043005 Avon at Amesbury 1998
Measuring authority: EA Grid reference: 41 (SU) 151 413 Catchment area (sq km): 323.7
First year: 1965 Level stn. (m OD): 67.10 Max alt. (m OD): 294
Daily mean gauged discharges (cubic metres per second)
DAY JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
1 4.070 5.972 4.079 3.215 4.605 3.273 3.384 1.962 1.485 2.116 6.106 4.675
2 5.929 5.887 4.184 3.254 4.539 3.417 3.071 1.953 1.525 2.041 6.712 4.636
3 7.129 5.787 4.497 3.373 4.441 3.549 2.910 1.949 1.578 1.936 6.350 4.626
4 8.104 5.635 4.442 3.646 4.392 3.451 2.796 1.936 1.629 1.848 6.010 4.565
5 9.667 5.506 4.211 3.980 4.353 3.358 2.702 1.873 1.628 1.794 5.371 4.510
6 10.300 5.451 4.490 5.040 4.362 3.318 2.676 1.834 1.638 1.739 4.945 4.414
7 9.883 5.466 5.222 4.231 4.339 3.256 2.621 1.809 1.645 1.393 4.752 4.331
8 9.497 5.346 4.766 4.171 4.195 3.257 2.553 1.776 1.649 1.348 4.798 4.454
9 8.895 5.274 4.383 5.518 4.102 3.245 2.497 1.731 1.627 1.605 5.181 4.671
10 8.526 5.128 4.290 6.079 4.052 3.413 2.470 1.662 1.627 1.702 5.309 4.788
11 8.246 5.154 4.289 5.448 4.095 3.391 2.498 1.632 1.610 1.702 5.099 5.173
12 7.936 5.090 4.146 5.341 4.073 3.216 2.648 1.608 1.689 1.663 4.986 4.949
13 8.007 4.955 4.039 4.757 3.996 3.458 2.664 1.608 1.669 1.657 5.114 4.841
14 8.020 4.899 3.990 4.532 3.945 4.351 2.539 1.612 1.630 1.672 5.152 4.800
15 7.742 4.850 3.936 5.323 3.851 3.873 2.490 1.623 1.610 1.680 4.995 4.776
16 7.524 4.830 3.892 5.891 3.799 3.531 2.419 1.605 1.579 1.712 4.829 4.736
17 7.170 4.686 3.817 5.224 3.777 3.455 2.372 1.609 1.529 1.851 4.754 4.694
18 8.615 4.642 3.723 4.734 3.716 3.349 2.330 1.600 1.475 2.066 4.717 4.862
19 9.181 4.598 3.666 4.719 3.642 3.333 2.285 1.593 1.458 1.980 4.679 5.158
20 7.888 4.554 3.612 4.835 3.634 3.177 2.283 1.592 1.452 1.878 4.624 4.965
21 7.441 4.559 3.581 4.537 3.624 2.999 2.262 1.587 1.438 1.845 4.511 4.742
22 7.218 4.435 3.536 4.452 3.573 2.951 2.227 1.592 1.422 1.978 4.498 4.675
23 7.015 4.352 3.496 4.551 3.555 2.925 2.228 1.636 1.386 2.104 4.540 5.075
24 6.811 4.307 3.453 4.658 3.535 2.898 2.180 1.697 1.389 2.885 4.675 5.390
25 6.663 4.226 3.602 4.797 3.531 2.826 2.095 1.669 1.413 4.080 4.810 5.868
26 6.581 4.206 3.886 5.010 3.564 2.931 2.082 1.612 1.569 3.741 4.700 8.042
27 6.538 4.158 3.796 5.141 3.554 3.938 2.087 1.583 1.873 3.233 4.632 8.655
28 6.414 4.139 3.566 5.351 3.514 3.840 2.077 1.481 2.021 3.548 4.776 7.681
29 6.294 3.444 5.025 3.440 3.268 2.016 1.487 2.066 3.673 5.050 6.931
30 6.191 3.335 4.781 3.349 3.507 1.995 1.540 2.135 3.376 4.772 6.801
31 6.086 3.223 3.305 1.959 1.487 4.253 6.729
Average 7.599 4.932 3.955 4.720 3.886 3.358 2.433 1.675 1.615 2.261 5.048 5.329
Lowest 4.070 4.139 3.223 3.215 3.305 2.826 1.959 1.481 1.386 1.348 4.498 4.331
Highest 10.300 5.972 5.222 6.079 4.605 4.351 3.384 1.962 2.135 4.253 6.712 8.655
Monthly total
(million cu m) 20.35 11.93 10.59 12.24 10.41 8.70 6.52 4.49 4.19 6.06 13.09 14.27
Runoff (mm) 63 37 33 38 32 27 20 14 13 19 40 44
Rainfall (mm) 112 11 64 121 16 125 36 25 103 135 61 78
Statistics of monthly data for previous record (Feb 1965 to Dec 1997)
Mean Avg. 5.422 6.159 5.448 4.585 3.488 2.652 1.970 1.640 1.563 1.879 2.552 3.943
flows: Low 1.249 1.237 1.207 1.083 0.871 0.652 0.492 0.388 0.670 0.926 1.137 1.421
(year) 1976 1976 1976 1976 1976 1976 1976 1976 1976 1997 1973 1990
High 10.630 13.860 9.208 7.571 5.249 4.345 3.104 2.438 2.598 3.681 6.395 9.427
(year) 1994 1990 1995 1979 1979 1979 1971 1979 1974 1993 1974 1992
Runoff: Avg. 45 46 45 37 29 21 16 14 13 16 20 33
Low 10 10 10 9 7 5 4 3 5 8 9 12
High 88 104 76 61 43 35 26 20 21 30 51 78
Rainfall: Avg. 80 57 62 47 55 56 49 60 67 70 77 85
Low 12 5 14 1 8 3 15 7 11 4 31 17
High 169 147 150 100 121 143 113 152 179 161 185 160
Summary statistics Factors affecting runoff
1998
For 1998 For record As % of $ Flow influenced by groundwater abstraction
preceding 1998 pre-1998 and/or recharge.
Mean flow 3.895 3.428 114
Lowest yearly mean 1.475 1976
Highest yearly mean 4.580 1994
Lowest monthly mean 1.615 Sep 0.388 Aug 1976
Highest monthly mean 7.599 Jan 13.860 Feb 1990
Lowest daily mean 1.348 8 Oct 0.183 22 Aug 1976
Highest daily mean 10.300 6 Jan 22.210 4 Feb 1990
10% exceedance 6.149 6.618 93
50% exceedance 3.843 2.731 141
95% exceedance 1.562 1.113 140
Annual total (million cu m) 122.80 108.20 113
Annual runoff (mm) 379 334 113
Annual rainfall (mm) 887 765 116
{1961-90 rainfall average (mm) 745}
Station and catchment description
Crump profile weir (crest 9.14m broad) flanked by broad-crested weirs. Small bypass channel approx. 2m u/s of weir -
included in rating. Full range station. During summer, flows are naturally augmented from gw draining from northern half
of R. Bourne catchment. May go non-modular at low flow in exceptional summers. Some gw pumping also takes place within
the catchment. Data reprocessed in 2001, resulting in decrease in high flows.
Predominantly permeable (Chalk) catchment with a small inlier of Upper Greensand and Gault. Land use: rural.
Topographical and gw catchments do not coincide.
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