Water vanishes underground and arrives all at once
Brazilian aquifers went years without recharge, Chiba endured its heaviest daily rain since at least 1976, and Hawaii prepared for hurricane rainfall and surge. Slow depletion and sudden deluge expose different clocks of climate risk.
Science··Night
A deficit accumulating in aquifers
Across a broad part of Brazil, the water hazard accumulated slowly through years of inadequate aquifer recharge. Augusto Getirana of NASA Goddard and colleagues combined 398 monitoring wells with gravity-satellite data and geology to reconstruct monthly groundwater from 2002 to 2023. At roughly 10 km resolution, the work covers portions of the São Francisco, Paraná, Southeast Atlantic and East Atlantic basins totalling 1.97 million square kilometres. Severe and persistent losses extend across about 23 per cent of the country’s land area. Getirana attributes the underlying deficit to climate and says extraction and land-use change probably amplify it, while the study does not assign the loss to individual pressures. The study appeared in Science Advances on June 3. The effects do not stay underground. Groundwater supplies 55 per cent of Brazil’s water, and hydropower provides 60 per cent of its electricity. That link carries slow underground change into the country’s daily infrastructure needs. Longer, harsher droughts can therefore exert a slow pressure that travels from wells to rivers and onward to power generation.[1]
Rainfall compressed into 12 hours in Chiba
Chiba experienced a fast-moving water hazard. The prefecture east of Tokyo received 367 millimetres of rain in one day, its highest daily total since at least 1976. Of that amount, 348 millimetres fell in only 12 hours, reaching about three times the region’s usual rainfall for the entire month of August. At least 8 people died, travellers were stranded at Narita and tens of thousands of homes lost power. The Japan Meteorological Agency issued its highest-level heavy-rain warning for the region for the first time. In the weather pattern described by the agency, humid air moving north from southern Japan met a cold mass at roughly the 6,000 metre level above Honshu and destabilized the atmosphere. Kai Chen of the Yale Center on Climate Change and Health notes that warmer air can hold more moisture, raising the ceiling for downpours of this kind. The damage in Chiba shows why the speed at which water arrives can matter as much to infrastructure and health as an annual total.[2]
Preparing in Hawaii before landfall
In Hawaii, the danger had not yet moved beyond the forecast as Tropical Storm Lala strengthened. With winds reaching 137 kilometres an hour, the storm was expected to reach the Big Island on Saturday; a hurricane warning covered Hawaii County, with tropical-storm warnings for Maui, Molokai and Kahoolawe. Forecasters expected about 30 centimetres of rain across Maui and the Big Island, reaching 64 centimetres in places, along with a storm surge of 0.3 to 0.9 metres. Rough conditions were expected to continue into Sunday. NOAA also calculates a 69 per cent chance that the developing El Nino could exceed every event since 1950 when it peaks from October to December; El Nino conditions tend to encourage hurricanes in the Pacific and damp them in the Atlantic. That probability describes the developing ocean pattern, while the warnings describe Lala’s near-term track. Brazil’s years-long deficit, Chiba’s 12-hour deluge and Hawaii’s preparation over several days show how water hazards open very different response windows for public authorities.[3], [1], [2]
