342 THE STUDY OF PLANT COMMUNITIES * Chapter XII 



reflected in the general water supply. In many agricultural areas 

 with adequate rainfall, there are water problems that did not exist 

 at the time of settlement. Where once streams and springs were 

 abundant and flowed continuously, now they are intermittent, 

 and summer water supplies are often low. In Ohio, the water table, 

 as evident in well depths, is from fifteen to fifty feet lower than 



FlG. 183. The type of dam and spillway being installed primarily for 

 water conservation. When full, this reservoir extends fifteen miles upstream 

 over an area of 10,000 acres. The flow from the dam can be controlled, there- 

 by providing constant flow during dry periods and reducing danger of flood- 

 ing with high water.— U. S. Soil Conservation Service. 



originally. Floods appear to be more frequent and are certainly 

 more destructive than before. On the credit side, there are now no 

 malaria problems related to undrained swamps or typhoid epi- 

 demics resulting from improper city water supplies. 223 The adverse 

 conditions result partially from the removal of natural vegetation 

 for agriculture. As much water falls today as before, but more of it 

 runs off rapidly. Thus summer drought and spring floods are par- 

 tially explainable. 



There are other contributing factors. Roads, so important to the 

 farmer for transportation, likewise serve to drain off water from 

 his fields. This has been especially bad in the mid-western states 

 where all roads were originally laid out in an east-west, north- 



