Notes:

The river discharge in some rivers can be negative (Florida during droughts).  Because the intended use of these data are indicating the amount of freshwater flow
being delivered to the Gulf of Mexico, I have replace negative discharge with 0.0 values.  The missing data flag is -999.0.  Data near the end of the record, or
perhaps for the entire previous "water year" (water year is a USGS term for the period 1-October to 30-September) may be provisional until they finish their quality
control efforts.  In some cases, a river is listed twice because old gages are discontinued, and new ones started - perhaps with long overlaps. Or some gages may
be closer to the river mouth.  Pay attention to my comments at the right of the table and you will know which river to choose.

DO NOT JUST BLINDLY USE ALL 55 Rivers listed below, or you will have some rivers contributing twice. 

Data for the first two rivers (Mississippi and Atchafalaya) come from the U.S. Army Corps of Engineers.
http://www.mvn.usace.army.mil/cgi-bin/wcmanual.pl?01100
http://www.mvn.usace.army.mil/cgi-bin/watercontrol.pl?03045

The rest come from the USGS
http://waterdata.usgs.gov/fl/nwis/uv/?site_no=02330150  (use river_ID to get other stations)

Rive_ID:    Station identifier
Start  :    First available record
End    :    Last record collected
GageLAT:    Latitude of the gage location
GageLON:    Longitude of the gage location
MouthLA:    Latitude of the estimated location of the river mouth
MouthLO:    Longitude of the estimated location of the river mouth
River_Name: The name of the gaging station
Man_Flow:   Record length mean flow in cubic meters per second

Questions or comments:  Matthew Howard, mkhoward@tamu.edu,  979-862-4169

river ID   Start       End     GageLAT GageLON  MouthLA MouthLO  River_Name                                             Mean_Flow
01100mis 01/01/1930 10/31/2010 31.0083 -91.6236 28.8853 -89.4456 Mississippi R at Tarbert Landing, MS                  ( 13794 m^3/s)
03045atc 01/01/1930 10/31/2010 30.9825 -91.7983 29.3989 -91.3655 Atachafalya at Simmesport, LA                         (  5659 m^3/s)
02292010 05/19/2008 10/31/2010 26.8333 -81.0889 26.4499 -81.9905 Caloosahatchee Canal                                  (    18 m^3/s)
02296750 04/01/1931 10/31/2010 27.2206 -81.8764 26.7091 -82.2624 PEACE R at Arcadia, FL         36 miles from mouth    (    30 m^3/s)
02298880 03/01/2008 10/31/2010 27.1853 -82.3558 26.7091 -82.2624 Myakka R nr Laurel, FL                                (     5 m^3/s)
02310525 10/01/1993 10/31/2010 28.5186 -82.5825 28.5350 -82.6546 Weeki Wachee R nr Brooksville, FL                     (     4 m^3/s)
02310747 10/01/2002 10/31/2010 28.9064 -82.6239 28.9199 -82.7140 Crystal R at Bagley Cove nr Crystal R, FL             (    24 m^3/s)
02313100 01/01/1965 10/31/2010 29.0492 -82.4478 28.9825 -82.7750 Rainbow R at Dunnellon, FL                            (    19 m^3/s)
02320500 07/01/1931 10/31/2010 29.9556 -82.9278 29.2774 -83.1818 Suwannee R at Branford, FL     75 miles from mouth    (   193 m^3/s)
02324000 03/01/1950 10/31/2010 29.7864 -83.3217 29.6660 -83.4164 Steinhatchee R nr Cross City, FL                      (     8 m^3/s)
02324400 10/01/1955 10/31/2010 30.0981 -83.4719 29.9699 -83.7880 Fenholloway R nr Foley, FL                            (     1 m^3/s)
02325000 08/10/1977 10/31/2010 30.0711 -83.6625 29.9699 -83.7880 Fenholloway R nr Perry, FL                            (     5 m^3/s)(This may be a better Fenholloway)
02326000 02/01/1950 10/31/2010 30.1706 -83.8239 30.0357 -83.9290 Econfina R nr Perry, FL                               (     4 m^3/s)
02330000 07/01/1926 10/31/2010 30.3831 -84.6550 29.9603 -84.3383 Ochlockonee R nr Bloxham, FL   65 miles from mouth    (    48 m^3/s)
02330150 08/07/1996 10/31/2010 30.1764 -84.6681 29.9603 -84.3383 Ochlockonee R nr Smith Creek                          (    54 m^3/s)(This may be a better Ochlockonee)
02359000 12/01/1912 10/31/2010 30.5339 -85.1653 29.5403 -84.9721 Chipola R nr Altha, FL         54 miles from mouth    (    42 m^3/s)
02359170 10/01/1997 10/31/2010 29.9492 -85.0156 29.5403 -84.9721 Apalachicola R nr Sumatra, FL  21 miles from mouth    (   693 m^3/s)
02366500 10/01/1930 10/31/2010 30.4508 -85.8983 30.3519 -86.5167 Choctawhatchee R nr Bruce, FL  21 miles from mouth    (   198 m^3/s)
02368000 08/01/1938 10/31/2010 30.7528 -86.6292 30.3084 -87.3076 Yellow R at Milligan, FL       40 miles from mouth    (    33 m^3/s)
02369000 08/01/1938 10/31/2010 30.6972 -86.5708 30.3084 -87.3076 Shoal R nr Crestview, FL                              (    31 m^3/s)
02369600 09/26/2001 10/31/2010 30.5694 -86.9236 30.3084 -87.3076 Yellow R nr Milton, FL                                (    64 m^3/s)(This is better Yellow R)
02370000 04/01/1950 10/31/2010 30.8333 -86.7347 30.3084 -87.3076 Blackwater R nr Baker, FL                             (    10 m^3/s) 
02375500 10/01/1934 10/31/2010 30.9650 -87.2342 30.3084 -87.3076 Escambia R nr Century, FL                             (   176 m^3/s)(I think this is a better Escambia)
02376033 11/20/1983 09/30/2009 30.6681 -87.2667 30.3084 -87.3076 Escambia R nr Molino, FL                              (   198 m^3/s)(Funny station - too tidal I think).
02376500 06/09/1941 10/31/2010 30.6903 -87.4403 30.2529 -87.5541 Perdido R at Barrineau Park, FL                       (   781 m^3/s) 
02428400 10/01/1975 10/31/2010 31.6114 -87.5531 30.2074 -88.0606 Alabama R at Claiborne L&D nr Monroeville,AL          (   887 m^3/s) 
02469761 10/01/1960 10/31/2010 31.7583 -88.1292 30.2074 -88.0606 Tombigbee R at Coffeeville L&D nr Coffeeville,AL      (   834 m^3/s) 
02479000 10/01/1930 10/31/2010 30.9789 -88.7269 30.3607 -88.6050 Pascagoula R at Merril, MS                            (   279 m^3/s)(if use 02479000 then add 02479160+02479300)
02479160 10/01/1971 10/31/2010 30.8533 -88.9136 30.3607 -88.6050 Black Creek nr Wiggins, MS                            (    35 m^3/s)
02479300 07/17/1958 10/31/2010 30.7361 -88.7811 30.3607 -88.6050 Red Creek at Vestry, MS                               (    24 m^3/s)
02479310 10/01/1993 09/30/2009 30.6103 -88.6406 30.3607 -88.6050 Pascagoula R at Graham Ferry,MS                       (   326 m^3/s)(contains 02479160 + 02479300)
02481510 08/01/1971 10/31/2010 30.4861 -89.2744 30.2819 -89.3123 Wolf River NR Landon, MS                              (    17 m^3/s)
02489500 10/01/1938 10/31/2010 30.7931 -89.8208 30.1743 -89.5246 Pearl River near Bogalusa, LA                         (   282 m^3/s)
02492000 10/01/1937 10/31/2010 30.6292 -89.8972 30.1743 -89.5246 Bogue Chitto River nr Bush, LA                        (    56 m^3/s)
07375500 10/01/1938 10/31/2010 30.5064 -90.3617 30.1413 -89.6126 Tangipahoa R at Robert, LA                            (    32 m^3/s)
07378500 09/01/1938 10/31/2010 30.4639 -90.9903 30.1413 -89.6126 Amite R near Denham Springs, LA                       (    59 m^3/s)
07385500 05/01/1949 02/12/2006 30.3972 -91.9306 29.4270 -91.4845 Bayou Teche at Arnaudville, LA                        (    26 m^3/s)(May have been decommissioned)
07386980 10/01/1973 10/31/2010 29.9511 -92.1561 29.7378 -92.1125 Vermillion River at Perry, LA                         (    31 m^3/s)
08012000 10/01/1938 10/31/2010 30.4806 -92.6318 29.7213 -93.0113 Bayou Nezpique nr Basile, LA                          (    23 m^3/s)
08015500 09/01/1922 10/31/2010 30.5028 -92.9153 29.7446 -93.3429 Calcasieu R nr Kinder, LA                             (    73 m^3/s)
08030500 10/01/1924 10/31/2010 30.3036 -93.7436 29.6109 -93.8272 Sabine R nr Ruliff, TX                                (   234 m^3/s)
08041000 08/01/1904 10/31/2010 30.3556 -94.0931 29.6109 -93.8272 Neches R at Evadale, TX                               (   178 m^3/s)
08041500 06/01/1924 10/31/2010 30.3978 -94.2633 29.6109 -93.8272 Village Ck nr Kountze, TX                             (    25 m^3/s)
08066500 05/01/1924 10/31/2010 30.4250 -94.8506 29.3460 -94.7131 Trinity R at Romayor, TX                              (   223 m^3/s)
08068090 05/01/1984 10/31/2010 30.0858 -95.2997 29.3460 -94.7131 West Fork San Jacinto abv Lake Houston nr Porter      (    19 m^3/s)
08075000 05/25/1936 10/31/2010 29.6969 -95.4119 29.3460 -94.7131 Brays Bayou @ Houston                                 (     5 m^3/s)
08116650 04/01/1967 10/31/2010 29.3494 -95.5822 28.8739 -95.3791 Brazos R nr Rosharon, TX                              (   232 m^3/s)
08117500 05/01/1954 10/31/2010 29.3133 -95.8936 28.8510 -94.4389 San Bernard R nr Boling, TX                           (    15 m^3/s)
08162500 05/01/1948 10/31/2010 28.9739 -96.0122 28.4125 -96.3176 Colorado R near Bay City, TX                          (    73 m^3/s)
08164000 08/13/1938 10/31/2010 28.9597 -96.6861 28.4125 -96.3176 Lavaca R nr Edna, TX                                  (    11 m^3/s)
08176500 11/04/1934 10/31/2010 28.7928 -97.0128 28.4125 -96.3176 Guadalupe R at Victoria, TX                           (    56 m^3/s)
08188500 07/01/1924 10/31/2010 28.6494 -97.3844 27.8203 -97.0211 San Antonio R at Goliad, TX                           (    22 m^3/s)
08189500 07/01/1939 10/31/2010 28.2917 -97.2789 27.8203 -97.0211 Mission R at Refugio, TX                              (     4 m^3/s)
08189700 03/27/1964 10/31/2010 28.2822 -97.6206 27.8203 -97.0211 Aransas R nr Skidmore, TX                             (     1 m^3/s)
08211000 08/05/1939 10/31/2010 28.0381 -97.8600 27.8203 -97.0211 Nueces R nr Mathis, TX                                (    20 m^3/s)