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Supposed water level recovery after forest Clearence at Ainsdale
The preliminary CEH review (section 5.3.2) also states that the Ainsdale study found a rise of 0.3 m in the water table under the forest at Ainsdale resulting from forest clearance, when they compared two sets of water level records from the same wells. The first set was from 1991 to 1993 and the second set between 2001 and 2003. They estimated the recovery of the water table by comparing the water levels of previous forested wells, to wells which were located in open dunes. It is acknowledged in the CEH review that the Ainsdale research can not be analysed in more detail because of the long break in water level records.
No rainfall record for Ainsdale is readily available, but a water level record and a simulated water balance model for Ainsdale can be found on the internet at http://www.civil.soton.ac.uk/ResearchContracts/(617-4)%20Fig3.jpg (Clarke, 2007) and is shown in figure 1. This is remarkably similar to the well records and the balance model for Newborough Hollingham (2006) shown in figure 2. Well 1E (NW3) at Newborough was chosen simply because it has the longest record. When the Newborough graph is overlain on top of the Ainsdale graph there is a good match, shown in figure 3.
Figure 1. Water level and simulated water balance for Ainsdale 1971 to 1999
Figure 2. Water level and simulated water balance for Newborough 1989 to 2006
Figure 3. Water level and simulated water balance for Ainsdale and Newborough overlain.
There is great similarity in the water table fluctuations at Newborough and Ainsdale. The main difference between the Newborough and Ainsdale records is that Ainsdale received less recharge in 1999 and 2000. It seems that both sites had low amounts of recharge from 1989 to 1999, but since 2000 recharge has returned back to normal levels.
However the average rise in water levels in Ainsdale is based on the difference between 1991 to 1993 and 2001 and 2003. The observed rise in water levels after forest clearence at Ainsdale is due to the difference in rainfall, and not the felling of the forest there. If we applied the same analysis to the newborough records there would be an even greater rise than at Ainsdale and yet there was no major forest clearence.
Copyright © Martin Hollingham