In late August and early September 2017, Hurricane Harvey made landfall on the southeastern coastline of Texas and produced a record amount of rainfall, leading to widespread flooding. From August 25 through September 1, 2017, some areas in southeastern Texas received more than 60 inches of rain with large areas receiving at least 40 inches of rain. Hurricane Harvey was the largest rainfall event in United States history in terms of spatial extent and rainfall totals since rainfall records began in the 1880s (Watson and others, 2018). The five most heavily flooded river basins in Texas during this storm included the Brazos River, where the U.S. Geological Survey (USGS) collected water-quality samples at the Brazos River near Rosharon, Tex. (USGS station 08116650, hereinafter referred to as the Brazos River site). Two water-quality samples were collected by the USGS at the Brazos River site in response to Hurricane Harvey in August and September 2017. Water-quality samples are also routinely collected at the Brazos River site approximately 14 times a year as part of the USGS National Water-Quality Assessment Project. Concentrations of selected water-quality constituents in the two water-quality samples collected at the Brazos River site during the period of higher discharge associated with Hurricane Harvey are documented in this data release along with the constituent concentrations measured in samples collected at this site immediately before and after Hurricane Harvey for comparison purposes. Water-quality changed in response to the period of higher discharge at the Brazos River site that resulted from the storm; this data release documents those changes. Results from all water-quality analyses of field properties, major ions, nutrients, trace elements, and pesticides are included in this data release. Discharge is computed continuously (15-minute intervals) at the Brazos River site and those values have been related to the water-quality samples based on collection time. This data release documents how specific conductance and concentrations of most of the major ions analyzed (calcium, magnesium, potassium, sodium, bicarbonate, chloride, sulfate, and dissolved solids) as well as selected trace elements (lithium, strontium, and boron) decreased (relative to samples collected before Hurricane Harvey) in the water-quality samples collected during the period of higher discharge that resulted from Hurricane Harvey at the site. Conversely, concentrations of suspended sediment and iron increased (relative to samples collected before Hurricane Harvey) in the water-quality samples collected during the same period of higher discharge. Detections of pesticides generally were not measured in samples collected during the period of higher discharge that resulted from Hurricane Harvey except for atrazine and a few of its degradates, for which lower concentrations were documented in water-quality samples collected during higher discharge at the Brazos River site compared to the concentrations measured during lower discharge before the storm event.