There is very little understanding on the part of our government and water company staff of the
importance of the Cat Ditch catchment to the Ivel.
This is illustrated by the following map published by the Upper & Bedford Ouse Catchment
Partnership map, that incorrectly labels the Cat Ditch as the River Ivel, while not identifying the Ivel
branch that runs into Baldock at all.
DEFRA & the EA recognise that the River Ivel is made up of several discrete water bodies &
catchments.
The branch of the River Ivel that flows up via Radwell to Baldock is called the “Ivel (US Henlow)
Water Body.
DEFRA & the EA assign the following catchment areas to the Henlow to Baldock branch of the Ivel.
DEFRA & the EA then go on to assign the following key attributes to the Cat Ditch catchment.
Taken together the total lengths and areas appear to be as follows.
As recharge & runoff is a function of areas, it can readily be appreciated how the Cat Ditch is more important to the flows in the Ivel downstream of Astwick (the confluence) than the Ivel.
From the following marked map of the Ivel Catchment which shows the approximate limit of the permeable chalk strata in dark blue, & the Bedfordshire Gault clay that is very much less permeable, in light blue, it can be readily appreciated that the effective chalk catchment area associated with the Baldock Ivel is much smaller still.
Taking into consideration that much of the Ivel Catchment described by DEFRA & the EA (in figure 2) is either underlain by impermeable Gaults, or overlain by impermeable urban areas, it can be appreciated that the key attributes of the Baldock Ivel & Cat Ditch are as follows.
At less than 29% of the effective permeable area underlying the former Ivel catchment no longer available to recharge, it can be appreciated why Ivel Springs have failed for the past three years. In the face of unsustainably high levels of abstraction by Affinity Water, there is little or no chance of these springs returning.
The situation by 2040 will be even more dire, as the effective Ivel Catchment over Chalk will reduce
from 1737 hectares in 2023 to 1611 hectares.
We have to protect the Cat Ditch Catchment, & then enhance its physical properties by working with the existing land owners to farm for water as a crop, rather than casting it aside as a problem.
1 https://ubocp.org.uk/catchments/ivel/
2 https://environment.data.gov.uk/catchment-planning/WaterBody/GB105033037720
3 https://environment.data.gov.uk/catchment-planning/WaterBody/GB105033037720
4 https://environment.data.gov.uk/catchment-planning/WaterBody/GB105033037740
Kindly produced by Nick Balmar
