The complexities of irrigation efficiency: Groundwater data, agro-hydrology, and water decision-making in Central Oregon.

Irrigation efficiency projects aim to conserve water for in-stream flow and agricultural use by reducing water losses throughout the system. Piping irrigation canals is a common irrigation efficiency method that results in trade-offs: while it increases efficiency of irrigation water conveyance, it reduces incidental groundwater recharge. This paper focuses on the data and decision-making of canal piping, focusing primarily on understanding the potential impacts of reduced canal leakage on shallow wells. By conducting a spatial analysis of shallow wells in the basin at risk of being impacted by canal piping, and combining this with interviews with water managers in central Oregon's Upper Deschutes Basin, we demonstrate the complex socio-natural dynamics and politics of water conservation decision-making. The research finds that irrigation canal piping is fully supported by water managers in the study area as a means of physically shifting flows of water towards particular valued uses, yet at the same time there is not enough data to understand the potential impacts of canal piping on water users reliant on canal seepage. Given the lack of localized shallow groundwater monitoring data, water managers are reliant upon basin-scale model predictions when defining the trade-offs in canal piping. Broadly, the research demonstrates that well-intended water management decisions can have trade-offs and impacts that are not well understood, pointing to the need for more groundwater monitoring and critical attention to the multiple scales of irrigation efficiency to inform the co-management of surface water and groundwater for the many water users within a basin. • Irrigation efficiency can impact basins in ways that are not understood. • Water managers rely on incomplete evidence when making efficiency decisions. • Irrigation efficiency efforts may negatively impact shallow domestic wells. • The politics of data gaps must be taken seriously in water management. • Critical lenses help to understand the complexity of irrigation efficiency. [ABSTRACT FROM AUTHOR]