The tabular data sets and associated maps in this data release represent water-quality data that were collected between April and November of 2017 and between July and November of 2019 to describe baseline conditions prior to or sometimes following treatments using herbicides or other methods to reduce the biomass of non-native water primrose (Ludwigia) within off-channel water bodies of the Willamette River near Albany and Keizer, Oregon. The water-quality parameters measured in this study included water temperature, specific conductance, pH, dissolved oxygen, turbidity, total chlorophyll, phycocyanin (blue-green algae pigment), and fluorescing dissolved organic matter in surface water.