Monthly Water Situation Report Yorkshire Area

Monthly water situation report Yorkshire Area

Summary – July 2019 Another unsettled month containing some very heavy, localised storms towards the end of the month. Above average monthly rainfall totals were recorded across Yorkshire. Normal or higher river flows in the Pennine catchments and below normal river flows in the groundwater fed catchments. The soils were wet in the western areas and drier to the east, groundwater levels continued to decrease, and overall reservoir stocks were above the long term average.

Rainfall An unsettled month ensured July was very wet across Yorkshire although the second half of the month was considerably wetter, recording 74% to 96% of the total recorded rainfall. The high totals were caused by successions of storm fronts passing through the county, with some producing highly localised, very heavy downpours at the end of the month.

Two particularly wet periods occurred between:

 the 19th July to the 23rd July where 17% to 45% of the month’s total rain fell in localised areas. Significant daily totals occurred on the 19th, 21st, and the 23rd.  the 26th July to the 31st July where 37% to 77% of the month’s total rain fell in localised areas. Significant daily totals occurred on the 27th, 28th, and especially on the 30th and 31st.

South Yorkshire and West Yorkshire experienced some intense storm over the weekend of the 27th and 28th July. Localised areas around Sheffield recorded 80% to 110% of the monthly long term average (LTA) on Saturday while some locations in the upper Calder catchment recorded 70% to 105% of the monthly LTA on Sunday.

Then on Tuesday 30th, Malham Tarn in the upper Aire recorded 85% of its monthly LTA in 12 hours, with a very intense storm hitting the upper Swale catchment. Arkle Town raingauge recorded virtually all of its monthly LTA rain in 1 hour and almost 150% of its monthly LTA in 6 hours. The daily total at Arkle Town raingauge was a little over 100mm, or 158% of its monthly LTA.

All catchments received above the LTA monthly rainfall, with the Don and Calder catchments recording around twice the LTA.

Soil Moisture Deficit (SMD) Rising SMD occurred through the first half of the month in response to the relatively dry weather. By mid-July, central and eastern Yorkshire was classed as being dry with the rest of the Area being classed as normal. Once the unsettled weather arrived, the SMD started to decline. By the end of the month, the western most Pennine ridge had returned to a wet classification, the north-eastern and southern edges were normal, and central and eastern areas were still within the dry classification.

River Flows Within the Pennine fed catchments, river flows declined steadily until the 18th July and the majority of catchments were starting to show flows that were classed as below normal for the time of year. The ensuing rainfall had an immediate impact within the rivers and produced numerous high flow peaks. The end of the month had daily mean flows well above what would normally be expected for the time of year.

The upper Swale recorded a significant peak on the 30th July in response to a very intense storm. The fluvial gauge at Reeth, located on Arkle Beck, rose by 1.6m in 1.5 hours and also recorded its highest level from a 21 year record. However, the level was truncated, possibly reaching the bank top and overflowing into the

All data are provisional and may be subject to revision. The views expressed in this document are not necessarily those of the Environment Agency. Its officers, servants or agents accept no liability for any loss or damage arising from the interpretation or use of the information, or reliance upon views contained herein. © Environment Agency 2019

surrounding area. Levels on the main River Swale recorded peaks that were lower than the peak level reached in March 2019 although still showed notable rates of rise. Grinton Bridge, on the River Swale immediately downstream of Reeth, rose by 2m in 2 hours while Catterick Bridge, further downstream, rose by 1.8m in 30 minutes.

With regards to the monthly mean flow, the Pennine catchments were classed as having normal flows for the time of year or were higher.

In the groundwater dominated catchments in the east, declining flows were common. The River Derwent was experiencing below normal river flows at the beginning of July and they slowly declining to notably low flows by the 18th. The flow remained low until the very end of the month before there were signs of rising up into the normal range expected for the time of year. The monthly mean flow for the River Derwent was classed as being notably low for the time of year. Within the upper River Hull, as monitored at Wansford Snakeholm Lock, the flow slowly declined throughout the month and was classed as being below normal until the very last day, which saw an increase into the normal range expected for the time of year. The watercourses of Mires Beck and the River Foulness that flow directly into the Humber Estuary declined steadily, below what would normally be expected for the time of year, until the 18th July before fluctuating in response to the rainfall.

Groundwater Levels Magnesian Limestone The groundwater level at Brick House Farm continued to fall below the drought trigger level for the time of year.

Millstone Grit The groundwater level at Hill Top Farm was at average levels for the time of year.

Sherwood Sandstone The groundwater level in the north of the Sherwood Sandstone had fallen to average or slightly above the average for the time of year. The level in the south of the aquifer as measured at Pincheon Green was below average for the time of year.

Corallian Limestone The groundwater levels at Sproxton & East Ness had decreased, remaining close to drought trigger levels.

Chalk The groundwater level in the northern area of the aquifer, as monitored at Wetwang, had continued to decrease and was at the drought trigger level for the time of year. At Dalton Estate in the south of the aquifer the groundwater level had decreased to well below average for the time of year.

Reservoir Storage The overall reservoir stocks decreased by 5% during the first half of the month although were still above the LTA. They then increased back up by 7% in response to the very wet weather during the second half of the month.

Environmental Impact There were 7 abstraction licences that had Hands off Flow (HOF) in force within the Derwent catchment. An additional 124 abstractors were on advance warning notifications although they were still able to abstract.

Author: Yorkshire Hydrology

Rainfall

Above average rainfall Below average rainfall 1-Month Period for Swale (NE) 1-Month Period for Ure

250% 250%

200% 200%

150% 150%

100% 100%

50% 50%

0% 0% Aug-18 Sep-18 Oct-18 Nov-18 Dec-18 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Jun-19 Jul-19 Aug-18 Sep-18 Oct-18 Nov-18 Dec-18 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Jun-19 Jul-19

1-Month Period for Nidd 1-Month Period for Ouse

250% 250%

200% 200%

150% 150%

100% 100%

50% 50%

0% 0% Aug-18 Sep-18 Oct-18 Nov-18 Dec-18 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Jun-19 Jul-19 Aug-18 Sep-18 Oct-18 Nov-18 Dec-18 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Jun-19 Jul-19

1-Month Period for Wharfe 1-Month Period for Dales North Sea Tribs

250% 250%

200% 200%

150% 150%

100% 100%

50% 50%

0% 0% Aug-18 Sep-18 Oct-18 Nov-18 Dec-18 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Jun-19 Jul-19 Aug-18 Sep-18 Oct-18 Nov-18 Dec-18 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Jun-19 Jul-19

1-Month Period for Rye 1-Month Period for Derwent (NE)

250% 250%

200% 200%

150% 150%

100% 100%

50% 50%

0% 0% Aug-18 Sep-18 Oct-18 Nov-18 Dec-18 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Jun-19 Jul-19 Aug-18 Sep-18 Oct-18 Nov-18 Dec-18 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Jun-19 Jul-19

Above average rainfall Below average rainfall 1-Month Period for Aire 1-Month Period for Calder

250% 250%

200% 200%

150% 150%

100% 100%

50% 50%

0% 0% Aug-18 Sep-18 Oct-18 Nov-18 Dec-18 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Jun-19 Jul-19 Aug-18 Sep-18 Oct-18 Nov-18 Dec-18 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Jun-19 Jul-19

1-Month Period for Don 1-Month Period for Hull and Humber

250% 250%

200% 200%

150% 150%

100% 100%

50% 50%

0% 0% Aug-18 Sep-18 Oct-18 Nov-18 Dec-18 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Jun-19 Jul-19 Aug-18 Sep-18 Oct-18 Nov-18 Dec-18 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Jun-19 Jul-19

Soil Moisture Deficit

River Flow

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data Addingham, WHARFE Birstwith, NIDD Ranking derived from data for the period Dec-1973 to Dec-2017 Ranking derived from data for the period Dec-1976 to Dec-2017

20 45 18 40 16 35 14 30 12 25 10 20 8 15

Flow (cumecs) Flow (cumecs) Flow 6 10 4 5 2 0 0 Oct-18 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19 Oct-18 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data Briggswath, ESK Buttercrambe, DERWENT Ranking derived from data for the period Jan-1993 to Dec-2017 Ranking derived from data for the period Sep-1973 to Dec-2017

20 50

40 15

30 10 20 Flow (cumecs) Flow (cumecs) Flow 5 10

0 0 Oct-18 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19 Oct-18 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19

Crakehill Topcliffe, SWALE Doncaster, DON Ranking derived from data for the period Jun-1980 to Dec-2017 Ranking derived from data for the period Jul-1959 to Dec-2017

70 50

60 40 50 30 40

30 20

Flow (cumecs)Flow 20 (cumecs)Flow 10 10

0 0 Oct-18 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19 Oct-18 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19

Elland, CALDER Hunsingore, NIDD Ranking derived from data for the period Jul-1971 to Dec-2017 Ranking derived from data for the period Oct-1968 to Dec-2017

25 25

20 20

15 15

10 10 Flow (cumecs) Flow (cumecs) Flow

5 5

0 0 Oct-18 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19 Oct-18 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19

Kildwick, AIRE Kilgram Bridge, URE Ranking derived from data for the period Aug-1971 to Dec-2017 Ranking derived from data for the period Aug-1971 to Dec-2017

25 50 20 40 15 30

10 20 Flow (cumecs)Flow (cumecs)Flow

5 10

0 0 Oct-18 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19 Oct-18 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data Ness, RYE Skelton, OUSE Ranking derived from data for the period Sep-1974 to Dec-2017 Ranking derived from data for the period Sep-1969 to Dec-2017

12 160 10 140

8 120 100 6 80

4 60 Flow (cumecs) Flow (cumecs) Flow 40 2 20 0 0 Oct-18 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19 Oct-18 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19

Tadcaster, WHARFE Walden Stubbs, WENT Ranking derived from data for the period Jul-1991 to Dec-2017 Ranking derived from data for the period Oct-1979 to Dec-2017

3 60 3 50 2 40

2 30

20 1 Flow (cumecs)Flow (cumecs)Flow

10 1

0 0 Oct-18 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19 Oct-18 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19

Wansford Snakeholm Lock - West Beck, WEST BECK Whittington, ROTHER Ranking derived from data for the period Nov-1988 to Dec-2017 Ranking derived from data for the period Nov-1979 to Dec-2017

8 7

7 6 6 5 5 4 4 3 3

Flow (cumecs) Flow (cumecs) Flow 2 2

1 1

0 0 Oct-18 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19 Oct-18 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19

Groundwater Levels

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data Brick House Fm Dalton Estate Well Ranking derived from data for the period Oct-1979 to Nov-2017 Ranking derived from data for the period Jan-1889 to Nov-2017

18 23

17 21 16 19 15

14 17

13 15 Level (mAOD) Level 12 (mAOD) Level 13 11

10 11 Oct-16 Feb-17 Jun-17 Oct-17 Feb-18 Jun-18 Oct-18 Feb-19 Jun-19 Oct-16 Feb-17 Jun-17 Oct-17 Feb-18 Jun-18 Oct-18 Feb-19 Jun-19

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data Great Ouseburn Hill Top Fm Ranking derived from data for the period Jan-1976 to Nov-2017 Ranking derived from data for the period Oct-1973 to Nov-2017

17 128

128 17 127 16 127

16 126

126 15 Level (mAOD) Level (mAOD) Level 125 15 125

14 124 Oct-16 Feb-17 Jun-17 Oct-17 Feb-18 Jun-18 Oct-18 Feb-19 Jun-19 Oct-16 Feb-17 Jun-17 Oct-17 Feb-18 Jun-18 Oct-18 Feb-19 Jun-19

Riccall Approach Farm Sproxton Ranking derived from data for the period Feb-1977 to Nov-2017 Ranking derived from data for the period May-1975 to Nov-2017

7 50

7 49 6 48 6 5 47 5 46

4 45

Level (mAOD) Level 4 (mAOD) Level 44 3 3 43 2 42 Oct-16 Feb-17 Jun-17 Oct-17 Feb-18 Jun-18 Oct-18 Feb-19 Jun-19 Oct-16 Feb-17 Jun-17 Oct-17 Feb-18 Jun-18 Oct-18 Feb-19 Jun-19

Wetwang Ranking derived from data for the period Oct-1971 to Nov-2017

Level (mAOD) Level 21

17 Oct-16 Feb-17 Jun-17 Oct-17 Feb-18 Jun-18 Oct-18 Feb-19 Jun-19

Reservoir Stocks – Data from Water Company

Yorkshire Supply (data supplied by Water Company) 100

30 Percentage live of capacity

Weekly LTA (historic) 10 Maximum (historic) Minimum (historic) 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec This graph is produced from Yorkshire Water © Crown Copyright data.

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).

Artesian The condition where the groundwater level is above ground surface but is prevented from rising to this level by an overlying continuous low permeability layer, such as clay.

Artesian borehole Borehole where the level of groundwater is above the top of the borehole and groundwater flows out of the borehole when unsealed.

Cumecs Cubic metres per second (m3s-1)

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

Flood Alert/Flood Warning Three levels of warnings may be issued by the Environment Agency. Flood Alerts indicate flooding is possible. Flood Warnings indicate flooding is expected. Severe Flood Warnings indicate severe flooding.

Groundwater The water found in an aquifer.

Long term average (LTA) The arithmetic mean calculated from the historic record, usually based on the period 1961-1990. However, the period used may vary by parameter being reported on (see figure captions for details). mAOD Metres Above Ordnance Datum (mean sea level at Newlyn Cornwall).

MORECS Met Office Rainfall and Evaporation Calculation System. Met Office service providing real time calculation of evapotranspiration, soil moisture deficit and effective rainfall on a 40 x 40 km grid.

Naturalised flow River flow with the impacts of artificial influences removed. Artificial influences may include abstractions, discharges, transfers, augmentation and impoundments.

NCIC National Climate Information Centre. NCIC area monthly rainfall totals are derived using the Met Office 5 km gridded dataset, which uses rain gauge observations.

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

Reservoir gross capacity The total capacity of a reservoir.

Reservoir live capacity The capacity of the reservoir that is normally usable for storage to meet established reservoir operating requirements. This excludes any capacity not available for use (e.g. storage held back for emergency services, operating agreements or physical restrictions). May also be referred to as ‘net’ or ‘deployable’ capacity.

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