018005 Allan Water at Bridge of Allan 2000
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 10.330 31.370 10.930 4.025 4.428 2.277 1.252 2.805 5.300 5.043 7.964 15.230
2 11.740 11.670 32.810 5.280 3.946 2.344 1.257 2.977 3.905 4.723 7.669 16.520
3 13.210 9.147 12.770 4.605 3.667 1.859 1.268 2.178 2.980 12.150 5.992 13.190
4 12.370 21.010 8.751 3.749 3.368 2.468 1.215 1.475 2.561 11.830 5.149 21.160
5 30.960 10.870 13.670 3.322 3.118 2.617 1.262 1.276 2.987 6.699 4.757 18.750
6 21.960 9.346 16.110 3.098 2.956 2.456 1.263 1.179 26.350 5.279 24.670 20.160
7 23.160 16.330 18.180 2.907 2.800 2.434 1.168 1.109 10.780 9.730 19.050 11.640
8 18.690 11.900 18.340 2.853 2.629 7.778 1.240 1.101 7.435 7.408 8.391 39.100
9 11.210 10.140 12.800 2.685 2.493 5.407 5.028 4.436 6.005 36.980 7.029 28.790
10 20.840 18.490 12.310 2.601 2.396 5.476 4.190 3.002 4.736 18.040 7.359 18.850
11 10.830 20.350 8.439 2.933 2.298 5.625 1.956 1.703 48.630 9.722 13.980 15.280
12 8.774 16.830 6.977 14.630 2.206 5.134 1.515 1.506 14.640 8.597 14.310 31.450
13 7.141 10.930 6.331 6.185 2.133 5.040 1.339 1.639 8.010 6.685 9.126 19.560
14 6.026 14.880 5.549 4.148 2.044 3.153 1.253 2.408 7.962 7.082 6.775 11.630
15 5.305 13.360 4.950 3.590 2.839 2.507 1.186 2.198 5.699 5.584 7.781 8.560
16 4.868 9.632 4.557 3.310 3.655 2.205 1.121 3.009 4.598 5.476 9.310 7.124
17 4.617 8.920 4.214 3.345 4.016 2.039 1.072 2.716 4.504 18.180 6.050 6.154
18 4.421 13.840 3.903 3.226 2.674 1.940 1.047 2.408 6.415 15.130 6.036 5.764
19 4.121 9.184 3.693 3.455 2.413 1.859 1.019 6.851 5.571 6.984 5.240 12.450
20 3.942 9.925 3.501 4.353 2.306 1.819 0.989 4.588 19.310 6.052 4.641 21.280
21 3.701 14.200 3.359 3.760 2.308 2.076 0.980 3.455 7.914 5.201 4.326 9.476
22 3.556 7.958 3.343 3.525 2.133 2.321 0.968 2.535 17.660 4.565 8.570 7.301
23 3.297 16.820 7.807 4.350 2.822 1.887 0.961 2.007 8.235 7.312 6.419 6.389
24 3.155 13.180 7.985 4.480 2.766 1.742 0.939 1.707 6.354 15.910 5.298 5.687
25 2.927 14.580 5.371 9.811 2.628 1.624 0.932 1.667 6.490 22.140 10.190 5.135
26 2.787 19.130 4.251 40.600 2.588 1.669 0.943 5.443 18.090 8.482 7.556 4.542
27 3.001 50.070 3.693 16.650 2.332 1.615 0.930 4.404 21.070 11.500 6.402 4.113
28 14.470 25.290 3.395 8.461 2.258 1.586 1.210 3.286 11.030 18.750 12.650 4.000
29 13.030 19.430 3.262 6.319 2.131 1.362 1.680 3.426 7.062 46.560 10.870 3.675
30 32.070 3.166 5.123 1.906 1.290 1.496 3.068 5.663 13.560 9.086 3.405
31 36.920 3.134 1.831 1.493 9.336 9.047 4.088
Average 11.400 15.820 8.308 6.246 2.713 2.787 1.425 2.932 10.260 11.950 8.755 12.920
Lowest 2.787 7.958 3.134 2.601 1.831 1.290 0.930 1.101 2.561 4.565 4.326 3.405
Highest 36.920 50.070 32.810 40.600 4.428 7.778 5.028 9.336 48.630 46.560 24.670 39.100
Monthly total
(million cu m) 30.54 39.64 22.25 16.19 7.26 7.22 3.82 7.85 26.61 32.00 22.69 34.60
Runoff (mm) 145 189 106 77 35 34 18 37 127 152 108 165
Rainfall (mm) 186 203 83 94 56 70 61 125 182 195 118 166
Statistics of monthly data for previous record (Jul 1971 to Dec 1999)
Mean Avg. 12.320 9.966 9.813 5.412 3.755 2.722 2.315 2.916 4.833 7.769 9.105 10.630
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. 157 116 125 67 48 34 30 37 60 99 112 136
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. 162 115 130 71 77 76 82 90 122 140 138 149
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
2000
For 2000 For record As % of $ Flow reduced by industrial and/or
preceding 2000 pre-2000 agricultural abstractions.
Mean flow 7.927 6.786 117
Lowest yearly mean 4.270 1975
Highest yearly mean 9.124 1998
Lowest monthly mean 1.425 Jul 0.649 Aug 1984
Highest monthly mean 15.820 Feb 28.570 Jan 1993
Lowest daily mean 0.930 27 Jul 0.578 27 Aug 1984
Highest daily mean 50.070 27 Feb 139.300 16 Jan 1993
10% exceedance 18.410 15.570 118
50% exceedance 5.166 4.050 128
95% exceedance 1.218 0.909 134
Annual total (million cu m) 250.70 214.10 117
Annual runoff (mm) 1194 1020 117
Annual rainfall (mm) 1539 1352 114
{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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