WATExR: Seasonal climate predictions and ecosystem impact modeling for improved water resources management under climate change

Seasonal forecasting of water quantity, quality and ecology has great potential to support water management, given reliable-enough predictions. Clean, healthy freshwaters are vital, for example for drinking water, healthy fish stocks and recreation. However, many rivers and lakes are under intense pressure from human activities. Poor water quality is common and is exacerbated by unexpected wet, dry or warm seasons. Freshwater management is therefore highly challenging. If management decisions could be based on advance warning of likely conditions over the coming months, there could be great economic, ecological and societal benefits. This was the focus of the WATExR project, which developed and explored the value of seasonal forecasting tools for freshwater management. Firstly, researchers and water managers co-developed state-of-the-art forecasting tools, linking seasonal climate forecasts and freshwater ecosystem impact models to predict how river, lake and reservoir conditions will evolve a season in advance. Tools were developed at five pilot case study sites, four in Europe and one in Australia. In Norway, we focused on Lake Vansjø, an important drinking water source and recreational area which suffers from high nutrient inputs and toxic algal blooms. The new forecasting tools were then tested at each site, to see how useful they were for supporting practical decision making. To do this, researchers issued hindcast bulletins, i.e. water quality forecasts for past seasons, generated using historic seasonal climate forecasts. These historic forecasts were compared to observed historic events to evaluate forecast reliability and performance. Stakeholders then provided feedback on whether forecasts were thought to be providing useful and trustworthy information to help avoid harmful climate impacts a season in advance. Additional hindcast experiments were then carried out to look more closely at the sources of forecasting skill, to help understand when and where seasonal forecasting can most usefully be carried out, as a pointer for future development of seasonal forecasting systems. Researchers and stakeholders both agreed that seasonal forecasting is challenging, a key barrier being the unreliability of the seasonal climate model forecasts used as input to the freshwater forecasting tools. However, at each site we found a number of ?windows of opportunity?, i.e. seasons or events which could be forecasted well. Stakeholders were generally excited about these, as even small glimpses into the future were thought to be very useful. The co-development process in itself was also of great value, strengthening communication and understanding between researchers and water managers. Overall, promising results at the pilot study sites suggest there is potential for seasonal forecasting to support water management more widely in Norway and Europe, especially after further improvement to seasonal climate models.

WATExR developed novel seasonal forecasting tools for water quality and assessed the value of tools for supporting water management. All underlying data and code are open source and publicly available, and have been disseminated to the research community via scientific journals and conferences, and to water managers through meetings and workshops, a webinar, videos and websites. Expected longer-term project outcomes and impacts include: (1) increased focus on seasonal forecasting for water quality management by the research community; (2) increased international research collaboration, with a focus on seasonal forecasting; (3) within Norway, additional pilot studies focused on the value of seasonal forecasting to support a range of sectors; (4) application of research results (water forecasting tools) by water managers involved in the project.

WATExR aims to integrate state-of-the-art seasonal climate predictions and water quality simulations, to enable efficient decision making and adaptation of water resources management to an increasing frequency of climate extreme events (CEE). To do this, WATExR will co-develop standardized tools tailored to end-user demands in seven representative catchments across Europe, which cover a wide range of water management issues affected by CEE, including recreation, fisheries, drinking water supply, and the implementation of the EU Water Framework Directive. In each case study, WATExR will build an original, standardized modelling workflow system programmed as a QGIS plug-in. WATExR will assess the potential of the new tools for improving mid-term decision making in the water quality sector when facing CEE and for defining adaptation strategies to future increases in CEE. WATExR will integrate climate and impact models in two complementary ways: 1. State-of-the-art seasonal climate prediction products will be tailored to the different case studies and impact models, and the whole modelling chain will be integrated through a QGIS plug-in. 2. WATExR will contribute to a wider assessment of the impacts of an increase in frequency of CEE in the future by defining a new sector of impact models related to water quality in ISIMIP2. All these activities will be framed within a co-development workflow to guarantee user adoption of the new tools. Thus, WATExR integrates across the whole chain of CS development from research to feedback from users.