Terrestrial freshwater discharges into the Southern California Bight (SCB) contains nutrient and carbonate system constituents that make the region susceptible to eutrophication. This respository contains comprehensive time series discharge and constituent data of point and non-point sources, which consist of ocean outfalls, inland wastewater treatment plants, and rivers, to the SCB from the past twenty years and more. Constituents include nitrogen (N), phosphorus (P), carbon (C), iron (Fe), silica (Si) and carbonate system parameters. Many local and state government and non-government organization databases were accessed to construct this data set. In-house data that was previously not publicly available are published here as well. Predictive models and expert analysis addressed unmonitored sources and data gaps. The spreadsheet 'rivers_1997_2017_daily.xlsx' contains the data from 1997 to 2017 for 75 rivers alphabetically. River constituents include discharge volume, ammonium, nitrate, dissolved oxygen, temperature, pH, total N, total P, phosphate, organic P, total organic C, organic N, total Fe, alkalinity, salinity, dissolved Fe, total inorganic C, and silicate. File 'major_potw_1971_2017.xlsx' contains data from 1971 to 2017 for the four large POTWs in the SCB, of which data before 2007 was not publicly available until now. Constituents in this file are discharge volume, ammonium, nitrate, nitrite, dissolved oxygen, temperature, biological oxygen demand, pH, TP, phosphate, OP, TOC, ON, TN, total Fe, silicate, alkalinity, salinity, and dissolved Fe. The 'minor_potw_1997_2017.xlsx' contains data from 1997 to 2017 for the 19 minor POTWs alphabetically. Data from year 2000 was not publicly available until now. Constituents in this file are discharge volume, ammonium, nitrate, nitrite, dissolved oxygen, temperature, biological oxygen demand, pH, TP, phosphate, OP, TOC, ON, TN, total Fe, silicate, alkalinity, salinity, and dissolved Fe. The 'inland_POTW.xlsx' file contains averaged data from the year 2009, unless otherwise noted, for the 18 inland POTWs. The region and city given for each plant. The discharge volume, TN, TP, dissolved inorganic N, and dissolved inorganic P are listed for each plant. The 'natural_rivers.xlsx' file contains summarized annually averaged input of natural riverine sources for each region of the SCB. The approximate watershed area of each region is given and constituents in this file are TN, TP, DIN, and DIP.