018005 Allan Water at Bridge of Allan 2001
Measuring authority: SEPA Grid reference: 26 (NS) 786 980 Catchment area (sq km): 210.0
First year: 1971 Level stn. (m OD): 11.20 Max alt. (m OD): 633
Daily mean gauged discharges (cubic metres per second)
DAY JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
1 16.220 5.171 2.979 9.414 2.947 1.361 2.188 1.448 1.686 29.130 5.344 16.200
2 23.010 8.291 2.780 6.668 2.671 1.288 1.579 3.073 1.721 18.340 5.116 8.259
3 12.890 9.101 2.659 6.305 2.463 1.207 1.766 3.153 1.593 11.850 5.221 13.860
4 16.660 6.832 2.635 5.452 2.314 1.147 2.598 2.055 1.493 9.278 4.833 13.740
5 8.877 5.915 3.470 4.441 2.208 1.138 1.536 1.816 1.436 13.700 8.605 11.980
6 9.946 21.390 3.326 4.325 2.116 1.135 1.379 1.596 1.377 10.070 6.261 10.210
7 8.786 29.350 6.174 4.264 2.036 1.136 8.390 2.355 1.381 15.820 5.561 12.860
8 6.485 10.720 6.262 3.616 1.960 1.082 5.175 2.729 1.330 16.180 5.813 7.594
9 5.465 7.308 6.241 4.691 1.912 1.426 2.583 1.859 1.258 7.427 4.520 6.100
10 4.722 17.680 6.408 4.667 1.886 1.412 5.819 1.561 1.236 8.809 6.175 5.216
11 4.251 57.150 9.261 3.520 1.837 1.179 6.922 1.655 1.229 10.150 4.885 4.572
12 4.013 20.340 10.050 3.183 1.790 1.128 3.765 2.238 1.384 11.200 6.028 4.179
13 3.726 11.250 5.757 2.993 1.759 1.100 4.228 4.685 1.782 8.958 4.237 3.870
14 3.333 9.306 4.667 3.005 1.720 1.098 6.909 12.930 1.568 12.620 3.714 3.738
15 3.318 8.876 4.065 2.823 1.763 1.447 7.989 8.218 1.402 18.120 3.481 3.630
16 3.189 6.883 3.507 2.603 2.105 2.187 4.637 4.126 1.303 9.173 3.237 3.664
17 3.049 5.866 3.236 2.557 2.026 1.490 3.089 2.959 1.248 6.528 3.074 3.341
18 2.967 5.341 3.139 2.432 1.861 1.301 2.428 2.480 1.196 10.610 3.196 3.097
19 2.872 5.268 2.953 2.309 1.718 1.916 2.055 11.030 1.174 6.885 7.038 2.980
20 2.770 4.859 2.819 2.220 1.662 3.990 1.880 8.577 1.142 21.080 6.632 2.833
21 2.760 4.738 2.831 2.332 1.605 1.848 2.032 5.066 1.139 17.920 6.019 2.845
22 3.969 4.191 2.854 4.412 1.535 1.389 1.976 4.293 1.136 15.080 4.485 2.548
23 9.855 3.785 5.399 5.808 1.473 1.230 1.772 3.114 1.119 14.790 3.862 2.534
24 16.210 3.471 5.625 4.033 1.427 1.152 1.786 2.617 1.108 11.500 3.955 2.555
25 9.638 3.355 4.791 4.554 1.458 1.080 1.811 2.366 1.141 9.639 7.270 2.355
26 13.470 3.438 3.818 5.324 1.439 1.160 1.828 2.161 1.154 7.697 4.541 2.346
27 8.316 2.918 3.753 4.121 1.377 1.400 1.565 1.965 1.189 6.875 11.310 4.191
28 5.483 3.076 6.542 4.249 1.450 1.467 1.426 1.852 2.564 5.542 10.400 7.562
29 4.581 7.515 4.303 1.672 2.568 1.363 1.822 6.922 8.991 12.090 3.721
30 5.109 5.403 3.633 1.747 4.300 1.526 1.885 15.870 12.300 25.520 2.967
31 4.992 17.150 1.557 1.648 1.726 7.411 2.758
Average 7.449 10.210 5.099 4.142 1.855 1.559 3.085 3.529 2.043 12.050 6.414 5.752
Lowest 2.760 2.918 2.635 2.220 1.377 1.080 1.363 1.448 1.108 5.542 3.074 2.346
Highest 23.010 57.150 17.150 9.414 2.947 4.300 8.390 12.930 15.870 29.130 25.520 16.200
Monthly total
(million cu m) 19.95 24.70 13.66 10.74 4.97 4.04 8.26 9.45 5.30 32.29 16.63 15.41
Runoff (mm) 95 118 65 51 24 19 39 45 25 154 79 73
Rainfall (mm) 73 109 85 60 28 66 104 86 80 212 112 48
Statistics of monthly data for previous record (Jul 1971 to Dec 2000)
Mean Avg. 12.290 10.170 9.761 5.440 3.719 2.724 2.285 2.917 5.015 7.909 9.094 10.710
flows: Low 4.073 3.631 3.152 1.655 1.189 0.945 0.726 0.649 0.906 0.972 3.641 3.709
(year) 1997 1986 1975 1974 1980 1974 1984 1984 1972 1972 1972 1975
High 28.570 22.490 24.460 10.410 15.430 5.424 6.309 12.390 15.180 18.170 17.760 22.420
(year) 1993 1995 1994 1993 1986 1972 1985 1985 1992 1998 1984 1994
Runoff: Avg. 157 118 124 67 47 34 29 37 62 101 112 137
Low 52 42 40 20 15 12 9 8 11 12 45 47
High 364 259 312 129 197 67 80 158 187 232 219 286
Rainfall: Avg. 163 118 129 72 76 76 81 91 124 142 137 150
Low 52 21 42 4 13 17 17 13 6 29 42 40
High 379 317 299 123 201 151 218 223 249 255 258 270
Summary statistics Factors affecting runoff
2001
For 2001 For record As % of $ Flow reduced by industrial and/or
preceding 2001 pre-2001 agricultural abstractions.
Mean flow 5.244 6.824 77
Lowest yearly mean 4.270 1975
Highest yearly mean 9.124 1998
Lowest monthly mean 1.559 Jun 0.649 Aug 1984
Highest monthly mean 12.050 Oct 28.570 Jan 1993
Lowest daily mean 1.080 25 Jun 0.578 27 Aug 1984
Highest daily mean 57.150 11 Feb 139.300 16 Jan 1993
10% exceedance 11.280 15.690 72
50% exceedance 3.505 4.079 86
95% exceedance 1.169 0.919 127
Annual total (million cu m) 165.40 215.40 77
Annual runoff (mm) 787 1026 77
Annual rainfall (mm) 1063 1359 78
{1961-90 rainfall average (mm) 1335}
Station and catchment description
Velocity-area station; recorder sited in natural reach with vertical stone wall on rb. Lb steep to 2.6m. Flood rating
stable but large boulders make c/m a problem at low flows. As site is within a caravan park the low flow control is
susceptible to rearrangment by children. Station useful for obtaining flood data, as flooding frequently occurs in the
town of Bridge of Allan.
The Allan Water occupies a broad flat valley with steep lateral tributaries. Geology: predominantly Old Red Sandstone.
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