043005 Avon at Amesbury 1999
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 6.763 8.784 5.903 4.149 3.376 3.022 2.491 1.521 1.636 2.746 2.618 3.368
2 7.163 8.498 6.114 4.006 3.333 3.398 2.432 1.601 1.613 2.655 2.542 3.250
3 8.099 8.305 6.657 3.993 3.284 3.493 2.364 1.634 1.602 2.645 2.504 3.193
4 8.696 8.174 6.535 3.999 3.219 3.270 2.283 1.758 1.553 2.594 2.468 3.049
5 8.326 7.947 6.224 3.983 3.189 3.224 2.236 1.689 1.519 2.442 2.686 3.001
6 7.747 7.780 5.919 3.954 3.172 3.645 2.268 1.711 1.499 2.323 3.029 2.979
7 7.742 7.673 5.753 3.948 3.187 3.350 2.191 1.716 1.485 2.277 2.893 3.021
8 8.066 7.546 5.616 3.912 3.293 3.092 2.131 1.791 1.507 2.252 2.771 3.218
9 7.888 7.415 5.452 3.857 3.220 2.908 2.091 2.644 1.493 2.217 2.768 3.332
10 7.566 7.109 5.316 3.834 3.160 2.853 2.066 2.949 1.495 2.188 2.659 3.236
11 7.411 6.906 5.242 3.830 3.106 2.807 2.011 2.966 1.495 2.195 2.663 3.379
12 7.944 6.807 5.228 3.924 3.013 2.769 1.967 2.477 1.494 2.137 2.653 3.749
13 8.325 6.755 5.226 3.948 3.031 2.712 1.948 2.223 1.468 2.105 2.636 3.706
14 8.196 6.662 5.078 3.859 3.330 2.659 1.979 2.101 1.480 2.077 2.629 3.678
15 8.517 6.663 4.993 3.817 3.319 2.596 1.963 1.993 1.422 2.056 2.619 3.507
16 10.110 6.515 4.935 3.751 3.126 2.539 1.926 2.051 1.543 2.044 2.640 3.391
17 10.090 6.346 4.881 3.697 3.021 2.463 1.928 2.015 1.542 2.027 2.645 3.350
18 9.215 6.243 4.828 3.686 2.987 2.444 1.928 2.215 1.550 1.986 2.713 3.477
19 10.810 6.299 4.770 3.678 2.948 2.408 1.938 2.225 1.771 1.985 2.799 3.517
20 12.500 6.294 4.731 4.040 2.894 2.413 1.942 2.033 2.042 2.024 2.737 3.441
21 11.870 6.230 4.799 4.513 2.854 2.381 1.929 1.903 2.094 2.107 2.669 3.752
22 10.590 6.156 4.779 4.207 2.807 2.304 1.907 1.853 2.041 2.181 2.628 5.456
23 10.650 5.978 4.683 4.269 2.736 2.307 1.821 1.854 2.090 2.502 2.607 6.781
24 10.640 6.030 4.640 5.065 2.697 2.294 1.765 1.816 2.276 3.089 2.600 7.676
25 10.520 5.917 4.629 4.443 2.689 2.270 1.732 1.852 2.335 3.433 2.577 10.330
26 10.700 5.882 4.610 4.187 2.674 2.231 1.757 1.909 2.655 3.083 2.733 11.710
27 11.710 5.995 4.515 4.024 2.653 2.246 1.713 1.973 2.844 2.761 3.073 11.910
28 10.540 5.832 4.465 3.694 2.623 2.316 1.659 1.880 2.746 2.644 3.052 10.580
29 9.625 4.482 3.562 2.944 2.653 1.638 1.805 2.746 2.545 3.186 9.075
30 9.293 4.325 3.452 3.732 2.699 1.632 1.744 2.627 2.562 3.609 9.220
31 9.043 4.249 3.080 1.572 1.671 2.597 9.978
Average 9.237 6.884 5.148 3.976 3.055 2.726 1.974 1.986 1.855 2.403 2.747 5.268
Lowest 6.763 5.832 4.249 3.452 2.623 2.231 1.572 1.521 1.422 1.985 2.468 2.979
Highest 12.500 8.784 6.657 5.065 3.732 3.645 2.491 2.966 2.844 3.433 3.609 11.910
Monthly total
(million cu m) 24.74 16.65 13.79 10.31 8.18 7.07 5.29 5.32 4.81 6.43 7.12 14.11
Runoff (mm) 76 51 43 32 25 22 16 16 15 20 22 44
Rainfall (mm) 116 38 33 61 63 75 13 120 111 66 51 127
Statistics of monthly data for previous record (Feb 1965 to Dec 1998)
Mean Avg. 5.488 6.123 5.404 4.589 3.500 2.673 1.983 1.641 1.565 1.890 2.626 3.983
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 21 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. 81 55 62 49 54 58 48 59 68 72 77 85
Low 12 5 14 1 8 3 15 7 11 4 31 17
High 169 147 150 121 121 143 113 152 179 161 185 160
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 3.926 3.442 114
Lowest yearly mean 1.475 1976
Highest yearly mean 4.580 1994
Lowest monthly mean 1.855 Sep 0.388 Aug 1976
Highest monthly mean 9.237 Jan 13.860 Feb 1990
Lowest daily mean 1.422 15 Sep 0.183 22 Aug 1976
Highest daily mean 12.500 20 Jan 22.210 4 Feb 1990
10% exceedance 7.863 6.603 119
50% exceedance 3.013 2.772 109
95% exceedance 1.608 1.119 144
Annual total (million cu m) 123.80 108.60 114
Annual runoff (mm) 382 336 114
Annual rainfall (mm) 874 768 114
{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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