The next event will be on the 15th of April, where Roy McGurn will be giving his talk on The Geology of War
A very informative talk was given by Kevin Voyce ( Hydrogeologist, Environment Agency) on the strategic water resource management of the River Severn catchment.
The upper River Severn catchment, here in Mid-Wales, is underlain by Ordovician and Silurian mudstones, shales and grits. These rocks have a low permeability and therefore do not store water, so that most of the water stored is above ground. The Clywedog dam was built in the 1960's to regulate the flow in the River Severn. If flow in the river is low, a release valve can be opened to release water from the reservoir and into the river to provide flow. The ground water storage in Mid-Wales contrasts sharply with that found across the border in Shropshire. Here the rocks consist of Permo-Triassic sediments of sandstones and mudstones. The sandstones have large pore spaces and therefore large storage capacity and high transmissivity. A scheme for supplementing the River Severn flow via use of the ground water has been set up. This required the drilling of a line of boreholes which draw water from the groundwater reserves and pump the water into the river to enhance flow.
Thus the hydrogeologist needs to understand the properties of the rock, how much water it can store and its transmissivity. Also knowledge the presence of joints and faults in the rock is necessary as this can markedly affect storage and flow within the aquifer. Abstracting water from the aquifer may also lead to problems in nearby areas, for example with a wildlife reserve or a private borehole. Therefore safeguards must be put in place to protect other water users and monitoring must be undertaken. This includes checks on water levels, chemical analysis and monitoring of wildlife populations. The aim of the agency is to have a minimal environmental impact.
With growing population and therefore increasing requirements for water and the challenge of climate change the Environment Agency must work to be able to balance the growing needs with that of a dwindling resource. This will require water resource planning for the longer term and to secure the preservation of surface and ground water reserves.
The next event will be on the 18th of March where guest speaker Kevin Voyce of the Environment Agency will be giving a talk on "Strategic groundwater management"
Bill gave a really interesting talk on quartz and other forms of silica. The talk commenced with a general description of the elements that go to make up the earth's crust. Bill then delved more deeply into the chemical structure of silica and polymorphism and then into the different branches of the quartz family. This consists of, firstly, basic quartz types, for example Rock crystal, Rose Quartz and Citrine. Then there is amorphous quartz, including Opal and Obsidian. The Chalcedony branch includes Chrysophrase, Onyx, Heliotrope and the Agates. Most of these are fairly well known, but what are not quite so well known are some of the quartz/silica polymorphs. These are varieties that have been altered by heat or pressure or by both heat and pressure. These include minerals such as Keatite and Coesite. Silica also is present in many rock types, eg. Granite. These groups were then looked at in much more detail, accompanied by photographs of each mineral. Finally, the role of silica in technology was discussed from the use in quartz time-pieces to modern uses in nanotechnology.
Alongside the talk Bill brought along a large number of superb specimens for all to view.
The next talk will be on Wednesday 18th March, when guest speaker Kevin Voyce (Environment Agency) will give a talk entitled: “Strategic Ground Water Management”
Our next event will be on the 18th of February at 7:15 with Bill Bagley's talk "Quartz and other forms of silica"
