The Tanker Drought - 1995 to 1998

There were again several drier months during 1996, though February and November were exceptions. January 1997 was much drier than average throughout the UK, meaning that water stocks were not being replenished as they usually are during the winter; however February was wet, providing some relief. After a dry spring, allowing water supplies to become well below average, there was a wet June, but only from November 1997 onwards was there consistently more rainfall than average.

The plot below shows the monthly North Atlantic Oscillation (NAO) Index for the periods before, during and after the drought. The NAO is a prominent teleconnection pattern in all seasons, and strong positive phases tend to be associationed with above-average temperatures in northern Europe, whilst negative phases of the NAO tend to be associated with below-average temperatures. There is more information available here.

The duration of the 1995-1998 event ranks highly in the top 10 events in northern England, the Midlands, East Anglia and southern England. In these same regions, the event ranks highly within the top 10 for the mean deficit, in many catchments in northern and central England ranking as the most severe by this characteristic. This owes to the combination of a long event with some of the most severe drought minima seen within the 125 year period in these regions. Drought minima ranks within the top three events across northern England and the far north of Scotland, but was also ranked regularly within the top 10 across East Anglia and southern England. In terms of all characteristics, this event was not highly ranked in terms of duration, mean deficit or drought event minima in western parts of the UK although deficits in flows occurred coherently (to varying degrees) across the country in this period.

Before the drought, groundwater levels in all the major aquifers were at or above the long-term seasonal average in the spring of 1995. The meteorological drought first effected northern England in the summer of 1995, with below average groundwater levels being recorded at Dalton Holme (see figure below) and Wetwang observation boreholes as early as June 1995. However, because of the relatively slow or delayed response of groundwater levels in the Permo-Triassic Sandstone aquifer of the north west of England groundwater levels didn’t fall below seasonal averages until between November 1995 (Skirwith) and January 1996 (Heathlanes) (see groundwater hydrographs below).

Apart from the south west of England (see the groundwater level hydrograph for Ashton Farm), the groundwater drought developed widely during 1996, with areas of the Chalk in the south east experiencing particularly low recharge over the 1995/96 winter (Marsh, 1995). New monthly minima were recorded towards the end of the summer of 1996, for example, a new minimum groundwater level for November was recorded at Dalton Holme in November 1996 (Marsh, 1995). Due to low recharge during the winter of 1996-97, groundwater levels were close to the seasonal minima at the start of the summer in 1997 with only 1979 and 1992 recording lower spring levels (Marsh, 1995). These exceptionally low levels persisted throughout the summer of 1997, particularly over the southern Chalk (see Redlands Hall and Stonor Park groundwater level hydrographs), although locally there was some recovery for example in the north east Chalk such as at Dalton Holme.

Recovery from the groundwater drought was also highly variable between the regions. The Chalk of the north east recovered to long-term seasonal averages during the winter of 1997-98. However, for large parts of the southern Chalk, and for the more rapidly responding Permo-Triassic Sandstone of the north west (such as Skirwith) recovery in groundwater was much weaker with levels not reaching long-term seasonal averages until the following winter of 1998-99 (see for example the Redlands Hall and Stonor Park hydrographs). At the very slowly responding observation borehole in the sandstones at Heathlanes, average groundwater levels were not re-established until autumn 1999.

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The lowered groundwater levels associated with drought led to reductions in the network of groundwater dependent streams particularly over the Chalk aquifer. The resulting ecological stress impacted macrophyte populations (Westwood et al. 2006); there was an associated increase in levels of nitrate (Morecroft et al. 2000); and algal blooms made worse by low flows and high temperatures effected water supplies (Ferguson et al. 1996) and caused problems with recreational water use (Everard, 1996). Despite these issues and the disruption of fisheries (Everard, 1996). Many of these acute issues were caused by high temperatures in the summer of 1995; however issues surrounding the long term depletion of water resources, such as the build-up and subsequent flushing of nutrients and the loss of the headwater stream network, were due to the longevity of the drought period.

Several water companies enforced Drought Orders (Marsh, 1995), for example, there were 97 drought orders over the 1995- 1996 period, and Yorkshire Water were forced to tanker water to some of their customers during the 1995 summer as a result of supply issues (Fowler & Kilsby, 2002). In response to the enforced rota cuts in supply, Yorkshire Water invested £50 million in a water transfer scheme from the River Tees to the River Ouse (Taylor et al. 2009). Other areas also installed new schemes, with the Suffolk Hartismere Resource Zone providing two new groundwater sources and improved infrastructure for transfer.

Grass shortages made farmers look for other options to feed their livestock, such as winter forage and straw. Because of the increased demand, fodder and straw prices increased considerably. Milk production and quality across Britain was seriously affected by the drought, leading to shortages for dairy companies. To cope with the 10% cut in milk production Milk Marque, the British dairy co-operative, invoked an emergency clause in August 1995 to reduce its supply to dairies to about 3% below the contracted volumes. Dairy Crest closed its Davistow cheddar factory for at least a month to divert the milk supply to the company's fresh milk diaries.

“Dairy farmers are urged to check milk protein levels as hot weather drives down feed intake of cows. [...] Not only are cows eating less in the heat, but herbage available is becoming stemmy and less digestible. Quality has fallen because grass is maturing so quickly” 'Protein warning as heat clobber cow appetites, Farmers Weekly, 4 Aug 1995, vol 123 (5), p 37'

_{Extracts from the Historic droughts inventory of references from agricultural media 1975 to 2012}

Both voluntary and compulsory restrictions to irrigation abstraction applied in many regions. Threats of severe water shortages for irrigating crops were forcing potato and carrot growers to consider switching from rain guns to more water-efficient trickle irrigation systems. In the summer of 1996, voluntary restrictions were agreed between farmers and the EA, plus mandatory restrictions and total bans were imposed in the most affected areas. Voluntary restrictions rose by nearly 40% in two weeks in July 1996. Again in April 1997, restrictions were imposed on farmers in the West Midlands and East Anglia as they faced the driest conditions in 200 years. BAWAG (the Broadland Agricultural Water Abstraction Group) was formed in 1997 in the wake of this severe drought to represent 170 abstractors in two CAMS areas.

“Like many growers, his 60ha crop of Nadine potatoes has now stopped growing, yielding about 40 t/ha compared with an anticipated 64 t/ha. Much of this shortfall is being made good by the rapid increase in prices. In the past 10 days, the value of his crop, sold to wholesalers in Birmingham, has risen from £110/t to £212/t delivered”. 'Potato consensus: Rain would be too late now, Farmers Weekly, 18 Aug 1995, vol 123 (7), p 19'

_{Extracts from the Historic droughts inventory of references from agricultural media 1975 to 2012}

During the summer of the year 1995, Parliament debated the adoption of the Environment Act 1995. This Act led to a series of changes in the regulatory framework for drought. The most important of these was the establishment of the Environment Agency, whose powers include issuing drought permits. More generally, the debate about drought management focuses on environmental impact and conservation. Droughts now start to be considered as an environmental problem rather than an unforeseeable natural phenomenon. While the regulatory changes were clearly connected to droughts, it appears that MPs discussed drought in abstract terns, rather than drew a connection to the specific drought experienced in 1995. Discussion about the need for infrastructure investment, including in the pipe network in order to reduce leakage is, however, linked to the drought experienced in Yorkshire between the summer and winter of 1995.