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Causes & effects of upstream-downstream flow regime alteration over Catchment-Estuary-Coastal systems

The construction of large dams along rivers has significantly changed the natural flow regime, reducing the inflow into many lakes and terminal wetlands. However, the question of the impact of dam operation on downstream estuarine wetlands has less been taken into account.

Faisal Bin Ashraf / Published on 12 December 2022

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Baubekova, A., Akbari, M., Etemadi, H., Bin Ashraf, F., Hekmatzadeh, A. and Torabi Haghighi, A. (2023). Causes & effects of upstream-downstream flow regime alteration over Catchment-Estuary-Coastal systems. Science of The Total Environment, 858 (3).

Spatio-temporal flow regime alteration in the Mond River shows the complexity of drivers affecting the estuary-coastal system named the Mond-Protected Area in southern Iran. To this end, the authors applied river impact (RI) and Indicator of hydrological alteration (IHA) methods on monthly and daily river flow data across the basin. Based on the river impact method, a “drastic” impact below two in-operation (Tangab and Salman Farsi) dams, with RI values of 0.02 and 0.08, diminish to a ‘severe’ impact with RI value of 0.35 at the last gauge (Ghantareh) on the main corridor of the Mond river due to the addition of flow from a large mid-basin (about 20,254 km2). Furthermore, the degree of hydrological alteration (daily flow analysis) at mid-stream (e.g., Dehram gauges) was similar to the unregulated upstream tributaries (e.g., Hanifaghan gauges).

The remote sensing analysis in the Mond Protected Area showed the prevailing impact of sea-level rise in the Persian Gulf with the inundation of the coastal area and a shift of vegetation in a landward direction which complied with standardized precipitation index (SPI) values as a meteorological drought indicator. Thus, the consequence of climate change (e.g., sea-level rise, draught) has a higher impact on the protected area than the upstream river regulation and land-use change in the Mond basin. The holistic approach and the catchment-level study allowed the authors to see the complexity of the drivers influencing the estuary-coastal system.


  • Coupling the catchment and coastal processes uncovers the complexity of estuary ecotone.
  • The catchment-level study covers climate, land use, and damming impact on the estuary.
  • Hydrological alteration at the outlet is lower than at unregulated upstream gauges.
  • Low water consumption in the mid-basin allows recovery of the downstream flow regime.
  • The impact of climate change on the coastal area is higher than upstream regulation.
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SEI author

Faisal Ashraf
Faisal Bin Ashraf

Research Fellow

SEI Headquarters

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Topics and subtopics
Water : Water resources
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