The Multi-Watershed Nutrient Study collected stream water samples from 11 small agricultural watersheds between 2014 and 2020. Samples were collected during flow events like rainfall and snow melt, as well as during baseflow conditions across all four seasons. Samples were collected over the rise, peak, and fall of water during these events in the streams, to collect water chemistry information at a higher frequency than typical for stream water sampling. The dataset includes stream sensor data and flow data from stream monitoring stations, meteorological data from nearby weather stations, and water quality data collected through sampling. See Supplemental Information for station numbers and relevant information. Sample water quality parameters included total phosphorus, total filtered phosphorus, metals, total nitrogen, phosphate, dissolved nitrogen, turbidity, suspended solids, dissolved carbons, and sulphate. Data users are STRONGLY ENCOURAGED to review the associated Summary document prior to using this dataset. Six of the watersheds in the Multi-Watershed Nutrient Study were also sampled during the Pollution from Land Use Activities Reference Group (PLUARG) study conducted in the 1970s. More information on PLUARG can be found by visiting https://atrium.lib.uoguelph.ca/ and searching for PLUARG. High-Frequency water quantity data is provided courtesy of Water Survey of Canada/Government of Canada.