendix to the Journals of the Senate and Assembly of the ..session of the Legislature of the State of California . s stirred so as to produce a nuilch three inches deep the evapora-tion was three-fourths of an inch, or 12J per cent of the water applied,and when the mulch was nine inches in depth the loss from evaporationamounted to only four-tenths of an inch of water or less than 7 per centof that applied. The conclusions deduced from the experiments are: 1. A dry, granular mulch three inches deep will save, otherconditions being equal, at least one-half of the loss from anunmulched surface. 2. A like mulch six inches deep, will save 75 per cent of theevaporation from an unnuilched surface. 128 BIKNNIAL KElOHT OF DKlAUTM KNT OF ENGINEERING. 3 111 eomparing the effieioncy of a six-inch mulch with a nine-inch iinih^li the result shows a considerable savmg m water by thedeeper iimlcli but the cost of cultivation and other practical con-siderations would seem to limit the depth to six inches or foHowin- figure graphically illustrates the loss occurring fromevaporation as just described. swcA. LJs of cuUivation on prevention of ^^/l^vaporation from -^-, U. S. Department hat this is not the only preventable loss. Ditches excavated inbroken rock and absorbent soil lose a large part of the water carriedby them. Different degrees of porosity, of course, affect the amountof loss from percolation. In some cases in mind, where the water isconveyed several miles in side-hiU ditches, it is found that when only100 second-feet of water is available at the head of the ditch the lossbetween that point and the nearest point of use is 100 per cent. Ihatis to say, all is lost and unless more than the quantity stated can beturned in no attempt is made to take any. Government investigators have reported that the average losses otwater in its application for irrigation was 60 per cent, and not intre-quently only 20 per cent of that delivered to the land was usefully ap
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