018005 Allan Water at Bridge of Allan 1996
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 12.080 2.906 4.045 3.016 5.251 5.310 1.677 0.965 1.030 2.523 14.200 31.650
2 13.750 2.781 3.804 3.070 4.365 3.761 1.636 0.900 1.090 1.764 23.680 24.230
3 11.820 2.589 3.696 2.925 3.482 10.100 2.622 0.843 0.969 9.727 37.400 11.970
4 27.290 2.532 3.326 2.871 3.073 5.259 2.088 0.827 0.895 15.960 32.000 9.689
5 23.570 2.639 3.063 2.617 2.944 9.061 1.785 0.799 0.876 4.417 30.770 7.089
6 13.350 2.647 2.888 2.444 2.925 4.472 1.468 0.795 0.861 2.813 33.800 5.570
7 20.560 2.505 2.811 2.347 2.997 3.260 1.344 0.788 0.832 2.462 13.800 9.552
8 19.640 2.489 2.689 2.417 2.686 2.728 1.226 0.804 0.807 2.276 14.490 14.700
9 13.650 6.961 2.597 2.498 2.458 2.564 1.191 0.854 0.793 2.110 13.360 9.049
10 10.070 30.690 2.511 3.103 2.320 3.595 1.141 2.137 0.767 1.767 8.805 6.739
11 8.484 21.740 12.880 3.337 2.302 11.090 1.152 1.544 0.760 6.194 7.138 5.560
12 9.167 30.200 31.240 3.081 2.226 6.204 1.131 1.091 0.752 40.830 5.893 4.893
13 9.627 11.710 9.275 2.717 2.107 3.793 1.087 0.942 0.725 10.110 5.370 4.298
14 14.350 7.686 6.258 4.928 2.005 3.017 1.040 0.889 0.732 14.430 5.279 4.361
15 9.815 19.600 5.153 5.750 1.916 2.546 1.003 0.811 0.730 32.380 4.653 3.951
16 7.857 16.200 5.221 7.359 1.908 2.255 0.963 0.810 0.733 20.960 4.490 3.752
17 7.429 17.270 6.515 16.090 1.905 2.049 0.939 0.802 0.728 10.340 5.145 3.750
18 6.184 12.340 6.924 17.160 2.010 1.900 0.928 0.776 0.714 8.522 4.118 25.600
19 5.377 6.786 6.747 11.340 2.264 1.803 0.912 0.787 0.707 7.498 3.828 15.720
20 4.793 5.320 6.085 8.486 2.817 1.727 0.894 0.969 0.688 7.371 3.468 7.787
21 4.388 4.917 6.271 12.690 3.115 1.630 0.902 1.131 0.686 6.259 4.912 5.847
22 4.138 4.639 5.640 11.360 5.957 1.561 1.430 1.135 0.698 4.832 5.071 4.961
23 3.837 7.115 5.190 11.080 5.527 1.500 1.228 1.315 0.696 4.197 3.878 4.505
24 3.532 7.489 5.598 8.607 3.960 1.434 1.078 1.438 0.777 7.561 4.406 4.092
25 3.279 6.594 4.819 6.275 3.317 1.447 0.970 1.298 0.857 10.810 4.947 3.691
26 3.247 5.303 4.017 5.544 2.748 1.419 0.929 1.133 0.912 18.410 4.136 3.543
27 3.238 5.043 3.585 4.868 2.472 1.385 0.898 1.154 1.248 38.450 3.570 3.412
28 3.352 4.633 3.689 4.081 5.015 1.476 0.991 1.513 9.769 68.180 6.575 3.097
29 3.181 4.443 3.452 3.913 4.239 1.394 1.066 1.118 7.517 17.990 11.210 2.985
30 3.025 3.082 3.737 7.857 1.334 0.981 0.971 5.031 12.630 13.870 2.873
31 2.967 2.864 9.462 0.949 0.897 19.540 2.707
Average 9.260 8.889 5.675 5.990 3.472 3.369 1.214 1.040 1.479 13.330 11.140 8.117
Lowest 2.967 2.489 2.511 2.347 1.905 1.334 0.894 0.776 0.686 1.764 3.468 2.707
Highest 27.290 30.690 31.240 17.160 9.462 11.090 2.622 2.137 9.769 68.180 37.400 31.650
Monthly total
(million cu m) 24.80 22.27 15.20 15.53 9.30 8.73 3.25 2.78 3.83 35.71 28.88 21.74
Runoff (mm) 118 106 72 74 44 42 15 13 18 170 138 104
Rainfall (mm) 98 112 73 111 85 69 56 73 68 255 180 79
Statistics of monthly data for previous record (Jul 1971 to Dec 1995)
Mean Avg. 12.520 9.446 10.110 5.247 3.726 2.583 2.262 3.030 4.964 7.385 8.956 10.280
flows: Low 4.751 3.631 3.152 1.655 1.189 0.945 0.726 0.649 0.906 0.972 3.641 3.709
(year) 1985 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 15.060 17.760 22.420
(year) 1993 1995 1994 1993 1986 1972 1985 1985 1992 1995 1984 1994
Runoff: Avg. 160 110 129 65 48 32 29 39 61 94 111 131
Low 61 42 40 20 15 12 9 8 11 12 45 47
High 364 259 312 129 197 67 80 158 187 192 219 286
Rainfall: Avg. 166 104 134 67 75 73 82 93 124 135 135 146
Low 62 21 42 4 13 17 17 13 6 29 42 40
High 379 296 299 123 201 151 218 223 249 248 258 270
Summary statistics Factors affecting runoff
1996
For 1996 For record As % of $ Flow reduced by industrial and/or
preceding 1996 pre-1996 agricultural abstractions.
Mean flow 6.073 6.703 91
Lowest yearly mean 4.270 1975
Highest yearly mean 9.090 1986
Lowest monthly mean 1.040 Aug 0.649 Aug 1984
Highest monthly mean 13.330 Oct 28.570 Jan 1993
Lowest daily mean 0.686 21 Sep 0.578 27 Aug 1984
Highest daily mean 68.180 28 Oct 139.300 16 Jan 1993
10% exceedance 13.860 15.480 90
50% exceedance 3.521 4.005 88
95% exceedance 0.791 0.889 89
Annual total (million cu m) 192.00 211.50 91
Annual runoff (mm) 914 1007 91
Annual rainfall (mm) 1259 1334 94
{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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