Tracing nutrient fluxes with turbidity sensors€¦ · SFB 564 Applying turbidity technology in Mae Sa Contrast with Vietnam: very different land use Estimate contributions of different

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SFB 564

Tracing nutrient fluxes with

turbidity sensorsA time saving alternative for better

understanding fluxes at landscape level

International Symposium "Sustainable Land Use and Rural Development

in Mountainous Regions of Southeast Asia"

21-23 July 2010 Hanoi, Vietnam

J. Slaets, P. Schmitter, A. Bürger, T. Hilger, G. Dercon ,

T.T.L. Ha, N. Lam, T.D.Vien, G. Cadisch

SFB 564 – The Uplands Program

„Sustainable Land Use and Rural Development in Mountainous Regions of Southeast Asia“

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SFB 564

1. Background

2. Methodology

3. Preliminary results in Chieng Khoi, Vietnam

4. Application in Mae Sa, Thailand

5. Planned work

Outline

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SFB 564 BackgroundSFB 564

1. Introduction – 2. Topic x – 3. Topic y – 4. Topic z – 5. Conclusions

Population pressure and intensified cultivation

on steep slopes severe erosion

Reallocation of nutrients also affects lowlands

Irrigation channel acts as nutrient conveyor

Picture Anna BuergerPicture Petra Schmitter

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SFB 564 Rationale of the studySFB 564

Need to understand nutrient fluxes at catchment level:

Automatic water samplers

interesting data but

expensive and

labour intensive

Turbidity sensors

continuous and

cost-effective

alternative?

Picture Petra Schmitter

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SFB 564

“The cloudiness or haziness of water,

caused by suspended solids”

How can we measure it?

Optical backscatter technology

Wiper avoids biofouling

What are the units?

Nephalometric Turbidity Units (NTU)

For our sensors 0 to 4000 NTU

What is turbidity?

1. Introduction – 2. Topic x – 3. Topic y – 4. Topic z – 5. Conclusions

IR beams

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SFB 564

• Turbidity has been used extensively as a measure for total suspended solids

• Good correlation between turbidity and particle size (Ziegler, 2007)

Proxy for sediment quantity

1. Introduction – 2. Topic x – 3. Topic y – 4. Topic z – 5. Conclusions

iTotal suspended solids (TSS) as a function of (a) turbidity (TNU) and (b) discharge (Q). The relationships are based

on 234 samples collected during all three periods during 2006 and 2007 (adapted from Ziegler, 2007).

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SFB 564

• Turbidity has been used extensively as a measure

for total suspended solids

• Good correlation between turbidity and particle

size (Ziegler, 2007)

Hypothesis: Turbidity can be calibrated with total

nitrogen and total organic carbon in the river and

irrigation channel water of Chieng Khoi watershed

Proxy for sediment quality

1. Introduction – 2. Topic x – 3. Topic y – 4. Topic z – 5. Conclusions

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SFB 564

Method for turbidity

Calibration, applied in

Vietnam

Sensors suspended in

perforated pvc pipes

Calibrating turbidity sensorsSFB 564

1. Introduction – 2. Topic x – 3. Topic y – 4. Topic z – 5. Conclusions

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SFB 564

Method for turbidity

Calibration, applied in

Vietnam

Probe “floating” in water

column, depth below

surface similar for all flow

ranges

Calibrating turbidity sensorsSFB 564

1. Introduction – 2. Topic x – 3. Topic y – 4. Topic z – 5. Conclusions

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SFB 564

Chieng Khoi watershed

• Son La province,

Northwest Vietnam

• Climate:Rainy season April - Sept

Annual rainfall 1200 mm

Annual temperature 22 °C

• Soils:Alisols and Luvisols

Study site in Vietnam

1. Introduction – 2. Topic x – 3. Topic y – 4. Topic z – 5. Conclusions

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SFB 564

Chieng Khoi watershed

• From composite

swidden agriculture to

monocropping

• Rice paddies fed by

irrigation channel and

draining into river

Study site in Vietnam

1. Introduction – 2. Topic x – 3. Topic y – 4. Topic z – 5. Conclusions

Picture Petra Schmitter

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SFB 564

Method for turbidity

Calibration, applied in

Vietnam

Five sensors at strategic

locations in the catchment

SFB 564

1. Introduction – 2. Topic x – 3. Topic y – 4. Topic z – 5. Conclusions

Methodology

Outlet

Reservoir

= Sensor

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SFB 564

Taking water samples

Bottles held horizontally in

the direction of the flow

Storm-based sampling,

catching a range of rainfall

intensities and baseflow

MethodologySFB 564

1. Introduction – 2. Topic x – 3. Topic y – 4. Topic z – 5. Conclusions

1 2

3 4

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SFB 564

Analyzing water samples

• Total suspended solids (weighing)

• Total (organic) carbon, total nitrogen of both

particulate and dissolved fraction (combustion)

• Texture (Mid Infrared Spectroscopy)

MethodologySFB 564

1. Introduction – 2. Topic x – 3. Topic y – 4. Topic z – 5. Conclusions

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SFB 564

Turbidity data

Preliminary resultsSFB 564

1. Introduction – 2. Topic x – 3. Topic y – 4. Topic z – 5. Conclusions

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SFB 564

filling

Preliminary resultsSFB 564

1. Introduction – 2. Topic x – 3. Topic y – 4. Topic z – 5. Conclusions

Irrigation channel versus river

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SFB 564

Calibration: Example based on dataset of 2008 (4 events)

Preliminary resultsSFB 564

1. Introduction – 2. Topic x – 3. Topic y – 4. Topic z – 5. Conclusions

(Data: Petra

Schmitter)

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SFB 564 OutlookSFB 564

1. Introduction – 2. Topic x – 3. Topic y – 4. Topic z – 5. Conclusions

• Turbidity could be a powerful tool in monitoring

nutrient flows on a landscape scale

• Potentially useful in understanding C and N fluxes in

Chieng Khoi catchment, Vietnam

• Different application of turbidity: in site with very

different types of land use, example of Mae Sa,

Thailand

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SFB 564

Applying turbidity technology in Mae Sa

Contrast with Vietnam: very different land use

Estimate contributions of different land uses to sediment in

river by monitoring subwatersheds with characterised

land use

Goal: compare the C and N flows at different levels of

land use intensification

Estimating contributions of land use typesSFB 564

1. Introduction – 2. Topic x – 3. Topic y – 4. Topic z – 5. Conclusions

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SFB 564

Mae Sa watershed

• Chiang Mai province, Northwest

Thailand

• Climate: Rainy season May – Oct

Annual rainfall 1200 mm

Annual temperature 20 °C

• Soils:Acrisols and

Cambisols

Estimating contributions of land use types

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SFB 564

• 70 percent mixed

deciduous and

evergreen forest

Estimating contributions of land use types

• Rest is agricultural production,

dominated by:

vegetables

litchi and flower production

bell pepper cultivated in greenhouses

Land use in Mae Sa

Picture Walaya Sanchan

Picture Walaya Sanchan

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SFB 564

• Map mae sa with locations

Location of

installed

turbidity

sensors in

Mae Sa

Outlet

Headwater

Estimating contributions of land use types

Sensor

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SFB 564SFB 564

1. Introduction – 2. Topic x – 3. Topic y – 4. Topic z – 5. Conclusions

Planned work

• Establish calibration between turbidity and nutrient

content for Mae Sa and Chieng Khoi

• Use this calibration to monitor nutrient flows in and

out the catchments

• Compare these nutrient flows in the two

catchments with different level of land use

intensification

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Thank you for your attention!

Questions?

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SFB 564SFB 564

1. Introduction – 2. Topic x – 3. Topic y – 4. Topic z – 5. Conclusions

Considerations

• Turbidity and organic matter: is a calibration

possible?

• Saturation: sensors go up to 4000 NTU