"It's a resource with a huge amount of potential," said Jude Cobbing, who led a new study for charities WaterAid, Earthwatch and WWF on how groundwater is managed in India, Bangladesh, Nepal, Nigeria and Ghana. Little is understood about how much groundwater is available, particularly at local level, and poor organisation between government agencies can mean it does not reach people effectively, said the independent water governance expert. "We value what we can see, not what we can't," he said. This can lead to "hydro-schizophrenia" among government officials and water planners, who often put a greater focus on managing visible surface water, he noted. Groundwater makes up about 30% of the planet's freshwater - nearly all that is not locked up in ice, scientists estimate. By comparison, surface sources - lakes, rivers, wetlands, soil, plants and the atmosphere - account for just 0.4% of global freshwater. The drying of underground aquifers due to excessive pumping is a well-known problem in some parts of the world, including the western United States and northern China, Cobbing said. But in some places - particularly sub-Saharan Africa - huge supplies of groundwater remain almost untapped and could help support communities hit by drought linked to climate change and other problems, the report said. In others, where groundwater is scarcer, it needs to be managed carefully so that it does not deplete, the study said. Globally, only about 8% of the groundwater that is available and could be replaced annually through natural recharge is pumped each year, the report said. Broader and smarter use of that water, where available, could help countries achieve a global goal to ensure everyone has sustainable access to water and sanitation by 2030, it said. Already, worsening drought and surface water shortages are driving a new focus on extracting groundwater, the report noted. The Southern African Development Community has set up an institute that is producing guidance on operating and maintaining groundwater extraction systems in the drought-hit region, said Cobbing, a hydrologist. The African Union also has a continent-wide body analysing groundwater and seeking to coordinate its use between member states, as well as integrating surface and groundwater management. Among countries, Sudan has a national groundwater ministry and Botswana has similarly made groundwater a growing priority, Cobbing noted. "Drought tends to concentrate minds," he said. But with responsibility for water falling across a range of government departments - including agriculture, public health, environment and industry - coordinating groundwater policies and use can be a challenge. SAFE WATER Keeping safe groundwater flowing through pumps in rural Bangladesh, for instance, requires everything from ensuring a reliable power supply to treating the often arsenic-laced water, Cobbing said. Bangladesh, a leader in climate change adaptation, has made big strides in dealing with many climate risks - but treating arsenic contamination, a public health threat that about affects 35 million people, has been a challenge for decades, he added. Filtering systems to tackle the problem are available, but getting them in place in remote regions with little political clout has proved a struggle, he said. "It's still thought of as a tech problem but it's actually an institutional and governance problem," he said. India, meanwhile, has a "relatively sophisticated" national groundwater management system, which produces annual figures on availability and quality, and coordinates efforts to recharge groundwater sources, the researcher said. But its national-level planning does not always filter down to the state and local level and what happens on the ground to track and manage water, he said. In Nepal and Nigeria, water records are often kept on paper or in digital formats that are hard to share and can leave governments "blindly making policies that are ill-informed", the report said. Without the right knowledge, governments might build roads or other infrastructure through spring-rich areas that recharge groundwater supplies or site a dump where it could pollute groundwater, the report said. And in places where groundwater is less abundant, ministries allocating it to farmers or industry - without considering other users - could lead to over-pumping and shortages. "Unless groundwater is protected, many communities risk not having enough water for their basic needs in the future, particularly as surface water sources may be altered through climate change," the report warned. Vincent Casey, a water security expert with WaterAid, said "the clock is ticking" on managing groundwater more effectively. "If efforts are not made to better understand, value and protect this vital resource, making it a central feature of climate change adaptation strategies, then we face a very bleak future," he predicted.