https://earthwise.bgs.ac.uk/index.php?title=Hydrogeology_of_Wales:_Ordovician_and_Silurian_aquifers_-_groundwater_occurrences&feed=atom&action=historyHydrogeology of Wales: Ordovician and Silurian aquifers - groundwater occurrences - Revision history2024-03-29T13:12:01ZRevision history for this page on the wikiMediaWiki 1.41.0https://earthwise.bgs.ac.uk/index.php?title=Hydrogeology_of_Wales:_Ordovician_and_Silurian_aquifers_-_groundwater_occurrences&diff=25637&oldid=prevDbk: Protected "Hydrogeology of Wales: Ordovician and Silurian aquifers - groundwater occurrences" ([Edit=Allow only administrators] (indefinite) [Move=Allow only administrators] (indefinite)) [cascading]2016-02-18T08:31:07Z<p>Protected "<a href="/index.php/Hydrogeology_of_Wales:_Ordovician_and_Silurian_aquifers_-_groundwater_occurrences" title="Hydrogeology of Wales: Ordovician and Silurian aquifers - groundwater occurrences">Hydrogeology of Wales: Ordovician and Silurian aquifers - groundwater occurrences</a>" ([Edit=Allow only administrators] (indefinite) [Move=Allow only administrators] (indefinite)) [cascading]</p>
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</td></tr></table>Dbkhttps://earthwise.bgs.ac.uk/index.php?title=Hydrogeology_of_Wales:_Ordovician_and_Silurian_aquifers_-_groundwater_occurrences&diff=6728&oldid=prevDbk at 15:58, 29 January 20152015-01-29T15:58:13Z<p></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[Hydrogeology of Wales: References|'''Glendining (1981)''']] assigned percentage flow to shallow, intermediate and deep flow paths using estimates of hydraulic gradients for each flow path. This enabled the overall hydraulic conductivity for the rock mass to be calculated. The value is of the order 10<sup>-3</sup> m d<sup>-1</sup>, however, this has little bearing on the majority of groundwater flow which takes place in the near-surface weathered zone and which may be of the order 1 m d<sup>-1</sup>.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[Hydrogeology of Wales: References|'''Glendining (1981)''']] assigned percentage flow to shallow, intermediate and deep flow paths using estimates of hydraulic gradients for each flow path. This enabled the overall hydraulic conductivity for the rock mass to be calculated. The value is of the order 10<sup>-3</sup> m d<sup>-1</sup>, however, this has little bearing on the majority of groundwater flow which takes place in the near-surface weathered zone and which may be of the order 1 m d<sup>-1</sup>.</div></td></tr>
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<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">==Hydrogeology of Wales - contents==</ins></div></td></tr>
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</table>Dbkhttps://earthwise.bgs.ac.uk/index.php?title=Hydrogeology_of_Wales:_Ordovician_and_Silurian_aquifers_-_groundwater_occurrences&diff=3791&oldid=prevDbk at 07:47, 20 May 20142014-05-20T07:47:27Z<p></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 07:47, 20 May 2014</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l8">Line 8:</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Although awareness of the importance of groundwater in the Ordovician and Silurian strata is relatively new (e.g. [[Hydrogeology of Wales: References|'''Haria and Shand, 2004''']]), its role in supporting low flow in upland streams has long been recognised. One of the earliest investigations into groundwater occurrence in the Ordovician and Silurian strata was a reconnaissance study of the Afon Dulas subcatchment of the Dyfi north of Machynlleth ([[Hydrogeology of Wales: References|'''Glendining, 1981)''']]. The catchment comprises a series of folded, well-cleaved and fractured turbiditic mudstones and slates with a north-easterly strike, younging towards the south-east. There are volcanic rocks in the north-west corner of the catchment. The superficial cover includes head and scree deposits, peat and valley alluvium. The cleavage planes trend north-easterly and are subvertical to 60<sup>o</sup> in dip, the main joints are normally vertical and are orientated between 120<sup>o</sup> and 140<sup>o</sup>, the faults also are subvertical. Surface drainage is strongly influenced by this structure, with the Tal-y-Llyn and Dyfi valleys following major fault lines and many first order streams following the 120<sup>o</sup> joint directions; groundwater flow is mainly constrained by the structure and jointing ('''Figure P859264''').</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Although awareness of the importance of groundwater in the Ordovician and Silurian strata is relatively new (e.g. [[Hydrogeology of Wales: References|'''Haria and Shand, 2004''']]), its role in supporting low flow in upland streams has long been recognised. One of the earliest investigations into groundwater occurrence in the Ordovician and Silurian strata was a reconnaissance study of the Afon Dulas subcatchment of the Dyfi north of Machynlleth ([[Hydrogeology of Wales: References|'''Glendining, 1981)''']]. The catchment comprises a series of folded, well-cleaved and fractured turbiditic mudstones and slates with a north-easterly strike, younging towards the south-east. There are volcanic rocks in the north-west corner of the catchment. The superficial cover includes head and scree deposits, peat and valley alluvium. The cleavage planes trend north-easterly and are subvertical to 60<sup>o</sup> in dip, the main joints are normally vertical and are orientated between 120<sup>o</sup> and 140<sup>o</sup>, the faults also are subvertical. Surface drainage is strongly influenced by this structure, with the Tal-y-Llyn and Dyfi valleys following major fault lines and many first order streams following the 120<sup>o</sup> joint directions; groundwater flow is mainly constrained by the structure and jointing ('''Figure P859264''').</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>[[Image:P859264.jpg|thumb|center|688px|Schematic flow system for the Afon Dulas catchment controlled by topography, fracture orientation and fracture permeability (after Glendining, 1981. <del style="font-weight: bold; text-decoration: none;">[https://bgsintranet/asset-bank/action/viewFullSizedImage?id=446353&size=1000 </del>P859264.<del style="font-weight: bold; text-decoration: none;">]</del>]]</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[Image:P859264.jpg|thumb|center|688px|Schematic flow system for the Afon Dulas catchment controlled by topography, fracture orientation and fracture permeability (after Glendining, 1981. P859264.]]</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div><center></div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div><center></div></td></tr>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The bulk catchment properties suggest that total river flow equates to total effective rainfall. This assumes that changes in storage and soil moisture deficit are negligible over the long term and that underflow from the catchment is small. Base flow separation of the catchment run-off was calculated, and divided between alluvium (15 km<sup>2</sup> in area in the catchment) and bedrock (456 km<sup>2</sup>). Infiltration into the alluvium was assumed to be equal to total effective rainfall ('''Figure P859265'''). The effective rainfall over bedrock was divided between the amount needed to make up the overall base flow (estimated from the base flow separation calculation minus base flow from or effective rainfall into the alluvium) and run-off (see '''the effective infiltration table '''). This shows that the average annual infiltration to the bedrock is about 316 mm or 19 per cent of the effective rainfall (compared with 1685 mm or 100 per cent to the alluvium). This is likely to be an overestimate as it disregards soil and scree interflow, short flow-path discharge through the near valley-bottom weathered zone and the capacity of the rock to accept recharge.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The bulk catchment properties suggest that total river flow equates to total effective rainfall. This assumes that changes in storage and soil moisture deficit are negligible over the long term and that underflow from the catchment is small. Base flow separation of the catchment run-off was calculated, and divided between alluvium (15 km<sup>2</sup> in area in the catchment) and bedrock (456 km<sup>2</sup>). Infiltration into the alluvium was assumed to be equal to total effective rainfall ('''Figure P859265'''). The effective rainfall over bedrock was divided between the amount needed to make up the overall base flow (estimated from the base flow separation calculation minus base flow from or effective rainfall into the alluvium) and run-off (see '''the effective infiltration table '''). This shows that the average annual infiltration to the bedrock is about 316 mm or 19 per cent of the effective rainfall (compared with 1685 mm or 100 per cent to the alluvium). This is likely to be an overestimate as it disregards soil and scree interflow, short flow-path discharge through the near valley-bottom weathered zone and the capacity of the rock to accept recharge.</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>[[Image:P859265.jpg|thumb|center|329px|Analysis of throughflow volumes in the Afon Dulas catchment (after Glendining, 1981). <del style="font-weight: bold; text-decoration: none;">[https://bgsintranet/asset-bank/action/viewFullSizedImage?id=446354&size=1000 </del>P859265.<del style="font-weight: bold; text-decoration: none;">]</del>]]</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[Image:P859265.jpg|thumb|center|329px|Analysis of throughflow volumes in the Afon Dulas catchment (after Glendining, 1981). P859265.]]</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[Hydrogeology of Wales: References|'''Glendining (1981)''']] assigned percentage flow to shallow, intermediate and deep flow paths using estimates of hydraulic gradients for each flow path. This enabled the overall hydraulic conductivity for the rock mass to be calculated. The value is of the order 10<sup>-3</sup> m d<sup>-1</sup>, however, this has little bearing on the majority of groundwater flow which takes place in the near-surface weathered zone and which may be of the order 1 m d<sup>-1</sup>.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[Hydrogeology of Wales: References|'''Glendining (1981)''']] assigned percentage flow to shallow, intermediate and deep flow paths using estimates of hydraulic gradients for each flow path. This enabled the overall hydraulic conductivity for the rock mass to be calculated. The value is of the order 10<sup>-3</sup> m d<sup>-1</sup>, however, this has little bearing on the majority of groundwater flow which takes place in the near-surface weathered zone and which may be of the order 1 m d<sup>-1</sup>.</div></td></tr>
</table>Dbkhttps://earthwise.bgs.ac.uk/index.php?title=Hydrogeology_of_Wales:_Ordovician_and_Silurian_aquifers_-_groundwater_occurrences&diff=3630&oldid=prevDbk at 14:17, 19 May 20142014-05-19T14:17:23Z<p></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 14:17, 19 May 2014</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The bulk catchment properties suggest that total river flow equates to total effective rainfall. This assumes that changes in storage and soil moisture deficit are negligible over the long term and that underflow from the catchment is small. Base flow separation of the catchment run-off was calculated, and divided between alluvium (15 km<sup>2</sup> in area in the catchment) and bedrock (456 km<sup>2</sup>). Infiltration into the alluvium was assumed to be equal to total effective rainfall ('''Figure P859265'''). The effective rainfall over bedrock was divided between the amount needed to make up the overall base flow (estimated from the base flow separation calculation minus base flow from or effective rainfall into the alluvium) and run-off (see '''the effective infiltration table '''). This shows that the average annual infiltration to the bedrock is about 316 mm or 19 per cent of the effective rainfall (compared with 1685 mm or 100 per cent to the alluvium). This is likely to be an overestimate as it disregards soil and scree interflow, short flow-path discharge through the near valley-bottom weathered zone and the capacity of the rock to accept recharge.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The bulk catchment properties suggest that total river flow equates to total effective rainfall. This assumes that changes in storage and soil moisture deficit are negligible over the long term and that underflow from the catchment is small. Base flow separation of the catchment run-off was calculated, and divided between alluvium (15 km<sup>2</sup> in area in the catchment) and bedrock (456 km<sup>2</sup>). Infiltration into the alluvium was assumed to be equal to total effective rainfall ('''Figure P859265'''). The effective rainfall over bedrock was divided between the amount needed to make up the overall base flow (estimated from the base flow separation calculation minus base flow from or effective rainfall into the alluvium) and run-off (see '''the effective infiltration table '''). This shows that the average annual infiltration to the bedrock is about 316 mm or 19 per cent of the effective rainfall (compared with 1685 mm or 100 per cent to the alluvium). This is likely to be an overestimate as it disregards soil and scree interflow, short flow-path discharge through the near valley-bottom weathered zone and the capacity of the rock to accept recharge.</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><del style="font-weight: bold; text-decoration: none;"><center></del></div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">[[Image:P859265.jpg|thumb</ins>|center|<ins style="font-weight: bold; text-decoration: none;">329px</ins>|Analysis of throughflow volumes in the Afon Dulas catchment (after Glendining, 1981). [https://bgsintranet/asset-bank/action/viewFullSizedImage?id=446354&size=1000 P859265.]<ins style="font-weight: bold; text-decoration: none;">]]</ins></div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><del style="font-weight: bold; text-decoration: none;">{</del>| <del style="font-weight: bold; text-decoration: none;">class="wikitable" width="100pt" style="margin-left:0px; margin-right:0px; margin-bottom:10px; float:</del>center<del style="font-weight: bold; text-decoration: none;">; text-align:left;"</del></div></td><td colspan="2" class="diff-side-added"></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>| <del style="font-weight: bold; text-decoration: none;"><img src="https://bgsintranet/asset-bank/action/directLinkImage?assetId=446354&width=329&height=268"></del></div></td><td colspan="2" class="diff-side-added"></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><del style="font-weight: bold; text-decoration: none;">|-</del></div></td><td colspan="2" class="diff-side-added"></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>| Analysis of throughflow volumes in the Afon Dulas catchment (after Glendining, 1981). [https://bgsintranet/asset-bank/action/viewFullSizedImage?id=446354&size=1000 P859265.]<del style="font-weight: bold; text-decoration: none;">)</del></div></td><td colspan="2" class="diff-side-added"></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><del style="font-weight: bold; text-decoration: none;">|}</del></div></td><td colspan="2" class="diff-side-added"></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><del style="font-weight: bold; text-decoration: none;"></center></del></div></td><td colspan="2" class="diff-side-added"></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[Hydrogeology of Wales: References|'''Glendining (1981)''']] assigned percentage flow to shallow, intermediate and deep flow paths using estimates of hydraulic gradients for each flow path. This enabled the overall hydraulic conductivity for the rock mass to be calculated. The value is of the order 10<sup>-3</sup> m d<sup>-1</sup>, however, this has little bearing on the majority of groundwater flow which takes place in the near-surface weathered zone and which may be of the order 1 m d<sup>-1</sup>.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[Hydrogeology of Wales: References|'''Glendining (1981)''']] assigned percentage flow to shallow, intermediate and deep flow paths using estimates of hydraulic gradients for each flow path. This enabled the overall hydraulic conductivity for the rock mass to be calculated. The value is of the order 10<sup>-3</sup> m d<sup>-1</sup>, however, this has little bearing on the majority of groundwater flow which takes place in the near-surface weathered zone and which may be of the order 1 m d<sup>-1</sup>.</div></td></tr>
</table>Dbkhttps://earthwise.bgs.ac.uk/index.php?title=Hydrogeology_of_Wales:_Ordovician_and_Silurian_aquifers_-_groundwater_occurrences&diff=3629&oldid=prevDbk at 14:16, 19 May 20142014-05-19T14:16:30Z<p></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 14:16, 19 May 2014</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l10">Line 10:</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[Image:P859264.jpg|thumb|center|688px|Schematic flow system for the Afon Dulas catchment controlled by topography, fracture orientation and fracture permeability (after Glendining, 1981. [https://bgsintranet/asset-bank/action/viewFullSizedImage?id=446353&size=1000 P859264.]]]</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[Image:P859264.jpg|thumb|center|688px|Schematic flow system for the Afon Dulas catchment controlled by topography, fracture orientation and fracture permeability (after Glendining, 1981. [https://bgsintranet/asset-bank/action/viewFullSizedImage?id=446353&size=1000 P859264.]]]</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{| class="wikitable"</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{| class="wikitable"</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>|+ Effective infiltration (equal to base flow divided between alluvium and bedrock in the Afon Dulas catchment (after Glendining, 1981).</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>|+ Effective infiltration (equal to base flow divided between alluvium and bedrock in the Afon Dulas catchment (after Glendining, 1981).</div></td></tr>
</table>Dbkhttps://earthwise.bgs.ac.uk/index.php?title=Hydrogeology_of_Wales:_Ordovician_and_Silurian_aquifers_-_groundwater_occurrences&diff=3626&oldid=prevDbk at 14:14, 19 May 20142014-05-19T14:14:52Z<p></p>
<table style="background-color: #fff; color: #202122;" data-mw="interface">
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<col class="diff-marker" />
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 14:14, 19 May 2014</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l8">Line 8:</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Although awareness of the importance of groundwater in the Ordovician and Silurian strata is relatively new (e.g. [[Hydrogeology of Wales: References|'''Haria and Shand, 2004''']]), its role in supporting low flow in upland streams has long been recognised. One of the earliest investigations into groundwater occurrence in the Ordovician and Silurian strata was a reconnaissance study of the Afon Dulas subcatchment of the Dyfi north of Machynlleth ([[Hydrogeology of Wales: References|'''Glendining, 1981)''']]. The catchment comprises a series of folded, well-cleaved and fractured turbiditic mudstones and slates with a north-easterly strike, younging towards the south-east. There are volcanic rocks in the north-west corner of the catchment. The superficial cover includes head and scree deposits, peat and valley alluvium. The cleavage planes trend north-easterly and are subvertical to 60<sup>o</sup> in dip, the main joints are normally vertical and are orientated between 120<sup>o</sup> and 140<sup>o</sup>, the faults also are subvertical. Surface drainage is strongly influenced by this structure, with the Tal-y-Llyn and Dyfi valleys following major fault lines and many first order streams following the 120<sup>o</sup> joint directions; groundwater flow is mainly constrained by the structure and jointing ('''Figure P859264''').</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Although awareness of the importance of groundwater in the Ordovician and Silurian strata is relatively new (e.g. [[Hydrogeology of Wales: References|'''Haria and Shand, 2004''']]), its role in supporting low flow in upland streams has long been recognised. One of the earliest investigations into groundwater occurrence in the Ordovician and Silurian strata was a reconnaissance study of the Afon Dulas subcatchment of the Dyfi north of Machynlleth ([[Hydrogeology of Wales: References|'''Glendining, 1981)''']]. The catchment comprises a series of folded, well-cleaved and fractured turbiditic mudstones and slates with a north-easterly strike, younging towards the south-east. There are volcanic rocks in the north-west corner of the catchment. The superficial cover includes head and scree deposits, peat and valley alluvium. The cleavage planes trend north-easterly and are subvertical to 60<sup>o</sup> in dip, the main joints are normally vertical and are orientated between 120<sup>o</sup> and 140<sup>o</sup>, the faults also are subvertical. Surface drainage is strongly influenced by this structure, with the Tal-y-Llyn and Dyfi valleys following major fault lines and many first order streams following the 120<sup>o</sup> joint directions; groundwater flow is mainly constrained by the structure and jointing ('''Figure P859264''').</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><del style="font-weight: bold; text-decoration: none;"><center></del></div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">[[Image:P859264.jpg|thumb</ins>|center|<ins style="font-weight: bold; text-decoration: none;">688px</ins>|Schematic flow system for the Afon Dulas catchment controlled by topography, fracture orientation and fracture permeability (after Glendining, 1981. [https://bgsintranet/asset-bank/action/viewFullSizedImage?id=446353&size=1000 P859264.]<ins style="font-weight: bold; text-decoration: none;">]]</ins></div></td></tr>
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<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><del style="font-weight: bold; text-decoration: none;">| <img src="https://bgsintranet/asset-bank/action/directLinkImage?assetId=446353&width=688&height=150"></del></div></td><td colspan="2" class="diff-side-added"></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>|<del style="font-weight: bold; text-decoration: none;">-</del></div></td><td colspan="2" class="diff-side-added"></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>| Schematic flow system for the Afon Dulas catchment controlled by topography, fracture orientation and fracture permeability (after Glendining, 1981. [https://bgsintranet/asset-bank/action/viewFullSizedImage?id=446353&size=1000 P859264.]<del style="font-weight: bold; text-decoration: none;">)</del></div></td><td colspan="2" class="diff-side-added"></td></tr>
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</table>Dbk