Sediment dynamics
Objective and research questions
Measure and forecast changes in sediment flux/delivery to downstream areas.
What are the rates of sediment release by glaciers in active recession?
What is the current capacity of lakes to store sediments released by glacier recession?
Are contemporary rates of sedimentation comparable with those of the recent past
How will downstream fluvial reaches be impacted by changing sediment dynamics brought about by deglaciation and lake development?
Generate scientific baseline information about the physical and geochemical conditions of Sibinacocha Lake for improved water resource management.
What are the bathymetry, erosion rates and flow circulation patterns in the lake?
What is the geochemical composition (heavy metals, organic matter, grain size distribution) of sediments?
Is there a risk to human communities and wildlife downstream due to contamination from the release of contaminants stored in glacierized areas?
How does the sediment quality of Lake Sibinacocha compare to other high Andean lakes?
Main results
There is no significant difference in the water volume supplied to Laguna Sibinacocha as a consequence of the lake development at Chumpe Glacier. The lake at Chumpe Glacier does regulate the peak discharge for the catchment, but only slightly. The difference in lake effect between different climate scenarios is large.
The lake at Chumpe Glacier has a big impact in moderating the volume of sediment delivered downstream and into Laguna Sibinacocha. Interestingly, this impact is greater for the scenario RCP 2.6, rather than for the RCP 8.5, by the end of the century.
Coming soon, the results of the geochemical characterization of Sibinacocha Lake.
Methodology
The work of the sediment dynamic team focused on the Cordillera Vilcanota, particularly in the Sibinacocha Lake catchment. This glacial-fed reservoir covers around 20 km2 and is dammed for hydropower since the 1990s, regulating water flow into a minor river feeding the Vilcanota-Urubamba basin.
The modeling was centered on the catchment upstream of Laguna Sibinacocha, with particular emphasis on the outlet of the Chumpe Glacier. In this location, an evolving glacial lake is anticipated to experience further and more rapid growth until the year 2050.
To measure and forecast changes in sediment flux and its delivery to downstream areas, CAESAR-Lisflood (a 2D Reduced-Complexity Landscape Evolution Model) was adapted to include the influence of proglacial lakes in regulating discharge and sediment supply. The model could then be used to simulate catchment discharge and sediment supply, with and without the effects of the lake.
For the geochemical analysis, over 20 surface sediment samples were collected from various points across the lake and analyzed for grain size distribution, trace metals and organic matter content.
Bathymetry measurements were conducted using a 600 kHz Teledyne RD Instruments RiverRay ADCP. The estimated range of average annual soil erosion intensity was calculated using the Revised Universal Soil Loss Equation (RUSLE) model.
As a comparative study, the fieldwork at Lake Sibinacocha was replicated in Laguna Rinconada, located in the Cordillera Apolobamba in Puno. This lake is heavily impacted by gold mining activities in its upper watershed. Laguna Rinconada is the source of the Ramis River, the largest tributary of Lake Titicaca.