Collective Impact of Upstream Anthropogenic Interventions and Prolonged Droughts on Downstream Basin’s Development in Arid and Semi-arid Areas: The Diyala Transboundary Basin

Abstract

The integrated management of transboundary waters has increasingly becoming a heavy burden facing decision-makers and water managers, especially in downstream countries. Human-intervention activities upstream combined with prolonged droughts have intensified the challenges encounter the water governance in a sustainable manner. This study quantifies the combined effects of upstream man-made modifications and basin-wide extended droughts on temporal river flow paradigms of the downstream riparian country. The Diyala watershed of about 32,000 km² shared between Iraq and Iran was chosen as an example case study. The Indicators of the Hydrologic Alteration (IHA) and the Range of Variability Approach (RVA) were adopted to characterise the streamflow alteration. Findings reveal that the joint impact has destructively influenced the development of the middle and lower portions of the basin in the downstream country, including the security of the irrigated agriculture, domestic and industrial water demands, and prompted people to leave their homes and lands coupled with growing conflicts between tribes. Prolonged severe droughts were marked between 1999 and 2015. The size and magnitude of the joint impact are anticipated to increase in the foreseeable future when under construction and future planned water withdrawal facilities upstream will be commissioned. The two successive acute droughts of (1999–2001) and (2008–2009) twinned with upstream regulation practices have hindered the socio-economic activities and deteriorated the environmental system of the middle and lower portions of the Diyala basin in the lower country.