018005 Allan Water at Bridge of Allan 1997
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 2.561 2.468 42.860 3.410 2.232 1.557 4.145 1.882 1.351 1.285 1.987 4.432
2 2.529 3.839 25.760 3.245 1.985 1.487 2.568 1.491 3.599 1.236 1.908 3.906
3 2.493 15.350 19.500 3.127 1.927 1.437 2.341 1.313 19.030 1.214 1.823 3.530
4 2.380 6.919 11.990 3.317 13.640 1.406 2.106 1.196 7.334 1.246 1.791 3.349
5 2.221 4.142 11.270 3.413 6.319 1.411 1.838 1.123 6.367 1.414 2.297 7.471
6 2.213 7.255 8.436 3.002 3.871 1.659 1.716 1.084 3.206 3.188 4.163 12.680
7 2.137 7.543 16.090 2.819 3.190 1.629 1.667 1.065 2.284 2.278 2.832 7.835
8 2.088 17.650 9.265 2.602 3.386 1.761 1.583 1.039 1.829 1.777 5.107 6.802
9 2.022 16.940 7.093 2.408 2.891 1.579 1.474 1.025 1.556 11.110 4.178 8.058
10 1.985 28.070 6.099 2.295 2.682 1.773 1.447 1.055 1.403 10.680 6.327 13.370
11 4.268 28.720 5.416 2.201 3.219 7.084 1.429 1.069 1.314 3.930 6.244 18.630
12 14.030 51.520 4.967 2.137 11.160 10.070 1.431 1.043 1.325 2.792 3.800 9.444
13 7.116 18.240 5.351 2.091 5.956 4.540 1.792 1.615 1.325 2.329 3.102 8.234
14 6.477 10.230 5.070 2.039 3.852 3.968 1.665 1.497 1.452 3.277 4.022 6.427
15 5.144 7.620 5.443 1.955 3.036 2.818 1.663 1.208 5.733 5.564 3.738 5.495
16 4.000 9.522 7.158 1.887 2.674 2.322 1.939 1.127 25.670 13.830 4.126 4.928
17 5.801 57.010 5.598 1.851 3.163 2.038 1.512 1.062 6.124 25.000 4.733 4.538
18 10.900 24.500 9.191 1.857 8.902 5.077 1.364 1.028 3.544 12.840 14.640 26.500
19 6.899 58.920 6.179 1.880 6.258 7.371 1.287 1.022 2.729 6.793 9.690 21.190
20 4.595 73.580 4.729 1.739 4.719 6.074 1.232 1.064 2.355 4.794 12.270 20.380
21 3.906 35.030 4.111 1.734 4.447 10.850 1.197 1.452 2.144 3.939 13.280 10.770
22 3.571 17.670 6.853 1.670 3.419 11.470 1.180 1.256 1.957 3.398 6.781 8.418
23 3.175 20.180 6.148 9.037 2.931 5.343 1.203 1.103 1.817 2.999 5.436 15.500
24 4.029 21.400 4.799 7.306 2.604 3.937 1.254 1.046 1.712 2.685 7.515 24.420
25 3.495 18.190 4.615 3.051 2.396 3.480 1.178 0.994 1.640 2.503 9.106 30.310
26 3.211 10.180 13.960 2.460 2.213 3.168 1.167 0.947 1.594 2.344 6.554 14.880
27 2.963 19.520 9.358 2.369 2.046 2.548 1.174 0.998 1.569 2.202 7.548 9.649
28 2.701 14.540 6.063 3.005 1.944 2.257 1.140 0.994 1.560 2.081 5.746 7.689
29 2.574 4.703 2.730 1.844 2.091 1.334 0.991 1.596 2.005 7.791 6.457
30 2.431 4.084 2.442 1.701 2.101 1.882 0.983 1.391 2.057 5.496 10.160
31 2.336 3.660 1.627 3.075 1.012 2.094 8.354
Average 4.073 21.670 9.220 2.836 3.943 3.810 1.677 1.154 3.884 4.674 5.801 11.090
Lowest 1.985 2.468 3.660 1.670 1.627 1.406 1.140 0.947 1.314 1.214 1.791 3.349
Highest 14.030 73.580 42.860 9.037 13.640 11.470 4.145 1.882 25.670 25.000 14.640 30.310
Monthly total
(million cu m) 10.91 52.42 24.69 7.35 10.56 9.88 4.49 3.09 10.07 12.52 15.04 29.70
Runoff (mm) 52 250 118 35 50 47 21 15 48 60 72 141
Rainfall (mm) 52 317 122 48 92 124 53 51 115 98 110 165
Statistics of monthly data for previous record (Jul 1971 to Dec 1996)
Mean Avg. 12.390 9.424 9.936 5.277 3.716 2.614 2.222 2.954 4.830 7.613 9.040 10.200
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. 158 110 127 65 47 32 28 38 60 97 112 130
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. 163 105 132 69 75 73 81 92 122 139 137 143
Low 62 21 42 4 13 17 17 13 6 29 42 40
High 379 296 299 123 201 151 218 223 249 255 258 270
Summary statistics Factors affecting runoff
1997
For 1997 For record As % of $ Flow reduced by industrial and/or
preceding 1997 pre-1997 agricultural abstractions.
Mean flow 6.048 6.677 91
Lowest yearly mean 4.270 1975
Highest yearly mean 9.090 1986
Lowest monthly mean 1.154 Aug 0.649 Aug 1984
Highest monthly mean 21.670 Feb 28.570 Jan 1993
Lowest daily mean 0.947 26 Aug 0.578 27 Aug 1984
Highest daily mean 73.580 20 Feb 139.300 16 Jan 1993
10% exceedance 13.770 15.410 89
50% exceedance 3.179 3.983 80
95% exceedance 1.082 0.882 123
Annual total (million cu m) 190.70 210.70 91
Annual runoff (mm) 908 1003 91
Annual rainfall (mm) 1347 1331 101
{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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