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Title: The impact of climate change on severe droughts: River-flow reconstructions and implied groundwater levels
Author: P.D. Jones
Author: A. Leadbetter
Author: T.J. Osborn
Author: J.P. Bloomfield
Author: Environment Agency
Document Type: Monograph
Annotation: Environment Agency Project ID:EAPRJOUT_1508, Representation ID: 526, Object ID: 2655
Rainfall records for Eden and Ely Ouse catchments have been extended back on a monthly basis to 1800. Many of the records are not listed in the Met Office archives, but are available in the 10-year books held at the Met Office. An essential part of this work is to assess these long records for homogeneity. Monthly average river flows on the catchments were then extended back to this date, using a statistically based rainfall-runoff model, which has been used in a number of earlier studies. This model uses pre-determined equations that relate monthly rainfall totals to runoff, incorporating lags of up to 3 months for the Eden and 18 months for the Ely Ouse. Earlier work has shown that the model reproduces over 90 per cent of the variance of the monthly flows. The extended sets of flow records were assessed for the lowest flow sequences of 6 months duration on the Eden catchments and 18 months for the Ely Ouse. On the Eden, three of the four most severe drought periods (according to this definition) occurred within the instrumental gauging period (since the early 1960s). The three droughts were in 1989, 1995 and 1996. The second most severe drought since 1800 was estimated to have occurred in 1826. A number of other, but less severe, drought episodes also occurred prior to the instrumental period. On the Ely Ouse catchment, the most severe drought was in 1803, with a number of other droughts prior to instrumental gauging on the catchment (which began in the late 1920s). Five of the worst 12 droughts occurred in the instrumental period. The long series have been used, in an analogue approach, to develop daily series for 204 years for all intake points on the respective water resource systems in the two regions. These longer sequences will be used with reservoir and other water resource systems to reassess reliable yields in a later part of the study. Groundwater level records, like runoff records, are also relatively short in most regions of England and Wales. Using annual minimum groundwater-level data for the past 30-50 years, regression models have been developed based on monthly rainfall and temperature records for two sites. The different integrating nature of the system means that the lowest levels are only loosely related to the lowest reconstructed flows.
Publisher: Environment Agency
Subject Keywords: RiversCatchment basinsDroughtGroundwaterWater levels
Geographic Keywords: Eden (river, Cumbria)Ouse (Yorkshire)
Extent: 59
Total file downloads: 263

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