041019 Arun at Alfoldean 1998
Measuring authority: EA Grid reference: 51 (TQ) 117 331 Catchment area (sq km): 139.0
First year: 1970 Level stn. (m OD): 21.40 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 8.500 0.847 0.436 0.742 0.979 0.425 0.815 0.521 0.183 2.263 10.780 1.024
2 14.390 0.815 0.548 1.040 1.041 0.675 0.507 0.301 0.230 2.579 6.801 0.925
3 14.300 0.776 4.813 2.960 0.927 0.465 0.412 0.250 0.480 0.793 5.140 0.901
4 10.650 0.744 6.462 4.373 0.858 0.385 0.343 0.236 0.580 0.526 2.724 0.871
5 13.070 0.719 2.346 3.463 0.826 0.342 0.311 0.214 0.982 0.385 1.638 0.814
6 7.342 0.711 3.720 8.700 0.792 0.336 0.269 0.216 0.502 0.600 1.407 0.739
7 11.500 0.794 8.759 4.213 0.651 0.540 0.329 0.209 0.319 0.506 1.188 0.673
8 10.860 0.700 4.807 2.817 0.659 0.480 0.314 0.205 0.348 0.367 5.305 0.974
9 5.317 0.685 2.419 5.768 0.606 0.657 0.271 0.200 0.592 0.393 7.018 2.530
10 3.690 0.659 1.942 7.070 0.565 0.728 0.286 0.194 0.672 0.449 7.251 6.106
11 2.929 0.642 3.091 5.531 0.543 0.519 0.457 0.200 0.417 0.834 3.278 5.545
12 2.243 0.621 2.180 3.495 0.540 0.427 0.989 0.189 0.306 0.588 2.839 4.118
13 5.341 0.597 1.725 2.276 0.514 1.823 0.658 0.181 0.265 0.485 2.769 3.341
14 8.512 0.589 1.478 1.918 3.881 1.444 0.404 0.181 0.226 0.486 5.357 2.393
15 6.430 0.568 1.277 5.608 1.245 0.871 0.345 0.193 0.268 0.403 2.607 3.041
16 6.059 0.579 1.153 5.864 0.719 0.584 0.473 0.186 0.247 0.503 1.755 3.151
17 3.636 0.536 1.062 4.957 0.548 0.420 0.360 0.181 0.224 4.388 1.433 2.173
18 11.410 0.524 0.947 2.835 0.483 0.396 0.319 0.169 0.224 1.558 1.281 2.379
19 5.282 0.531 0.843 4.057 0.423 0.316 0.285 0.183 0.217 0.791 1.034 2.577
20 3.039 0.552 0.753 4.939 0.389 0.324 0.292 0.178 0.212 0.509 0.973 1.763
21 2.247 0.640 0.706 2.785 0.384 0.295 0.276 0.185 0.211 1.599 0.886 1.402
22 1.949 0.564 0.707 2.081 0.365 0.275 0.268 0.181 0.214 1.345 0.849 1.381
23 1.684 0.510 0.683 3.166 0.358 0.318 0.302 0.261 0.208 3.441 0.807 8.425
24 1.482 0.461 0.647 3.024 0.342 0.464 0.263 0.247 0.224 10.640 1.072 6.708
25 1.356 0.443 0.781 7.413 0.335 0.633 0.239 0.204 0.205 6.794 1.394 6.517
26 1.237 0.441 1.283 3.499 0.691 0.425 0.230 0.194 0.718 2.108 1.174 11.470
27 1.106 0.460 1.054 2.196 0.738 1.186 0.279 0.190 0.410 2.545 1.053 7.234
28 1.075 0.454 0.862 1.847 0.705 0.760 0.258 0.187 0.296 4.004 1.729 3.863
29 0.994 0.892 1.503 0.520 0.702 0.266 0.184 0.279 1.906 1.734 2.828
30 0.951 0.979 1.344 0.422 2.351 0.257 0.184 0.937 1.445 1.248 2.275
31 0.907 0.803 0.471 0.244 0.178 9.818 2.635
Average 5.467 0.613 1.941 3.716 0.726 0.652 0.365 0.212 0.373 2.098 2.817 3.251
Lowest 0.907 0.441 0.436 0.742 0.335 0.275 0.230 0.169 0.183 0.367 0.807 0.673
Highest 14.390 0.847 8.759 8.700 3.881 2.351 0.989 0.521 0.982 10.640 10.780 11.470
Monthly total
(million cu m) 14.64 1.48 5.20 9.63 1.95 1.69 0.98 0.57 0.97 5.62 7.30 8.71
Runoff (mm) 105 11 37 69 14 12 7 4 7 40 53 63
Rainfall (mm) 119 8 71 115 47 93 36 16 102 160 61 83
Statistics of monthly data for previous record (May 1970 to Dec 1997----incomplete or missing months total 0.1 years)
Mean Avg. 3.996 2.829 2.107 1.593 0.955 0.628 0.339 0.350 0.576 1.677 2.378 3.145
flows: Low 0.528 0.689 0.418 0.272 0.223 0.131 0.138 0.078 0.161 0.150 0.167 0.492
(year) 1992 1981 1993 1997 1976 1976 1976 1976 1971 1972 1978 1971
High 10.770 9.828 4.413 3.829 3.313 3.054 1.274 1.618 5.443 11.580 10.030 7.022
(year) 1988 1990 1981 1983 1981 1971 1991 1985 1974 1987 1974 1993
Runoff: Avg. 77 50 41 30 18 12 7 7 11 32 44 61
Low 10 12 8 5 4 2 3 2 3 3 3 9
High 207 171 85 71 64 57 25 31 102 223 187 135
Rainfall: Avg. 86 56 62 51 52 56 47 56 69 83 86 85
Low 16 7 7 4 3 8 12 2 13 9 15 19
High 183 138 127 110 115 147 103 155 201 224 209 167
Summary statistics Factors affecting runoff
1998
For 1998 For record As % of $ Augmentation from effluent returns.
preceding 1998 pre-1998
Mean flow 1.863 1.711 109
Lowest yearly mean 0.589 1973
Highest yearly mean 2.845 1974
Lowest monthly mean 0.212 Aug 0.078 Aug 1976
Highest monthly mean 5.467 Jan 11.580 Oct 1987
Lowest daily mean 0.169 18 Aug 0.051 8 Aug 1983
Highest daily mean 14.390 2 Jan 64.770 2 Oct 1993
10% exceedance 5.419 3.867 140
50% exceedance 0.763 0.565 135
95% exceedance 0.197 0.149 132
Annual total (million cu m) 58.75 54.00 109
Annual runoff (mm) 423 388 109
Annual rainfall (mm) 911 789 115
{1961-90 rainfall average (mm) 806}
Station and catchment description
Asymmetrical compound Crump profile weir (crests: 4.0m and 6.0m broad). Crest tapping not currently used; over-estimation
of high flows (structure drowns frequently); but post-1995 flows truncated at c15 cumecs. Stilling well leakage can
influence water levels. Limited impact of artificial influences on runoff - small net augmentation due to sewage
effluent, which can significantly affect low flow patterns.
Principally an impervious (Weald Clay) catchment - mainly rural but includes Horsham.
In line with Natural Environment Research Council policy, the provision of data from the National River Flow Archive confers only a right to use the data. Ownership of the data, or the associated Intellectual Property Rights, will not normally be transferred. Data received from the NRFA must not be sold, or passed on to any third party. Reproduction is authorised, except for commercial purposes, provided the sources is acknowledged.
Through the use of quality control procedures every effort is made to maintain and improve the quality of data. However, NERC, the Environment Agency, the Scottish Environment Protection Agency and the Rivers Agency accepts no liability for any loss or damage, cost or claims arising directly or indirectly their use.