PEATLAND DRAINAGE IMPACTS ON HYDROLOGY Bjrn Klve Process and - - PowerPoint PPT Presentation

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PEATLAND DRAINAGE IMPACTS ON HYDROLOGY Bjrn Klve Process and - - PowerPoint PPT Presentation

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1 PEATLAND DRAINAGE IMPACTS ON HYDROLOGY Bjrn Klve Process and Environmental Engineering Department Water Resources and Environmental Engineering Laboratory bjorn.klove@oulu.fi 21.1.2014 2 PEATLAND DRAINAGE IMPACT ON HYDROLOGY

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PEATLAND DRAINAGE IMPACTS ON HYDROLOGY

21.1.2014

Bjørn Kløve

Process and Environmental Engineering Department

Water Resources and Environmental Engineering Laboratory bjorn.klove@oulu.fi

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PEATLAND DRAINAGE IMPACT ON HYDROLOGY

  • Changes at catchment scale
  • Changes in peat soil
  • Changes in hydrology
  • initial changes
  • drainage at steady state
  • afteruse and hydrology
  • Special topics floods, drought and snow melt

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Peatland forestry

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COMPLEX DRIANAGE PATTERNS

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HYDROLOGICAL CHARACTERISTICS OF PRISTINE PEATLAND CATCHMENTS

  • Upland forests and peatland interactions
  • Ponds, springs, streams in complex

interactions

  • Groundwater, precipiatation (rain and

snow) and cacthment runoff inflows

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CLASSICAL CONCEPTUAL MODELS

  • Fen

Bog

  • Peatland hydrology is often a combination of these concepets

including hillslope processes

21.1.2014 P8

GW and SW inflow SW/GW P

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DETAIL PEAT AND WATER FLOW

  • Flow high close to the surface
  • Flow can occure in erosion channels even, so water can flow

even in well decomposed peat layers

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Overland flow/flow in channels Flow in porous media (Darvy flow) Preferential erosion channels GW

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HILLSLOPES AND INTERACTIONS

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Aquifer Aquitard Peatland Precipitation Surface runoff Groundwater

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PEATLAND HILLSLOPE HYDROLOGY?

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KIITOS

Björn Klöve, 19.4.2012

SNOW ACCUMULATION AND MELT

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SNOW, FROST AND SNOWMELT

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SNOW AND MELT

  • Drains probably result in uneven distrubtion of snow (as

more snow in ditches)

  • Snow melt intensity and soil cover
  • Bare peat result probly in higher melt intensity (swhen

snow partly melted)

  • Forests decrease melt rates
  • Open field have high melt rates
  • Pristine peatlands probably also have high melt rates
  • Frost result in lower K values and snow melt runoff as
  • verland flow
  • Snowmelt runoff can be low in

nutrients from drained peat soilx

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IMPACT OF DRAINAGE ON HYDROLOGY

  • Pristine

Drained

  • 3D flow

2 D flow

  • Topography driven

Drain driven

  • Flow in surficial layers

Flow through decomposed peat

  • Overland flow-runoff

Infiltration-runoff Drainage influence flow direction!

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GROUNDWATER LEVEL AND SOIL PROPERTIES

  • On average the GWL depends on net rainfall, K and pF (soil

hydraulic properties)

  • Low K results in high GWL
  • IF little effective porosity (special pF curve shape) then GWL

fluctuate easily

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P ET

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RUNOFF AMOUNT?

In Finland on average P = 600 mm and ET = 300 mm (100-400 mm), R = 300 mm Land cover changes:

  • Cutover peatlands (no vegetation) ET?
  • Bare soil maximum maybe 100-200 mm?
  • Forested peatlands ET depends on LAI and

climate

  • Young stands and mature stands ET (200-500 mm?)
  • North 150-200 mm and South 250-350 mm
  • Arable lands (yield depends on ET)
  • North and South 200-300 mm?

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  • No major changes in runoff volumes
  • Volumes increase on cutover peatlands
  • Volumes reduce with dense plant cover
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FLOW VARIATION (LOW AND HIGH FLOWS)

  • Low flows depend on the amount of groundwater flow to the

peatland (natural and pristine)

  • Impacts of drianage on low flows form peatlands is not well

studied, but drianage could perhaps reduce low flows dending

  • n impacts on ET?
  • Impacts on peak flows
  • Reducing factors: drinage increase unstaurated soil, infiltration

control

  • Incresing, due to intense drain network, also roads and

preparation of main channels will increase runoff as less flow resistance is provided (not much studied)

  • The impacts of drainage on flow variation probably not so

significant and case dependent

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Pristine Impacted

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DOWNSTREAM CHANNEL CONTROLS

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CONCLUSIONS

  • Peatland hydrology measurements often difficult to carry
  • ut and there is still a lack of research on the topic
  • Peatland hydrology often complex where different upland

processes, channel controls, and interactions with surface and groundwater are present

  • Drainage changes soil properties and flow patterns

resulting in more water beeing infiltrated through the soil

  • Drainage networks chnage flow routes
  • Other hydrological changes are:
  • Changes in total annual runoff depend on vegetation

cover

  • Changes in low flow might occur
  • Changes in peak flows case dependent (overestimated

in old litterature, but currently considered quite minor)

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22 21.1.2014

Thank you for your attention

EC 7FP , Academy of Finland, VALUE DP , MMM, EAKR, MVTT , Renlund, Thule, Vapo Oy, etc