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USGS Daily Statistics for the Nation

The statistics generated from this site are based on approved daily-mean data and may not match those published by the USGS in official publications. The user is responsible for assessment and use of statistics from this site. For more details on why the statistics may not match, click here.

USGS 01646000 DIFFICULT RUN NEAR GREAT FALLS, VA


Fairfax County, Virginia
Hydrologic Unit Code 02070008
Latitude  38°58'33", Longitude  77°14'46" NAD27
Drainage area 57.8  square miles
Gage datum 150.94 feet above NAVD88
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00060, Discharge, cubic feet per second,
Day of
month		 Mean of daily mean values for each day for water year of record in, ft3/s   (Calculation Period 1934-10-01 -> 2025-09-30)

Calculation period restricted by USGS staff due to special conditions at/near site
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
1 86 67 80 100 81 61 47 56 59 70 39 55
2 78 71 72 104 72 59 40 42 37 55 35 50
3 78 85 88 90 72 84 53 34 27 35 42 49
4 78 87 86 84 88 71 49 48 40 25 39 60
5 69 80 91 89 82 75 48 44 44 31 50 61
6 62 71 86 84 103 49 42 46 106 37 45 63
7 68 84 91 82 91 67 38 40 43 29 54 68
8 63 68 77 81 74 48 83 41 86 46 62 58
9 81 59 78 86 72 52 66 40 53 36 52 73
10 71 64 76 80 61 54 39 51 47 47 48 59
11 60 69 75 69 65 59 51 45 40 35 45 102
12 67 78 89 67 91 55 49 66 33 41 65 64
13 61 87 85 97 84 73 59 68 37 30 68 65
14 78 93 93 73 72 64 59 31 38 43 48 69
15 68 77 79 93 80 59 49 30 26 36 50 74
16 62 80 78 102 111 51 48 29 37 44 65 88
17 55 72 89 85 76 48 36 35 33 34 51 66
18 64 82 78 66 75 56 35 56 36 31 41 73
19 87 93 89 64 89 68 38 30 31 52 40 50
20 86 74 85 83 70 71 40 50 23 41 55 48
21 72 75 122 73 68 82 65 48 32 39 48 74
22 62 88 94 75 68 321 58 41 39 32 55 67
23 65 103 110 65 81 104 65 36 62 58 47 74
24 86 97 95 65 63 58 55 36 39 33 48 66
25 93 91 75 68 55 59 39 47 48 53 65 72
26 88 92 92 86 81 72 30 36 75 59 53 80
27 67 75 88 84 61 58 31 36 45 60 55 60
28 88 77 99 86 77 52 43 37 40 57 80 56
29 64 74 98 65 71 43 45 28 38 67 73 64
30 64   92 96 61 49 33 22 47 56 60 65
31 63   89   66   31 33   36   66