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and precipitating the negatively charged soil particles (Irwin and Stevenson^ 

 1951 )o However, if even the most fertile body of water is sxibjected to severe 

 and continuous inflow of erosion silt the fertility will be dissipated and the 

 turbidity may become permanent „ Once established the turbidity excludes light 

 necessary for the synthesis of organic matter and, in the natural course of 

 events, the fertility may not be replenished to the point sufficient to cause 

 precipitation of the soil particles responsible for the turbidity. Then only 

 by artificial treatment, or the natural inundation or inflow of large quan- 

 tities of organic matter^ can the water be cleared sufficiently to once more 

 enable the aquatic organisms to establish a cycle of organic matter synthesis 

 and decomposition that can keep the water fertile — and clearo 



Siltation, or the settling and accumulation of transported materials is 

 also common to highly turbid waters o The relationship of this blanketing 

 action to bottom organisms, to fish reproduction, and to the biology of lake 

 and stream bottoms is itself a fertile field for study, Siltation is also 

 important, and costly, by its filling of reservoir basins and reducing the 

 area of aquatic production„ The siltation of Lake Mead provides the classic 

 example., When constructed in 1936 it impounded 155,723 acres, and extended 

 for a length of 115 mileSo By 1950 siltation had reduced the length to 85 

 miles (Wallis, 1950), with enough silt added each year to cover to a depth 

 of 5 inches an area equal to the maximum area of the lake (Moffett, 1943)= 

 The encroachment in ponds is also great o During the course of this investigation 

 many pondowners were amazed to learn that ponds having 8-foot depths a few 

 years before now measure only 3 to 4 feeto Complete loss of water in many 

 Oklahoma ponds during the 1954 drouth was due to the fact that siltation had 

 reduced their storage capacities o Such losses invariably occurred in the 



