Ten years of biogeochemical monitoring in the highly urbanized tropical Saigon-Dong Nai River estuary (2015-2025), Vietnam

This dataset comprises quality-controlled biogeochemical observations from the Saigon-Dong Nai River estuary collected over a 10-year period (July 2015 - July 2025). The monitoring program addresses a critical data gap in Southeast Asian tropical estuaries by providing sustained, high-frequency measurements across the freshwater-to-marine continuum in the Ho Chi Minh City metropolitan region. The dataset includes two complementary components: (1) Fixed-station time series: biweekly sampling at four stations (HA, PC, BD, BK) spanning upstream-to-estuarine gradients, yielding 894 observations from 225 campaigns over 10 years. (2) Longitudinal transects: seasonal surveys at 27 sites covering 140 km of the river-estuary system, comprising 162 observations from 13 campaigns (2017-2022). Parameters measured (20 total): Temperature, pH, dissolved oxygen, electrical conductivity, salinity, oxidation-reduction potential, total suspended solids, nitrate, ammonium, total nitrogen, phosphate, total phosphorus, dissolved silicate, dissolved organic carbon, particulate organic carbon, total organic carbon, chlorophyll-a, and total alkalinity (2020-2025). All measurements include parameter-specific quality control flags (5-tier system) documenting data quality, analytical precision, and gap explanations. Overall data completeness is 96.6% (flags 1-3), with 83.8% classified as Good quality (flag 1). The dataset provides approximately 20,000 individual measurements with complete metadata, reproducible processing code, and comprehensive documentation.