053008 Avon at Great Somerford 1997
Measuring authority: EA Grid reference: 31 (ST) 966 832 Catchment area (sq km): 303.0
First year: 1964 Level stn. (m OD): 57.60 Max alt. (m OD): 207
Daily mean gauged discharges (cubic metres per second)
DAY JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
1 1.598 0.786 5.849 1.438 0.627 0.728 0.612 0.370 1.954 0.611 0.696 8.659
2 1.538 0.741 5.480 1.328 0.617 0.720 0.595 0.373 1.541 0.593 0.683 9.686
3 1.464 0.796 5.597 1.261 0.684 0.708 0.584 0.413 1.487 0.604 0.653 7.281
4 1.412 0.766 5.115 1.233 0.757 0.697 0.573 0.527 1.454 0.579 0.676 6.321
5 1.330 0.749 4.609 1.194 0.689 0.679 0.556 0.497 1.368 0.568 0.715 5.775
6 1.282 0.758 4.189 1.139 0.640 0.665 0.523 0.602 1.297 0.612 0.663 5.288
7 1.233 0.725 4.450 1.117 0.695 0.639 0.506 0.689 1.256 0.625 0.776 5.161
8 1.168 0.739 4.316 1.068 0.701 0.647 0.486 0.543 1.194 1.006 1.287 5.362
9 1.113 1.364 3.878 1.033 0.826 0.612 0.476 0.480 1.108 1.026 1.519 5.882
10 1.086 1.826 3.551 0.975 1.176 0.619 0.463 0.448 1.078 1.248 1.967 9.966
11 1.063 5.364 3.258 0.980 1.073 0.653 0.460 0.440 1.119 1.418 1.756 7.257
12 1.038 7.581 3.118 0.896 0.872 0.621 0.461 0.433 1.124 1.621 1.583 5.771
13 1.002 4.622 2.966 0.855 0.817 0.586 0.494 0.400 1.056 1.421 1.529 5.318
14 0.968 3.824 2.810 0.829 0.767 0.551 0.397 0.396 1.024 1.354 1.487 5.071
15 0.949 3.822 2.658 0.817 0.739 0.511 0.383 0.396 0.998 1.395 1.520 4.674
16 0.942 5.719 2.558 0.806 0.739 0.482 0.372 0.392 0.970 1.356 1.577 4.394
17 0.912 10.470 2.478 0.777 0.836 0.479 0.386 0.354 0.930 1.165 1.622 4.225
18 0.925 9.512 2.333 0.784 0.928 0.478 0.381 0.337 0.907 1.169 2.768 8.000
19 0.861 8.710 2.244 0.759 1.347 0.471 0.403 0.330 0.927 1.073 3.348 6.338
20 0.849 6.918 2.139 0.745 1.688 0.544 0.340 0.329 0.878 1.045 11.010 5.347
21 0.893 6.178 2.068 0.711 1.425 0.569 0.351 0.332 0.834 0.988 8.102 4.879
22 0.872 6.331 2.026 0.648 1.263 0.577 0.355 0.346 0.804 0.968 5.811 5.053
23 0.851 12.140 1.965 0.664 1.122 0.525 0.338 0.349 0.771 0.927 5.360 6.215
24 0.855 14.980 1.855 0.894 1.036 0.497 0.367 0.544 0.736 0.891 6.168 10.680
25 0.829 10.670 1.796 0.978 0.975 0.639 0.400 0.863 0.692 0.866 6.068 13.810
26 0.806 8.270 1.713 0.903 0.932 0.844 0.425 0.558 0.677 0.846 5.580 15.430
27 0.779 7.167 1.627 0.771 0.902 0.801 0.403 0.517 0.676 0.821 6.022 10.140
28 0.771 6.558 1.593 0.708 0.874 0.729 0.355 0.671 0.651 0.763 13.100 8.658
29 0.782 1.549 0.684 0.838 0.689 0.311 1.005 0.628 0.723 8.646 7.844
30 0.767 1.516 0.658 0.777 0.660 0.355 1.298 0.622 0.710 7.136 8.472
31 0.766 1.472 0.728 0.357 2.433 0.688 10.510
Average 1.023 5.289 2.993 0.922 0.906 0.621 0.435 0.570 1.025 0.957 3.661 7.338
Lowest 0.766 0.725 1.472 0.648 0.617 0.471 0.311 0.329 0.622 0.568 0.653 4.225
Highest 1.598 14.980 5.849 1.438 1.688 0.844 0.612 2.433 1.954 1.621 13.100 15.430
Monthly total
(million cu m) 2.74 12.79 8.02 2.39 2.43 1.61 1.16 1.53 2.66 2.56 9.49 19.65
Runoff (mm) 9 42 26 8 8 5 4 5 9 8 31 65
Rainfall (mm) 9 99 19 26 83 82 28 132 22 61 105 95
Statistics of monthly data for previous record (Jan 1964 to Dec 1996)
Mean Avg. 7.084 6.336 4.704 3.044 2.194 1.490 0.955 0.729 0.900 1.990 3.789 6.146
flows: Low 1.493 1.545 1.077 1.055 0.518 0.327 0.185 0.153 0.235 0.263 0.314 0.984
(year) 1976 1976 1993 1976 1990 1976 1976 1976 1990 1990 1964 1964
High 12.700 13.750 10.260 6.354 8.850 5.220 6.271 3.778 4.697 6.329 10.750 15.990
(year) 1995 1977 1981 1966 1983 1971 1968 1985 1974 1967 1992 1965
Runoff: Avg. 63 51 42 26 19 13 8 6 8 18 32 54
Low 13 13 10 9 5 3 2 1 2 2 3 9
High 112 110 91 54 78 45 55 33 40 56 92 141
Rainfall: Avg. 82 60 66 50 67 61 56 61 73 74 78 89
Low 12 6 17 5 7 6 10 3 23 6 33 19
High 152 145 151 107 159 144 127 139 172 169 173 176
Summary statistics Factors affecting runoff
1997
For 1997 For record As % of $ Flow influenced by groundwater abstraction
preceding 1997 pre-1997 and/or recharge.
Mean flow 2.125 3.268 65
Lowest yearly mean 1.344 1973
Highest yearly mean 4.235 1986
Lowest monthly mean 0.435 Jul 0.153 Aug 1976
Highest monthly mean 7.338 Dec 15.990 Dec 1965
Lowest daily mean 0.311 29 Jul 0.112 2 Sep 1976
Highest daily mean 15.430 26 Dec 61.350 11 Jul 1968
10% exceedance 6.094 7.967 76
50% exceedance 0.913 1.803 51
95% exceedance 0.376 0.330 114
Annual total (million cu m) 67.01 103.10 65
Annual runoff (mm) 221 340 65
Annual rainfall (mm) 761 817 93
{1961-90 rainfall average (mm) 804}
Station and catchment description
Compound Crump profile weir - low flow crest between two flanking sections. Situated 90m d/s of Great Somerford road
bridge. Full range station. All except extreme flows (e.g. Jul 1968) contained. Flows augmented by gw scheme in
catchment.
Geology: mainly Oolitic L'st with lb tributaries draining off clays. Land use: predominantly rural.
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