17 USGS Streamgages · Mississippi River system
Big Sioux River flows and levels
Big Sioux River is gauged at 17 USGS streamgages in South Dakota and Iowa, each tracked by Rivermatics. The mainstem runs about 398 miles (641 km) from headwaters to outlet. It drains into the Mississippi River system. Drainage area at the gauges ranges from 68 square miles at Big Sioux River near Florence, SD up to 8,430 at Big Sioux River at Sioux City, IA. The gauged reach falls about 718 feet, from 1,791 feet down to 1,073. Rivermatics issues a daily machine-learned 14-day flow outlook at 13 of them.
Gauges on this river, upstream to downstream
Ordered by drainage area, which is how far down the river each gauge sits. April and July figures are long-term median daily flows for that month from the USGS record — historical normals, not a forecast and not today's reading.
| Gauge | State | Drainage sq mi | Elevation ft | April p50 cfs | July p50 cfs | Forecast |
|---|---|---|---|---|---|---|
| Big Sioux River near Florence, SD | SD | 68 | 1,791 | 24.7 | 1.9 | 14-day |
| Big Sioux River near Watertown, SD | SD | 525 | 1,732 | 58.6 | 11.3 | 14-day |
| Big Sioux River at Lake Kampeska near Watertown, SD | SD | 539 | 1,720 | — | — | — |
| Big Sioux River at Watertown, SD | SD | 806 | 1,715 | 70.8 | 16 | 14-day |
| Big Sioux River at Broadway at Watertown, SD | SD | 870 | 1,720 | — | — | — |
| Big Sioux River below Watertown, SD | SD | 1,000 | 1,703 | 173.4 | 45.6 | 14-day |
| Big Sioux River near Castlewood, SD | SD | 1,096 | 1,685 | 156.3 | 56.9 | 14-day |
| Big Sioux River near Bruce, SD | SD | 2,396 | 1,621 | 345.7 | 156.1 | 14-day |
| Big Sioux River near Brookings, SD | SD | 3,338 | 1,555 | 430.1 | 162.1 | 14-day |
| Big Sioux River near Dell Rapids, SD | SD | 3,927 | 1,463 | 619.8 | 257.4 | 14-day |
| Big Sioux River below Diversion at Sioux Falls, SD | SD | 3,999 | 1,420 | — | — | — |
| Big Sioux River at Sioux Falls, SD | SD | 4,642 | 1,422 | 393 | 265.4 | 14-day |
| Big Sioux River at North Cliff Ave at Sioux Falls, SD | SD | 4,662 | 1,301 | 978.4 | 474.5 | 14-day |
| Big Sioux River near Hawarden, IA | SD | 7,566 | 1,162 | 2,621.3 | 2,207.4 | 14-day |
| Big Sioux River at Akron, IA | IA | 7,879 | 1,125 | 1,448 | 909.8 | 14-day |
| Big Sioux River near Jefferson, SD | SD | 8,400 | 1,079 | 3,052.7 | 2,575.5 | 14-day |
| Big Sioux River at Sioux City, IA | IA | 8,430 | 1,073 | 3,299 | 2,477.4 | — |
Typical flow by month at Big Sioux River at Sioux City, IA
The furthest-downstream gauge on this river, so the fullest flow it carries here. Long-term daily discharge percentiles from the USGS record (up to 11 years of data), averaged within each month. These describe the historical normal range — they are not a forecast and not today's reading.
| Month | Low p10 | Typical p50 | High p90 | Range |
|---|---|---|---|---|
| January | 221.3 | 953.9 | 3,191 | |
| February | 242.6 | 974.2 | 3,559.6 | |
| March | 559.1 | 1,819.8 | 18,361.3 | |
| April | 948.3 | 3,299 | 17,266.7 | |
| May | 1,186.8 | 4,357.4 | 14,745.2 | |
| June | 1,004.2 | 3,603.3 | 24,690 | |
| July | 617.4 | 2,477.4 | 12,089 | |
| August | 475.1 | 1,348.7 | 5,053.9 | |
| September | 230.4 | 1,259.3 | 14,462.7 | |
| October | 274.2 | 1,006.9 | 9,692.3 | |
| November | 306.7 | 1,336.7 | 6,925.7 | |
| December | 293.9 | 1,344.8 | 3,835.2 |
All values in cubic feet per second (cfs).
Common questions
- When does the Big Sioux River run highest?
- May, on the long-term record at Big Sioux River at Sioux City, IA — the furthest-downstream gauge Rivermatics tracks on this river. Median daily flow there is about 4,357.4 cfs that month, against 953.9 cfs in January, the lowest. Upstream gauges peak on their own schedule; the table on this page gives April and July for each.
- How many gauges are on the Big Sioux River?
- Rivermatics tracks 17 USGS streamgages on the Big Sioux River, across South Dakota and Iowa. Each has its own page with the site's full flow record and monthly normals. The river may carry other gauges that publish neither daily values nor discharge statistics; those are not tracked here.
- Is there a flow forecast for the Big Sioux River?
- Yes, at 13 of the 17 gauges. Rivermatics trains a machine-learned model — a temporal-fusion transformer — on each basin's observed flows, weather and snowpack, and issues a daily outlook reaching 14 days ahead: a median estimate inside a confidence band, not a single number to bet on. Every forecast is scored against days the model never trained on, and that track record is published on each gauge's live screen.
- What river system is the Big Sioux River part of?
- The Big Sioux River drains into the Mississippi River system — it is a tributary somewhere in that chain, following the flowpath down to its terminal river. Rivermatics builds this from the USGS/geoconnex reference-mainstem network rather than from names.
- Can I use Big Sioux River data for flood or safety decisions?
- No. Rivermatics provides estimates, not guarantees, and the readings and forecasts here may be delayed, inaccurate, or wrong. Do not use them for navigation or for any safety, rescue, or emergency decision. Check the National Weather Service and USGS directly, and use your own judgment.
Other rivers in the Mississippi River system
- Missouri River 52 gauges
- James River 15 gauges
- Kansas River 12 gauges
- Smoky Hill River 12 gauges
- Platte River 11 gauges
- Rapid Creek 11 gauges
- Republican River 11 gauges
- Yellowstone River 10 gauges