We’ve had the driest start to the year since 1929 in Britain, and Wales has been no exception. We’ve had very little serious rain (by which I mean a week or so of wet weather) since the snow melted in January, and in mid June the spring that feeds our water supply dried up. A combination of this and the World Cup has distracted me from posting for a while. Since July started the weather has broken though, and we’ve had a couple of weeks of changeable weather including some good downpours.
The pond had been feeling the heat too. Water levels dropped steadily over the drought and by mid June levels were approaching a 6″ below the winter maximum. The photograph on the left gives an impression of this (though it’s surprisingly hard to take a good photo of this sort of thing). Water levels were getting so low that the upper ‘shelf’ of the pond was starting to become exposed, and one corner of the pond was dry altogether. Unlike many people, I didn’t have the option of turning on the hosepipe (and even if I did I don’t think I would have used it) so the pond just had to sit and wait.
It’s interesting to see what’s been happening during the dry period. The frogs seem to have been using the pond a lot at night. There have been absolutely no water quality problems such as algal blooms, and in fact the blanket weed may well have declined. Since there are so many different pondweeds in the water that’s probably not surprising – although low water levels concentrate the nutrients in the water, they also concentrate the aquatic plants which will be using them up. More significant is likely to be low oxygen levels, and any sensitive species such as mayflies may have struggled.
Since the recent rain, water levels have risen quite markedly. This picture shows the same piece of the pond, only shot from the other side (the stone at the bottom of this one is in the middle of the other picture). Much of the bare slate waste has now been covered by water. This change in water levels seems to provide an opportunity for plants and animals. Although the water level has risen, the vegetation hasn’t, so there is now a shallow layer of warm water above the whole pond. Most of the plants are growing upwards towards the new water surface but this process is likely to take a couple of weeks. In the meantime water beetles and the few remaining toad tadpoles are making use of the open water. The plants are growing back though, and it’s fascinating to see how the aquatics are switching from their stunted terrestrial growth forms to longer underwater shoots.
This photo shows this phenomenon for water milfoil. The yellow-green bases to the stems are the terrestrial sections; the bushy red growth is the new growth since it has rained.
Finally this week (and nothing to do with the pond), the dry weather has been very good for butterflies and moths. We’ve seen several species we don’t normally get including Small Pearl-bordered fritillary, but the highlight were four of this amazing caterpillar. It’s an Emperor Moth, Britain’s only native silkmoth. This one was eating my Tayberries but I don’t begrudge it a single leaf!