Abstract: In this talk Dr. Monismith will discuss aspects of the (fascinating) long-running saga of environmental effects and regulation of freshwater flows passing through the Sacramento-San Joaquin Delta and entering into the magnificent San Francisco Bay. To frame the issues involved he will briefly review both major structural features of California's developed water resources and the shifting landscape of the ecology of the estuary. The key connection between these two is the observed multi-decadal declines of many fish species, both resident and anadromous, and most notably the (famous) endangered Delta Smelt. These declines have been attributed in large part to the operation of State and Federal water projects, especially the effects of diversions of water entering the Delta by large pumping plants in the South Delta. Thus, as he will discuss, hydrodynamic processes play a key role in thinking about how to mitigate or manage the effects of these diversions so as to minimize their environmental effects. However, other factors influencing ecosystem function have also emerged including modification of the Bay/Delta food web by invasive organisms and changes in habitat connectivity of the estuary due to changes in flows as well as concomitant changes in stratification. From an engineering standpoint, the problem of balancing environmental and human freshwater needs may be viewed as either a plumbing problem or an habitat problem, or some combination of both. He will discuss proposed (and tried) solutions to what might be termed "The Great California Water Balancing Act", including the 30 year old (and often criticized) X2 standard and the Delta Conveyance Project (aka the Delta tunnel(s).

Bio: Native Son of the Golden West, and Bay Area native[1] Stephen Monismith, the Obayashi Professor in the School of Engineering at Stanford University, received all his degrees (in Civil Engineering) from UC Berkeley. Following completion of his thesis, he did a postdoc in Western Australia focusing on the fluid mechanics of stratified flows in lakes. He has been at Stanford in the Dept of Civil and Environmental Engineering since 1987, and was department chair between 2009 and 2016. Since 2022, he has been a member of the recently formed Stanford Doerr School of Sustainability Oceans Department. His research portfolio includes (diverse) studies of estuarine and lake physics, as well as of nearshore flows with waves and stratification, with a particular (inclusive) focus on mixing and transport processes that are (equally) relevant to ecology, biogeochemistry and environmental management. Through his work on estuarine dynamics, he has been active in San Francisco Bay-Delta issues, including helping to develop the scientific underpinnings of freshwater flow regulations and serving for ca. 10 years as the chair of the IEP[2] Science Advisory Group. In recent years, much of his effort has focused on the physics of coral reef flows, with fieldwork and modeling carried out on reefs in the Red Sea, and in nearshore waters of Hawaii, Moorea, Palmyra Atoll, American Samoa, and Palau. He has parallel interests studying the inner shelf flows found near and inside the (much more chill(y)) kelp forests of California (north and south of the border). He is a fellow of the Fluid Dynamics division of the American Physical Society and was elected to the National Academy of Engineering in 2022.