Pumping schedule assignment using chromatic graphs to reduce groundwater pumping energy consumption

Abstract

In this paper, groundwater pumping schedules are examined, in terms of pumping energy consumption minimization. Chromatic graphs are used for the first time to assign groundwater pumping schedules. Assuming that a finite number of users pumps from a common aquifer, we examine the following three pumping scenarios: (a) all users pump simultaneously, (b) users pump during one out of two different periods, (c) users pump during one out four different periods. A computational code, based on Theis equation, is constructed to calculate the drawdowns and, subsequently, the energy consumption, for various well locations, numbers of wells, flow rates, pumping period durations and aquifers' characteristics. We use nearest neighbor graphs and chromatic graphs to represent the interactions of the well users. We compare the results obtained when chromatic graphs are used, to the optimum, which is obtained using genetic algorithms (GAs). Our results indicate that: (a) performance of chromatic graphs is good, (b) when two pumping periods are used, it is sufficient for each player to cooperate with their nearest neighbor and pump alternately. In typical cases, the energy consumption reduction can be around 10–40%. The benefit is even higher if four pumping periods are used. HIGHLIGHTS Pumping groundwater alternately from a system of wells results in lower energy consumption than pumping simultaneously.; The overall energy consumption of the system approaches the optimum when the users pump alternately to their nearest neighbours.; Chromatic graphs are compared to genetic algorithms, and they are found to be an accurate, simple way of assigning pumping schedules.;

Keywords

• alternate pumping
• chromatic graphs
• energy consumption
• genetic algorithms
• nearest neighbors
• system of wells