Maureen A. Stapleton, general manager of the San Diego County Water Authority since 1995, is planning to retire, the agency said Wednesday. “The positive impact of Maureen’s leadership of the Water Authority and management of this region’s water supply cannot be overstated,” said Jim Madaffer, chair of the Water Authority’s Board of Directors. “She has also been an important leader in our civic affairs for three decades and has dedicated countless hours to the betterment of our entire region. She will be greatly missed.”