194 CONSERVATION OF GROUND WATER 



LOWERED WATER TABLE IN DRAINED AREAS 



The total acreage of cultivated land has been increased 

 materially by drainage of swampy areas and lakes. There are 

 drainage projects in practically every state, but they are 

 especially numerous in those states where the last glacial ad- 

 vance of the Ice Age left thousands of lakes, swamps, and 

 undrained depressions. In Michigan about 14,000 square 

 miles of land has been subjected to artificial drainage, ac- 

 complished by about 23,000 miles of open or tiled ditches. 

 The regional water table has been lowered significantly in 

 about one-third of this area, where 90 per cent of the drainage 

 ditches are located. 



In many places the drainage has not been as beneficial as 

 anticipated. Some drains have made land suitable for plowing 

 earlier in the spring but have also reduced the available water 

 supplies for crops in the critical late-summer months. Com- 

 monly the effects of drainage have extended considerably be- 

 yond the troublesome swampy area, and the water table has 

 been lowered to the disadvantage of the surrounding areas. 

 Drainage of natural depressions has in many areas aggravated 

 the flood capabilities of streams, by providing an outlet for 

 surplus runoff that, prior to drainage, had been held within 

 the area. 



The history of the Everglades Drainage District in southeast 

 Florida reveals drainage problems of greater variety than 

 usually encountered in a single area. 



The Everglades and Miami, Fla. 30 The Everglades is 

 favored with an ample supply of water on an annual basis, 

 but the seasonal distribution of precipitation is not all that 

 could be desired. Generally during the months from Janu- 

 ary to May water is required for irrigation of crops, and on 



so References: Jones, L. R., et al., Soils, Geology, and Water Control in the 

 Everglades Region, Univ. Florida Agr. Exp. Sta. Bull. 442, 

 p. 168, 1948. 

 Parker, G. G., et al., Water Resources of Southeast Florida, 

 U.S. Geol. Survey Water Supply Paper, in preparation. 



