Philippines Groundwater Outlook (PhiGO) Half of the world's cities with populations above 100,000 are located within water basins where over half of the available water supply is depleted for part of the year. These water-stressed cities are finding it extremely difficult and expensive to secure the additional water supplies needed to support their growth. Water security is of particular concern for Filipino cities, which have been designated amongst the worst in Asia for urban water security. Changing climate and increasing urban population density will put more stress on their water resources. Current projections of climate up to 2050 suggest the Philippines will become warmer, with increasing temperature and decreasing rainfall during the dry season and more extreme rainfall events during the wet season. This will undoubtedly exacerbate both water availability during periods of drought and the magnitude of flood events during periods of heavy rainfall. This susceptibility has led to the Philippines being consistently ranked near the top of countries most at risk to climate change. In addition to water stresses from a changing climate, population is expected to increase by ~50% up to 2050, with urban population set to double over the same period. This will further exacerbate pressures on future water resources.  The influence of climate and population change will have an acute impact on groundwater, which currently supplies more than 50% of the potable water supply and 85% of the piped water supply in the Philippines. Groundwater is strategically and economically important to current and future water supply and is the principle source of dry season river flows, which in turn are often used for potable supply. Despite the high reliance on groundwater resources, reasonable coverage of groundwater datasets and several regional-level groundwater management plans, there has been little in the way of real-time monitoring, routine monthly forecasting or impact assessment of climate and population stressors. Through a programme of data gathering, knowledge exchange, fieldwork, numerical modelling and stakeholder engagement the Philippines Groundwater Outlook (PhiGO) project seeks to undertake assessments of population and climate change impacts on regional groundwater resources and translate these into usable forecasts of flood and drought risk. There are two distinct timeframes at which uptake and potential benefits of the project will be realised. Short term, seasonal-scale forecasts will aid in reactive preparedness, whilst long term, decadal-scale forecasts can be used to take proactive steps towards reducing the future physical and economic impacts of extreme hydrometeorological events. To better understand the potential socio-economic impacts of groundwater level extremes and potential water management strategies, PhiGO is also focussed on quantifying the cascading impacts of flood and drought through key infrastructure and analysing the cost-benefit of differing water management and urban planning scenarios. The Newton Fund builds research and innovation partnerships with developing countries across the world to promote the economic development and social welfare of the partner countries.