Information is presented on the frequency, duration, and spatial pattern of spring flooding, as well as on the hydrologic processes and mechanisms which control lake levels from break-up to freeze-up. This information is used to interpret the hydrological regime of three lake types found in the delta with respect to spring flood recharge, rapid spring drainage, and summer lake evaporation. Two characteristics are shared by all the lakes: the spring flood is the dominant hydrologic event, and evaporation is greater than summer precipitation and is similar to or greater in amount to annual precipitation. Each lake type also has its own particular combination of processes and mechanisms which controls the water level. Some lakes, however, are more sensitive to summer evaporation losses than others, causing them to have a negative annual water balance until flooding occurs. -from Author