Yorkshire Area

Monthly water situation report Yorkshire Area

Summary – August 2021 Monthly rainfall totals were below average, despite frequent occurrence of rain in many catchments between the 4th and the 22nd. Monthly mean river flows were also below the long term average for August in most catchments, with a brief period of higher flows in the second week. Groundwater levels decreased a little in most aquifers but remained either at normal levels or above. Reservoir stocks declined slightly but remained above average for the time of year. Soils were wet in the west of the Area, and by month end were dry or very dry elsewhere.

Rainfall August was a month of below average rainfall, with 50% to 60% of the long term average (LTA) received in the Swale and Ure catchments, 60% in the Don, and between 70% and 85% of the LTA in most other catchments in Yorkshire. These values are based on the Met Office Had-UK data set of catchment-averaged rainfall. The rainfall map on the third page of this report shows that the Swale and Ure catchments have received only around 70% of their LTA rainfall over the past three months combined. The Don has received 85% and other catchments close to 90-100% of the three-month LTA rainfall. The first three days of August were dry across much of Yorkshire. In the Pennine catchments and also the Rye and Derwent, rainfall was frequent during the 4th to the 22nd of the month, with particularly wet periods from the 4th to the 9th and the 21st to the 22nd. The last nine days of the month were drier. Approximately 40% of the month’s recorded rain fell on the 7th at Lower Dunsforth in the Ure catchment, Scargill in the Nidd and Grimwith in the Wharfe catchment. In the Don catchment in South Yorkshire and the Hull catchment in East Yorkshire, rainfall was concentrated into the same wet periods from the 5th to the 9th and the 21st to the 22nd, with the rest of the month featuring low amounts of rainfall over these areas.

Soil Moisture Deficit Along the western Pennine ridge, soil moisture conditions changed from wet to normal in the first few days of August, and back to wet by the 10th. Soils remained wet here to the end of August, although SMD values fluctuated slightly with rainfall. Across the central, eastern and southern parts of the Area, SMD values in late August were 10-25mm greater than at the end of July, having become lower (less dry) from the 3rd to the 10th and increased again both mid- month and in the final week. At month end, soils were classed as dry, apart from the lower Ouse which had reached very dry status.

River Flows On the Pennine-fed rivers, flows fell during the first few days of August, then increased in response to rainfall to reach a peak on the 8th, 9th or 10th. On the Wharfe, Aire and Calder the daily mean flows reached the exceptionally high range for August during this period, and on the upper Aire this peak put the monthly mean flow into the above normal range, at 124% of the LTA. Flows then receded throughout the Pennine catchments; a subsequent temporary increase in flow from the 21st to the 23rd was much smaller. Flows fell below normal from mid-month on the Swale and upper Ure, and during the last few days of August on the lower Ure, Ouse, Wharfe and Don. Monthly mean flows were below normal on the Swale, Ure, Ouse and Don (27%-74% of the LTA) and normal on the Nidd, Wharfe and Calder (64% to 105% of the LTA). On the Rother flows were below normal for much of August and exceptionally low from the 24th onwards. The Rother’s overall monthly mean flow at Whittington was classed as notably low at 43% of the LTA. On the Derwent, Rye and Esk, monthly mean flows were in the normal range, between 60% and 73% of the LTA. Again, the highest flows were during the 6th to the 10th and the 21st to the 24th following rainfall episodes.

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 2021

On the Chalk-fed West Beck, an underlying trend of decreasing baseflow was recorded through the month, with temporary increases in flow on the 6th to the 7th and the 21st to the 22nd. The monthly mean flow was in the normal range, at 107% of the LTA. On Mires Beck and the River Foulness to the west of the Hull catchment, short duration flow peaks occurred on the 6th and the 9th respectively but underlying flows were steady through the month.

Groundwater Levels In summary, groundwater levels across Yorkshire decreased slightly during August, with little change in classification relative to the long term record. Magnesian Limestone The groundwater level in the Magnesian Limestone, as measured at Brick House Farm, decreased slightly but remained exceptionally high for the time of year. Millstone Grit The groundwater level in the Millstone Grit, as measured at Hill Top Farm, showed a slight decline but was still above average for August. Sherwood Sandstone The groundwater level in the Sherwood Sandstone declined slightly at Great Ouseburn, but remained exceptionally high for the time of year. At Riccall Approach, the groundwater level rose slightly and remained in the normal range for the time of year. Corallian Limestone The groundwater level in the Corallian Limestone, as measured at Sproxton, exhibited a slight decline. The groundwater level remained normal for the time of year. Chalk The groundwater level in the chalk declined again in August, as observed at two of our Chalk Key Well monitoring boreholes. The groundwater level at both Wetwang (north western chalk) and Dalton Estate (central chalk) remained in the normal range.

Reservoir Storage Reservoir stocks increased by just under 4% from the 2nd to the 9th of August, then decreased for the following three weeks. This resulted in a small overall decline during the month. The average historic rate of late summer decline has been greater, and overall reservoir stocks were 4.6% above the LTA at month end.

Environmental Impact At the end of August almost 50 Hands Off Flow restrictions were in force. Many of these had been temporarily lifted for a short period earlier in the month and then re-imposed close to month-end. 75 abstractors had been given advance notice that flows are low but were still able to abstract.

On 24th August pumps were deployed to aerate the River Foss in York city centre following reports of fish dying and in distress due to low dissolved oxygen levels. Oxygen levels improved, further fish deaths were averted and the pumps were removed at the end of the month. Investigations into the cause of the incident are ongoing at the time of writing this report.

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%

Mar-21 Mar-21 Sep-20 Oct-20 Nov-20 Dec-20 Jan-21 Feb-21 Apr-21 May-21 Jun-21 Jul-21 Aug-21 Sep-20 Oct-20 Nov-20 Dec-20 Jan-21 Feb-21 Apr-21 May-21 Jun-21 Jul-21 Aug-21

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

250% 250%

200% 200%

150% 150%

100% 100%

50% 50%

0% 0%

Mar-21 Mar-21 Sep-20 Oct-20 Nov-20 Dec-20 Jan-21 Feb-21 Apr-21 May-21 Jun-21 Jul-21 Aug-21 Sep-20 Oct-20 Nov-20 Dec-20 Jan-21 Feb-21 Apr-21 May-21 Jun-21 Jul-21 Aug-21

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

250% 300%

250% 200%

200% 150%

150%

100% 100%

50% 50%

0% 0%

Mar-21 Mar-21 Sep-20 Oct-20 Nov-20 Dec-20 Jan-21 Feb-21 Apr-21 May-21 Jun-21 Jul-21 Aug-21 Sep-20 Oct-20 Nov-20 Dec-20 Jan-21 Feb-21 Apr-21 May-21 Jun-21 Jul-21 Aug-21

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

300% 250%

250% 200%

200% 150%

150%

100% 100%

50% 50%

0% 0%

Mar-21 Mar-21 Sep-20 Oct-20 Nov-20 Dec-20 Jan-21 Feb-21 Apr-21 May-21 Jun-21 Jul-21 Aug-21 Sep-20 Oct-20 Nov-20 Dec-20 Jan-21 Feb-21 Apr-21 May-21 Jun-21 Jul-21 Aug-21

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%

Mar-21 Mar-21 Sep-20 Oct-20 Nov-20 Dec-20 Jan-21 Feb-21 Apr-21 May-21 Jun-21 Jul-21 Aug-21 Sep-20 Oct-20 Nov-20 Dec-20 Jan-21 Feb-21 Apr-21 May-21 Jun-21 Jul-21 Aug-21

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

250% 200%

200% 150%

150%

100%

50% 50%

0% 0%

Mar-21 Mar-21 Sep-20 Oct-20 Nov-20 Dec-20 Jan-21 Feb-21 Apr-21 May-21 Jun-21 Jul-21 Aug-21 Sep-20 Oct-20 Nov-20 Dec-20 Jan-21 Feb-21 Apr-21 May-21 Jun-21 Jul-21 Aug-21

Soil Moisture Deficit

August 2021

11.80 97.90 87.10

12.30 76.60 94.40 93.70

13.10 111.90 124.80 116.50

90.60

River Flow

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data

Addingham, River Wharfe Birstwith, River Nidd Ranking used data from 18/12/1973 to 31/12/2017 Ranking used data from 16/12/1976 to 31/12/2017 180 80

160 70

140 60

120 50 100 40 80 30 60

Daily Flow(cumecs) Mean Daily Flow(cumecs) Mean Daily 20 10

0 0 31-Oct-20 31-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 31-Aug-21 31-Oct-21 31-Oct-20 31-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 31-Aug-21 31-Oct-21

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data

Briggswath, River Esk Buttercrambe, River Derwent Ranking used data from 02/10/1992 to 31/12/2017 Ranking used data from 04/09/1973 to 31/12/2017 100 140

90 120 80

70 100

60 80 50 60 40

30 40

20 Daily Flow(cumecs) Mean Daily Daily Flow(cumecs) Mean Daily 20 10

0 0 31-Oct-20 31-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 31-Aug-21 31-Oct-21 31-Oct-20 31-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 31-Aug-21 31-Oct-21

Crakehill Topcliffe, River Swale Doncaster, River Don Ranking used data from 29/05/1980 to 31/12/2017 Ranking used data from 01/01/2008 to 31/12/2017 250 250

200 200

150 150

100 100

50 50

Daily Flow(cumecs) Mean Daily Flow(cumecs) Mean Daily

0 0 31-Oct-20 31-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 31-Aug-21 31-Oct-21 31-Oct-20 31-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 31-Aug-21 31-Oct-21

Elland, River Calder Hunsingore, River Nidd Ranking used data from 01/06/1971 to 31/12/2017 Ranking used data from 05/10/1966 to 31/12/2017 140 160

120 140

120 100

100 80 80 60 60

Daily Flow(cumecs) Mean Daily Flow(cumecs) Mean Daily 20 20

0 0 31-Oct-20 31-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 31-Aug-21 31-Oct-21 31-Oct-20 31-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 31-Aug-21 31-Oct-21

Kildwick, River Aire Kilgram Bridge, River Ure Ranking used data from 29/07/1971 to 31/12/2017 Ranking used data from 01/01/1968 to 31/12/2017 90 250

200 70

60 150 50

40 100 30

Daily Flow(cumecs) Mean Daily Flow(cumecs) Mean Daily 10

0 0 31-Oct-20 31-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 31-Aug-21 31-Oct-21 31-Oct-20 31-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 31-Aug-21 31-Oct-21

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data

Ness, River Rye Skelton, River Ouse Ranking used data from 07/08/1974 to 31/12/2017 Ranking used data from 19/09/1969 to 31/12/2012 60 450

400 50 350

40 300

250 30 200

20 150

100 Daily Flow(cumecs) Mean Daily Daily Flow(cumecs) Mean Daily 10 50

0 0 31-Oct-20 31-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 31-Aug-21 31-Oct-21 31-Oct-20 31-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 31-Aug-21 31-Oct-21

Tadcaster, River Wharfe Walden Stubbs, River Went Ranking used data from 27/06/1991 to 31/12/2017 Ranking used data from 19/10/1979 to 31/12/2017 250 16

14 200 12

10 150

100 6

Daily Flow(cumecs) Mean Daily Flow(cumecs) Mean Daily 2

0 0 31-Oct-20 31-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 31-Aug-21 31-Oct-21 31-Oct-20 31-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 31-Aug-21 31-Oct-21

Wansford Snakeholm Lock, West Beck Whittington, River Rother Ranking used data from 08/10/1988 to 31/12/2017 Ranking used data from 08/11/1979 to 31/12/2017 8 35

7 30

6 25

5 20 4 15 3

Daily Flow(cumecs) Mean Daily Flow(cumecs) Mean Daily 1 5

0 0 31-Oct-20 31-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 31-Aug-21 31-Oct-21 31-Oct-20 31-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 31-Aug-21 31-Oct-21

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

23 18 21 16 19

14 17

Level (mAOD) Level (mAOD) Level 12 13

10 11 Nov-18 Mar-19 Jul-19 Nov-19 Mar-20 Jul-20 Nov-20 Mar-21 Jul-21 Nov-18 Mar-19 Jul-19 Nov-19 Mar-20 Jul-20 Nov-20 Mar-21 Jul-21 End of month ranking extrapolated from period of record single mid-month dip readings End of month ranking extrapolated from period of record single mid-month dip readings

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

127 16

126

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

14 124 Nov-18 Mar-19 Jul-19 Nov-19 Mar-20 Jul-20 Nov-20 Mar-21 Jul-21 Nov-18 Mar-19 Jul-19 Nov-19 Mar-20 Jul-20 Nov-20 Mar-21 Jul-21 End of month ranking extrapolated from period of record single mid-month dip readings End of month ranking extrapolated from period of record single mid-month dip readings 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 52 6 50

5 48

Level (mAOD) Level (mAOD) Level

3 44

2 42 Nov-18 Mar-19 Jul-19 Nov-19 Mar-20 Jul-20 Nov-20 Mar-21 Jul-21 Nov-18 Mar-19 Jul-19 Nov-19 Mar-20 Jul-20 Nov-20 Mar-21 Jul-21 End of month ranking extrapolated from period of record single mid-month dip readings End of month ranking extrapolated from period of record single mid-month dip readings Wetwang Ranking derived from data for the period Oct-1971 to Nov-2017

Level (mAOD) Level 23

17 Nov-18 Mar-19 Jul-19 Nov-19 Mar-20 Jul-20 Nov-20 Mar-21 Jul-21 End of month ranking extrapolated from period of record single mid-month dip readings

Reservoir Stocks – Data from Water Company

Yorkshire Supply (data supplied by Water Company) 100

30 Percentage of of Percentagelivecapacity

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).