The latest Sierra snowpack survey shows a slight improvement after recent storms. Jack Pardee of the California Cooperative Snow Survey said runoff from the Kings and San Joaquin rivers is now expected to be 41% to 43% of normal, compared to an April 1 survey indicating 39%. Nevertheless, Pardee said, the overall water supply outlook for this year "is still pretty grim." Meanwhile, the City Hall fountain was shut off as San Francisco's first water-rationing program in more than a decade got under way. All ornamental fountains will be dry during the city's mandatory program aimed at forcing a 25% cutback in water usage. Restaurants started serving water only on request. Residents bought shower flow-control units, cut back on garden watering and put bricks in their toilet tanks. Water customers will be notified May 15 of how much water they will be allowed, based on their 1987 usage.