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IOWA ACADEMY OF SCIENCE Voi,. XXVII, 1920 
fall. Most of that used for domestic, civic or industrial purposes 
ultimately joins the run-off and is of little further immediate 
direct service. Hence a more conservative use of water by man 
will go far toward reducing this alarming lowering of the water 
table which is such a vital factor in the preservation of all life. 
If as has been stated, “the upper level of the ground water is not 
far from the limit of its availability for crop growth” (Beyer) 
it is evident that the condition is really alarming and must be 
remedied. It is not only the crop grower who is concerned. The 
crop consumer is equally vitally concerned. He too must take 
steps to retard and if possible prevent the catastrophe that seems 
to be impending. 
Another element which, although necessary, has assisted in 
lowering the water level, is artificial drainage. Doctor Beyer, 
in the address to which reference has been made, urges strongly 
the abandonment of the open ditch as it both increases the run-off 
and wastes valuable land. Tile drainage, on the other hand, 
equalizes the run-off while reducing the wastage of the land. 
Furthermore by the very act of lowering the water table a few 
feet it reduces the losses through evaporation. Probably the great- 
est part of the work of drainage, with its consequent lowering of 
the water table, has been completed, so that it will not be a 
serious factor in the future. 
It is clear that agriculture must be made to conserve soil 
moisture rather than dissipate it. How shall it be done? The 
details are for the trained agriculturist; only a few principles 
can be given here. Soil wastage must be stopped. Soil conserva- 
tion must be enforced. Deforestation must cease or at least be 
very intelligently practiced and furthermore it should be ac- 
companied by reforestation and even by the enlargement of the 
forests and groves. Proper treatment of the soil in plowing and 
in cultivating of crops will go far to preserve the water which is 
brought up by the great centrifugal pump, capillarity, and to 
prevent its excessive evaporation. Keeping the surface of the 
soil of the field loose and fine, fall plowing, allowing a field to 
lie fallow for a time; these all help in increasing percolation 
and reducing run-off. In spite of the great amount of transpir- 
ation from vegetation a cover of plants reduces the amount of 
evaporation from a given surface in a large degree. Let me cite 
the following relative rates of evaporation as given by Meyer. 
He says: “Considering the rate of evaporation from the bare 
ground surface at a given mean temperature as 1.0, the rate of 
