After two weeks of falling water levels in the Tilshead Borehole we have had a sudden upturn in the last 48 hours. This is almost certainly due to the snow melt that has taken place over the last week on top of the rain from the week before.
As we go in to the last week of the annual monitoring round, we expect the levels to continue rising for a day or two more, then fall away at an increasing rate. We are expecting some rain or drizzle over the weekend and into the early part of next week. The weather is expected to turn colder again, but any snow showers should be confined to the north of the country. More wet weather is predicted for April.
Apologies for the late publication of this weeks data, but Andy has been away and not able to get online. Here is the good news. Despite all the snow and a fair bit of rain, water levels in the Tilshead aquifer have begun to fall. Not a lot, but enough to provide a good indicator that Spring really is on the way. Yet again, we have confirmation that winter 2017-2018 has been drier than the 5-year average.
We are expecting a spell of heavy rain towards the end of the week, with more showers and rain towards the end of the monitoring period on 31st March.
We are bringing you this a day early this week for operational reasons. Despite all the snowmelt and some rain early in the week, the borehole levels have stayed prety much the same.
Overall, levels are slightly below average and we would expect them to begin to fall as Spring begins and grass and trees begin to take up water as their annual growth cycle begins. However, we have rain in the short term forecast, perhaps heavy at times, and wet weather continuing into early April, so this years flood season may not be quite over yet. Watch this space.
The snow we predicted last week arrived yesterday – and with a vengeance. March really did come in like a lion!
As I write, the A303 is closed in both directions to the west of the village and the A360 at Longbarrow closed both north and south. We’ve had no rain over the last week and the rain gauge used by Janet Abbott doesnt seem to cope well with snow. We seem to have had 4-6 inches of snow yesterday. That’s about 100 to 150mm. However, the caution here is that we had high winds, so these estimates may be too low or too high. How does depth of snow equate to rainfall? Well, an old, often used idea is that the ration is about 10:1. However, that figure has been largely debunked in recent years – it all depends on the temperature at which the snow is laid down. The ratio varies between 5:1 and 20:1. That would mean we have had somewhere between 5mm and 30mm of rain equivalents yesterday. That’s a huge variation and whilst 5mm would have only a minor impact on aquifer levels 30mm might have a major impact – so the next week or so is going to be critical.
Aquifer levels are still slightly below average, reflecting the driest February (39mm of rain) in the last 5 years. Contrast that with 2013-2014 when we had 136mm in February. Look at the March rainfall levels below:
Given that we have rain forecast for most days next week, and we may have already had 5-30mm rainfall equivalents, then we seem set for at least an average March and possibly an exceptionally wet one. Watch the weather forecasts carefully. How the aquifer responds to thawing snow and rain will be determined by how frozen the ground really is – will the meltwater run off directly into the River Till, or will it soak into the ground?
More snow, or freezing rain is forecast for later in the day, so conditions could worsen before they start to improve over the weekend. As we’ve already said, there is the prospect of more rain and sleet in the coming week, but the longer term situation seems less clear, with a battle between easterly and south westerly weather systems. Only when the latter win out will we see the start of more Spring-like weather. Will March go out like a lamb?