286 CONSERVATION OF GROUND WATER 



periods as well as to provide capacity for passing the flood 

 flows during wet seasons. 



The precipitation is abundant, and only a small part of the 

 infiltration is actually used. Salt-water encroachment is limited 

 both in area and in extent. In many sections drainage, rather 

 than ground-water availability, is the major problem. 



The elements of the control problem in this area are quite 

 simple. They consist primarily in the avoidance of excessive 

 pumping in the vicinity of areas close to shallow, brackish 

 water. More important, but still simple, is the control re- 

 quired to prevent bringing salt-water canals on an uncon- 

 trolled basis into close contact with the underoround strata. 



Peoria, III. The gravel deposits in the vicinity of the Illi- 

 nois River watercourse between Peoria and Pekin are almost 

 100 feet in thickness. They provide about 85 million gallons 

 a day from wells. The water levels are receding, and the pump- 

 age for some years apparently has exceeded replenishment by 

 seven or eight million gallons a day. Conservation measures 

 primarily directed toward reducing pumpage have resulted 

 in recessions of the water levels in recent years of less than a 

 foot a year. In Peoria itself the saturated part of the aquifer 

 is relatively thin. The inflow of water is insufficient to main- 

 tain the present uses. 



The studies in the region indicate that recharge from the 

 Illinois River is less satisfactory than in many other areas 

 over the country. Impoundment on the Illinois River has 

 played a part in the replenishment, but siltation appears to 

 be impeding recharge near Peoria. Artificial recharge through 

 large filter beds is now being practiced experimentally and 

 gives some promise of valuable results. 



The control program should be somewhat more elaborate 

 than in some of the other examples listed. Control of siltation 

 and of pumping, coupled with improved techniques for in- 

 creased recharge, should all be part of the management pro- 

 gram. This is one of the striking examples of the desirability 

 of extending the water-management program to land-manage- 



