Irrigation Reliability Under Climate Change Scenarios: A Modeling Investigation in a River-Based Irrigation Scheme in New Zealand1

Abstract

Srinivasan, M.S., J. Schmidt, S. Poyck, and E. Hreinsson, 2011. Irrigation Reliability Under Climate Change Scenarios: A Modeling Investigation in a River-Based Irrigation Scheme in New Zealand. Journal of the American Water Resources Association (JAWRA) 47(6):1261–1274. DOI: 10.1111/j.1752-1688.2011.00568.x Abstract: The impact of climate change (CC) on irrigation reliability in a river-based irrigation scheme in New Zealand was investigated. Reliability was defined as the river’s ability to meet the demand. Two future periods were considered, 2030-49 (“2040”) and 2080-99 (“2090”), and reliability at these periods were compared against those in 1980-99 (“current”). A hydrology model, calibrated and validated for current condition, was applied to simulate flows for CC scenarios. Annual precipitation and mean temperatures were predicted to increase under CC scenarios over current condition. Occurrence of high intensity rainfall events indicated large flows under CC scenarios, though these increases could be occurring outside the irrigation season (September-April). Compared to current condition, under CC scenarios, the number of days per season supply falling below demand could increase by 5 (2040) to 17% (2090). Snow storage plays a major role in sustaining flows in early spring under current condition. However, with increasing temperatures under CC scenarios, the average annual snow water storage could decrease from 155 mm (current) to 97-134 mm (2040) and 40-90 mm (2090). Under CC scenarios, to sustain the current levels of land and water uses in this scheme, storage options need to be explored.