Figure 7. The Mildred Island tidal excursions are short, a maximum of 1 mile, because of (1) the weak tidal energy in this part of the Delta and (2) a narrow (25 yard) opening. Franks Tract and Sherman Lake, for example, have multiple openings. Because of the overall minimal exchange into Mildred Island, the tidal excursions between spring (B) and neap (A) are not as pronounced as they are in Franks Tract.