Connecting changes in Euphrates River flow to hydropattern of the Western Mesopotamian Marshes

The Mesopotamian Marshlands are the largest wetland system in the Middle East. Historically, these marshes served as the floodplains of the Tigris and Euphrates rivers, and they are currently connected to these rivers via surface water feeder canals. Historically, the Mesopotamian marshes received consistent flood pulses during the spring season from March to May. In recent decades, however, several large dams have been constructed in the Tigris and Euphrates basins for irrigation purposes and power generation, severely altering the flow regime, which along with other direct anthropogenic activities, has severely degraded the marsh ecosystem. This work quantifies changes in the riverine flow regime and how they have affected the hydro-pattern of the western Mesopotamian marshes (focusing on the western Al-Hammar marsh) and describes the role of hydrological drivers that are important for marsh restoration. The total area of the Al-Hammar marshes has been reduced from an average of 2800 km² before 1970 to a minimum of 240 km² in recent decades, concomitant with reductions in annual average Euphrates River flow (at Hit) from 967 to 602 m³/s and marked flow regime alteration. While climate warming and reduced precipitation were observed in the basin, changes in the fundamental precipitation-flow relationship implicate infrastructural changes (upstream dams) as the primary reason for these changes. This analysis quantified how flow variability under historic and contemporary conditions have affected wetland area and other hydro-pattern characteristics and suggests that at an annual average of least 70 m³/s of water deliveries to the western Mesopotamian marsh are required to restore 1000 km² of wetland area. Our hope is that this focus on the river-marsh connection will help inform predictive models and scenario analysis for restoration of this unique social-ecological system.