38

The following table shows the maximum and mean depths of water for 1893 and 1900, the maximum and mean depths of silt for 1900, and the percentage of silting up at the respective stations:

The maximum depth of silt is not always equal to the difference between the maximum depth of water for 189 3 and 1900, as the channel shifted at several points. This is very noticeable at station 13.7, known as the Santa Monica (or Sulphur) Springs station. The last column ("Amount of silting up," etc.) gives the ratio that the present cross section of silt bears to the original cross section of water. Thus at Santa Monica Springs (station 13.7) 78.9 per cent of the original cross section has filled with silt. In February, 1900, there were 43,460,000 cubic

yards of water in the main channel of the lake beneath the level of the top of the dam (equivalent to 42.1 feet on a' square-mile base) and 38.8 feet of silt. Thus 48 per cent of the original storage capacity of the lake was at that time mud. Up to that date the average rate of deposit, or a square-mile base, was 5.8 feet per year.