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