Water situation for Upper Ivel – Oct 2022.
All data presented courtesy of the Environment Agency and Met Office.
Rainfall:
The first half of the month was dry, with typically only 20-30% of the long-term average monthly rainfall up to the 16th of October. The second half of the month saw much wetter conditions with a succession of frontal systems bringing in wet weather from the Atlantic. The period 19th– 20th October was notable wet with some weather gauges in the Bedford Ouse catchment recording totals more than 30mm. The rest of the month remained wet but with rain most days.
Soil Moisture Deficit (SMD)
The soil moisture conditions showed a significant wetting through the month. The Met Office MORECS grid squares covering the Ivel were at 50-60mm SMD by the end of the month which is in the normal range (green zone in graph below).
Definitions:
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).
Field Capacity (FC)-The amount of water the soil can hold is generally called field capacity which is the amount of water that remains after gravitational forces have drained water from the soil.
Ground Water (GW):
Ground water generally continued to recede during October.
Recovery in GW levels are unlikely until soil moisture deficit fall below 30-40mm SMD.
Ground water levels ended October generally below normal (yellow zone in figure below).
Environment Agency data is presented from the Bath Spring, Charlton, Near Hitchin.
This data is broadly representative to what is going on in our chalk catchment.
Springs and River flows:
The main spring and second spring at the Ivel Springs nature reserve in Baldock have no water.
The main spring stopped at the end April 2022 (having flowed for only 8 weeks) and the 2nd spring stopped by end June 2022.
There are no springs flowing at Norton and the first spring to be active is at the far end of Radwell meadow. Any standing water in the riverbed at the iron bridge and at Radwell meadows is from A1/M road / hard surface runoff or directly from the rain event in later Oct 2022.
The river remains very low through Radwell and Stotfold.
The river flows are officially measured at Blunham. The river has been low to notable low through the summer but returned to normal (green zone) mainly thanks to the rain event on 19-20th October. The geology of the lower river catchment means it is likely to respond more positively to specific rainfall events.
Reservoir Stocks:
Water from the Ouse is transferred at Offord into Grafham Water.
Grafham Water is currently 40% full.
Looking forward:
October has been relatively wet. The months November – March need to continue in the same fashion.
The figure below shows the predicted GW level for the CAM chalk.
