A drought emergency will affect more than 7 million people in Pennsylvania, New York, New Jersey and Delaware if reservoirs do not fill, the Delaware River Basin Commission warned. Commissioners from the four states agreed that mandatory conservation measures aimed at reducing water use by 15% should take effect if levels in the upper basin reservoirs drop to the emergency storage zone and remain there for five days. A New York City official said reservoirs for that city could cross the emergency line this week. Normally at the start of spring the reservoirs should have about 250 billion gallons. Instead, after a winter of very light snowfall, they hold about 129 billion gallons.