The Physical Impact of Mining Yacuambi River Basin, Southern EcuadorMay 2011
Emily Shimada, Environmental Science, University of IdahoResearch Team B: Watershed Management in the Andean ParamoFaculty Advisors: Dr. Alex Fremier, Department of Fish & Wildlife Resources, University of Idaho
Carlos Iñiguez A. Instituto de Ecología Universidad Técnica Particular de Loja
Introduction: Sediment in Fluvial Environments
Bedload (D>1mm)Suspended load (D<0.05mm)Wash load (D<0.0063mm)
Name Diameter (mm)
BouldersCobblesGravelSandSiltClay
>25664-256
2-640.062-2
.004-.062<0.004
Texture Classification
Introduction: Cause & Effect of Increased Fluvial Sediment
Source ImpactNatural Anthropogenic Course grain/ Bedload Fine grain/ Suspended load
ClimateVegetationTopographyGeology & soilTectonicsBase levelSurface erodibilityTime/history
MiningAgricultureDeforestationUrbanizationDamsTraffic/Roads/
ConstructionGrazing
Increased water levelFlooding potentialAlterations in channel
dimensionsAlterations in the
stream substratesAlterations in aquatic
organism habitat
Increased flow viscosity & reduced settling velocity ->increase transport grain size & bedload
Reduced depth for sunlight penetration ->hinders photosynthesis
Background: Tropical Mountain Stream Ecosystems
Source Impact
Natural Anthropogenic MiningCourse sedient build up-> increases channel bed elevation (decreasing flow)Decreased aquatic biological activity
Steep topography Tropical Climate High rainfall Abundant vegetation
Land use managementMining activities
Research Objectives1. What is the observed grain size distribution in:Streams considered “un-impacted” from human land use activities
(mining) Impacted stream
Above & Below sites with changes in land use
2. What is the predicted grain size distribution based on measurable stream dimensions in:
Streams considered “un-impacted” from human land use activities (mining)
Impacted stream- Above & Below sites with changes in land use
3. Is there a relationship between: Observed & predicted D50 in different streams and stream reachesLand use gradient & observed grain size distributionPhysical stream properties & ecological functioning of the stream?
Study Site
Site SelectionImpacted & un-impactedAbove & Below areas of distinct land use differences (mining) Establish sites at the Stream Reach scale
Length = approx. 10X Width
Relatively uniform slope, dimensions, velocity
Methods: 1) Field Work
Sediment Property MeasurementsPebble Count Median Grain Size (D50)
Wet Sieving Median Grain Size (D50)
For sediment diameters 1mm & 2mm
64mm
1mm
General Stream MeasurementsVelocityCross-sectional Area Wetted PerimeterTurbiditySlopeDepthBankfull width
Methods: 2) Analytical Work1) Predicted grain size distribution:
D50 that moves at observed flow
D50 that moves at bankfull flowbf = gRS
€
τ cr = ηg(ρ s − ρ)π
6D tanφ
Additional Measurements•Discharge Q=VA•Turbidity•Manning’s roughness
€
n =k(R2/3S1/2)
V
Initiation of Motion
2) Establish relationship between predicted & observed D50:
Between & within un-impacted stream reachesBetween & within impacted stream reaches
(above and below land use site)
3) Compare grain size distribution between impacted & un-impacted streamsIs there a clear correlation of grain size
distribution to land use gradient?Is there an ecological impact?
€
D50 =τ
τ cr (ρ s − ρ)g
G = gRS
(shear stress)
Relevance & Connection
Physical Impact of current land uses
Bio-indicator Framework
Current watershed uses & policies
Cultural & political Perceptions of watershed use & resulting impacts
Is there an observed ecological impact?
What is the relationship between land use and
ecological impact?What needs to be done?
Is there an interest and/or agenda for
watershed protection?
What can be done at the local & international level order to accommodate cultural values and stakeholders’ interests,
while promoting sustainable land use practices and policies?
Watershed use & policy jurisdiction
(stakeholders)
Societal/Political affect on watershed use & the ecosystem
Thanks & References Images: http://www.amazonrainforestnews.com/2011_04_01_archive.html http://www.nativerevegetation.org/learn/manual/ch_5.aspx http://www.amazonconservation.org/news/newsletter/0812/index.html http://www.uwsp.edu/geo/faculty/lemke/geomorphology/lectures/03_stream_sediment.html
Top Related