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as early as 1930 when the lake was only eight years old. In 1936 a complete 
survey of the lake was made by the United States soil conservation service, 
the state water survey, the Illinois agricultural experiment station, and the 
city of Decatur. 
E. D. Walker, extension soil conservationist and associate professor in 
agronomy extension at the University of Illinois college of agriculture, has 
reported the results of this and subsequent surveys. The 1936 survey dis- 
closed that sediment had been filling the lake at the rate of 1 per cent of 
its capacity each year. By 1946, only 24 years after the lake had been built, 
more than one-fourth of its capacity had been filled with precious topsoil. 
The lake’s surface had been reduced by 201 acres. Mud bars topped with tall 
weeds appeared where before there had been only water. 
Naturally this became a matter of great concern to the city of Decatur, 
which in 1941 established the upper Sangamon valley conservation service 
and employed two soil conservationists to help with the problem. Engineers 
also were put to work to find an answer to the city’s dwindling water 
supply. 
The engineers subsequently recommended that the city build two new 
lakes upstream, each with a capacity comparable to that of the present lake; 
also, that the dam on the present lake be raised to increase the capacity of 
that reservoir. The cost is estimated at 6 to 10 million dollars. 
Harry R. Beeson, a conservationist employed by the city of Decatur, re- 
cognizes that these projects in themselves won’t solve the problem of the 
lake. A comprehensive program of conservation must be followed. Such a 
program will include not only conservation of the soil, but also of all wild- 
life, which is dependent for its existence upon the productivity of the soil. 
Fish do not thrive in a lake where the silt is so thick it covers their 
spawning areas or prevents them from feeding. Larks do not sing in eroded 
meadows denuded of tall grass. Feathered creatures do not abound on un- 
productive farm land, too poor to produce food, too barren to offer cover of 
shrubs and trees. 
As Beeson puts it: “If you have a good program which will maintain 
highly productive soils, you will have wildlife.” 
In the meantime, while the people of Decatur and their industries need 
more water each year, the lake is supplying water in ever diminishing 
quantities. 
Walker says that “what is happening here is happening all over the 
country. Because of uncontrolled erosion we are losing the food producing 
layer of our soil.” 
Lake Decatur serves merely as an example of our wasteful methods of 
land management, says Walker. He warns that much the same story can be 
told of some of the other 500 lakes in Illinois, particularly those where a 
large part of the watershed is in cultivation. 
Spring lake, at Macomb, IIl., for example, is approximately half full of 
sediment. Lake Calhoun, near Galva, IIl., is so nearly full of sediment that 
it has lost much of its value as a recreational center. 
“Even though there is not always a lake to catch the runaway soil, we 
