Effect of dams on mountainous bedrock rivers

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This study examines the adjustment of river systems in the Golan Heights to reservoir construction in small basaltic mountainous catchments where total water flow is impounded, and discusses comparisons with the effects of large dams on alluvial rivers. Annual rainfall ranges from 500 mm to 900 mm, and no major springs are found in the area. About 3/4 of total runoff is in the form of floods caused by rainstorms. The 11 dams receive drainage from about 20% of the total catchment, and a third of the total runoff. Changes in the river channels were studied at 28 field stations. Flood marks provided peak stage levels for largest season discharge, and 8 nearby hydrometric stations provided a continuous hydrological record. Bed material was sampled at each cross-section site. The main effect of river impoundment is a sharp decrease in flood peaks below the reservoirs to about one-third of their previous natural regime. The channel cross-sectional area decreased, but no temporal adjustment can be established, as most of the reservoirs were built in the last 5-8 years. Channel-flow hydraulics are competent enough to transport the suspended material, but evidence of aggradation was found in the channel reaches close to the dams. Bedload transport and the size of transported cobbles and boulders decreased downstream from the dams. Increased vegetation cover downstream from the dams was the most pronounced effect. Adjustment of the fluvial system to dam building in mountainous streams seems to be less sensitive than in alluvial channels.

Original languageEnglish
Pages (from-to)305-319
Number of pages15
JournalPhysical Geography
Issue number4
StatePublished - 1990

Bibliographical note

Funding Information:
Acknowledgments: The author thanks H. Glassman and Y. Kaplan from the Nature Reserve Authority who participated in the field work; M. Church,A.P.Schick and two anonymous referees for useful suggestions, and Aliza Gold for drawing the figures. The project has been supported by the Golan Research Institute.


  • Dams
  • Environmental changes
  • Fluvial geomorphology
  • Israel
  • Water reservoirs

ASJC Scopus subject areas

  • General Environmental Science
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • General Earth and Planetary Sciences


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