Monthly water situation report

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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 Environment Agency. Its officers, servants or agents accept no liability for any loss or damage arising from the interpretation or

Monthly water situation report

Summary – September 2018

September was another month of below average rainfall with Soil Moisture Deficits remaining high as a result. Despite this dry period groundwater levels are still benefitting from the recharge received from the wet March and April with levels at all sites ‘Normal’ or ‘Above normal’. River flows decreased at most sites and as a result the Trent-Witham-Ancholme, Slea Augmentation and Gwash-Glen transfer schemes are now all in operation.

Rainfall

September was another drier than average month. The Area only received an average of 28.5mm of rainfall, 59% of the long term average for September. The Louth, Grimsby and Ancholme rainfall unit in the north of the Area received the highest rainfall of 35.4mm which was classified a ‘Normal’ for September. The Lower Welland and Nene rainfall unit was the driest with only 22mm of rainfall which is ‘Below Normal’ for this time of year.

September rainfall was classified as ‘Normal’ or ‘Below Normal’ with rainfall totals for the Area over the last year classified as ‘Below Normal’ or ‘Notably Low’.

Soil Moisture Deficit/Recharge

SMDs didn’t change significantly in September due to the below average rainfall and stayed well above the long term average. Soil Moisture Deficits are classified as ‘Notably High’ or ‘Exceptionally High’ for most catchments.

SMDs in the Lower Welland and Nene catchment are ‘Above Normal’.

River Flows

River Flows in September decreased at all monitoring locations with the exception of Partney on the River Lymn where flows increased slightly. Flows in the north of the Area are classified as ‘Normal’ with all other sites classified as ‘Below Normal’ or ‘Notably Low’.

Groundwater Levels

Groundwater levels fell in line with the seasonal trend with levels classified as ‘Normal’ at all sites with the exception of Castlethorpe Bridge on the North Lincolnshire Limestone where levels are ‘Above Normal’ for this time of year.

Reservoir Storage/Water Resource Zone Stocks

Reservoirs are at or slightly below their normal operating curves.

Environmental Impact

The River Trent to River Witham and River Witham to River Ancholme water transfers continued to be operated during September. The Slea Augmentation scheme has been operating throughout the month and the Gwash- Glen transfer was switched on on the 5^th September. There are currently 7 cessation notices in force.

Forward Look

Probabilistic ensemble projections for river flows at key sites

December 2018: There is an increased probability of notably low flows or lower in the River Nene this December.

March 2019: There is an increased probability of notably low flows in the River Nene next March.

Probabilistic ensemble projections for groundwater levels in key aquifers

March 2019: There is an increased probability of below normal groundwater levels in the Lincolnshire chalk.

September 2019: There is an increased probability of below normal groundwater levels next September.

Author: Hydrology and Operations Contact details: 03708 506506

Lincolnshire and Northamptonshire Area

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Rainfall

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Total Rainfall in Millimetres Long Term Average Rainfall in Millimetres

0 20 40 60 80 100 120 140

Oct-17 Nov-17 Dec-17 Jan-18 Feb-18 Mar-18 Apr-18 May-18 Jun-18 Jul-18 Aug-18 Sep-18

Rainfall mm

1-Month Period for Louth Grimsby and Ancholme

0 20 40 60 80 100 120 140

Rainfall mm

1-Month Period for Steeping Great Eau and Long Eau

0 20 40 60 80 100 120 140

Rainfall mm

1-Month Period for Witham to Chapel Hill

0 20 40 60 80 100 120 140

Rainfall mm

1-Month Period for South Forty Foot and Hobhole

0 20 40 60 80 100 120 140

Rainfall mm

1-Month Period for Upper Welland and Nene

0 20 40 60 80 100 120 140

Rainfall mm

1-Month Period for Lower Welland and Nene

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Soil Moisture Deficit

Exceptionally Low Notably Low Below Normal Normal

Above Normal Notably High Exceptionally High ─── Latest data

0 20 40 60 80 100 120 140

160

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

SMD (mm)

Witham to Chapel Hill

Ranking derived from data for the period Jan-1961 to Dec- 2012

0 20 40 60 80 100 120 140

160

SMD (mm)

Ancholme Grimsby Louth

Rankingderived from data for the period Jan-1961 to Dec- 2012

0 20 40 60 80 100 120 140

160

SMD (mm)

South Forty Foot and Hobhole

Ranking derived from data for the period Jan-1961 to Dec- 2012

0 20 40 60 80 100 120 140

160

SMD (mm)

Steeping Great Eau and Long Eau Ranking derived from data for the period Jan-1961 to Dec-

2012

0 20 40 60 80 100 120 140

160

SMD (mm)

Upper Welland and Nene

Ranking derived from data for the period Jan-1961 to Dec-2012

0 20 40 60 80 100 120 140

160

SMD (mm)

Lower Welland and Nene

Ranking derived from data for the period Jan-1961 to Dec-2012

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River Flow

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Exceptionally high Notably high Above normal Normal

Below normal Notably low Exceptionally low ─── Latest data

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0

Dec-17 Feb-18 Apr-18 Jun-18 Aug-18 Oct-18

Flow (cumecs)

Louth Weir, LUD

Ranking derived from data for the period Jul-1968 to Dec-2012

0.0 0.5 1.0 1.5 2.0 2.5 3.0

Flow (cumecs)

Rase Bishopbridge, ANCHOLME

Ranking derived from data for the period Jun-1967 to Dec-2012

0 1 2 3 4 5 6 7 8

Flow (cumecs)

Claypole, UPPER WITHAM

Ranking derived from data for the period May-1959 to Dec-2012

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0

Flow (cumecs)

Partney, LYMN & STEEPING

Ranking derived from data for the period May-1962 to Dec-2012

0 1 2 3 4 5 6

Flow (cumecs)

Fulsby and Fulsby Model combined, BAIN Ranking derived from data for the period Oct-1962 to Dec-2012

0 1 2 3 4 5 6 7 8 9 10

Flow (cumecs)

Langworth, BARLINGS EAU

0 1 2 3 4 5 6 7

Flow (cumecs)

Ashley, WELLAND

Ranking derived from data for the period Oct-1970 to Dec-2012

0 1 2 3 4 5 6 7

Flow (cumecs)

Kates Bridge plus King Street, GLEN Ranking derived from data for the period Jan-1991 to Dec-2012

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0 1 1 2 2 3 3 4 4 5 5

Flow (cumecs)

Upton Mill Total, NENE - KISLINGBURY BRANCH Ranking derived from data for the period Jan-1970 to Dec-2012

0 1 1 2 2 3 3 4 4 5 5

Flow (cumecs)

St.Andrews total, NENE - BRAMPTON BRANCH Ranking derived from data for the period Jan-1970 to Dec-2012

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Groundwater Levels

14 15 16 17 18 19 20 21 22 23

Level (mAOD)

Dunholme Rd, Scothern

Ranking derived from data for the period Nov-1979 to Dec-2012

-1 -1 0 1 1 2 2 3 3

Level (mAOD)

Castlethorpe Bridge

Ranking derived from data for the period Nov-1996 to Dec-2012

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9 11 13 15 17 19 21

Level (mAOD)

Leasingham Exploratory

Ranking derived from data for the period Sep-1972 to Dec-2012

8 10 12 14 16 18 20 22

Level (mAOD)

Grange Farm, Aswarby

Ranking derived from data for the period Dec-1970 to Dec-2012

5 7 9 11 13 15 17

Level (mAOD)

Greatford, Liffington

4 6 8 10 12 14 16 18

Level (mAOD)

Hanthorpe

5 7 9 11 13 15 17 19 21

Level (mAOD)

Grainsby

Ranking derived from data for the period Oct-1977 to Dec-2012

-1 0 1 2 3 4 5 6 7 8

Level (mAOD)

Barton Horkstow Road

Ranking derived from data for the period Apr-1980 to Dec-2012

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Reservoir Stocks

Normal Operating Curve --- Drought Curve ---- 1995-1996 - - - - 2017-2018 ---

0 10 20 30 40 50 60 70 80 90 100

Jan Mar May Jul Sep Nov Jan Mar May Jul Sep Nov Jan

Percentage of live capacity

Rutland

0 10 20 30 40 50 60 70 80 90 100

Pitsford

1996-97

0 10 20 30 40 50 60 70 80 90 100

Combined Ravensthorpe & Hollowell

0 10 20 30 40 50 60 70 80 90 100

Covenham

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Forward Look – River Flows

Exceptionally high or low levels are those which would typically occur 5% of the time within the historic record. Notably high or low levels are those which would typically occur 8% of the time. Above normal or below normal levels are those which would typically occur 15% of the time. Normal levels are those which would typically occur 44% of the time within the historic record.

Probabilistic ensemble projections of river flows at key indicator sites in December 2019. Pie charts indicate probability, based on climatology, of the surface water flow at each site being e.g.

exceptionally low for the time of year. (Source: Centre for Ecology and Hydrology, Environment Agency) Geological map reproduced with kind permission from UK Groundwater Forum, BGS © NERC. Crown copyright. All rights reserved. Environment Agency, 100026380, 2018.

^ “Naturalised” flows are projected for these sites’

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Forward Look – River Flows

Probabilistic ensemble projections of river flows at key indicator sites in March 2019. Pie charts indicate probability, based on climatology, of the surface water flow at each site being e.g. exceptionally low for the time of year. (Source: Centre for Ecology and Hydrology, Environment Agency) Geological map reproduced with kind permission from UK Groundwater Forum, BGS © NERC. Crown copyright. All rights reserved. Environment Agency, 100026380, 2018.

^ “Naturalised” flows are projected for these sites’

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Forward Look - Groundwater

Exceptionally high or low levels are those which would typically occur 5% of the time within the historic record. Notably high or low levels are those which would typically occur 8% of the time. Above normal or below normal levels are those which would typically occur 15% of the time. Normal levels are those which would typically occur 44% of the time within the historic record.

Probabilistic ensemble projections of groundwater levels at key indicator sites for end of March 2019. Pie charts indicate probability, based on climatology, of the groundwater level at each site being e.g. exceptionally low for the time of year. (Source: Environment Agency) Geological map reproduced with kind permission from UK Groundwater Forum, BGS © NERC. Crown copyright. All rights reserved. Environment Agency, 100026380, 2018.

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Forward Look - Groundwater

Probabilistic ensemble projections of groundwater levels at key indicator sites for end of

September 2019. Pie charts indicate probability, based on climatology, of the groundwater level at each site being e.g. exceptionally low for the time of year. (Source: Environment Agency) Geological map reproduced with kind permission from UK Groundwater Forum, BGS © NERC. Crown copyright. All rights reserved. Environment Agency, 100026380, 2018.

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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).

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).

Monthly water situation report