WATER LOSSES FROM WET AREAS 



69 



TABLE 24 



' Tank Nos. 13, 14 and 15 contained disturbed soil, all others contained soil in place. 



about 1000 gTams, was air dried and screened to the point of refusal. 

 Results at Santa Ana show that about 40 per cent of the sample was 

 retained on a No. 100 screen and nearly half that amount passed the 

 No. 200 screen. 



Soil at the San Bernardino station was finer and a larger per- 

 centage passed the No. 200 screen. 



Moisture Equivalent 



Moisture equivalent is a measure of the value of the moisture 

 retentiveness of a soil and is obtained by subjecting a sample of 80 

 grams to a constant centrifugal force of 1000 times the force of gravity 

 for a period of 30 minutes. Experiments by many investigators have 

 determined that moisture equivalent is a close measure of the field 

 capacity. Tt is more easily interpreted as regards soil moisture reten- 

 tion than is possible by sej)aration of soil particles into groups as 

 determined by mechanical analysis. Colloidal matter in the soil, as an 

 important factor in affecting specific yield or s])ecific retention, is not 

 apparent in determinations of mechanical analysis, but does affect the 

 percentage of moisture retained. High moisture equivalents are 

 obtained from fine grained soils containing quantities of colloidal 



