043005    Avon at Amesbury                                                                                         2000


           Measuring authority: EA            Grid reference:     41    (SU) 151 413     Catchment area (sq km):    323.7
           First year: 1965                   Level stn. (m OD):   67.10                            Max alt. (m OD):  294



 Daily mean gauged discharges (cubic metres per second)


 
        DAY         JAN      FEB      MAR      APR      MAY      JUN      JUL      AUG      SEP      OCT      NOV      DEC

          1         9.227    5.707    7.691    4.647    8.400    5.756    3.501    2.439    2.171    2.867   11.840    9.908
          2         8.815    6.207    6.511    4.749    8.092    5.571    3.473    2.441    2.187    2.805    9.599   10.230
          3         8.996    5.959    6.922    6.689    8.058    5.375    3.428    2.502    2.166    2.749   10.250    9.676
          4         9.518    5.755    6.584    7.969    7.933    5.245    3.899    2.583    2.121    2.581    8.939   10.860
          5         8.995    5.624    6.158    6.499    7.810    5.130    5.276    2.644    2.063    2.465    8.744   13.800

          6         8.952    5.516    5.994    5.705    7.740    5.091    5.589    2.550    2.024    2.446   11.100   14.560
          7         8.608    5.724    6.095    5.440    7.718    4.911    4.686    2.523    2.011    2.466   15.340   16.800
          8         8.250    6.110    5.941    5.242    7.593    4.775    4.266    2.505    2.015    2.576   12.550   20.480
          9         8.000    5.658    5.782    5.125    7.461    4.690    4.080    2.464    1.992    2.945   11.050   23.580
         10         7.816    5.610    5.676    4.913    7.273    4.662    4.152    2.433    1.979    4.110   10.570   20.780

         11         7.777    5.724    5.649    4.959    7.165    4.566    4.150    2.377    1.973    5.174   10.800   20.130
         12         7.746    5.753    5.602    5.715    6.983    4.453    3.897    2.281    1.957    4.388   11.620   19.490
         13         7.884    5.567    5.566    6.585    6.894    4.390    3.668    2.328    1.934    3.711   11.050   21.730
         14         7.743    5.387    5.542    5.900    6.688    4.302    3.554    2.353    1.941    3.382   10.130   21.490
         15         7.473    5.376    5.429    6.429    6.492    4.273    3.391    2.344    2.218    3.267    9.717   19.120

         16         7.291    5.384    5.412    7.068    6.370    4.177    3.236    2.264    2.409    3.189   10.270   17.740
         17         7.166    5.279    5.386    7.145    6.262    4.159    3.116    2.229    2.235    3.036   10.250   16.410
         18         7.069    5.306    5.345    7.550    6.247    3.950    2.988    2.397    2.233    3.090    9.478   15.610
         19         6.929    5.102    5.275    9.652    6.136    3.840    2.895    2.653    2.370    3.126    9.292   15.100
         20         6.810    4.833    5.240    9.528    6.014    4.037    2.914    2.815    2.530    3.060    8.968   14.110

         21         6.716    4.765    5.178    8.929    6.103    3.967    2.847    2.637    2.665    3.101    8.953   13.130
         22         6.639    4.711    5.142    8.068    5.925    3.905    2.735    2.467    2.503    3.101    9.081   12.350
         23         6.480    4.649    5.354    7.791    5.930    3.960    2.722    2.394    2.330    3.068    8.705   11.740
         24         6.348    4.875    5.537    7.735    6.040    3.871    2.722    2.284    2.257    3.072    8.559   11.550
         25         6.207    6.337    5.245    9.054    5.915    3.787    2.716    2.226    2.317    3.071    8.967   12.010

         26         6.083    5.903    5.147    9.010    6.068    3.697    2.693    2.283    2.416    3.057   10.060   11.240
         27         5.957    5.605    5.063    8.396    6.680    3.602    2.648    2.266    2.521    3.092   10.020   10.470
         28         5.955    6.732    4.880    8.493    7.745    3.574    2.601    2.247    2.605    3.967   10.490   10.030
         29         5.945    7.706    4.804    9.881    8.600    3.504    2.554    2.202    2.779    5.844   10.210    9.642
         30         5.769             4.756    9.089    6.964    3.527    2.486    2.165    2.781    7.734    9.395    9.198
         31         5.629             4.677             6.080             2.456    2.144            14.420             9.443
 


 Average            7.380    5.616    5.599    7.132    6.948    4.358    3.398    2.401    2.257    3.773   10.200   14.590
 Lowest             5.629    4.649    4.677    4.647    5.915    3.504    2.456    2.144    1.934    2.446    8.559    9.198
 Highest            9.518    7.706    7.691    9.881    8.600    5.756    5.589    2.815    2.781   14.420   15.340   23.580

 Monthly total
  (million cu m)    19.77    14.07    15.00    18.49    18.61    11.30     9.10     6.43     5.85    10.11    26.44    39.09


 Runoff   (mm)       61       43       46       57       57       35       28       20       18       31       82      121  
 Rainfall (mm)       27       95       31      160       86       25       70       69       87      152      131      138  


 Statistics of monthly data for previous record  (Feb 1965 to Dec 1999)

 Mean      Avg.     5.598    6.144    5.397    4.572    3.487    2.675    1.983    1.651    1.573    1.905    2.629    4.020
 flows:    Low      1.249    1.237    1.207    1.083    0.871    0.652    0.492    0.388    0.670    0.926    1.137    1.421
           (year)    1976     1976     1976     1976     1976     1976     1976     1976     1976     1997     1973     1990
           High    10.630   13.860    9.208    7.571    5.249    4.345    3.104    2.438    2.598    3.681    6.395    9.427
           (year)    1994     1990     1995     1979     1979     1979     1971     1979     1974     1993     1974     1992

 Runoff:   Avg.      46       46       45       37       29       21       16       14       13       16       21       33  
           Low       10       10       10        9        7        5        4        3        5        8        9       12  
           High      88      104       76       61       43       35       26       20       21       30       51       78  

 Rainfall: Avg.      82       55       62       49       55       58       47       61       69       71       76       86  
           Low       12        5       14        1        8        3       13        7       11        4       31       17  
           High     169      147      150      121      121      143      113      152      179      161      185      160  


 
 Summary statistics                                                           Factors affecting runoff
                                                                    2000
                                   For 2000       For record        As % of   $ Flow influenced by groundwater abstraction
                                                  preceding 2000    pre-2000    and/or recharge.
 Mean flow                        6.143           3.456                 178
 Lowest yearly mean                               1.475        1976
 Highest yearly mean                              4.580        1994
 Lowest monthly mean              2.257    Sep    0.388    Aug 1976
 Highest monthly mean            14.590    Dec   13.860    Feb 1990
 Lowest daily mean                1.934 13 Sep    0.183 22 Aug 1976
 Highest daily mean              23.580  9 Dec   22.210  4 Feb 1990

 10% exceedance                  10.350           6.629                 156
 50% exceedance                   5.506           2.784                 198
 95% exceedance                   2.214           1.128                 196
 Annual total (million cu m)     194.30          109.10                 178
 Annual runoff (mm)               600             337                   178
 Annual rainfall (mm)            1071             771                   139
         {1961-90 rainfall average (mm)           745} 


 Station and catchment description

 
  Crump profile weir (crest 9.14m broad) flanked by broad-crested weirs. Small bypass channel approx. 2m u/s of weir -
  included in rating. Full range station. During summer, flows are naturally augmented from gw draining from northern half
  of R. Bourne catchment. May go non-modular at low flow in exceptional summers. Some gw pumping also takes place within
  the catchment. Data reprocessed in 2001, resulting in decrease in high flows.
  Predominantly permeable (Chalk) catchment with a small inlier of Upper Greensand and Gault. Land use: rural.
  Topographical and gw catchments do not coincide.


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