The first water bills since the Marin Municipal Water District’s historic rate increases are causing sticker shock for some residents. The county’s largest water supplier significantly overhauled its rates in July as it works to increase water supplies at a level not seen in decades and to recover financial losses from the recent drought. Prior to the rate increase, the district told ratepayers that the median single-family home would likely have a 20% increase in the bimonthly water bill during the first year of the four-year rate plan. But some residents state their September and October bills say otherwise.