Water Situation Report Yorkshire Area
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Monthly water situation report Yorkshire Area Summary – February 2020 A persistently wet month with well above average rainfall across the area. River flows were in the exceptionally or notably high range and new record monthly mean flows for February were set on the Pennine fed rivers. Soils remained saturated throughout the month. Groundwater levels increased in all aquifers, and set new maximum observed levels at monitoring locations in the Millstone Grit and parts of the Sherwood Sandstone. Reservoirs were close to full capacity throughout the month. Rainfall Yorkshire experienced extremely wet weather during February. The Pennine fed catchments of the Swale, Ure, Nidd, Wharfe, Aire, Calder and Don received between 320% and 375% of the monthly Long Term Average (LTA) rainfall. The lower Ouse, Rye, Derwent and Hull further east received between 245% and 295% of the LTA. Most days in February were wet apart from a brief settled period from the 4th to the 6th. The three most significant rainfall episodes were: the 8th to 9th February, named Storm Ciara. Heavy rainfall associated with a frontal weather system was widespread across Yorkshire, with bands of particularly intense rainfall along the Pennine Ridge. Locations in the Aire, Calder and upper Nidd catchments received 106% to 128% of the February LTA in 48 hours. the 15th to 16th February, named Storm Dennis. Widespread rainfall on the afternoon of the 15th, followed by two phases of intense rainfall particularly over the lower reaches of the Dales catchment and the Don valley. 60% to 80% of the February LTA was recorded at many locations over 48 hours, increasing to over 90% near the east coast where the background LTA values are more modest. The 21st to 24th February. A prolonged and fairly static area of heavy rainfall over the upper Dales catchments on the 21st, with further spells of rain crossing the region on the 22nd and 23rd. Some snowfall and rapid snowmelt occurred on the 24th. Although rainfall was less intense than the above two named storms, this four day period produced significant depths of precipitation over the Pennine catchments. Storms Ciara and Dennis together produced between 30% and 50% of February 2020’s recorded rainfall at most sites. When the 21st to 24th February totals are added, these three periods accounted for 60% to 70% of the month’s recorded rainfall. Using the Met Office Had-UK dataset, with records commencing in 1891, February 2020 was the wettest February on record in the Swale, Ure, Nidd, Wharfe, Aire, Calder and Don catchments. It was the second wettest in the Hull and Ouse catchments and the third wettest in the Derwent. Soil Moisture Deficit Across the Yorkshire area, SMD was zero or very close to zero throughout the month. All catchment soils were classified as Wet, representing saturated conditions. River Flows Monthly mean river flows during February were in the notably high to exceptionally high range in almost all Yorkshire’s major catchments, reflecting the wet weather conditions. The Pennine fed rivers recorded between 275% and 375% of the LTA, while the Rye, Derwent and Esk recorded between 140% and 165% of the LTA. Only the Chalk-fed West Beck in the upper River Hull catchment recorded monthly mean flows in the normal range, at 129% of the LTA. The highest February monthly mean flows on record were achieved at many locations, namely within the Swale, Ure, Nidd, Ouse, Wharfe, Aire, Calder, Don and Rother catchments. 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 2020 Up to the 8th February, flows in the Pennine fed catchments were mostly in the normal range, although the Swale, Ure and Aire had a brief period of higher flows within the 1st to the 3rd of the month. With the arrival of Storm Ciara, flows rose quickly across all catchments on the 9th, producing sharp flood peaks on the 9th or 10th. Flows remained in the above normal to exceptionally high range for the remainder of the month, with further flow peaks occurring on the 16th or 17th after Storm Dennis and multiple peaks between the 22nd and 25th. Significant river level peaks were recorded on the upper Dales rivers on the 9th and 10th February, following Storm Ciara. The 2nd to 5th ranked peaks on record occurred on the Swale, Ure, Nidd and Wharfe at locations with between 25 and 48 years of record. On the upper Aire at Gargrave, the highest river level in 43 years was recorded. In the Calder catchment the peak ranked highest on record at Dewsbury (in 23 years) and Colne Bridge (in 54 years), and second highest at Hebden Bridge, Mytholmroyd and Elland. Peak river levels associated with Storm Dennis the following week were generally lower, except on the Rivers Don and Rother and on the lower Swale. The Don at Doncaster recorded its fifth highest level in 43 years during this event. In addition to the peak flows, the last three weeks of February featured large volumes of baseflow passing out of the Dales to the lowland river reaches and floodplains, as persistent rainfall did not allow river flows to recede fully between peaks. This was particularly noticeable on the lower Swale and River Ouse. Flows in the River Derwent were in the below normal range until 8th February, then rose quickly on the 9th to a peak on the 10th to 11th, with sustained high flows for the remainder of the month, including a further peak from the 17th to the 18th. Flows in the River Rye showed a similar pattern. Flows in the River Esk in the north-east of the area were exceptionally low during the first week of the month. Flows increased rapidly in response to rainfall, with a peak occurring on the 9th and again on the 16th, the river fluctuating between normal and exceptionally high flow ranges. In the River Hull in the east of the area, flows for the first half of the month were mostly in the normal range, apart from short duration higher flow peaks on the 9th and the 16th. Flows increased above normal and continued rising from the 17th to the 25th, becoming steady for the last few days of the month. A similar pattern was observed on Mires Beck, with a gradual increase in baseflow through the month. Groundwater Levels There was a rise in groundwater levels throughout the area due to the large rainfall totals occurring during February. Magnesian Limestone The groundwater level at Brick House Farm rose and equalled the highest previously recorded level for February. Millstone Grit The groundwater level at Hill Top Farm rose to a new maximum level observed at this site (for any month) in a 46 year record. Sherwood Sandstone Groundwater levels in the Sherwood Sandstone increased this month. At Riccall Approach they were well above average for the time of year and at Great Ouseburn they reached a new maximum observed level (for any month) in a 44 year record. Corallian Limestone The groundwater levels at Sproxton & East Ness increased this month and were above average for the time of year. Chalk The groundwater level in the northern area of the aquifer, as monitored at Wetwang, increased and was above average for the time of year. At Dalton Estate in the south of the aquifer the groundwater level remained steady and was well above average for the time of year. 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 2020 Reservoir Storage Reservoir stocks increased slightly through the month and were at almost full capacity. By month end, overall reservoir stocks were 5% above the LTA (based on records from 1990). Environmental Impact No Hands off Flow restrictions were in force after the first week of February. In January, twenty-four abstractors had been issued with advance warning notifications of low flows, although they were still able to abstract, and during February flows rose back above the warning threshold at all of these sites. Author: Yorkshire Hydrology 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 2020 Rainfall © Environment Agency 2020 Above average rainfall Below average rainfall 1-Month Period for Swale (NE) 1-Month Period for Ure 350% 400% 350% 300% 300% 250% 250% 200% 200% 150% 150% 100% 100% 50% 50% 0% 0% Sep-19 Sep-19 Mar-19 Apr-19 May-19 Jun-19 Jul-19 Aug-19 Oct-19 Nov-19 Dec-19 Jan-20 Feb-20 Mar-19 Apr-19 May-19 Jun-19 Jul-19 Aug-19 Oct-19 Nov-19 Dec-19 Jan-20 Feb-20 1-Month Period for Nidd 1-Month Period for Ouse 400% 250% 350% 200% 300% 250% 150% 200% 100% 150% 100% 50% 50% 0% 0% Sep-19 Sep-19 Mar-19 Apr-19 May-19 Jun-19 Jul-19 Aug-19 Oct-19 Nov-19 Dec-19 Jan-20 Feb-20 Mar-19 Apr-19 May-19 Jun-19 Jul-19 Aug-19 Oct-19 Nov-19 Dec-19 Jan-20 Feb-20 1-Month Period for Wharfe 1-Month Period for Dales North Sea Tribs 400% 250% 350% 200% 300% 250% 150% 200% 100% 150% 100% 50% 50% 0% 0% Sep-19 Sep-19 Mar-19