The sections of the Ivel discussed here are from the river source at Ivel Springs, just north of Baldock down to Stotfold Mill, a distance of 3.65 Km. The first 2.5 Km from Ivel Springs to just below Radwell Mill the river can be described as a “Classic chalk stream”1 with clear warm water, below that it flows out onto the clay and becomes increasingly turbid from runoff. There are several main sources for historical evidence of flow: watercress beds, mills and fisheries, which were, or are, on this stretch of river. The minimum perennial flow required by all three operations was 5 Ml/day, and 14 Ml / day for the mills further downstream.

Watercress beds

Both the Ordnance Survey 18802 and 1892-19143 25 inch maps show extensive watercress beds immediately below Ivel Springs. These were probably built in about 1850 after the railway line came to Baldock which enabled fresh cress to be easily transported to the London markets daily. Watercress was known as ‘the poor man’s bread’4.

The Ordnance Survey 1:10560 maps of 1949 – 69 shows the “Old watercress Beds” 5 so it can be
assumed they existed for about 100 years. Measured in a GIS mapping application, the area of the beds in about 1900 was 2.0952 Ha or 5.117 Acres.

Table 1 shows from a range of sources the average flow required for this size of beds, which was
was a little over 5 Ml / day.

Water Mills

There are 4 water mills on this stretch of the river. Blackhorse Mill, Norton Mill, Radwell Mill and
Stotfold Mill. The latter two get a mention in the Domesday book 9. Baldock in its current form was established after 1086 so Blackhorse Mill may have been the one mentioned in Weston 10, which covered that land at the time, but this is uncertain. It certainly was a substantial mill structure by 1760 11.

In any case it is possible to say there have been mills on this stretch of the Ivel for at least 1000 years. Before the railway came it was not easy to transport heavy or bulky goods great distances. These mills were a critical infrastructure which relied on a constant flow of water to make staple foodstuff out of local grain for local people all year round.

With reference to table 2, both Radwell mill and Stotfold mill are of a size to run 2 stones @ c.15 Hp which required c. 400 l/sec. 12 It seems unlikely the river ever had a flow like this, but that is the reason for Radwell Mill pond, which has a reserve capacity of about 7 Ml. If the incoming flow was at least 165 l/sec or 14 Ml/day the miller would be able to run at full power for 8 hours without depleting the reserve, and it would have refilled before work started the next day.

Stotfold Mill has a much smaller reserve, and it takes about 1 1/2 hours for water to travel between them, so if both mills started work at about the same time the slug of water from Radwell would be arriving just as Stotfold’s own reserve was running out. Both mills could work the same hours and were both dependent on a flow equivalent to about 14 Ml/day at Radwell.

Same as Radwell or Stotfold, Norton Mill had an overshot wheel with about the same fall, but was much narrower and was probably only capable of running one stone. Nevertheless, this would still have required a continuous flow of at least 7 Ml/day which is entirely possible because the springs at

Nortonbury were also a very active source, A Garden City document of 1904 says: Constant springs are found at Nortonbury and Baldock 13 . Norton Mill has quite a large pond, and it was probably linked to the old moat and pond at Nortonbury Farmhouse 14 which today has almost completely gone, but it was a substantial body of water. It is entirely reasonable to think Nortonbury Springs and Ivel Springs combined could have supplied 7 – 10 Ml/day to Norton Mill.

Blackhorse mill had much less fall than the others, and likely had a breastshot or undershot wheel so it probably wasn’t very efficient which explains why it was the first to fall into disuse as a mill in the middle of the 19th Century. As industrialisation increased through the late 19th century even the efficient local mills lost their competitiveness, but there was still plenty of water, so both Norton Mill and Radwell Mill became fisheries, but it appears they ceased operation in about 1915, probably because of the war. Stotfold Mill continued operating as a mill until the 1960’s. It was restored in the early 2000’s and is operating again as a museum 15.


A Letchworth Garden City document of 1903 says: At Norton mill there is an establishment for fish culture, where all kinds of trout are hatched and reared, and where advice may be obtained as to stocking of lakes, rivers Etc. The extensive trout fisheries at Radwell were also built at about that time and are still shown on the map today.16 Both would have needed the sort of continuous flow of clean water the mills had – and we never see today.

There is more work to do: The Hertfordshire county archives contain much useful information about the Ivel, most of which we have yet to see. For example there is a substantial body of papers relating to the case in 1904 of Cookson and others (from Norton & Radwell fisheries) v Baldock Urban District Council over the alleged poisoning of fish as the result of a sewage overflow caused by two sequential thunderstorms, some human error, and the failure of a pump. It took 3 years, but the fisheries won a substantial compensation. We have found references to river flow data included in the case evidence, but not the data itself – yet.


1 Smith et al 2003 Water & Environmental Management Journal, A method to identify chalk rivers and assess their nature conservation value.
2 Garden city Heritage collection: http://www.gardencitycollection.com/object-plan919
3 National Library of Scotland https://maps.nls.uk/geo/explore/side-by- side/swipe/#zoom=17&lat=51.99672&lon=-0.18893&layers=168&right=BingHyb

4 http://www.missfoodwise.com/2013/06/british-watercress-and-poor-mans-bread.html/ 5 National Library of Scotland https://maps.nls.uk/geo/explore/side-by- side/swipe/#zoom=17&lat=51.99672&lon=-0.18893&layers=193&right=BingHyb
6 Email correspondence with a leading watercress grower

7 History of Harpenden watercress beds http://www.harpenden-history.org.uk/page_id__55.aspx
8 Environment Agency paper 2009 Watercress growing and its environmental impacts on chalk rivers in England (NECR027) http://publications.naturalengland.org.uk/publication/40010
9 Opendomesday; Radwell https://opendomesday.org/place/TL2335/radwell/ Stotfold: https://opendomesday.org/place/TL2136/stotfold/
10 Opendomesday: https://opendomesday.org/place/TL2530/weston/
11 http://www.gardencitycollection.com/object-lbm3000-47
12 Fall (in metres) x Flow (litres per second) x Gravity 9.81 = Power (Watts).
13. http://www.gardencitycollection.com/object-lbm3058-7-14
14 http://www.gardencitycollection.com/object-2007-60-9
15 https://www.stotfoldmill.com/
16 https://maps.nls.uk/geo/explore/side-by-side/swipe/#zoom=17&lat=52.00739&lon=- 0.20475&layers=10&right=BingHyb

Richard Meredith Hardy
June 2020