This report concludes the first phase of the project “OptiWells”, which focuses on the optimization of drinking water well field operation with respect to energy efficiency. The purpose of this document is to provide sound answers to questions that utilities and well field operators are facing. Thus, it is built as a thematically organized sequence of main questions and answers rather than an extensive manuscript-like report. In total, 13 questions are addressed in detail, while 3 main “unanswered” questions and issues are detailed at the end of this report. The focus of this report is identical to the project’s focus: it addresses energy efficiency issues within the well field system. Thus, the main area of focus of the project lies in the interactions between the groundwater, the well, the pump and raw water pipe system. Drinking water treatment, as well as water distribution is not included in this study. This document, in combination with the other project deliverables, shall provide an overview of the potential optimizations for drinking water well fields. It shall yield both answers about saving potentials in general, and give some concrete examples from a French well field. By doing so, it shall assist the identification of solutions for an energyefficient groundwater abstraction, and provide a basis for a sound, practical methodology for well field energy audits and assessments.

This work was carried out within the framework of the project OPTIWELLS at the Kompetenzzentrum Wasser Berlin (KWB), a non-profit network society for water research and science transfer. The project addresses the modelling of a well field in order to minimise its energy demand. The first phase of the project is a feasibility study to identify the optimization possibilities of the energy demand. The first part of the study concerns the design and testing of a hydraulic model. At the beginning it was implemented on MS Excel and after with the help of Epanet, an opensource software. Data from the operator and manufacturers as well as measured data, gained during a site audit, were used to calibrate the model. Goals were to understand how the well field was working and to identify the energy demand drivers. The second part of the study concerned the choice and the implementation of scenarios with different operational conditions for the well field. Scenarios were focused on two aspects: the change of boundary conditions and the study of possible investments. A cost comparative assessment was carried out to estimate the payback times of the investigated scenarios. Results and according recommendations were communicated to the well field manager.

The optimisation of drinking water well field operation may significantly reduce the energy demand and associated costs, but is seldom applied in a systematic methodological approach. In this study, a well field was analysed using a coupled model that takes into account aquifer, wells, pumps and raw water pipes. This coupled approach enabled to identify and quantify the key energy demand drivers. The geometrical elevation was the most important driver, while pipe network losses were in the same order of magnitude as aquifer- and well losses. Using the modelling tool, the most energyefficient well field operation scheme could be derived and energy savings of up to 17% may be achieved by optimising well field operation only whereas further 5% may be saved by investing in new pump equipment. These findings show the potentials for significant energy savings in the field of drinking water abstraction.