Archive Project News
WATCH Technical Report Number 56 - Executive summary of the completed WATCH project The WATCH (Water and Global Change) project is a European Union funded project to improve our understanding of the terrestrial water cycle. It has brought together scientists from 25 European research Institutions (as well as others from America and Japan) from many disciplines - hydrology, climate, water resources, remote sensing etc) to achieve this common goal. This document provides a summary of the objectives, results and achievements of this project spanning the full of the project (2007-2011).
WATCH Secretary, December 05, 2011
Researchers provide extensive analysis of the world's water cycle The final report of the Water and Global Change programme (WATCH), an extensive analysis of the world’s water resources, is made available on October 13, 2011, significantly expanding our understanding of climate change and land use impacts on the global hydrological cycle.
EU WATCH Secretary / NERC - Centre for Ecology & Hydrology, October 13, 2011
WATCH Technical Report Number 53: Flood studies at the river basin scale: case study of the Thames at Kingston (UK) The Thames catchment in Southern England was used as a test basin for modelling and testing of high flow extremes and floods. The river basin hydrological model used was CLASSIC (Crooks and Naden, 2007), which is applied on a grid-square framework. CLASSIC was run using local data (observed rainfall and MORECS potential evaporation) and Watch Forcing Data (WFD) for 1961 to 2001 and the impacts on simulated flow of using different sets of input data were assessed. Analyses of discharge data for the Thames from three global hydrological models were compared with those from the River Basin Hydrology Models.
S.M. Crooks, August 18, 2011
WATCH Technical Report Number 51: Global-Scale Detection and Attribution Results Regarding the Hydrological Cycle The research picture for global-scale detection and attribution of changes in the hydrological cycle has moved on since the design of the WATCH project, and we have adapted our work accordingly. A recent study showed some evidence of a detectable signal of human influence on global precipitation, but the evidence was clearly rather weak, and the study acknowledged concerns about the long-term stability of the observation-based datasets used and the quality of the CMIP-3 (third Coupled Model Intercomparison Project) generation climate models as tools for simulating precipitation signals. A particular problem with the latter is the simulation of precipitation features in the wrong location, which we have attempted to address using a novel approach that adapts techniques from neuro-imaging. This shows considerable promise and we hope to make an important contribution to the Intergovernmental Panel on Climate Change (IPCC) 5th Assessment Report with CMIP-5 models when they become available.
A simple thermodynamic framework was investigated for assessing the change in regional flood risk under global surface warming attributable to anthropogenic greenhouse emissions. We present results for flood risk in England and Wales during the record-wet autumn of 2000.
Pardeep Pall, Jara Imbers, William Ingram, & Myles Allen, August 01, 2011
WATCH Technical Report Number 48: Space-time characteristics of large-scale droughts in Europe derived from streamflow observations and WATCH multi-model simulations This report presents a detailed analysis of major historical droughts in Europe in the last part of the 20th century using novel methods for drought characterization that account for spatial extent and severity. The analyses were based on observed streamflow as well as runoff simulated by the WATCH multi-model ensemble comprising nine large-scale models. The ensemble median of the models was found to perform better than the ensemble mean when comparing two benchmark indices against observed streamflow for nine different anomaly levels. Based on the ensemble median and the 20% threshold from the empirical distribution (non-exceedance frequency), two extended drought periods (40% or more of the grid cells in drought) were identified, namely the autumn 1975 to late summer 1976, and spring and summer of 1990. A detailed spatial and temporal analysis revealed major differences in the drought development of the two events (build-up, consolidation and recovery phase), and in the models’ ability to reproduce their behaviour. The occurrence of larger and longer drought events agreed largely among models, however, the spatial coverage and variability within the drought affected area varied considerably. In the last part of the report a comparison of various methods for deriving Severity-Area-Frequency (SAF) curves for different return periods is made, suggesting that the drought clustering method performs better than methods that do not account for spatial continuity.
Tallaksen, L., Stahl, K. & Wong, G., September 02, 2011
WATCH Technical Report Number 47: Climate change and irrigation: feedbacks and impacts This report summarises work done in WATCH's Work Block 3 on the effects of human activities on climate and the water balance and, vice versa, on climate impacts upon human water withdrawal. It includes three (preliminary) studies concerned with 1) impacts of potential future irrigation on regional climate (in southern Asia); 2) impacts of 21st century climate change on irrigation requirements globally; and 3) effects of dams on global river discharge.
Dieter Gerten, Stefan Hagemann, Hester Biemans, Fahad Saeed, Markus Konzmann, July 31, 2011
WATCH Technical Report Number 43: Drought at the global scale in the 21st Century This study has explored differences in drought in total runoff (surface runoff and subsurface runoff) at the global and the continental scale between seven different large-scale models (global hydrological models and land surface models). First drought characteristics (number of droughts and average drought duration) were investigated for the control period (1971-2000). Droughts derived from the large-scale models forced with WATCH Forcing Data (WFD, re-analysis dataset) and downscaled, bias-corrected climate output from three different GCMs (CNRM, ECHAM and IPSL) were intercompared. Next droughts for the 21st century (2021-2050 and 2071-2100) were explored to investigate different climate change, i.e. drought characteristics derived from large-scale models that were forced with climate output from the three GCMs for two emission scenarios (A2 and B1). The number and spatial distribution of drought events, and average drought duration do not clearly show a consistent change (increase or decrease) among the models due to variation of number of arid cells (cells with zero flow) that are found in the different simulation periods (control, mid and late 21st century). After the introduction of an equivalent drought measure, to remove arid cells, it seems that the large-scale models have relatively similar statistical values and therefore similar statistical properties for the WFD and GCM climate output. An increase in number of drought events was identified over the 21st century.
Gerald A. Corzo Perez, Henny A.J. van Lanen, Nathalie Bertrand, Cui Chen, Douglas Clark, Sonja Folwell, Simon N. Gosling, Naota Hanasaki, Jens Heinke & Frank Voβ, August 25, 2011
WATCH Technical Report Number 42: Drought at the global scale for the 2nd part of the 20th Century (1963-2001) Simulated gridded time series from ten different large-scale models, both GHMs and LSMs, are used to investigate to what extent these large-scale models capture historic hydrological drought events. Monthly aggregated total runoff values were used to determine hydrological drought events with different methods developed to identify spatio-temporal drought characteristics. For each continent one documented major drought event was selected and described in detail. It can be concluded that most major drought events are captured by the models, but the spatial extent of the drought events differ substantially between the models.
Van Huijgevoort, M.H.J., Hazenberg, P. van Lanen, H.A.J., Bertrand, N., Clark, D., Folwell, S., Gomes, S., Gosling, S., Hanasaki, N., Heinke, J. & Koirala, S., Stacke, T. & Voβ, F., July 27, 2011
WATCH Technical Report Number 41: High flow in the 21st Century: analysis with a simple conceptual hydrological models using the input of 3 GCMs (A2 scenario) In this study a conceptual hydrological model was applied, which was forced with the outcome from three GCMs (ECHAM, CNRM, IPSL) for the A2 scenario in the 21st century. The Q10 (streamflow that is equalled or exceeded in 10% of the time) was used a high flow metric. It was calculated for 1495 selected land points that are well distributed across the globe, which adequately represent the Köppen-Geiger major climate regions. The hydrological model was run for a soil with an intermediate soil water supply capacity and an intermediary responding groundwater system. First, high flows obtained with the hydrological model using the three GCMs were checked against those got from the re-analysis dataset (WATCH Forcing Data) for the control period (CTRL, 1970-2000). The median Q10s derived from the GCMs for the CTRL period differ at least tens of per cent from the Q10 obtained when using WFD as input for the hydrological model (i.e. about 30-60%). The differences for the arid and polar (B- and E-) climates are even higher (about 100% or more). The impact of climate change (median of Q10) is projected to increase over the 21st century according to all three GCMs for the C-, D- and E-climates. This is also expected for the A- and B-climates according to ECHAM and CNRM. IPSL provides for these two Köppen-Geiger major climate regions a more diffuse projection.
Van Lanen, H.A.J. & Wanders, N., August 25, 2011