Potomac River at Little Falls, MD
USGS gauge 01646500 · drainage 11,560 sq mi · observed Oct 16, 7:50 PM EDT · 61 min old
Last 7 days Live gauge
Source: USGS Water Data API (continuous values), observed to Oct 16, 7:50 PM EDT. Shaded band: 25th to 75th percentile of USGS daily statistics for each date; dashed: median. Flow in cfs.
Daily mean flow Live gauge
| Date (gauge-local) | Mean flow | Note |
|---|---|---|
| Oct 16, 2026 | 11,114 cfs | |
| Oct 15, 2026 | 16,182 cfs | |
| Oct 14, 2026 | 21,889 cfs | |
| Oct 13, 2026 | 12,366 cfs | |
| Oct 12, 2026 | 9,638 cfs | |
| Oct 11, 2026 | 3,487 cfs | |
| Oct 10, 2026 | 1,494 cfs | |
| Oct 9, 2026 | 1,434 cfs | |
| Oct 8, 2026 | – | Partial day |
Source: USGS Water Data API (continuous values); each mean uses readings on that gauge-local date, shown only with at least 80% of expected readings.
The same 50 days in earlier years Historical record
━ 2026 ╌ 2025 ╌ 2024 ╌ 2023
| Year | Mean flow | Highest day |
|---|---|---|
| 2026 | 3,400 cfs | 22,100 cfs |
| 2025 | 1,704 cfs | 2,760 cfs |
| 2024 | 6,655 cfs | 38,100 cfs |
| 2023 | 1,742 cfs | 5,510 cfs |
Source: USGS daily mean flows (Water Data API). Each line is the 50 days from Aug 27 to Oct 15, shifted to the same calendar dates in earlier years; gaps are days without a published value. Recent days are provisional.
Compared with this gauge’s record Historical record
| Measure | Value | When or rank |
|---|---|---|
| Peak daily flow, last 7 days | 22,100 cfs | Oct 14, 2026 |
| Last time daily flow was this high or higher | 22,200 cfs | May 31, 2026 (4 months earlier) |
| Last day above the 90th percentile for its date, before this peak | May 30, 2026 | 5 months earlier |
| Days above the 75th percentile for their date | 6 of 30 | last 30 days |
| October 1 to 15, mean flow | 5,530 cfs | rank 28 highest of 97 years |
Source: USGS daily mean flows (Water Data API), 1930 to 2026 (35,293 days), data through Oct 15, 2026, computed 2026-10-17; method record-v1. Percentiles are USGS daily statistics. Recent days are provisional.
Largest annual peaks Historical record
Ten largest peaks of record
| Date | Peak flow | Gage height at peak |
|---|---|---|
| Mar 19, 1936 | 484,000 cfs | 28.10 ft |
| Oct 17, 1942 | 447,000 cfs | 26.88 ft |
| Jun 24, 1972 | 359,000 cfs | 22.03 ft |
| Apr 28, 1937 | 347,000 cfs | 23.30 ft |
| Jan 21, 1996 | 347,000 cfs | 19.29 ft |
| Nov 7, 1985 | 317,000 cfs | 17.99 ft |
| Feb 16, 1984 | 222,000 cfs | 13.73 ft |
| Aug 20, 1955 | 216,000 cfs | 17.60 ft |
| Oct 11, 1976 | 208,000 cfs | 13.18 ft |
| Feb 26, 1979 | 206,000 cfs | 13.12 ft |
Five most recent annual peaks
| Date | Peak flow | Gage height at peak |
|---|---|---|
| May 16, 2025 | 156,000 cfs | 11.72 ft |
| Apr 5, 2024 | 94,100 cfs | 9.20 ft |
| Dec 24, 2022 | 44,800 cfs | 6.59 ft |
| May 9, 2022 | 118,000 cfs | 10.16 ft |
| Mar 3, 2021 | 97,600 cfs | 9.27 ft |
Source: USGS annual peak streamflow (Water Data API), 95 annual peaks, 1931 to 2025. A water year's peak is its highest instantaneous flow.
Water temperature by month Historical record
Source: USGS daily mean water temperature (parameter 00010, Water Data API), 1988 to 2026, mean of all published daily values in each calendar month (days counted under each month).
Water quality sensors Live gauge
| Measure | Latest value | Observed |
|---|---|---|
| Water temperature | 19 °C | Oct 16, 7:50 PM EDT |
| Dissolved oxygen | 9.5 mg/L | Oct 16, 7:50 PM EDT |
| Turbidity | 17 FNU | Oct 16, 7:50 PM EDT |
| pH | 8.0 pH units | Oct 16, 7:50 PM EDT |
| Specific conductance | 275 µS/cm | Oct 16, 7:50 PM EDT |
| Nitrate plus nitrite | 1.2 mg/L | Oct 16, 8:00 PM EDT |
Source: USGS Water Data API (continuous values). Values as reported by the gauge, provisional.
Flood stages Official NWS
| Category | Gage height (ft) |
|---|---|
| Action | 5.0 ft |
| Minor | 10.0 ft |
| Moderate | 12.0 ft |
| Major | 14.0 ft |
Source: National Weather Service forecast point BRKM2 (Potomac River near Washington DC (Little Falls)), fetched Oct 16, 8:42 PM EDT. Compare with the gage height above; thresholds belong to that forecast point.
Historic crests Official NWS
| Date | Crest stage | Flow |
|---|---|---|
| Mar 19, 1936 | 28.10 ft | 484,000 cfs |
| Oct 17, 1942 | 26.88 ft | 447,000 cfs |
| Apr 27, 1937 | 23.30 ft | 347,000 cfs |
| Jun 23, 1972 | 22.03 ft | 359,000 cfs |
| Jan 21, 1996 | 19.29 ft | 347,000 cfs |
| Nov 6, 1985 | 17.99 ft | 317,000 cfs |
| Sep 8, 1996 | 17.84 ft | 314,000 cfs |
| Aug 19, 1955 | 17.60 ft | 216,000 cfs |
| Oct 29, 1937 | 15.62 ft | 181,000 cfs |
| May 13, 1932 | 15.25 ft | 168,000 cfs |
Source: National Weather Service forecast point BRKM2 (Potomac River near Washington DC (Little Falls)), historic crests as published by the NWS; the NWS may have recorded them on an older gauge datum.
Flood impacts by stage Official NWS
| Stage | National Weather Service impact statement |
|---|---|
| 3.5 ft | The river reaches caution level for boaters, as defined by the State of Maryland. Fast moving water and changing currents will be experienced. |
| 4.5 ft | The river reaches danger level for boaters, as defined by the State of Maryland. Conditions for boating will be extremely hazardous. |
| 5.0 ft | Portions of the Potomac Heritage Trail begin to flood. Water begins to affect portions of the Billy Goat Trail between Great Falls and Carderock. These trails will be closed. |
| 5.5 ft | Water reaches the top of the ferry landing for Sycamore Island. Ferry service to the island will likely be suspended. |
| 7.0 ft | Upper portions of the River Trail at Great Falls National Park begin to flood and will be closed. |
| 9.0 ft | Several trails on both sides of the river between Great Falls and the Chain Bridge are flooded and will be closed. |
| 10.0 ft | Water begins to overflow the banks into low lying areas on the Maryland side of the river near Little Falls. Water begins to enter the canoe shed at Sycamore Island. |
| 11.0 ft | Water covers the towpath between Swains Lock and Pennyfield Lock, mileposts 17 to 19 on the C&O Canal. |
| 11.5 ft | Water covers the towpath in multiple spots between the Washington Aqueduct Dam and Pennyfield Lock, mileposts 15 to 19 on the C&O Canal. |
| 12.0 ft | The C&O Canal overflows at the Great Falls Tavern. Water covers the towpath in many areas. |
| 14.0 ft | Significant portions of the C&O Canal towpath are flooded. The Blockhouse Point Park is flooded. Water reaches the retaining wall at Overlook 1 at Great Falls National Park but does not overtop it. |
| 15.0 ft | Most of the C&O Canal towpath from Pennyfield downstream is flooded. |
| 16.0 ft | Water reaches the clubhouse on Sycamore Island. |
| 17.0 ft | Water overflows the overlooks at Great Falls National Park and approaches the lower level of the visitors center. Most of the C&O Canal towpath downstream of Pennyfield is flooded. There is approximately a foot of water in the clubhouse on Sycamore Island. |
Source: National Weather Service forecast point BRKM2 (Potomac River near Washington DC (Little Falls)). Statements are quoted from the NWS and describe that forecast point.
Sources and method
- Data: U.S. Geological Survey. Terms
- River forecasts and flood stages: National Weather Service. National Water Model guidance: NOAA.. Terms
USGS daily statistics, downloaded 2026-10-12
Percentile method: trailing 24 h mean vs USGS daily percentiles for calendar date 10-16.
Percentile is estimated from USGS published daily percentiles. Readings are provisional until USGS reviews them. Not endorsed by USGS, NOAA or the National Weather Service. Not for navigation or safety-of-life decisions; the absence of an alert is not a statement that conditions are safe.