Reducing Energy Use of Groundwater Pumping by Long-Range Planning

In many parts of the world large quantities of electrical energy are used to lift groundwater to the land surface.  Costs and associated carbon footprint are particularly high in areas with substantial depths to water.  In this talk we examine opportunities for urban water suppliers to reduce energy use associated with groundwater pumping by considering the long-term impacts of water level declines.  While current practice often includes short-term (e.g. daily) optimization of pumping schedules to reduce pumping costs, little attention has been given to the long-term impacts of groundwater pumping patterns on energy use.  To accomplish this it is necessary to consider the response of lifts at individual wells to pumping at other wells in the system.  We report on analysis of energy use that is conducted by the combined use of a simulation model (MODFLOW) and optimization (GWM – the Groundwater-Management Process for MODFLOW).   Results for hypothetical test aquifers and the Antelope Valley Basin in California are presented.  We explore alternate optimization formulations for minimizing energy use including formulations which minimize the product of flow rate and lift and those which minimize the maximum lift. Results are also compared with non-optimal pumping strategies to assess the importance of using optimization in this context.  Testing on the California site shows that substantial reductions in energy use are possible if the urban water distribution system can accommodate shifts in the pumping sites.  Groundwater management modeling can be a useful screening tool as a prelude to detailed hydraulic analysis of urban water systems.