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U.S. Geological Survey
Circular 1136

Nutrients in the Nation's Waters--Too Much of a Good Thing?

By David K. Mueller and Dennis R. Helsel

NAWQA Study Units

Locations of the 60 National Water-Quality Assessment study units and their proposed implementation dates.

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Study unit map id number, name, starting year              
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 1 Northern New England Basins (1994)                       
 2 Southeastern New England (1997)                          
 3 Connecticut, Housatonic, and Thames River Basins (1991)  
 4 Hudson River Basin (1991)                                
 5 Long Island-New Jersey Coastal Drainages (1994)          
 6 Delaware River Basin (1997)                              
 7 Lower Susquehanna River Basin (1991)                     
 8 Delmarva Peninsula (1997)                                
 9 Potomac River Basin (1991)                               
10 Allegheny and Monongahela Basins (1994)                   
11 Kanawha-New River Basin (1994)                           
12 Lake Erie-Lake Saint Clair Drainage (1994)               
13 Great and Little Miami River Basins (1997)               
14 White River Basin (1991)                                 
15 Upper Illinois River Basin (1997)                        
16 Lower Illinois River Basin (1994)                        
17 Western Lake Michigan Drainage (1991)                    
18 Upper Mississippi River Basin (1994)                     
19 Red River of the North (1991)                            
20 Albemarle-Pamlico Drainage (1991)                        
21 Upper Tennessee River Basin (1994)                 
22 Santee Basin and Coastal Drainage (1994)           
23 Apalachicola-Chattahoochee-Flint River Basin (1991)
24 Georgia-Florida Coastal Plain (1991)               
25 Southern Florida (1994)                            
26 Kentucky River Basin (1997)                       
27 Mobile River and Tributaries (1997)               
28 Mississippi Embayment (1994)                       
29 Acadian-Pontchartrain (1997)
30 Lower Tennessee River Basin (1997)                  
31 Eastern Iowa Basins (1994)                         
32 Ozark Plateaus (1991)                              
33 Canadian-Cimarron River Basins (1997)
34 Trinity River Basin (1991)                         
35 South Central Texas (1994)                         
36 Central Nebraska Basins (1991)                      
37 Kansas River Basin (1997)                          
38 Upper Arkansas River Basin (1997)                   
39 Middle Arkansas River Basin (1997)
40 Southern High Plains (1994)                        
41 South Platte River Basin (1991)                
42 North Platte River Basin (1997)               
43 Cheyenne and Belle Fourche Basins (1997)       
44 Yellowstone Basin (1997)                      
45 Upper Colorado Basin (1994)                    
46 Rio Grande Valley (1991)                      
47 Northern Rockies Intermontane Basins (1994)   
48 Great Salt Lake Basins (1994)                 
49 Upper Snake River Basin (1991)                
50 Central Arizona Basins (1994)                 
51 Central Columbia Plateau (1991)               
52 Yakima River Basin (1997)                    
53 Puget Sound Drainages (1994)                   
54 Willamette Basin (1991)                       
55 Sacramento Basin (1994)                       
56 Nevada Basin and Range (1991)                  
57 San Joaquin-Tulare (1991)                     
58 Santa Ana Basin (1997)                        
59 Oahu (1997)                                   
60 Cook Inlet Basin (1997)