Hydrological extremes and feedbacks in the changing water cycle

Lead Research Organisation: British Geological Survey
Department Name: Groundwater


The prospect of significant climate change over the next decades means that society must urgently face up to the implications for the changing water cycle, in particular increasing risks from extreme floods and droughts. Guidance for policy-makers to support adaptation to these risks and to support mitigation strategies to combat climate change is urgently required. However, the ability of climate scientists and hydrologists to predict the possible magnitudes of floods and droughts, and the frequency with which they are expected to occur, is still limited. This is due largely to gaps in knowledge of how best to use available data and models; of particular concern is the limited ability of climate and hydrological models to produce realistic extremes and changing hydrological behaviour. For example, regional climate models produce data which often requires to be downscaled to finer resolutions, but questions arise about what properties of the downscaled data are critical and how the downscaling should be done. As another example, drought planning requires inter-annual and inter-regional rainfall and evaporation to be represented accurately, however there is little guidance about how this can best be achieved under future climate using available models. In addition, there are weaknesses in the simulation of hydrology (for example, groundwater storage, river flows and evaporation) which act as hurdles to development of next generation climate models; in particular models currently used to simulate feedbacks from the earth surface to the atmosphere neglect important hydrological processes. This proposal will produce the science and models needed to address these questions, integrating climate and hydrological science to take impact modelling beyond the current state of the art. Specifically, the proposal: 1. exploits current generation climate science and statistical methods to improve and enhance projections of potential change in hydrologically-relevant metrics over a time-scale of 10 to 60 years, in particular extremes of heavy precipitation and drought; 2. builds on the analysis of historical data to improve scientific understanding and develop innovative methods for the modelling of extremes and non-stationarity in the hydrological response to climate variability; 3. seeks to improve the representation of hydrological processes in land surface models, in particular, the enhanced modelling of surface and subsurface processes for simulation of land-atmosphere feedbacks. In addressing these gaps in knowledge, the proposed project will cross all four themes of NERC's Changing Water Cycle programme: land-atmosphere interactions; precipitation modelling; understanding of change; and innovative ways to assess consequences. Case studies will include the Thames catchment and the Eden catchment. These catchments are broadly representative of lowland and upland UK with substantial climate and hydrological datasets from NERC and DEFRA-EA experimental programmes. This project will consider local to catchment scales, with the view that the resulting science and models will ultimately be integrated into global scale models. The main project outputs will be: 1) improved quantification of future variability and extremes of precipitation and evaporation over hydrologically relevant scales in the UK; 2) improved models of the hydrological water cycle response to these extremes, with the explicit inclusion of non-stationary conditions; 3) the inclusion of earth-atmosphere feedback processes and their effects in climate models, in particular the recognition and inclusion of unsaturated zone and groundwater storage and discharge. In all cases, new modelling tools will be developed to test the ideas of meteo-hydrological functioning.
Description We have developed a holistic understanding of how catchments work in terms of groundwater systems. The sub-surface element of the catchment is viewed as a whole rather than a series of disconnected aquifers. This has been developed and tested on both the River Thames and Eden catchments.
Exploitation Route The approach and models developed as part of HydEF can be used to explore water resources under extremes (floods and droughts) by the relevant decision-makers.
Sectors Education,Energy,Environment

URL http://www.bgs.ac.uk/changingwatercycle/hydef.html
Description BHS Conference (London) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact British Hydrological Society meeting on groundwater extremes. A poster was presented entitled *Developments in understanding and modelling extreme events from the atmosphere to the catchment* which summarised the main findings from the HydEF project and enabled the results to be disseminated to a wider audience.


Recent events such as the groundwater floods of winter 2000-01, 2012-13 and 2013-14, and the drought of 2010-
12 have demonstrated the need to improve our understanding of hydrological extremes. NERC has recognised this
need by funding research programmes like Flood Risk from Extreme Events (FREE), Changing Water Cycle (CWC)
and recently the Droughts and Water Scarcity Programme. These have enabled a body of research on hydrological
extremes, and in particular of groundwater events, to be undertaken. The FREE groundwater flooding project and
the CWC Hydrological Extremes and Feedbacks in the Changing Water Cycle (HydEF) projects are two such
HydEF is collaboration between Imperial College London, University College London, University of Reading and the
British Geological Survey, and aims to develop understanding and simulate of extreme hydrological behaviour by
considering processes across a range of scales: from the atmosphere to the abstraction borehole. The project has
developed methods to downscale the outputs from climate models to the basin or catchment scale. This includes
parameterisation of "atmospheric rivers", a phenomenon postulated as being responsible for the 2005 Carlisle
floods. The downscaled outputs from climate models are used to drive JULES, which provides the inputs to
groundwater models. A model of the Thames catchment has been developed, the Thames Integrated Model
(TIM). TIM can be used to study groundwater flooding, groundwater/surface water interactions or linked to
borehole-scale models to explore the impact of droughts. The current state of the research is outlined and its
application to understanding drought behaviour in abstraction sources is discussed.
Year(s) Of Engagement Activity 2013,2014
Description Planet Under Pressure - Poster 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Planet Under Pressure 2012 was the largest gathering of global change scientists leading up to the United Nations Conference on Sustainable Development (Rio+20) with a total of 3,018 delegates at the conference venue and over 3,500 that attended virtually via live webstreaming. The Plenary sessions and the Daily Planet news show continue to draw audiences world wide as they are available On Demand.

A poster "Towards the understanding, simulation and management of multi-aquifer basins: The Thames Basin, UK" was presented summarising the planned work to be undertaken on the Thames Basin for the HydEF project'
Year(s) Of Engagement Activity 2012
URL http://www.planetunderpressure2012.net/