Document ID: ./input/supremecourt_opinions/opinions/21pdf/143orig_1qm1.pdf
Page Number: 5.0

2 

MISSISSIPPI v. TENNESSEE 

Opinion of the Court 

issued  his  report,  which  recommends  that  this  Court  dis-
miss  Mississippi’s  complaint  with  leave  to  amend.    Both 
Mississippi and Tennessee have filed exceptions. 

I 
A 
Layers of rock, clay, silt, sand, and gravel exist below the
Earth’s  surface.    Groundwater  percolates  through  the 
spaces in and around these materials, sometimes forming 
underground reservoirs of water known as aquifers.  Some 
aquifers are small, while others span tens of thousands of 
square miles.  The Middle Claiborne Aquifer is one of the
latter.  It underlies portions of eight States in the Missis-
sippi River Basin: Alabama, Arkansas, Illinois, Kentucky,
Louisiana, Mississippi, Missouri, and Tennessee.  See Re-
port of Special Master 16; Hearing Tr. 278–279.  Many of 
these  States,  including  Mississippi  and  Tennessee,  draw 
significant amounts of groundwater from the aquifer.  Id., 
at 660–662, 1038–1040; Joint Exh. J–71. 

To  extract  water  from  an  aquifer,  people  drill  wells.
Pumps then draw water to the surface, where it is processed
and piped to customers.  Pumping does not just bring water 
to the surface; it also lowers water pressure at the site of 
the  well.  Water  is  naturally  drawn  to  this  area  of  lower 
pressure.  This,  in  turn,  “causes  a  pattern  of  lower  or  de-
pressed water levels around the wells.”  Report of Special
Master  13.    Hydrogeologists  call  such  areas  “cones  of  de-
pression.”  These cones of depression can be local—say, the
size of a backyard.  Or they can be regional, stretching out 
for  many  miles  from  a  pumping  site.    See  id.,  at  21–23; 
Hearing Tr. 176, 188, 435. 

The City of Memphis, through its public utility, the Mem-
phis  Light,  Gas  and  Water  Division  (MLGW),  pumps  ap-
proximately  120  million  gallons  of  groundwater  from  the 
Middle  Claiborne  Aquifer  each  day.    Id.,  at  186,  200;  Pl. 
Exh. P–157.  It does so using more than 160 wells located