Damming and water diversions along the Colorado River over the course of the last century have dramatically altered the downstream delta ecosystem. While it is clear that ecological change has occurred, very few data from the pre-dam era (before 1930) exist. Thanks to the preservability of molluscan shells, we can retrospectively establish baseline conditions for the benthic community. Using data from the living, recently dead (10s y.o.), and long-dead (100s-1000s y.o.) molluscan community in the delta, we are establishing a baseline and studying the ecological implications of the extensive water diversions along the Colorado River. With these data, my collaborators and I are also assessing the impacts of recent environmental flows on the molluscan community. If all goes according to plan, we will return to the delta in November 2016 to collect data on the response of the molluscan community (or lack thereof) to the environmental flows.