2021
  • Non-ICIMOD publication

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Early twenty-first century satellite-driven irrigation performance in the world’s largest system: Pakistan’s Indus Basin irrigated system

  • Jorge L Peña-Arancibia
  • Mobin-ud-Din Ahmad
  • Summary

Evaluating irrigation performance in large systems is often limited by the availability of reliable water use data. Satellite-driven actual evapotranspiration (ETa) estimates are used herein as water use surrogates to assess the year-to-year inter-seasonal irrigation performance in 46 canal commands in the Indus Basin irrigated system (IBIS), the largest in the world (~160 000 km2). The accuracy and reliability of the ETa estimates are verified using two previously published locally adjusted satellite-driven ETa estimates, as well as field ETa estimates. Inter-seasonal variability (canal command water use in time) and equity (inter- and intra-canal command water use) are assessed from 2000 to 2018 using violin-plots time-series for the two irrigation seasons, the wet 'Kharif' and dry 'Rabi'. The violin-plots probability density functions are used to assess intra-canal command equity; and their seasonal time-series to assess inter-seasonal variability. The long-term multi-year assessment conducted here, the first for the IBIS using consistent satellite-driven ETa time-series, shows that canal commands with ready access to groundwater exhibit more equity and less inter-seasonal variability when compared to canal commands chiefly reliant on surface water supplies; with the latter showing intra-canal command inequities between head-end and tail-end irrigated areas. Also, ETa in canal commands is mostly slightly increasing and there is low inter-seasonal variability in both irrigation seasons, except for two canal command at the system-end, which show higher inter-seasonal variability and inequity than their upstream counterparts. The methods employed here can be used in large irrigated systems elsewhere to assess ongoing irrigation performance and to verify results of targeted (non)structural irrigation management.