The monitoring and measurement of water flow in groundwater wells allows us to understand how aquifers transmit water. In this paper we develop a simple method, which we call T-POT, that allows flows to be estimated by tracking the movement of a small parcel of warmed water. The parcel is tracked using fibre optic temperature sensing - a technology that allows detailed measurements of temperature, and therefore flow using the T-POT method, to be made in the well.