Quantifying and tracking drought and intermittence patterns in the East Chilterns

Sefton, Catherine ORCID:; Parry, Simon ORCID:; Eastman, Michael ORCID:; England, Judy ORCID:; Angell, Geoffrey; Ross, Rebecca. 2019 Quantifying and tracking drought and intermittence patterns in the East Chilterns. Wallingford, Natural Environment Research Council, 38pp. (Issue No. 3, CEH Project no. C06283/2)

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Intermittent rivers and ephemeral streams (IRES) are hydrologically dynamic and ecologically diverse, under pressure from water resources and climate change, but underrepresented in protective legislation and monitoring programmes. The Springs and Sources dataset of Herts and North London Area is an internationally rare dataset of observations along intermittent rivers that has good resolution in hydrological state (flowing, ponded, dry), time (approx. monthly) and space (between 18 and 32 sites per river). The results delivered by this collaboration were threefold. Firstly, the development of the current water situation on the chalk streams of the East Chilterns was tracked throughout the project. There was a marked lack of network expansion through the winter months in comparison with expected long term average recovery (March 2004 – March 2019). The proportion of dry reach in March 2019 was comparable with that of March 2006, most notably on the groundwater-dominated rivers (Misbourne, Chess, Bulbourne, Gade, Ver and Mimram). Secondly, metrics have been provided that quantify the long term temporal availability of flowing, ponded and dry states at biological sampling sites to facilitate hydroecological assessment. Further metrics, quantifying the consecutive months of flow preceding a biological sample, and the distance from the site to flowing water in connectivity with the perennial reach have also been provided. Thirdly, visualisations have been designed for characterising IRES and communicating their behaviour with a view to future facilitation of assessing their response to climatic and artificial drivers. Heat maps using an extracted monthly dataset show the annual pattern of summer contraction and winter expansion on groundwater-dominated rivers such as the Chess, Bulbourne and the Gade and the greater frequency of flowing state along the whole survey length apparent on flashier rivers, such as the Rib and the Stort. Long term permanence is presented in graphical and map form revealing local augmentations and losing reaches. Challenges to the work highlight the need to infill gaps in the data. The accuracy of the statistical modelling techniques investigated was high for flowing and dry states, but limited for ponding, probably due to the small availability and the diversity of ponding observations on which to train the model. Further modelling work is recommended to infill the gaps, and explore the research potential and operational application of this rare and valuable dataset. Its value was highlighted by the launch, in April 2019, of a citizen science initiative ( to collate similar data across Europe.

Item Type: Publication - Report (Project Report)
UKCEH and CEH Sections/Science Areas: Rees (from October 2014)
Additional Pages: 5 appendices
Funders/Sponsors: Environment Agency
Additional Information. Not used in RCUK Gateway to Research.: The Environment Agency, who funded this work, would like it to be openly available, and it’s OK with us, now that we have published a paper of the research - message from Cath Selfton 22.11.22
Additional Keywords: ephemeral streams, intermittent rivers, ponding, intermittence mapping
NORA Subject Terms: Hydrology
Date made live: 06 Sep 2022 12:49 +0 (UTC)

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