All data are provisional and may be subject to revision. The views expressed in this document are not necessarily those of the Natural Resources Wales. Its officers, servants or agents accept no liability for any loss or damage arising from the interpretation or use the information, or reliance upon views contained herein.

Monthly Water Situation Report Rainfall Summary – September 2014

Natural Resources Wales

The monthly rainfall total received for Wales was 15% of the Long Term Average (LTA) during September.

Third driest September since records began in 1910.

In response to the low rainfall during September, Soil Moisture Deficit (SMD) levels have increased.

Rainfall*

The monthly rainfall total received for Wales was exceptionally low when compared to the Long Term Average (LTA) for September, making it the third driest September on record (after 1959 and 1910).

The rainfall totals recorded in catchments across Wales were between 8.1mm (Dee, 11% of LTA) to 27.6mm (Glaslyn/Dwyryd, 15% of LTA).

Rainfall Map National Rainfall Charts National& Areas North Area South East Area South West Area

* using NCIC (National Climate Information Centre) data (Source: Met Office © Crown Copyright)

Soil Moisture Deficit (SMD)/Recharge

SMDs have increased across Wales during September due to the exceptionally low rainfall. The SMD values for all MORECS squares are above the LTA for September, The largest increase compared to the previous month was square 122 which increased from 6mm to

109mm.

SMD Map National SMD Charts Compare to LTA Compare to previous years

All data on Water Situation Reports are provisional, based on spot readings, and are subject to revision.

Author: Lorna Scurlock Telephone: 02920 466127

All data are provisional and may be subject to revision. The views expressed in this document are not necessarily those of the Natural Resources Wales. Its officers, servants or agents accept no liability for any loss or damage arising from the interpretation or use the information, or reliance upon views contained herein.

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Natural Resources Wales

Figure 1: The Natural Resources Wales Water Situation Report features sites in the catchments shown. Parts of the Shropshire Plains and Mid Severn catchments are within the region. For full information on these catchments, please see the Environment Agency Midlands Region Water Situation Report.

For areas adjoining Natural Resources Wales, please see the reports for Environment Agency Midlands and North West Regions on the Environment Agency website.

All data are provisional and may be subject to revision. The views expressed in this document are not necessarily those of the Natural Resources Wales. Its officers, servants or agents accept no liability for any loss or damage arising from the interpretation or use the information, or reliance upon views contained herein.

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Rainfall

Figure 2: Calculated catchment average September rainfall totals as a percentage of the 1961- 90 September long term average for Natural Resources Wales catchments, using NCIC (National Climate Information Centre) data (Source: Met Office © Crown Copyright).

All data are provisional and may be subject to revision. The views expressed in this document are not necessarily those of the Natural Resources Wales. Its officers, servants or agents accept no liability for any loss or damage arising from the interpretation or use the information, or reliance upon views contained herein.

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Ra

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Rainfall Charts

Figure 3: Rainfall Charts: National and Areas Monthly total rainfall (mm) Long-term average rainfall (mm)

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Natural Resources Wales

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Monthly rainfall totals compared to the 1961-90 long term average for Natural Resources Wales Areas, using NCIC (National Climate Information Centre) data (Source: Met Office © Crown Copyright).

All data are provisional and may be subject to revision. The views expressed in this document are not necessarily those of the Natural Resources Wales. Its officers, servants or agents accept no liability for any loss or damage arising from the interpretation or use the information, or reliance upon views contained herein.

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Ra

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Figure 4: Rainfall Charts: South East Area Monthly total rainfall (mm) Long-term average rainfall (mm)

Usk

Valleys & Vale of Glamorgan

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Lower Wye Upper Wye

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Welsh Mountains

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Dec Jan Feb Mar Apr May Jun Jul Au g Sep Oct Nov

Monthly rainfall totals compared to the 1961-90 long term average for Natural Resources Wales Areas, using NCIC (National Climate Information Centre) data (Source: Met Office © Crown Copyright).

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All data are provisional and may be subject to revision. The views expressed in this document are not necessarily those of the Natural Resources Wales. Its officers, servants or agents accept no liability for any loss or damage arising from the interpretation or use the information, or reliance upon views contained herein.

Figure 5: Rainfall Charts: North Area Monthly total rainfall (mm) Long-term average rainfall (mm)

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Dee Upper Dee

160

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Dec Jan Feb Mar Apr May Jun Jul Au g Sep Oct Nov

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Dec Jan Feb Mar Apr May Jun Jul Au g Sep Oct Nov

Clwyd Ynys Môn

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Dec Jan Feb Mar Apr May Jun Jul Au g Sep Oct Nov

Conwy Lleyn & Eryri

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Dec Jan Feb Mar Apr May Jun Jul Au g Sep Oct Nov

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Dec Jan Feb Mar Apr May Jun Jul Au g Sep Oct Nov

Ogwen Dwyfor

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Dec Jan Feb Mar Apr May Jun Jul Au g Sep Oct Nov

0

Dec Jan Feb Mar Apr May Jun Jul Au g Sep Oct Nov

Monthly rainfall totals compared to the 1961-90 long term average for Natural Resources Wales Areas, using NCIC (National Climate Information Centre) data (Source: Met Office © Crown Copyright).

All data are provisional and may be subject to revision. The views expressed in this document are not necessarily those of the Natural Resources Wales. Its officers, servants or agents accept no liability for any loss or damage arising from the interpretation or use the information, or reliance upon views contained herein.

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Ra

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Monthly total rainfall (mm) Long-term average rainfall (mm)

Alwen Gwyrfai/Seiont

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Glaslyn/Dwyryd Artro

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Mawddach Dysynni

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Dyfi

400

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Dec Jan Feb Mar Apr May Jun Jul Au g Sep Oct Nov

Monthly rainfall totals compared to the 1961-90 long term average for Natural Resources Wales Areas, using NCIC (National Climate Information Centre) data (Source: Met Office © Crown Copyright).

All data are provisional and may be subject to revision. The views expressed in this document are not necessarily those of the Natural Resources Wales. Its officers, servants or agents accept no liability for any loss or damage arising from the interpretation or use the information, or reliance upon views contained herein.

Return to Summary

Ra

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Figure 6: Rainfall Charts: South West Area

Monthly total rainfall (mm) Long-term average rainfall (mm)

North Ceredigion

Teifi

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Dec Jan Feb Mar Apr May Jun Jul Au g Sep Oct Nov

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Pembrokeshire

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Carmarthenshire

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Swansea & Llanelli

350

Neath, Port Talbot and Bridgend

300 300

250 250

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0

Dec Jan Feb Mar Apr May Jun Jul Au g Sep Oct Nov

Monthly rainfall totals compared to the 1961-90 long term average for Natural Resources Wales Areas, using NCIC (National Climate Information Centre) data (Source: Met Office © Crown Copyright).

All data are provisional and may be subject to revision. The views expressed in this document are not necessarily those of the Natural Resources Wales. Its officers, servants or agents accept no liability for any loss or damage arising from the interpretation or use the information, or reliance upon views contained herein.

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Soil Moisture Deficit (SMD)

Figure 7: MORECS soil moisture deficits (mm) for real land use for Natural Resources Wales (Source: Met Office © Crown Copyright).

All data are provisional and may be subject to revision. The views expressed in this document are not necessarily those of the Natural Resources Wales. Its officers, servants or agents accept no liability for any loss or damage arising from the interpretation or use the information, or reliance upon views contained herein.

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Soil

Mois

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Deficit (

mm

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oil

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Natural Resources Wales - All Squares

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102 103 104 105 111 112 113 114 122 123 132 133 134 135 143 144 145 146 147 154 155 156 157

Figure 8: MORECS month end soil moisture deficits (mm) for real land use for Natural Resources Wales squares compared to the September 1961-90 long term monthly average (Source: Met Office © Crown Copyright).

─── LTA (1961-90) ─── 2010 ─── 2011 ─── 2012 ─── 2013 ─── 2014

Natural Resources Wales South East (Sq 146)

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Figure 9: MORECS month end soil moisture deficits (mm) for real land use for Natural Resources Wales over the last four years and compared to the 1961-90 long term monthly average (Source: Met Office © Crown Copyright). *no LTA available for Natural Resources Wales

All data are provisional and may be subject to revision. The views expressed in this document are not necessarily those of the Natural Resources Wales. Its officers, servants or agents accept no liability for any loss or damage arising from the interpretation or use the information, or reliance upon views contained herein.

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Glossary Term Definition

Aquifer A geological formation able to store and transmit water. Areal average rainfall The estimated average depth of rainfall over a defined area.

Expressed in depth of water (mm). Effective rainfall The rainfall available to percolate into the soil or produce

river flow. Expressed in depth of water (mm). Groundwater The water found in an aquifer

Meteorological Office Rainfall and Evaporation Calculating System (MORECS)

The Met Office provides climate data for grid squares measuring 40km by 40km across the UK using MORECS

Recharge The process of increasing the water stored in the saturated zone of an aquifer. Expressed in depth of water (mm).

Reservoir live capacity The reservoir capacity normally usable for storage to meet established reservoir operating requirements. It is the total capacity less that not available because of operating agreements or physical restrictions. Only under abnormal conditions, such as a severe water shortage might this additional water be extracted.

Soil moisture deficit (SMD) The difference between the amount of water actually in the soil and the amount of water that the soil can hold. Expressed in depth of water (mm).

Categories

Exceptionally high Value likely to fall within this band 5% of the time

Notably high Value likely to fall within this band 8% of the time Above normal Value likely to fall within this band 15% of the time Normal Value likely to fall within this band 44% of the time Below normal Value likely to fall within this band 15% of the time Notably low Value likely to fall within this band 8% of the time Exceptionally low Value likely to fall within this band 5% of the time

Units

cumecs Cubic metres per second (m3 s-1) mAOD Metres Above Ordnance Datum (mean sea level at Newlyn

Cornwall).