Our spring fed rivers drain the aquifer of the results of last winters’ rain. As summer turns to autumn the aquifer is reduced and the rivers flow decreases progressively. In my 20 year association with the Lathkill, 14 of those years living on its south bank, I can only remember the aquifer recharging quickly and the river coming back with a huge rise in levels. We call it ‘coming back in’; an association with its upper reaches being dry for the latter part of the summer and then, over-night, the river reappears.
The latest I can remember for this event is December 12th, a year that had me worried sick. Today the river ‘came back in’ with its usual gusto and caused excitement amongst the rivers inhabitants. Huge weed beds broke free of their roots, were smashed to thousands of smaller rafts and shot through a three mile beat in less than an hour. Trout were taking advantage of this displacement and eating shrimps and invertebrates which were losing their hold on the shifting starwort beds. Little Grebes and other waterfowl were much more active as they too ate from this bounty. In only a few hours I’ve noticed the appearance of shining patches of newly turned stones on the river bed as the hen brown trout, stimulated by the new current, are beginning to investigate places to lay their eggs.
Data beamed to my computer shows our new Mini-Hydro making the most of the new flows too. Its energy production doubles in the length of a day before the turbine seems to become confused by the high water. It settles down to its job quickly enough before steadily churning out enough electricity to feed 20 homes.
Wednesday, November 11, 2009
The symbiotic relationship between the host lichen which retains water for the photosynthetic algae is visible on this damp, north surfacing bridge. There are at least five separate colours visible including the algae trentepohlia, with contains carotenoid to make it orange, and the lichen Lepraria which is crusty white. The correct site, with good air quality and very little disturbance means these plants have an excellent chance of seeing it through the next hundreds years at least.