A water shortage in Dhaka, the capital city of Bangladesh, has grown so severe that authorities have called in the army to distribute drinking water to the city’s residents. The shortage is fueled by 6 percent annual population growth, mushrooming housing complexes, and severe pollution of the nearby Buriganga River. Riverside industries dump hundreds of tons of waste and toxic chemicals directly into the water, making it unsuitable for human use — but as the city’s clean water supply runs short, some people have no choice but to drink from the river. Groundwater levels have been falling by six feet per year, largely because of pumping from deep wells for irrigation and other purposes. A surface water treatment plant scheduled to open next June could help matters, but it will only have a daily capacity of 59 million gallons of water, compared to the 420 million gallons needed each day by residents.