102 



MOSQUITO ERADICATION 



4 to 6 days, its capacity is sufficient, from a mosquito control 

 standpoint, although this may not be the case from the stand- 

 point of agricultural drainage. 



TYPES OF INLAND DRAINAGE PROBLEMS 



Once the area in which the campaign is to be undertaken has 

 been gone over, it will often be found that the problems to be met 

 are varied and numerous. Some breeding-places may be handled 



(Photos by E. B. Johnson, C. E.) 



Fig. 66. — Left, large cat-tail swamp fed by a spring; right, ditch dug to lead 



water around the swamp. 



best by means of fish-control; others best by oiling; and still 

 others best by drainage. The director of the campaign will have 

 to study each problem by itself and decide which is the best 

 method of dealing with it. In case of doubt, the method that 

 seems cheapest for that particular problem should be adopted. 

 After eliminating those places in which fish-control and oil may 

 be used to best advantage, a considerable number of places 

 generally will be left that obviously require drainage. In any 

 large project, these will, as a rule, be of several different types, 

 and hence will require different methods of treatment. Among 

 the different types of areas requiring drainage may be the follow- 

 ing: Temporary puddles, stagnant ditches, blocked-up streams, 

 borrow-pits, ponds, lakes and swamps. 



