018005 Allan Water at Bridge of Allan 1999
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 7.597 6.669 17.010 6.275 3.007 3.220 3.127 2.884 1.401 10.420 14.530 16.520
2 30.940 5.921 29.670 5.263 2.870 3.340 2.430 3.504 1.464 6.798 13.480 17.710
3 24.410 6.756 21.750 4.743 2.704 5.737 10.000 2.277 1.296 4.577 9.052 16.080
4 34.920 11.240 11.700 4.595 2.604 5.105 5.377 1.836 1.286 3.670 14.600 9.755
5 23.520 6.528 8.056 8.717 2.497 4.110 3.531 1.701 1.326 3.217 34.670 33.910
6 15.290 5.346 6.733 13.590 2.766 4.904 2.854 1.613 7.266 3.014 10.320 52.030
7 10.990 4.615 5.805 6.137 2.785 5.243 2.561 1.571 4.504 3.564 7.524 38.240
8 8.590 4.098 5.145 5.044 5.347 4.089 2.450 1.505 4.032 4.198 6.523 33.720
9 7.026 3.786 4.860 4.515 11.720 3.206 2.183 1.394 3.609 3.988 5.228 23.050
10 6.031 3.567 4.454 4.766 17.320 2.744 2.037 1.348 2.177 5.705 4.541 11.440
11 5.519 3.560 4.172 8.762 15.380 2.512 1.930 1.329 1.962 4.185 4.114 14.100
12 5.624 3.669 5.538 6.800 8.748 2.910 1.797 1.342 1.997 3.252 3.802 12.820
13 17.740 3.377 4.476 5.033 6.953 3.040 1.836 1.519 1.837 2.942 3.520 8.203
14 18.140 4.823 4.091 4.397 5.197 3.004 1.734 1.586 1.712 2.753 3.299 6.602
15 47.520 3.995 7.813 4.002 4.819 2.740 1.672 1.420 1.495 2.578 3.155 5.660
16 14.170 3.665 7.796 3.571 4.018 2.463 1.749 1.316 10.270 2.428 2.967 18.310
17 15.870 3.419 5.001 3.382 3.642 2.510 2.274 1.339 8.693 2.297 2.774 18.890
18 31.730 7.483 4.555 4.489 3.321 2.156 2.584 1.457 4.788 2.171 2.613 7.636
19 39.120 7.516 3.815 4.333 3.025 10.760 8.631 1.358 3.798 2.148 2.459 5.763
20 18.940 9.557 4.300 20.270 2.798 5.866 13.290 1.239 30.960 3.156 2.389 4.944
21 11.810 21.600 7.347 14.070 4.033 3.308 4.684 1.193 11.170 4.040 2.363 6.163
22 12.230 8.095 4.337 22.780 5.047 2.774 3.087 1.160 5.844 12.430 2.351 31.050
23 24.500 6.117 3.926 9.032 3.524 2.499 2.474 1.135 11.800 5.326 3.082 21.250
24 21.300 5.242 5.133 6.435 3.420 2.264 2.364 1.127 14.760 5.251 5.355 55.060
25 21.180 9.061 4.092 5.370 3.378 2.084 2.102 1.456 7.733 5.162 5.052 34.000
26 18.740 7.387 3.640 4.777 7.478 2.159 1.883 2.291 5.309 3.709 13.790 15.680
27 11.820 8.793 3.279 4.266 4.040 3.398 1.722 1.571 4.494 3.867 19.890 10.650
28 10.960 53.990 31.000 3.839 6.576 2.529 1.636 1.288 4.077 4.744 56.920 8.022
29 11.590 34.890 3.513 14.670 2.136 1.591 1.287 8.353 3.492 15.600 6.671
30 9.752 11.810 3.262 5.379 2.102 1.544 1.699 6.112 4.263 51.560 10.940
31 8.046 7.889 3.895 1.487 1.596 10.860 15.600
Average 17.600 8.210 9.164 6.868 5.579 3.497 3.181 1.592 5.851 4.523 10.920 18.400
Lowest 5.519 3.377 3.279 3.262 2.497 2.084 1.487 1.127 1.286 2.148 2.351 4.944
Highest 47.520 53.990 34.890 22.780 17.320 10.760 13.290 3.504 30.960 12.430 56.920 55.060
Monthly total
(million cu m) 47.14 19.86 24.54 17.80 14.94 9.06 8.52 4.26 15.17 12.11 28.30 49.29
Runoff (mm) 224 95 117 85 71 43 41 20 72 58 135 235
Rainfall (mm) 251 125 113 94 136 95 80 61 166 85 169 249
Statistics of monthly data for previous record (Jul 1971 to Dec 1998)
Mean Avg. 12.120 10.030 9.837 5.358 3.688 2.693 2.284 2.964 4.797 7.885 9.041 10.350
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. 155 117 125 66 47 33 29 38 59 101 112 132
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. 159 114 131 70 75 76 82 91 120 142 137 146
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
1999
For 1999 For record As % of $ Flow reduced by industrial and/or
preceding 1999 pre-1999 agricultural abstractions.
Mean flow 7.959 6.744 118
Lowest yearly mean 4.270 1975
Highest yearly mean 9.124 1998
Lowest monthly mean 1.592 Aug 0.649 Aug 1984
Highest monthly mean 18.400 Dec 28.570 Jan 1993
Lowest daily mean 1.127 24 Aug 0.578 27 Aug 1984
Highest daily mean 56.920 28 Nov 139.300 16 Jan 1993
10% exceedance 18.020 15.530 116
50% exceedance 4.560 4.011 114
95% exceedance 1.424 0.899 158
Annual total (million cu m) 251.00 212.80 118
Annual runoff (mm) 1195 1013 118
Annual rainfall (mm) 1624 1343 121
{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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