053008 Avon at Great Somerford 1999
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 8.292 6.961 6.421 2.246 4.078 2.588 1.376 0.578 1.300 5.057 2.997 3.047
2 14.050 6.368 14.750 2.278 3.747 4.055 1.253 0.643 1.237 11.610 2.732 2.790
3 17.620 5.861 12.180 2.441 3.478 2.990 1.164 0.780 1.185 10.420 2.562 2.747
4 19.840 5.454 9.858 2.219 3.259 2.658 1.115 0.699 1.115 7.571 2.471 2.557
5 13.330 4.995 8.277 2.659 3.091 5.891 1.080 0.691 1.091 6.319 9.806 2.390
6 12.110 4.770 7.353 1.883 2.937 6.381 1.027 0.755 1.052 5.502 6.482 2.403
7 13.510 4.553 6.859 1.750 3.287 5.034 0.972 0.870 0.999 4.982 4.750 3.907
8 17.040 4.411 6.323 1.693 3.031 4.123 0.937 1.398 0.961 4.524 4.360 5.648
9 12.600 4.116 5.796 1.621 2.775 3.514 0.921 2.122 0.903 4.108 4.043 5.408
10 10.020 3.776 5.286 1.532 2.612 3.315 0.879 1.833 0.886 3.776 3.799 4.616
11 8.695 3.505 4.987 1.594 5.175 3.132 0.858 1.633 0.864 3.440 3.529 11.030
12 9.962 3.403 4.868 1.716 4.107 3.004 0.844 1.822 0.827 3.182 3.415 9.392
13 9.393 3.580 4.674 1.532 3.227 2.806 0.830 1.296 0.808 2.988 3.211 12.800
14 8.365 3.429 4.222 1.536 3.675 2.656 0.821 1.122 0.799 2.820 3.042 9.208
15 15.630 3.398 3.859 1.440 3.379 2.524 0.797 1.014 0.783 2.565 2.877 7.224
16 23.810 3.080 3.759 1.374 2.981 2.395 0.797 1.012 0.908 2.530 2.727 6.340
17 12.590 2.972 3.485 1.325 2.757 2.292 0.800 1.005 0.824 2.406 2.610 6.430
18 14.450 2.872 3.342 1.263 2.669 2.181 0.733 1.162 1.572 2.296 2.678 5.963
19 28.410 2.994 3.171 1.225 2.566 2.123 0.718 1.105 5.519 2.211 2.491 5.928
20 42.270 2.832 3.080 2.478 2.441 2.023 0.730 0.931 5.973 2.139 2.347 5.295
21 21.110 2.767 3.125 5.274 2.332 1.904 0.692 0.871 4.183 2.269 2.269 14.240
22 16.200 2.631 2.933 6.376 2.204 1.777 0.689 0.847 3.575 2.228 2.219 15.380
23 13.650 2.560 2.758 18.550 2.137 1.700 0.677 0.827 5.410 2.702 2.119 17.880
24 11.850 2.954 2.704 8.575 2.058 1.601 0.661 1.009 6.220 6.632 2.033 34.580
25 11.080 2.799 2.847 6.232 1.940 1.489 0.647 2.878 6.420 4.829 1.982 26.500
26 14.110 3.481 2.679 8.663 1.908 1.450 0.629 2.649 6.751 3.460 2.050 21.720
27 11.480 3.619 2.492 6.756 1.903 1.456 0.565 1.884 9.513 3.035 2.695 17.180
28 9.639 3.597 2.365 5.534 1.830 1.536 0.551 1.644 6.561 2.737 2.740 12.920
29 8.590 2.376 4.804 3.841 1.944 0.548 1.528 6.231 2.764 4.716 10.550
30 8.370 2.370 4.425 2.804 1.480 0.536 1.416 5.460 2.935 3.091 13.310
31 7.622 2.344 2.309 0.528 1.368 3.027 11.620
Average 14.380 3.848 4.888 3.700 2.921 2.734 0.818 1.271 2.998 4.099 3.295 10.030
Lowest 7.622 2.560 2.344 1.225 1.830 1.450 0.528 0.578 0.783 2.139 1.982 2.390
Highest 42.270 6.961 14.750 18.550 5.175 6.381 1.376 2.878 9.513 11.610 9.806 34.580
Monthly total
(million cu m) 38.51 9.31 13.09 9.59 7.82 7.09 2.19 3.40 7.77 10.98 8.54 26.87
Runoff (mm) 127 31 43 32 26 23 7 11 26 36 28 89
Rainfall (mm) 152 41 56 86 74 79 5 144 118 68 51 139
Statistics of monthly data for previous record (Jan 1964 to Dec 1998)
Mean Avg. 7.024 6.184 4.678 3.062 2.158 1.466 0.934 0.719 0.896 2.015 3.917 6.190
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 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. 62 50 41 26 19 13 8 6 8 18 34 55
Low 9 13 10 8 5 3 2 1 2 2 3 9
High 112 110 91 54 78 45 55 33 40 56 92 141
Rainfall: Avg. 81 59 65 51 66 63 55 63 73 76 79 89
Low 9 6 17 5 7 6 10 3 22 6 33 19
High 152 145 151 108 159 144 127 139 172 169 173 176
Summary statistics Factors affecting runoff
1999
For 1999 For record As % of $ Flow influenced by groundwater abstraction
preceding 1999 pre-1999 and/or recharge.
Mean flow 4.603 3.259 141
Lowest yearly mean 1.344 1973
Highest yearly mean 4.235 1986
Lowest monthly mean 0.818 Jul 0.153 Aug 1976
Highest monthly mean 14.380 Jan 15.990 Dec 1965
Lowest daily mean 0.528 31 Jul 0.112 2 Sep 1976
Highest daily mean 42.270 20 Jan 61.350 11 Jul 1968
10% exceedance 10.920 8.003 136
50% exceedance 2.863 1.762 162
95% exceedance 0.751 0.334 225
Annual total (million cu m) 145.20 102.80 141
Annual runoff (mm) 479 339 141
Annual rainfall (mm) 1013 820 124
{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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