Rising greenhouse gas levels and temperatures are intensifying the global hydrological cycle, with an overall net increase of rainfall, runoff and evapotranspiration, and will increasingly do so. Regionally predictions of future rainfall are fairly uncertain though clearer trends are emerging. Currently there are indications that the Mediterranean region will undergo reductions of rainfall and some equatorial regions such as India and the Sahel will see increases. The seasonality may also change, causing new and sometimes unexpected vulnerabilities. One example could be an increase in extremes of floods and droughts. There are also suggestions that inter-annual variability will increase leading to more droughts and large-scale flooding events. These cycles are global phenomena which will impact different regions simultaneously (although often in different ways). Therefore water cycle monitoring becomes a challenging need. Understanding the water cycle and how it will be modified by climate change will provide estimates of future events and will require action to prevent or mitigate them.
Building on previous geomatic monitoring of water resources, the project provides a better understanding of the drivers acting on the global water cycle. It has assessed and quantified the components of the past, present and future water resources, evaluated the uncertainties thereby identifying the overall vulnerability of global water resources related to the main societal and economic sectors. With a consortium including 25 EU partners, involvement of institutions from Japan and USA, and 110 scientists taking part, the project was funded under FP6 and coordinated by the Centre for Ecology & Hydrology (United Kingdom). Final results were made available in 2011.
The project’s main outcomes consist of (i) knowledge obtained from an assessment of the global water cycle on a daily time frame for the 20th and 21st Century, (ii) data products, (iii) methodology and (iv) model extrapolation produced within the project. In more details, these are -:
(i) Knowledge: The knowledge produced within WATCH focuses on water cycle at a global level. It also focuses on extreme floods and droughts at EU level.
(ii) Dataset: The first action line of the project. It includes global meteorological data and modeled river flow for the whole past century (and predictions for the next) into a single unified validated format. Through appropriate data analysing methods, the dataset should ultimately allow estimates of future changes on the water cycle.
(iii) Methodology WaterMIP: Developed within the Water Model Intercomparison Project, this exercise employed 12 different water cycle models and developed the WaterMIP methodology whose application allows direct comparison of the indicators of the different models.
(iv) Model extrapolation: The consortium conducted a test case with real observations to demonstrate that data from large scale models (50x50 km) are suitable to be extrapolated to a smaller scale (10x10 km) when there is no real data available at this level.
The project was completed in July 2011, but results are still being released and the coordinator continuously works on disseminating these. The outcomes focus on increasing the knowledge and making it available to the scientific community, researchers and water managers. In this context, the Technology Readiness Level is estimated at 3 on the TRL scale. The dataset can freely be used by anyone working on the water cycle with non-profit purposes: projects addressing carbon studies, recycling, river basin studies, etc. Moreover, policy makers could be interested by the computation results coming from the dataset. Changes in water availability, water vulnerability, floods and droughts, could potentially be predicted through the appropriate scientific analysis of these data. Based on these potential predictions, policy makers could carry out strategic planning actions to minimize the impact of future changes on local water cycle.