View source for OR/14/043 Site description - Craig Y Cilau/Waun Ddu

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{{OR/14/043}}
===Introduction===
Craig y Cilau is a Natural Nature Reserve (NNR) located within the Brecon Beacons National Park west of Crickhowell at SO1861016416. Craig y Cilau is part of the wider Mynydd Llangatwg SSSI and Waun Ddu, a raised bog, is located at the base of the escarpment within the NNR. The site has a peripheral stream that flows south between the raised bog (Waun Ddu) to the east and the large escarpment to the west. During the site visit no tufa deposits were identified.

===Geological and hydrogeological data===
The highest ground at Craig y Cilau comprises Carboniferous Twrch Sandstone Formation that overlies the Dowlias Limestone Formation, part of the Pembroke Limestone Group. Moving down the cliff face the Carboniferous Llanelly Formation, Cwmyniscoy Mudstone Formation and Abercriban Oolite are underlain by the Devonian Quartz Conglomerate Group. There is a large scree slope formed against the ridge and comprises a mixture of boulders from the Carboniferous strata in the area. Waun Ddu represents the principal superficial deposit (peat) in the study area.

The site comprises the margins of the southwards flowing stream that flows between Waun Ddu raised bog to the east and the large scree slope to the west. There are several possible and potentially complex water supply mechanisms to this site, the following description is based upon a single site visit and should not be considered a definitive account of the hydrology/hydrogeology of the site. The stream and its tributaries follow the periphery of the raised bog and diffuse seepage from the base of the bog, and even surface runoff will contribute to the stream water. Raised bogs are rainfall dominated (ombrotrophic) and also peat based, these are two factors that will influence the quality of the water flowing into the stream from its western banks. Some of the farm land to the east is located on the Devonian Brownstones and also drains into these ditches and streams and again it is reasonable to include these areas in the possible catchment. Moving to the west large parts of the karstic upland of Craig y Cilau could potentially be within the catchment for this site as tracer tests in other areas have proven long connections with sinkholes and spring sources. The junction between the limestone and Cwmyinscoy Mudstone Formations somewhere near the scree slope could also provide ideal locations for seepages and springs to occur and the series of springs across the base of the scree slope may support this idea. The scree slope itself will also act as a potential pathway allowing rainwater and seepage from the Carboniferous strata to reach the western banks of the stream.

One sample was collected from CyC1.5 a spring on the western side of the stream. The water was pH7.73 and had a small amount of nitrate 1.78&nbsp;mg/l as NO<sub>3</sub>. Field water quality measurements either side of the stream show that there are distinct differences between water entering from Waun Ddu compared to water from springs and seepages at the base of the scree slope. Water on the surface of Waun Ddu is acidic pH 4.14–4.38 and has a low specific electrical conductivity 38.1–54.9&nbsp;μs/cm, similar to many other upland areas and peat bogs. The springs and seepages from the western side of the stream have pH values ranging from 7.49–7.84 and specific electrical conductivities of 125–299&nbsp;μs/cm.

===Land use and pressures===
Craig y Cilau/Waun Ddu is part of a NNR and there is some, but limited footfall across the site. The general area is sheep grazed and there is evidence of both heavy sheep grazing and some poaching on the raised surface of Waun Ddu bog. There is no evidence of burning or obvious signs of nutrient enrichment at any part of the site. It is unlikely that there are any groundwater or surface water abstractions in the immediate area.

[[Image:OR14043fig55.jpg|thumb|center|500px|  '''Figure 55'''&nbsp;&nbsp;&nbsp;&nbsp;Craig  y  Cilau/Waun  Ddu  Ordnance  Survey  map  and  GPS  survey    points.<br>© Ordnance Survey.    ]]

[[Image:OR14043fig56.jpg|thumb|center|500px|  '''Figure 56'''&nbsp;&nbsp;&nbsp;&nbsp;Craig y Cilau/Waun Ddu Aerial photograph © UKP/Getmapping Licence No. UKP2006/01.    ]]

[[Image:OR14043fig57.jpg|thumb|center|500px|  '''Figure 57'''&nbsp;&nbsp;&nbsp;&nbsp;Craig y Cilau/Waun Ddu Bedrock Geology 1:50&nbsp;000. © BGS © Ordnance Survey.    ]]

[[Image:OR14043tab44.jpg|thumb|center|700px|  '''Table 44'''&nbsp;&nbsp;&nbsp;&nbsp;Craig y Cilau/Waun Ddu water quality.    ]]

[[Image:OR14043fig58.jpg|thumb|center|500px|  '''Figure 58'''&nbsp;&nbsp;&nbsp;&nbsp;Craig-y-cilau/Waun Ddu Vegetation map (note vast majority of Palustriella dominated vegetation on left (west) side of stream (stream with a high water level at the time of survey).    ]]

===Vegetation (spring) for Craig-y-Cilau/Waun Ddu===
Marginal stands of ''Palustriella falcata ''(up to 5&nbsp;m wide) occur along the west side of a spring run and central channel. To the east side of this central runnel is a bog with ''Sphagnum cuspidatum ''hollows and patches of ''Sphagnum cuspidatum ''frequently directly adjoin the east side of this channel. Very locally small patches of ''Palustriella ''dominated vegetation occur on the east side of the central channel (i.e. the bog side). Along the west side of the central channel (i.e. away from the bog) species-rich ''Palustriella ''dominated vegetation has developed with frequent ''Fissidens adianthoides, ''S''corpidium cossonii, Philonotis fontana, Philonotis calcarea'', occasional ''Bryum pseudotriquetrum. ''Locally, extensive stands of ''Campylium stellatum ''occur mixed with ''Scorpidium cossonii, ''occasional ''Plagiomnium ellipticum ''and occasional small hummocks of a non fertile ''Chiloscyphus ''species. The main winding central channel is relatively deep lower down (to 15&nbsp;cm at the time of survey during a period with heavy rain) with crystal clear water and a good assemledge of emergent flowering plants including ''Apium nodiflorum, Veronica beccabunga, Ranunculus flammula, Glyceria fluitans ''and locally dominant stands of ''Potamogeton polygoniferous. ''The upper spring heads are notable for a greater dominance of ''Crataneron filicinum.''

<center>
{| class="wikitable"
|+ Table 45&nbsp;&nbsp;&nbsp;&nbsp;Craig y Cilau/Waun Ddu Species list&nbsp;—&nbsp;''Palustriella'' dominated vegetation    
| ! scope="col" style="width: 300px;" | ''Agrostis stolonifera''
| ! scope="col" style="width: 100px;" | R (<1%)
|-
| ''Anagallis tenella''
| O
|-
| ''Aneura pinguis''
| F
|-
| ''Apium nodiflorum''
| O
|-
| ''Bellis perennis''
| O
|-
| ''Bryum pseudotriquetrum''
| R
|-
| ''Calliergonella cuspidata''
| R
|-
| ''Campylium stellatum''
| F
|-
| ''Cardamine pratensis''
| O
|-
| ''Carex demissa''
| O
|-
| ''Carex flacca''
| O
|-
| ''Chiloscyphus sp. ''(non fertile)
| O
|-
| ''Cirsium palustre''
| R
|-
| ''Cratoneuron filicinum''
| O
|-
| ''Ctenidium molluscum''
| O
|-
| ''Cynosurus cristatus''
| R (<1%)
|-
| ''Festuca ovina''
| F
|-
| filamentous algae (Chlorophyta)
| O
|-
| ''Fissidens adianthoides''
| O
|-
| ''Glyceria fluitans''
| R
|-
| ''Hydrocotyle vulgaris''
| R
|-
| ''Juncus acutiflorus''
| F
|-
| ''Juncus effusus''
| O
|-
| ''Jungermania atrovirens ''(per.)
| R
|-
| ''Palustriella commutata''
| R
|-
| ''Palustriella falcata''
| A
|-
| ''Philonotis calcarea''
| O
|-
| ''Philonotis fontana''
| R
|-
| ''Plagiomnium ellipticum ''(non fertile)
| R
|-
| ''Plantago lanceolata''
| R
|-
| ''Potamogeton polygonifolius''
| O
|-
| ''Pressia quadrata''
| R
|-
| ''Prunella vulgaris''
| R
|-
| ''Ranunculus flammula''
| O
|-
| ''Sagina cf nodosa''
| R
|-
| ''Scorpidium cossonii''
| F
|-
| ''Scorzoneroides autumnalis''
| R
|-
| ''Succisa pratensis''
| R
|-
| ''Taraxacum sp.''
| R
|-
| ''Veronica beccabunga''
| O
|}
</center>

Rocks within the area of flush/spring but above level of seepage water supporting occasional mixtures of calcareous as well as calcifuges bryophytes and lichens.

<center>
{| class="wikitable"
|+ Table 46&nbsp;&nbsp;&nbsp;&nbsp;Craig y Cilau/Waun Ddu Species list&nbsp;—&nbsp;Rocks (within area of flush/spring but above level of seepage water)    
| ! scope="col" style="width: 300px;" | ''Parmelia saxatilis''
| ! scope="col" style="width: 100px;" | O
|-
| ''Ptychomitrium polyphyllum''
| O
|-
| ''Scapania undulata''
| R
|-
| ''Schistidium sp.''
| O
|}
</center>
    
===Vegetation (adjoining spring) for Craig-y-Cilau/Waun Ddu===
Heavily sheep grazed and poached acid grassland (to 15&nbsp;cm height) dominated by ''Agrostis capillaris, Nardus stricta ''with scattered ''Pteridium''.            

<center>
{| class="wikitable"
|+ Table 47&nbsp;&nbsp;&nbsp;&nbsp;Craig y Cilau/Waun Ddu Species list&nbsp;—&nbsp;Acid grassland and bracken
| ! scope="col" style="width: 300px;" | ''Agrostis capillaris''
| ! scope="col" style="width: 100px;" | O
|-
| ''Dicranum scoparium''
| O
|-
| ''Galium saxatile''
| O
|-
| ''Hypnum jutlandicum''
| O
|-
| ''Nardus stricta''
| O
|-
| ''Potentilla erecta''
| R
|-
| ''Pteridium aquilinum''
| F
|-
| ''Rhytidiadelphus squarrosus''
| R (<1%)
|-
| ''Scleropodium purum''
| O
|-
| ''Thuidium tamariscinum''
| R
|}
</center>

Heavily sheep grazed and partly degraded bog dominated by ''Aulocomnium palustre, Polytrichum commune'' and with regular ''Sphagnum cuspidatum'' in hollows.

<center>
{| class="wikitable"
|+ Table 48&nbsp;&nbsp;&nbsp;&nbsp;Craig y Cilau/Waun Ddu Species list&nbsp;—&nbsp;Bog 
| ! scope="col" style="width: 300px;" | ''Aulocomnium palustre''
| ! scope="col" style="width: 100px;" | F
|-
| ''Campylopus intoflexus''
| O
|-
| ''Dicranum scoparium''
| R
|-
| ''Erica tetralix''
| R
|-
| ''Hypnum jutlandicum''
| R
|-
| ''Juncus effusus''
| R
|-
| ''Juncus squarrosus''
| O
|-
| ''Polytrichum commune''
| F
|-
| ''Sphagnum cuspidatum''
| F
|-
| ''Sphagnum subnitens''
| O
|-
| ''Thuidium tamariscinum''
| R
|}
</center>

[[Image:OR14043fig59a.jpg|thumb|center|500px|  '''Figure 59'''&nbsp;&nbsp;&nbsp;&nbsp;Craig y Cilau/Waun Ddu Transect vegetation and chemistry.    ]]

===Condition assessment===
The overall assessment is that Craig-y-Cilau/Waun Ddu should be classified as being in favourable ecological and hydrogeological condition.         
[[Category:OR/14/043 Survey, characterisation and condition assessment of Palustriella dominated springs 'H7220 Petrifying springs with tufa formation (Cratoneurion)' in Wales | 17]]