Document ID: ./input/supremecourt_opinions/opinions/21pdf/143orig_1qm1.pdf
Page Number: 9

6 

MISSISSIPPI v. TENNESSEE 

Opinion of the Court 

Following  motions  practice,  discovery,  and  a  five-day  evi-
dentiary hearing, the Special Master issued a report recom-
mending that we dismiss Mississippi’s complaint, but with
leave  to  amend.  He  first  determined  that  the  Middle 
Claiborne Aquifer is an interstate water resource.  He found 
that the aquifer is a “single hydrogeological unit,” that Ten-
nessee’s pumping affects groundwater beneath Mississippi, 
and  that  prior  to  such  pumping,  “groundwater  flowed  be-
tween Mississippi and Tennessee”—a fact Mississippi “does 
not dispute.”  Report of Special Master 15–24.

The Special Master then concluded that, because the aq-
uifer is an interstate water resource, equitable apportion-
ment is the appropriate remedy.  He recognized that equi-
table apportionment “stands alone as the federal common-
law principle for disputes over interstate water,” id., at 31, 
and  saw  “no  compelling  reason  to  chart  a  new  path  for 
groundwater  resources,”  id.,  at  26.  Because  Mississippi’s
complaint did not seek  equitable apportionment, the Spe-
cial  Master  recommends  that  we  dismiss  it.    But  he  also 
recommends  that  we  grant  Mississippi  leave  to  file  an
amended  complaint  seeking  equitable  apportionment, 
though the State has not yet sought such leave.

Mississippi  and  Tennessee  both  filed  exceptions  to  the 
Special Master’s report.  Mississippi objects to the Special
Master’s recommendation that we dismiss the suit.  It ar-
gues that the Special Master erred in finding the water in
the  Middle  Claiborne  Aquifer  subject  to  equitable  appor-
tionment.  Tennessee  objects  only  to  the  Special  Master’s 
recommendation that we grant Mississippi leave to amend
its complaint.

We “conduct an independent review of the record, and as-
sume the ultimate responsibility for deciding all matters.” 
Kansas  v.  Nebraska,  574  U. S.  445,  453  (2015)  (internal
quotation  marks  omitted).    Based  on  that  review,  we  dis-
miss Mississippi’s complaint and decline to grant leave to 
amend.