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| Titel |
Measurement of infilling rate in a small reservoir in a Mediterranean semi-arid area |
| VerfasserIn |
Antonio Moñino, Agustín Millares, Javier Herrero, María José Polo, Miguel Ángel Losada |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250055142
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| Zusammenfassung |
| The catchment of the Granadino dam, Southern Spain, encloses 480 km2, with important
presence of snow in the summits 3000 m on its right margin, and semiarid low range hills
with very erodible soils on its left margin. Gully erosion, landslides and stream bed-load
processes, extremely actives in this area, are responsible of important soil loss and
desertification problem with a high associated cost. The National Inventory of Soil
Erosion, carried out by the Spanish Ministry of Environment, assigns to this watershed
potential soil losses up to 200 Tn/ha/year in certain areas according to RUSLE model
simulations.
This hydraulic structure, a small dam with 12 m height from foundation, 100 m
wide and gravity type, is located 2 Km upstream of the Rules reservoir, a water
body for regulation, supply and irrigation purposes in the Mediterranean coast of
Granada. It was set into service in September 2002, with the aim of preventing
transported sediments by Guadalfeo River producing, therefore, the silting of Rules
reservoir.
Several works developed through monitoring this structure since 2003 with topographic and
bathymetric surveys, report about the sedimentation rates and the high speed of infilling
showing the importance of these full-scale sediment traps in Mediterranean areas. Also these
works allows the study of erosion dynamics by identifying the key associated processes,
related in this case with episodic rainstorms and intense snowmelt cycles combined with a
high rate of sediment availability.
Different pulse events, either induced by rainfall or snowmelt events, have forced during the
last 6 years the complete infilling of this reservoir, with an estimated volume of
3.3-
105 m3. Two storm events occurred during April-May 2004 caused 6000 m3 of
sediment retained by the dam; each event lasted no more than four days, and the
associated rainfall was not greater than 40 mm in any case. Another significant
increase is observed in June-September 2006, during which both snowmelt and storms
episodes induced the deposition of 7000 m3 of sediment associated to hillsides areas.
Finally, the intense and continuous precipitation in December 2009 contributed with a
total of 50.000 m3 of sediment, most of them coming from stream as bed-load
processes.
Accordingly to the field data and simulations, an average sediment transport rate close to 150
m3/day is to be expected which results in a reduction of useful-life of Rules reservoir in terms
of capacity if the system is left to its normal evolution. On the other hand, this work
shows an important contrast between channel and overland erosion allowing the
establishment of relationships between different types of events produced by forcing
agents. |
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