https://crudata.uea.ac.uk/cru/data/riverflow/ (site with information and data)

Riverflow reconstructions for England and Wales

Riverflow records in the UK are generally relatively short in length, many beginning in the late-1950s. Rainfall records, in contrast, are numerous with many extending back into the early decades of the 19th century. In the early-1980s, work began to extend riverflow records for a number of catchments using a simple rainfall-runoff model. The earliest work was funded by the Natural Environment Research Council and updated in the 1990s for the National Rivers Authority (NRA) and the Environment Agency (EA). Recent work has extended the reconstructions to 2002. The latest updating of the reconstructed flow series was funded by the UK Environment Agency (Science Report SC040052/SR; EA Project Manager Dr Rob Wilby). The full Project Report is linked alongside the catchment precipitation and reconstructed flow series.

           Project (No X1-045) datasets
        catchment	                   rainfall (mm)	reconstructed flows (cumecs)
1.	Wye to Redbrook (Wye)	               1865-2002	01/1865-12/2002
2.	Exe to Thorverton (Exe)	               1865-2002	01/1865-12/2002
3.	Eden to Temple Sowerby (Ed1)	       1865-2002	01/1865-12/2002
4.	Eden to Warwick Bridge (Ed2)	       1865-2002	01/1865-12/2002
5.	Tyne to Bywell (Tyn)	               1865-2002	01/1865-12/2002
6.	Tees to Broken Scar (Tee)	       1865-2002	01/1865-12/2002
7.	Wharfe to Addingham (Whf)	       1865-2002	01/1865-12/2002
8.	Wensum to Costessey Mill (Wns)         1865-2002	01/1865-12/2002
9.	Thames to Eynsham (Thm)	               1865-2002	01/1865-12/2002
10.	Ely Ouse to Denver Complex (Ous)       1865-2002	01/1865-12/2002
11.	Medway to Teston (Med)	               1850-2002        06/1850-12/2002
12.	Itchen to Highbridge/Allbrook (Ich)    1850-2002	04/1851-12/2002
13.	Teifi to Glan Teifi (Tef)              1855-2002	04/1855-12/2002
14.	Dee to Manley Hall/Erbistock (Dee)     1858-2002	05/1858-12/2002
15.	Derwent to Derby/Longbridge (Der)      1850-2002	10/1850-12/2002
Last updated: January 2005, Mike Salmon

By FZ: March 09,2020
Extracted, in a first instance, the precipitation greater to or equal to 150 and 200 mm. The corresponding files (e.g. wye-ex.txt) have both data series at the lines listed below.
In a second moment I decided to select, as extrema, the value greater to or equal to the average+1sigma and the average+2sigma. The last two colums are the start/end line for building both histograms from the Name-exsd.txt data files.
     150     200      1sig   2sig
Name l1,l2 & l1,l2 from line "l1" to line "l2"
Wye  2,175  177,221  2,270  271,346
Exe  2,340  342,459  2,269  271,338
Ed1  2,315  317,427  2,262  264,340
Ed2  2,398  400,550  2,263  265,334
Tyn  2,119  121,140  2,256  258,325
Tee  2,284  286,364  2,267  269,323
Whf  2,443  445,603  2,292  294,351
Wns  2,11    13,13   2,259  261,325
Thm  2,42    44,45   2,268  270,336
Ous  2,4     --,--   2,273  275,339
Med  2,55    57,60   2,265  267,343
Ich  2,88    90,110  2,268  270,338
Tef  2,428  430,587  2,260  262,336
Dee  2,447  449,612  2,265  267,340
Der  2,108  110,124  2,270  272,337

ex.bon produces the output plots name-ex.pdf and .png (extrema, 150 & 200 mm)
exsd.bon produces the output plots name-exsd.pdf and .png (extrema, 1 & 2 sigma; "sd" is "standard deviation")

The NFRA files have an "n" after the 3-characters name (e.g. wyen-mem.out instead of wye-mem.out). For those latter ones, I use only 1 and 2 sigma as limuts

       1sig   2sig
Namen l1,l2 & l1,l2 from line "l1" to line "l2"
Wyen  2 138 140 186
Exen  2 124 126 156
Ed1n  2  99 101 131
Ed2n  2  98 100 131
Tynn  2 116 118 142
Teen  2 114 116 145
Whfn  2 110 112 140
Wnsn  2 116 118 145
Thmn  2 136 138 170
Ousn  2 122 124 147
Medn  - --- --- --- 
Ichn  2 108 110 139
Tefn  2 116 118 148
Deen  2 138 140 180
Dern  2 148 150 179

stat.bon produces stat.out changed to stat-nfra.out
exsdn.f produces namen-exsd.txt
exsdn.bon, from namen-exsd.txt, produces the output plots namen-exsd.pdf and .png (extrema, 1 & 2 sigma; "sd" is "standard deviation")
fz 8.3.20. Updated: 22.3.20