USGS Streamgage 09421500
Colorado River below Hoover Dam, Az-Nv
Colorado River below Hoover Dam, Az-Nv is USGS streamgage 09421500 in Nevada, monitoring river discharge in hydrologic subbasin 15030101. It drains a watershed of about 171,700 square miles. Discharge records at this site go back to 1934. Typical flow runs near 14,846.1 cfs in July and 16,620 cfs in April, with the higher of the two arriving in April.
Gauge details
- State
- Nevada
- Drainage area
- 171,700 sq mi
- Gauge elevation
- 676 ft
- Subbasin (HUC-8)
- 15030101
- Coordinates
- 36.01526, -114.73859
- USGS site number
- 09421500
- Records begin
- 1934-04-01 (92 years)
Typical flow by month
Long-term daily discharge percentiles from the USGS record (up to 92 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 | 4,677.1 | 9,942.3 | 21,396.8 | |
| February | 5,470 | 11,169 | 21,255.2 | |
| March | 7,854.8 | 14,896.8 | 21,471 | |
| April | 9,492.3 | 16,620 | 22,383.3 | |
| May | 9,475.5 | 16,341.9 | 22,448.4 | |
| June | 9,550.3 | 15,260 | 21,416.7 | |
| July | 9,645.5 | 14,846.1 | 20,254.8 | |
| August | 8,798.7 | 13,871 | 19,780.6 | |
| September | 6,900.3 | 11,670 | 18,983.3 | |
| October | 5,348.4 | 10,035.8 | 18,406.5 | |
| November | 5,692 | 10,174.7 | 19,036.7 | |
| December | 5,192.9 | 9,606.8 | 19,822.6 |
All values in cubic feet per second (cfs).
Common questions
- When does Colorado River below Hoover Dam, Az-Nv normally run highest?
- April, on the long-term record. The median daily flow that month is about 16,620 cfs, against 9,606.8 cfs in December, the lowest month. These are historical normals for the date, not a forecast and not today's reading.
- What is a normal flow for Colorado River below Hoover Dam, Az-Nv?
- It depends on the month. In January, half of days historically fall near 9,942.3 cfs, with the middle 80% of days between 4,677.1 and 21,396.8 cfs. The month-by-month table on this page gives the full range.
- How long has Colorado River below Hoover Dam, Az-Nv been measured?
- Discharge records at USGS site 09421500 begin in 1934, about 92 years, covering roughly 9,123 days of published daily values. The long record is what makes the monthly percentiles on this page meaningful.
- Where is Colorado River below Hoover Dam, Az-Nv?
- The gauge sits at 36.01526, -114.73859, in Nevada, in hydrologic subbasin 15030101, at an elevation of about 676 feet, draining roughly 171,700 square miles.
- Can I use Colorado River below Hoover Dam, Az-Nv 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.