Discharge in the lower Mississippi River, Neptune Pass, and nearby systems.

A. Discharge in the Mississippi River at Belle Chasse, in Neptune Pass, and in the Mississippi River at the Olga upstream and downstream locations. B. Percent of water from the Mississippi River discharged through Neptune Pass, and through the Mississippi River downstream of Neptune Pass, Fort St. Philip and the nearby crevasse, i.e., Olga Downstream. C. Discharge through Southwest Pass (the main shipping channel), with all available data, and with low flow removed. D. Percent of the Mississippi River discharged through Southwest Pass, with all available data, and with low flow removed. Note that the magnitude and percent of water flowing through Southwest Pass, the river’s final distributary and main shipping channel, begins to decline in 2020, roughly contemporaneous with the expansion of Neptune Pass. To account for the impacts of extreme droughts in summer 2022 and 2023, the data is also presented with the low flow data removed. Data sources include US Geological Survey, US Army Corps of Engineers, and article authors.