053008 Avon at Great Somerford 2001
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 12.200 5.170 3.202 5.611 3.693 1.725 0.683 0.587 0.574 0.517 2.709 5.299
2 19.280 5.524 3.039 5.259 3.547 1.559 0.766 0.609 0.575 0.610 2.482 3.465
3 10.730 6.549 2.884 8.264 3.355 1.568 0.584 0.639 0.569 0.540 2.336 3.408
4 16.370 14.610 2.709 8.475 3.143 1.523 0.630 0.620 0.547 0.497 2.184 5.075
5 11.790 12.830 2.527 11.180 2.983 1.493 0.639 0.611 0.543 0.482 2.044 8.372
6 9.071 20.150 3.201 9.415 2.882 1.487 2.770 0.592 0.548 0.483 2.005 5.369
7 7.945 11.090 4.018 9.234 2.768 1.391 1.569 0.607 0.525 0.709 1.933 4.610
8 6.989 9.711 3.394 10.860 2.689 1.307 1.031 0.628 0.522 0.708 1.799 4.199
9 6.489 7.662 3.210 10.310 2.743 1.252 1.339 0.906 0.504 0.575 1.671 3.715
10 5.873 7.353 3.248 7.898 2.687 1.158 1.279 0.809 0.498 0.531 1.603 3.506
11 5.293 7.052 3.603 7.136 2.474 1.143 0.970 0.704 0.512 0.514 1.556 3.261
12 4.829 17.940 4.312 6.437 2.348 1.130 0.888 0.808 0.535 0.511 1.541 3.000
13 4.442 10.190 6.378 5.841 2.268 1.080 0.922 0.749 0.557 0.510 1.426 2.806
14 4.148 7.749 4.382 5.484 2.264 1.134 0.821 0.687 0.509 0.500 1.336 2.665
15 3.935 6.962 4.016 5.116 2.122 1.080 0.764 0.655 0.490 0.574 1.248 2.512
16 3.688 6.267 5.744 4.593 2.551 1.194 0.738 0.665 0.481 0.597 1.201 2.367
17 3.412 5.703 10.340 4.219 17.740 1.048 0.836 0.672 0.478 0.573 1.165 2.249
18 3.349 5.258 8.965 3.936 7.456 0.971 1.011 0.675 0.511 0.900 1.110 2.214
19 3.189 4.862 6.168 3.697 4.478 0.930 0.890 0.684 0.491 0.813 1.069 2.140
20 3.038 4.504 8.267 3.456 3.632 0.898 0.779 0.613 0.491 1.625 1.014 2.013
21 4.356 4.212 22.870 3.294 3.153 0.852 0.785 0.574 0.481 1.194 0.968 1.962
22 5.678 3.898 12.290 5.075 2.886 0.811 0.742 0.565 0.484 1.183 0.932 1.850
23 13.430 3.801 16.170 4.450 2.647 0.722 0.700 0.560 0.475 1.767 0.891 1.746
24 10.540 3.434 11.620 10.500 2.478 0.689 0.608 0.593 0.495 1.672 0.868 1.715
25 7.906 3.292 9.436 8.746 2.371 0.682 0.588 0.614 0.490 1.536 1.040 1.669
26 10.890 3.807 8.091 6.525 2.139 0.710 0.584 0.602 0.519 10.490 1.116 1.601
27 8.779 3.775 10.470 5.268 2.199 0.657 0.565 0.583 0.511 5.707 1.115 1.617
28 6.581 3.462 10.630 4.742 2.096 0.688 0.561 0.583 0.478 4.948 0.944 1.565
29 5.691 7.982 4.321 2.012 0.722 0.598 0.590 0.584 3.929 1.281 1.564
30 6.011 6.652 3.841 1.894 0.709 0.592 0.603 0.530 3.463 2.340 1.464
31 5.444 6.145 1.768 0.585 0.603 2.901 1.337
Average 7.463 7.386 6.967 6.439 3.338 1.077 0.865 0.645 0.517 1.663 1.498 2.914
Lowest 3.038 3.292 2.527 3.294 1.768 0.657 0.561 0.560 0.475 0.482 0.868 1.337
Highest 19.280 20.150 22.870 11.180 17.740 1.725 2.770 0.906 0.584 10.490 2.709 8.372
Monthly total
(million cu m) 19.99 17.87 18.66 16.69 8.94 2.79 2.32 1.73 1.34 4.45 3.88 7.80
Runoff (mm) 66 59 62 55 30 9 8 6 4 15 13 26
Rainfall (mm) 73 70 98 91 55 26 81 73 39 118 41 28
Statistics of monthly data for previous record (Jan 1964 to Dec 2000)
Mean Avg. 7.169 6.075 4.653 3.266 2.232 1.510 0.931 0.734 0.961 2.207 4.154 6.505
flows: Low 1.023 1.545 1.077 0.922 0.518 0.327 0.185 0.153 0.235 0.263 0.314 0.984
(year) 1997 1976 1993 1997 1990 1976 1976 1976 1990 1990 1964 1964
High 14.380 13.750 10.260 9.993 8.850 5.220 6.271 3.778 4.697 7.025 13.320 15.990
(year) 1999 1977 1981 2000 1983 1971 1968 1985 1974 2000 2000 1965
Runoff: Avg. 63 49 41 28 20 13 8 6 8 20 36 58
Low 9 13 10 8 5 3 2 1 2 2 3 9
High 127 110 91 85 78 45 55 33 40 62 114 141
Rainfall: Avg. 81 60 64 56 67 63 53 65 75 78 80 92
Low 9 6 17 5 7 6 5 3 22 6 33 19
High 152 145 151 178 159 144 127 144 172 169 173 176
Summary statistics Factors affecting runoff
2001
For 2001 For record As % of $ Flow influenced by groundwater abstraction
preceding 2001 pre-2001 and/or recharge.
Mean flow 3.376 3.356 101
Lowest yearly mean 1.344 1973
Highest yearly mean 5.516 2000
Lowest monthly mean 0.517 Sep 0.153 Aug 1976
Highest monthly mean 7.463 Jan 15.990 Dec 1965
Lowest daily mean 0.475 23 Sep 0.112 2 Sep 1976
Highest daily mean 22.870 21 Mar 61.350 11 Jul 1968
10% exceedance 8.382 8.216 102
50% exceedance 1.996 1.848 108
95% exceedance 0.509 0.339 150
Annual total (million cu m) 106.50 105.90 101
Annual runoff (mm) 351 350 101
Annual rainfall (mm) 793 834 95
{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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