The Des Moines Water Works board on Tuesday approved a 10 percent increase in water rates for all customers effective April 1 to cover a revenue shortfall of more than $3 million. The shortfall comes as residents and businesses conserve more water and a wet and cool summer reduced sales, said Bill Stowe, the utility’s CEO and general manager. The revenue is needed to cover the costs of removing nitrate from river water, to cover legal fees associated with the utility’s federal nitrate-pollution lawsuit, and to install a pipe that will take wastes from the nitrate-removal plant to the Des Moines area sewage treatment plant. That would eventually end the practice of dumping the contaminants back into the river downstream, Stowe added. The sewage treatment project, if approved, would cost $2 million for pipe work, plus $250,000 a year for operations.     Read our previous story about the proposed increase on BusinessRecord.com.