Wilcox, D. B. and K. W. Willis (1993).  Identification of constraints on river 
regulation. Lock and Dam 9 near Lynxville, Wisconsin, Upper Mississippi River 9-
foot channel project. U.S. Army Corps of Engineers, St. Paul District, Special 
Report EMTC93S012.
	
The timing, amplitude, frequency, and duration of water level fluctuations and 
changes in current velocity greatly affect river life. On regulated rivers such 
as the Mississippi, water level and velocity fluctuations are caused by natural 
hydrologic events that change river discharge and by operation of water control 
structures. The Upper Mississippi River System (UMRS) includes the Mississippi 
River upstream of the mouth of the Ohio River at Cairo, Illinois, to 
Minneapolis, Minnesota; the Illinois River; and navigable portions of the 
Kaskaskia, Black, St. Croix, and Minnesota Rivers. River regulation greatly 
influences habitat conditions in the river. Changes to the present system of 
river regulation could improve habitat conditions and ecological productivity of 
the UMRS. Any modifications to the existing regulation plans must be compatible 
with constraints on operation. The purpose of the report is to identify the 
constraints on regulation of Lock and Dam 9 in the Upper Mississippi River 9-
foot channel navigation system.