USGS · 01645704

DIFFICULT RUN

USGS · 01645704LIVE

DIFFICULT RUN ABOVE FOX LAKE NEAR FAIRFAX, VA

RESTON, VA38.8847°N, -77.3324°W Updated 28 min ago

FLOW RATE

33.2cfs

GAUGE HT

1.67ft

WATER TEMP

78°F

AIR TEMP

73°F

WIND

4mph NE

FISH INDEX

69SCORE / 100

GREAT · 4 OF 5

1D 7D 30D 1YR

Flow Rate Historical Avg

MEDIAN FLOW RATE · 1 DAY

33.2cfs 193.5% vs avg

Optimal band: 16–22 cfs

PERIOD HIGH

67cfs

PERIOD LOW

6.62cfs

RUNNABLE

13%

last 1 day in band

Gauge Height

1.67ft

Water Temperature

77.5°F

Water Turbidity

Precipitation History

Precipitation · YTD

Normal

Near-normal year

2026 to date

22.3in

≈ normal

22.34 in of precipitation so far this year — about average for this point in the season (normal 22.5 in).

YTD Total

22.3in

This year so far

Normal to Date

22.5in

30-yr average

Typical Range

16.7–28.7in

10th–90th pct YTD

Departure

-1%

vs 30-yr normal

By Month

This year

Typical range

Normal

Jan: 3.02" · normal 3.13" (1.7–4.5)

Jan

Feb: 2.66" · normal 2.85" (1.5–4.4)

Feb

Mar: 3.34" · normal 3.90" (1.7–5.2)

Mar

Apr: 1.99" · normal 3.49" (1.7–5.0)

Apr

May: 4.03" · normal 3.94" (2.1–6.5)

May

Jun: 3.97" · normal 3.64" (1.7–6.0)

Jun

Jul: 3.34" (so far)· normal 4.23" (2.1–7.0)

Jul

Aug: normal 3.77" (1.9–5.1)

Aug

Sep: normal 4.73" (1.4–8.3)

Sep

Oct: normal 3.49" (1.2–5.1)

Oct

Nov: normal 3.04" (1.1–5.5)

Nov

Dec: normal 3.54" (2.0–5.4)

Dec

Baseline 1991–2020 · Source: Open-Meteo03:01 UTC

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Station Location

38.8847, -77.3324

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DATA · USGS · NOAA · NWSUPDATED 2026-07-12 06:25 UTC

Site #01645704·USGS

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