The Indonesian capital has 300 days of rain a year and 13 rivers running through it, so it doesn’t lack freshwater; but rampant development has left much of its area paved over, preventing this water from replenishing the aquifers.Instead, the water it gets — from rain and from rivers — often leads to flooding because it can’t be absorbed into the ground and can’t run out to sea.City authorities and planning experts agree that the extraction of water from the aquifers must end, but to do so will require providing universal access to clean water.Efforts are underway to clean up waterways, educate the public to not dump waste in rivers, and build infiltration wells that will allow the earth to once again capture rainwater. JAKARTA — The Waladuna mosque is submerged in a meter of seawater, about 3 feet deep. It’s low tide in northern Jakarta. During high tide, the water creeps up to the moss- and seaweed-covered roof of the abandoned mosque, a building that has become a symbol of Jakarta’s direst problem. Children play on top of the 4-meter (13-foot) concrete barrier that was built next to the mosque to temporarily halt the advance of the Java Sea. A man fishes from a pile of rocks next to the inundated building, which dates back to the 1980s, when sea levels were much lower. Scattered nearby are the concrete skeletons of abandoned warehouses and fish factories, long since shut down and a reminder of both a thriving past and a not-so-bright future. Jakarta is sinking. And it’s doing so at a rate faster than any of the world’s megacities — from 1 centimeter (about half an inch) a year in some areas, up to 20 cm (8 in) in the worst-affected areas, like here in northern Jakarta. Rising sea levels pose a threat to many coastal cities around the world, with climate change the driving force in most of these cases — from Dhaka and Bangkok in Asia, to Alexandria and Lagos in Africa, to Houston and New Orleans in the U.S. Late last year, exceptionally high tides caused severe flooding in Venice. Forty percent of Jakarta is already below sea level, but the main reason why the city is sinking is not climate change. Instead, it’s a thirst for clean water. Less than half of the city’s population has access to piped water, leading to a proliferation of wells and pumps, often installed illegally. Over the decades, they’ve depleted the aquifers beneath the city, leading to land subsidence.