This presentation is about the conference article "Nonlinear estimation of a power law for the friction in a pipeline". The main goal of this article is the introduction of a new algorithm to continuously estimate the energy dissipation in a pipeline, i.e. the total head loss, without the knowledge of the relative roughness and the real length of a pipeline. The principal contribution of this article are: (1) A power law to represent the total head loss in a pipeline. (2) A simple method to estimate in real-time such a power law, including the exponent, with the following characteristics: (A) It is based on nonlinear state observers. (B) It only requires two pressure head recordings and a flow rate measurement. (C) It performs the estimation in short-time.