Exploring synergies and tradeoffs: Energy, water, and economic implications of water reuse in rice-based irrigation systems

Efficient use of water and energy resources are significant requirements for increasing irrigated rice productivity. However, the ever increasingly complex interplay between energy, water and agriculture in feeding both machinery and people, respectively, plus the added impact on and of climate change, have significant implications on the management of our natural resources. This paper holistically analysed a rice-dominated gravity-fed irrigation system using the Upper Pumpanga River Integrated Irrigation System (UPRIIS) in Central Luzon, the Philippines as demonstration example to quantify the water, energy and economic implications of water reuse at five different spatial scales. Water reuse was determined through daily measurements of all surface water inflows and outflows, rainfall, evapotranspiration, and the quantities of water internally reused through check dams and shallow pumping, and aggregated into seasonal totals for five spatial scales during the dry season of 2001. Energy auditing was later used to evaluate the energy implications of water reuse.