INLAND DRAINAGE 



103 



Hill 



Of these, the first three usually present no serious problems, 

 requiring simply open ditching or re-channeling. 



Borrow-pits should be treated in accordance with conditions. 

 If fairly shallow and advantageously located, they may be 

 ditched; many are too deep for other than vertical drainage, and 

 may, perhaps, be stocked with fish or oiled. If they are to be 

 drained by ditching, the procedure is generally simple. 



"It is when we come to ponds, lakes and swamps," says Metz, 1 

 "that the real problems arise, 

 and it is best perhaps to consi- 

 der these three together. Since 

 the difference between lakes and 

 ponds is only one of degree, and 

 since swamps may include either 

 or both of the other two, it is ob- 

 vious that, in actual practice, 

 little distinction can be made that 

 would involve different methods 

 of drainage. It is more impor- 

 tant to classify such areas accord- 

 ing to the sources of the water, 

 for, in this case, the distinc- 

 tions correlate with modes of 

 treatment. 



PROBLEMS OF POND, LAKE 

 AND SWAMP DRAINAGE 



"For instance, one pond or 

 swamp may be caused by the ac- 

 cumulation of rain-water and may 

 fluctuate greatlv with the sea- V 



sons, another may be simply a F ™. 67.-Seepag^ outcrop, Case No. 1. 



basin in the channel of a sluggish 



stream, while a third may be fed from springs and may be bordered by 



a seepage outcrop. 



"In the first of these, the rain-water swamp, it is merely necessary to 

 provide a small channel to carry off the surplus water left after the main 

 flood waters have passed. As a rule, one or two ditches will suffice. 



"In the second case, the situation is more difficult, for the water 

 supply is continuous and fluctuating. The swamp will vary in size 

 with high and low water in the stream, and a drainage operation of 



1 "Some Aspects of Malaria Control Through Mosquito Eradication," 

 U. S. Public Health Service, 1919. 



