A flowmeter profiling system for measuring a flow profile of water in a subsurface environment includes a tracer injection system positioned at least partially within the subsurface environment. The tracer injection system includes an injection tube that contains a tracer material, and an injection port that is coupled to the injection tube near a bottom of the injection tube. Additionally, the injection port is configured to inject the tracer material substantially horizontally into the subsurface environment. The injection port can include a plurality of exit holes such that the tracer material is injected substantially horizontally into the subsurface environment through each of the plurality of exit holes. The water can be in a groundwater production well having a cross-sectional plane, and the tracer material can be injected substantially horizontally into the groundwater production well through each of the plurality of exit holes to fill substantially the entire cross-sectional plane of the groundwater production well.