How big are WWALS watersheds?

Update 2015-11-01: After addition of the upper Suwannee River as WWALS territory.

Update 2015-06-16: For more maps and a pithy summary, see Suwannee River Basin watershed organizations and Suwannee-Satilla Regional Water Planning Council.

Update 2015-06-02: added HUC from a USGS summary, and Upper and Lower Suwannee with Extended Table, and corrected some arithmetic.

Seems like an easy question, but requires some research: how many square miles are drained by the rivers in WWALS watersheds?

River Basins of the United States: The Suwannee, by USGS, unknown date (but uses 1980 city populations),

The basin drainage area is 9,950 square miles, of which 5,720 square miles are in southern Georgia. The basin area of the Withlacoochee River, the largest tributary, is 2,360 square miles, of which 2,090 square miles are in Georgia. The basin area of the Alapaha River is 1,840 square miles, of which 1,726 are in Georgia.

Summary Table

So this appears to be the answer:

RiverGeorgiaFloridaTotal
Withlacoochee2,0902702,360
Alapaha1,7261141,840
Upper Suwannee River1,9048162,720
WWALS5,7201,2006,920

Apparently WWALS watersheds account for 73% about 67% 100% of the Suwannee Basin in Georgia, and 42% about 43% 70% of the entire Suwannee River Basin.

And WWALS rivers drain a total of about 4,200 6,920 square miles.

But stay tuned: there’s much more for comparison.

Divergent Sources

Or is that the answer? Suwannee River Watershed, Florida’s Water, Florida Department of Environmental Protection,

The Suwannee River originates in Georgia and flows southwest to the Gulf of Mexico. It is the largest watershed in the state, covering 7,702 square miles.

7,702 + 3,816 = 11,518, which is larger than 9,950, and doesn’t even include the parts of the upper Suwannee River in Georgia.

This Georgia River Network page on the Suwannee River also has a too-large number:

The Suwannee River Basin drains approximately 11,020 square miles….

Convergent Sources

River Basin Characteristics, in Suwanee River Basin Plan, by GA EPD, unknown date,

The portion of the Suwannee River basin located entirely in Georgia drains approximately 5,560 square miles. The Suwannee River Basin in Georgia includes the waters of the Alapaha and Withlacoochee Rivers which flow south into Florida and join the Suwannee River which empties into the Gulf of Mexico. The Suwannee River basin drains approximately 10,000 square miles, with approximately 5,560 square miles of the basin in Georgia….

The headwaters of the Suwannee River drain approximately 574 square miles of the Okefenokee Swamp. The Suwannee River flows southwest through Georgia for 33 miles before entering Florida. Once in Florida, the Suwannee converges with two of its tributaries, the Alapaha and Withlacoochee rivers, which both originate in Georgia. The Suwannee River is a blackwater stream with extremely acidic waters. A pH reading of 3.6 was recorded July 22, 1997 (U.S. Geological Survey, 1997).

The GA-EPD numbers more or less match the USGS numbers, with the FL-DEP (and GRN) numbers being much different.

In another publication FL-DEP agreed on the Suwannee and Alapaha River Basin totals, but not on the Withlacoochee River. Nutrient and Dissolved Oxygen TMDL for the Suwannee River, etc. 24 September 2008,

The Suwannee Basin drains approximately 10,000 square miles of south Georgia and north Florida, discharging an annual average of approximately 10,000 cubic feet per second (cfs). The Suwannee River is the second largest river in the state in terms of flow. Within the Suwannee Basin, the Alapaha, Withlacoochee, and Upper Suwannee watersheds lie almost entirely in Georgia. These are dominated by surface water runoff, as are the Florida portions of the basin in the Northern Highlands region. After crossing the Cody Scarp, ground water discharges from springs and diffuse seepage strongly influences the Suwannee River and makes up the baseflow of the river….

The Alapaha River drains approximately 1,800 square miles in Georgia and Florida and joins the Suwannee southwest of Jasper, Florida. The Alapaha River flows through karst terrain with numerous sinkholes, stream sinks, and springs. At times, sinkholes in the streambed capture the river’s entire flow. Once underground, the river flows through solution channels in the limestone for approximately 19 miles and is presumed to emerge at two springs: Alapaha Rise and Holton Creek. The Withlacoochee River, which drains approximately 1,500 square miles in Georgia and Florida, originates near Tifton, Georgia, and flows south past Valdosta, Georgia, to join the Suwannee River at Ellaville. The flow in the Withlacoochee River is highly variable, reflecting the river’s response to rainfall in the watershed. The river is affected by wastewater treatment plant discharges in Tifton and Valdosta and pulp mill discharge in Jumping Gully Creek at the state line.

Since 1,500 is quite a bit less than 2,360, it looks to me like FL-DEP forgot about the Little River tributary of the Withlacoochee River. If so, that gives us an estimate for the Little River: 2,360 – 1,500 = 860 square miles.

Here’s another tidbit. Appendix A, The Alapaha – Willacoochee River Watershed Restoration Action Strategy Implementation Project, Seven Rivers RCD, unknown date,

The Alapaha — Willacoochee River Subwatershed is located in south-central Georgia within the Alapaha River Watershed (HUC 03110202). It has an approximate land area of 148,286 acres (233 square miles) and flows through Ben Hill, Irwin, Coffee, Berrien and Atkinson counties.

So the Willacoochee River, being long and thin, doesn’t actually drain many square miles.

I’ll go with the numbers in the summary table.

Santa Fe and Ichetucknee Rivers

For comparison, from Chapter 2: Basin Overview, in Water Quality Assessment Report: Suwannee,

The Santa Fe River, a tributary to the Suwannee River, is in some respects a smaller version of the Suwannee. This river system drains about 1,400 square miles of north Florida, discharging an annual average of more than 1,600 cfs. The Santa Fe River flows west from its headwaters in the Santa Fe Lakes area, in the easternmost portion of the watershed, joining the Suwannee near Branford. Its two important tributaries, New River and Olustee Creek, have their headwaters in southern Baker County. A third tributary, the Ichetucknee River, is a clear, spring-fed stream and a very popular recreational site.

The Upper Santa Fe watershed, in the Northern Highlands, is dominated by surface water runoff. At the Cody Scarp, the river goes underground and reemerges supplemented by ground water flow. As the Santa Fe flows across the Gulf Coastal Lowlands, it gains significant flow from numerous springs, including the Ichetucknee River. Because ground water dominates its flow, the Lower Santa Fe is for the most part a spring-fed river.

The eastern two-thirds of the Santa Fe watershed has surface drainage features, including lakes, streams, and wetlands. The western third lacks surface drainage, except for the Santa Fe and Ichetucknee Rivers and Cow Creek. The upper watershed is characterized by nearly level pine flatwoods with gently rolling hills. Tributary streams are fairly well incised into the landscape, which occasionally opens into broad, forested floodplains. In the middle portion of the watershed, moderate to gently rolling hills with areas of prominent karstic features, such as sink depressions and captured streams, create surface relief. The lower watershed is primarily a broad, slightly undulating karst plain with interspersed wetlands.

So the Santa Fe River is much like the Alapaha River, except the Santa Fe is completely in Florida and has more springs, especially in its tributary the Ichetucknee River.

Why Divergent

That FL-DEP chapter has a clue to how FL-DEP can have another, much higher, square mile number: it also reports on other nearby rivers that do not actually flow into the Suwannee River, such as the Aucilla, Econofina, and Fenholloway Rivers. Indeed, it says right at the beginning of the chapter:

The Suwannee Group 1 Basin covers 7,702 square miles in north central Florida within all or part of 14 counties. Portions of the basin in several watersheds also extend into southern Georgia. The basin area discussed in this report encompasses most, but not all, of the area within the Suwannee River Water Management District (SRWMD). The Suwannee Group 1 Basin includes the watersheds of the following river basins, as identified by their eight-digit hydrologic unit codes (HUCs)— Upper Suwannee, Lower Suwannee, Alapaha, Withlacoochee, Aucilla, Econfina—Steinhatchee, Santa Fe, and Waccasassa.

So that larger Florida number is not actually for the Suwannee River Basin, and the USGS numbers in the table are correct.

USGS HUC square miles

USGS has a handy summary in Boundary Descriptions and Names of Regions, Subregions, Accounting Units and Cataloging Units which confirms that the larger area number includes several river systems that do not flow into the Suwannee:

Subregion 0311 — Suwannee: The coastal drainage and associated waters from the Withlacoochee River Basin boundary to and including the Aucilla River Basin. Florida, Georgia.
Area = 13800 sq.mi.

Accounting Unit 031101 — Aucilla-Waccasassa: The coastal drainage and associated waters from the Withlacoochee River Basin boundary to and including the Aucilla River Basin, excluding the Suwannee River Basin. Florida, Georgia.
Area = 3870 sq.mi.

Cataloging Units

03110101 — Waccasassa. Florida.
Area = 936 sq.mi.

03110102 — Econfina-Steinhatchee. Florida.
Area = 1930 sq.mi.

03110103 — Aucilla. Florida, Georgia.
Area = 1000 sq.mi.

None of those rivers are in the Suwannee River Basin proper. And Withlacoochee to Aucilla makes no sense to categorize their location since the Aucilla River is west of the Withlacoochee while the Waccasassa River is east.

Fortunately, that USGS HUC reference also has (much of) what we’re looking for:

Accounting Unit 031102 — Suwannee: The Suwannee River Basin. Florida, Georgia.
Area = 9930 sq.mi.

Cataloging Units

03110201 — Upper Suwannee. Florida, Georgia.
Area = 2720 sq.mi.

03110202 — Alapaha. Florida, Georgia.
Area = 1840 sq.mi.

03110203 — withlacoochee. Florida, Georgia.
Area = 1510 sq.mi.

03110204 — Little. Georgia.
Area = 884 sq.mi.

03110205 — Lower Suwannee. Florida.
Area = 1590 sq.mi.

03110206 — Santa Fe. Florida.
Area = 1390 sq.mi.

Extended Table

Here’s a slightly much extended version of the summary table above:

RiverHUCGeorgiaFloridaTotal

Withlacoochee River(inc. Little)2,09037%2706%2,36024%
WWALS%37%23%34%
Withlacoochee RiverHUC 03110203(1,206)21%(270)6%(1,510)15%
WWALS%21%23%22%
Little RiverHUC 03110204(860)15%(0)0%(860)9%
WWALS%15%0%12%

Alapaha RiverHUC 031102021,72630%1143%1,84018%
WWALS%30%9%27%
(Willacoochee River)(233)4%(0)0%(233)2%
WWALS%4%0%4%

Upper Suwannee RiverHUC 03102011,90433%81619%2,72027%
WWALS%33%68%39%

WWALS5,720100%1,20028%6,92070%
WWALS%100%100%100%
GA/FL WWALS%82%18%100%

Lower Suwannee RiverHUC 0311020500%1,59038%1,59016%
Santa Fe RiverHUC 0311020600%1,40033%1,40014%

Suwannee River BasinAU 0311025,720100%4,230100%9,950100%
GA/FL Basin%57%43%100%

So the Alapaha (with the Willacoochee) and Withlacoochee (with the Little River) are the largest tributaries of the Suwannee River, draining 4,200 square miles between them, in the original territory of WWALS. Add in the 2,720 square miles of the upper Suwannee River and total WWALS territory is 6,920 square miles.

For comparison:

  • 1,300 square miles: St Marys River (765 in Georgia; 535 in Florida)
  • 4,000 square miles: Satilla River
  • 5,540 square miles: Ogeechee River
  • 6,920 square miles: WWALS (5,720 in Georgia; 1,200 in Florida)
  • 8,510 square miles: WWALS with lower Suwannee River (5,720 in Georgia; 2,790 in Florida)
  • 8,460 square miles: Flint River
  • 8,770 square miles: Chattahoochee River (5,940 in Georgia and 2,830 in Alabama)
  • 10,577 square miles: Savannah River (5,821 in Georgia; 4,756 in South Carolina)
  • 13,600 square miles: Altamaha River (including Ocmulgee and Oconee)

And of course WWALS territory has much lower population than most of those other watersheds.

If somebody knows of a handy source for such figures, please let me know. Until then, this is what I’ve found.

-jsq