Monthly Water Situation Report Yorkshire Area

Monthly water situation report Yorkshire Area

Summary – September 2019 Well above average monthly rainfall totals as a result of a very wet period during the last 10 days of the month. Above normal or higher monthly mean river flows in the Pennine fed catchments and normal or below normal river flows in the groundwater fed catchments. Fully saturated soils in the west adjacent to the Pennines with normal conditions towards the east. The groundwater levels continued to decrease and overall reservoir stocks were well above the long term average.

Rainfall An unsettled month ensured September was very wet across Yorkshire with the last 10 days of the month being significantly wet. All catchments recorded well above the monthly long term average (LTA) total with the Don and Ouse catchments recording at least twice their monthly LTA.

The uppermost western catchments, adjacent to the Pennines, recorded 20% to 40% of their monthly LTA by the 5th September while the central and eastern catchments were relatively dry. Reasonably dry conditions then followed for the next 2 weeks before some very unsettled weather arrived, affecting the whole of Yorkshire. The last 10 days of the month experienced successions of storm fronts that produced long periods of prolonged rainfall. This resulted in 66% to 93% of the month’s recorded total rainfall, with individual raingauges within the Don, Swale, and Ouse catchments recording double their monthly LTA.

With regards to the individual catchment average rainfall totals, using the Met Office National Climate Information Centre (NCIC) dataset from 1891, it is showing to be the 6th wettest September for the Calder and the Don catchments, and the 7th wettest September for the Ouse and the Wharfe catchments It’s also the

 4th wettest 3-month total ending September within the Calder catchment,  3rd wettest 4-month total ending September within the Calder catchment and 4th wettest 4-month total ending September within the Don catchment,  3rd wettest 5-month total ending September within the Calder catchment and 6th wettest 5-month total ending September within the Don catchment.

Soil Moisture Deficit (SMD) Large sections of Yorkshire were classed as being dry at the beginning of September and the SMD didn’t alter a great deal for 3 weeks. The rain that arrived at the end of the month had an immediate impact on the soils and reduced the deficit significantly. By the end of September, the regions immediately adjacent to the Pennine ridge had become fully saturated, the northern regions were classed as wet, and the central and eastern catchments had returned to more normal conditions.

River Flows Leading up to the 22nd September, river flows within the Pennine fed catchments generally declined slowly. They did show some minor response to any rain that fell although the flow quickly fell once the rain passed. Low flow conditions were being experienced within the Foss, Esk, Rye, Rother, and lower Don rivers while the remaining catchments had flows within the normal range expected for the time of year. The rain falling from the storm fronts at the end of the month had an immediate impact in the rivers and produced frequent high flow peaks. River flows quickly rose above what would normally be expected for the time of year and the majority of catchments had several days with flows classed as being exceptionally high. With regards to the monthly mean flow, the Pennine catchments were classed as having above normal flows for the time of year or were higher.

In the groundwater dominated catchments in the east, very steady declining flows generally occurred until approximately the 22nd September. The River Derwent was experiencing below normal river flows until the rain

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

arrived. Flows quickly responded to this rain and had risen into the notably high flow range by the end of the month. The monthly mean flow for the River Derwent was classed as being below normal given the number of days experiencing low flows. Within the upper River Hull, as monitored at Wansford Snakeholm Lock, the flow was fairly constant and fluctuated slightly within the normal range expected for the time of year. It also rose at the end of the month in response to the rainfall although remained in the normal flow range expected. The watercourses of Mires Beck and the River Foulness that flow directly into the Humber Estuary also recorded fairly constant flows, often within the below normal range, until the rainfall at the end of the month. They quickly responded and rose into notably high, or higher, flow conditions at the end of September.

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 sharply decreased in September after a sudden rise in August and fell below the average level for the time of year.

Sherwood Sandstone The groundwater level in the Sherwood Sandstone, measured at both Great Ouseburn and Riccal Approach, fell slightly in September and remained just above average for the time of year.

Corallian Limestone The groundwater levels at Sproxton and East Ness had decreased, with the levels at Sproxton being below average for the time of year while the levels at East Ness were at the drought trigger level.

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

Reservoir Storage After a slight decline in overall reservoir stocks over 3 weeks of the month, the high rainfall totals over the final 10 days of September ensured the stocks rose significantly. The month end saw levels well above the LTA and heading towards full capacity.

Environmental Impact There were 6 abstraction licences that had Hands off Flow (HOF) in force with an additional 70 abstractors 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% Oct-18 Nov-18 Dec-18 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Jun-19 Jul-19 Aug-19 Sep-19 Oct-18 Nov-18 Dec-18 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Jun-19 Jul-19 Aug-19 Sep-19

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

250% 250%

200% 200%

150% 150%

100% 100%

50% 50%

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

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

250% 250%

200% 200%

150% 150%

100% 100%

50% 50%

0% 0% Oct-18 Nov-18 Dec-18 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Jun-19 Jul-19 Aug-19 Sep-19 Oct-18 Nov-18 Dec-18 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Jun-19 Jul-19 Aug-19 Sep-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% Oct-18 Nov-18 Dec-18 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Jun-19 Jul-19 Aug-19 Sep-19 Oct-18 Nov-18 Dec-18 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Jun-19 Jul-19 Aug-19 Sep-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% Oct-18 Nov-18 Dec-18 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Jun-19 Jul-19 Aug-19 Sep-19 Oct-18 Nov-18 Dec-18 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Jun-19 Jul-19 Aug-19 Sep-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 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19 Oct-19 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19 Oct-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 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19 Oct-19 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19 Oct-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 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19 Oct-19 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19 Oct-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 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19 Oct-19 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19 Oct-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 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19 Oct-19 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19 Oct-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 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19 Oct-19 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19 Oct-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 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19 Oct-19 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19 Oct-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 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19 Oct-19 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19 Oct-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 Dec-16 Apr-17 Aug-17 Dec-17 Apr-18 Aug-18 Dec-18 Apr-19 Aug-19 Dec-16 Apr-17 Aug-17 Dec-17 Apr-18 Aug-18 Dec-18 Apr-19 Aug-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 Dec-16 Apr-17 Aug-17 Dec-17 Apr-18 Aug-18 Dec-18 Apr-19 Aug-19 Dec-16 Apr-17 Aug-17 Dec-17 Apr-18 Aug-18 Dec-18 Apr-19 Aug-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 Dec-16 Apr-17 Aug-17 Dec-17 Apr-18 Aug-18 Dec-18 Apr-19 Aug-19 Dec-16 Apr-17 Aug-17 Dec-17 Apr-18 Aug-18 Dec-18 Apr-19 Aug-19

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

Level (mAOD) Level 21

17 Dec-16 Apr-17 Aug-17 Dec-17 Apr-18 Aug-18 Dec-18 Apr-19 Aug-19

Reservoir Stocks – Data from Water Company

Yorkshire Supply (data supplied by Water Company) 100

30 Percentage of live capacity of live Percentage

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).