Water situation for Upper Ivel – May 2023
All data presented courtesy of the Environment Agency and Met Office (Crown copy right 2023)
Early May was unsettled with a succession of frontal systems bringing rainfall to our region between 5th and 11th May. High pressure then dominated the UK weather during the second half of May bringing much drier conditions. Overall rainfall in our catchment reaching 97% of the expected long-term-average (LTA).
The 3-month average (March-May 2023) for our catchment has been 152% (exceptional high) and the six-month average at 113% of LTA.
Monthly rainfall totals for the past 12 months as a percentage of the 1961-1990 LTA
Soil Moisture Deficit (SMD)
The soil moisture deficits [SMD] remained low during the first ten days in May, and the rainfall continued to recharge aquifers. However, with the weather turning dry from the middle of the month, the deficit has risen sharply. The combination of dry weather, vegetation growth, long days and moderately strong winds with low-humidity air has led to the deficit rising by around 3mm per day throughout the second half of the month.
Soil Moisture deficits for week ending 31 May 2023. Data based on weekly MORECS data for real land use and compared to an analysis of historic 1961 – 1990 LTA dataset.
Soil Moisture deficit (SMD) – The difference between the amount of water in the soil and the amount of water that the soil can hold (field capacity).
Ground Water (GW):
With relatively low SMD going into May, the rainfall during the first two weeks of May led to a good recharge response in most boreholes monitoring groundwater levels in East Anglia. Groundwater recharge usually ends earlier in the spring but continued rainfall that has led to aquifer recharge into mid-May. Groundwater levels are now generally normal except in the Norfolk chalk aquifer where the dry summer and slower recharge in the autumn rainfall is still having impact.
Springs and River flows:
The main spring at Ivel Springs in Baldock started to flow on 14th January 2023.
The second spring at the Ivel Springs nature reserve (upstream of culvert) in Baldock started to flow on 1st January 2023. Flow at Blackhorse mill was seen by the end of the first week in January 2023.
Thanks to the continued aquifer recharge into early May, the springs in Baldock, and Radwell continue to flow. Despite the flow at the Ivel Springs, there are no invertebrates (water insect larvae) at the Baldock site due to the drying up of the river between June 2022 –Dec 2022. Chalk stream ecology is adapted to a constant environment and is high intolerant of repeated episode of drying up. Where the Ivel has managed to keep a constant flow of water (below Radwell Mill), aquatic life is flourishing and the RiverFlies team recorded their best ever sample including hundreds of Mayfly larvae. This is a clear indication of the potential of our chalk stream if we can establish a healthy flow regime year-round.
The river Ivel flows are officially measured at Blunham. The river had been low to notable low through the summer but returned to normal during October- January responding directly to significant rainfall events. Heavy rain events in March and early May saw increased flow which returned to Normal by the end of the month (Green Zone).
Water from the Ouse is transferred at Offord into Grafham Water reservoir. Recovery of reservoir stocks in Grafham continued during May and by the end of May the reservoir reached 94% full (blue line on graph) which is in line with the normal operating level of 90%+.
End of May 2023 Grafham Water reservoir stock compared to the Normal operating Curve, Drought Curve and 1995-1996 stock levels.
Recharge of the chalk aquifer relies on the amount of rainfall through the autumn and winter months. Overall, thelast 6 months has seen good recharge conditions with overall 113% of Long-Term Average (LTA).
The Upper Bedford Ouse catchment has been in official drought since end June 2022. The exceptional rain fall in March and continued aquifer recharge into mid-May 2023 has thankfully resulted in a change in status to “Recovering Drought, much to the relief of the Affinity Water and the Environment Agency.
Affinity Water has recently changed Ivel catchment classification from drought zone 1 to average. Sadly, Affinity Water seem to rely on such exceptional “GET OUT OF JAIL CARDS”, without any real plan other than continuing to abstract ground water (GW) as much as is legally and / or physically possible every month. For the nine months period of drought experienced in 2022/ 2023 Affinity did not instigate any hosepipe bans instead they continued to pump water from the ground and allowed the river to dry all the way from Baldock to Radwell (acknowledged result of their Drought Plan).
Since 2019, when RevIvel have been highlighting the plight of the chalk headwaters of the Ivel and Affinity Water have been making all the right noises, more water has been taken from the aquifer than ever before!
Consequently, the river Ivel and its associated flora and fauna continues to suffer……..