053008 Avon at Great Somerford 2000
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 9.950 2.873 7.460 1.804 8.314 3.318 1.099 0.779 0.617 2.320 21.750 15.850
2 8.699 4.610 6.545 4.909 7.474 3.045 1.046 0.806 0.550 2.601 31.420 13.040
3 9.929 3.225 8.158 26.300 6.676 2.845 1.050 0.905 0.514 2.223 25.490 10.510
4 9.769 3.067 6.157 14.620 6.105 2.683 1.069 0.839 0.476 2.010 17.040 19.170
5 8.350 2.897 5.591 7.247 5.515 2.564 1.723 0.771 0.520 1.837 20.310 18.750
6 8.278 2.900 5.186 5.784 4.695 2.435 1.538 0.778 0.530 1.813 27.430 20.040
7 7.279 3.657 4.865 4.884 4.152 2.307 1.129 0.796 0.505 2.036 17.580 26.290
8 6.514 4.079 4.618 4.590 4.001 2.237 1.021 0.797 0.511 1.987 13.650 30.770
9 5.909 3.534 4.281 4.185 3.769 2.231 1.023 0.762 0.498 7.081 10.900 16.410
10 5.466 5.270 3.880 3.881 3.577 2.068 1.058 0.754 0.480 9.823 9.318 19.340
11 5.183 4.006 3.710 4.527 3.413 1.967 1.007 0.697 0.479 10.980 13.570 21.690
12 5.284 4.913 3.476 8.805 3.239 1.898 0.949 0.700 0.449 5.760 10.760 25.880
13 7.026 4.097 3.297 6.590 3.066 1.828 0.943 0.750 0.449 4.496 8.454 37.470
14 5.310 4.086 3.100 5.741 2.906 1.779 0.907 0.764 0.518 4.070 7.348 22.010
15 4.775 4.421 2.920 9.080 2.767 1.720 0.863 0.746 0.841 3.756 7.714 16.370
16 4.427 4.335 2.810 7.592 2.681 1.630 0.838 0.787 0.653 3.436 12.460 13.150
17 4.171 3.804 2.693 8.646 2.672 1.566 0.804 0.743 0.578 3.185 8.284 11.090
18 3.824 3.599 2.581 16.180 2.646 1.492 0.776 0.829 0.983 3.910 7.379 9.485
19 3.689 3.266 2.487 16.070 2.464 1.446 0.765 1.038 1.117 3.438 7.065 8.828
20 3.391 3.110 2.357 13.860 2.446 1.439 0.757 0.802 1.803 3.234 6.514 8.064
21 3.194 3.014 2.298 12.550 2.407 1.455 0.765 0.739 1.096 3.693 7.589 7.154
22 3.093 2.913 2.197 12.380 2.260 1.463 0.755 0.713 1.031 3.317 10.630 6.412
23 2.966 2.940 2.812 12.410 2.343 1.301 0.742 0.725 0.920 3.090 9.037 5.951
24 2.856 5.452 2.638 11.430 2.352 1.206 0.742 0.702 0.955 3.052 7.983 7.691
25 2.701 6.693 2.318 12.680 2.239 1.166 0.736 0.700 2.647 3.000 11.810 8.821
26 2.577 4.154 2.219 13.400 3.364 1.121 0.755 0.754 2.986 2.823 17.540 6.570
27 2.468 6.657 2.049 11.660 5.804 1.110 0.840 0.738 3.312 2.849 14.390 5.754
28 2.454 10.230 1.950 13.750 11.150 1.085 0.770 0.688 4.762 8.280 14.960 5.288
29 2.390 12.880 1.877 14.880 5.868 1.271 0.841 0.310 2.872 22.840 11.060 4.850
30 2.342 1.801 9.352 4.062 1.195 0.810 0.365 2.532 60.110 10.180 4.456
31 2.270 1.727 3.506 0.788 0.525 24.720 6.605
Average 5.049 4.506 3.550 9.993 4.127 1.829 0.933 0.735 1.206 7.025 13.320 13.990
Lowest 2.270 2.873 1.727 1.804 2.239 1.085 0.736 0.310 0.449 1.813 6.514 4.456
Highest 9.950 12.880 8.158 26.300 11.150 3.318 1.723 1.038 4.762 60.110 31.420 37.470
Monthly total
(million cu m) 13.52 11.29 9.51 25.90 11.05 4.74 2.50 1.97 3.13 18.82 34.53 37.48
Runoff (mm) 45 37 31 85 36 16 8 7 10 62 114 124
Rainfall (mm) 27 87 29 178 88 31 53 67 111 166 141 140
Statistics of monthly data for previous record (Jan 1964 to Dec 1999)
Mean Avg. 7.228 6.119 4.684 3.079 2.179 1.501 0.931 0.734 0.954 2.073 3.900 6.297
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 6.354 8.850 5.220 6.271 3.778 4.697 6.329 10.750 15.990
(year) 1999 1977 1981 1966 1983 1971 1968 1985 1974 1967 1992 1965
Runoff: Avg. 64 49 41 26 19 13 8 6 8 18 33 56
Low 9 13 10 8 5 3 2 1 2 2 3 9
High 127 110 91 54 78 45 55 33 40 56 92 141
Rainfall: Avg. 83 59 65 52 66 64 53 65 74 75 78 90
Low 9 6 17 5 7 6 5 3 22 6 33 19
High 152 145 151 108 159 144 127 144 172 169 173 176
Summary statistics Factors affecting runoff
2000
For 2000 For record As % of $ Flow influenced by groundwater abstraction
preceding 2000 pre-2000 and/or recharge.
Mean flow 5.516 3.296 167
Lowest yearly mean 1.344 1973
Highest yearly mean 4.603 1999
Lowest monthly mean 0.735 Aug 0.153 Aug 1976
Highest monthly mean 13.990 Dec 15.990 Dec 1965
Lowest daily mean 0.310 29 Aug 0.112 2 Sep 1976
Highest daily mean 60.110 30 Oct 61.350 11 Jul 1968
10% exceedance 13.140 8.067 163
50% exceedance 3.189 1.812 176
95% exceedance 0.657 0.336 195
Annual total (million cu m) 174.40 104.00 168
Annual runoff (mm) 576 343 168
Annual rainfall (mm) 1118 824 136
{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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