Parris N. Glendening (D) yesterday declared Maryland’s first statewide drought emergency in history and said mandatory water conservation measures probably will be imposed as soon as next week. In the meantime, the state has suggested that residents take shorter showers, not wash cars, and not bother to water the lawn or flower beds. Glendening, speaking near the reservoirs that serve the Baltimore area: “If water consumption continues at the current rate, there is only a 35-day supply in these reservoirs.”