Louisiana’s governor declared a state of emergency in New Orleans on Thursday as the city’s malfunctioning water-pumping system and the threat of more rain left some neighborhoods at greater risk of flooding. The city scrambled to repair fire-damaged equipment at a power plant and shore up its drainage system less than a week after a flash flood from torrential rain overwhelmed the city’s pumping system and inundated many neighborhoods. Gov. John Bel Edwards described his emergency declaration as a precautionary measure. He and Mayor Mitch Landrieu tried to calm the jangled nerves of residents still angry about the city’s response to last weekend’s flooding.