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

1 PEATLAND DRAINAGE IMPACTS ON HYDROLOGY Bjørn Kløve Process and Environmental Engineering Department Water Resources and Environmental Engineering Laboratory bjorn.klove@oulu.fi 21.1.2014

2 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 21.1.2014

3 21.1.2014

Peatland forestry

COMPLEX DRIANAGE PATTERNS

7 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 21.1.2014

P8 CLASSICAL CONCEPTUAL MODELS • Fen Bog P GW and SW inflow SW/GW • Peatland hydrology is often a combination of these concepets including hillslope processes 21.1.2014

9 DETAIL PEAT AND WATER FLOW Overland flow/flow in channels Flow in porous media (Darvy flow) Preferential erosion channels GW • Flow high close to the surface • Flow can occure in erosion channels even, so water can flow even in well decomposed peat layers 21.1.2014

HILLSLOPES AND INTERACTIONS Surface runoff Groundwater Precipitation Aquifer Peatland Aquitard 10 21 January 2014

PEATLAND HILLSLOPE HYDROLOGY?

KIITOS SNOW ACCUMULATION AND MELT Björn Klöve, 19.4.2012

13 SNOW, FROST AND SNOWMELT 21.1.2014

14 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 overland flow • Snowmelt runoff can be low in nutrients from drained peat soilx 21.1.2014

15 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! 21.1.2014

16 GROUNDWATER LEVEL AND SOIL PROPERTIES ET P • 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 21.1.2014

17 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?  No major changes in runoff volumes  Volumes increase on cutover peatlands  Volumes reduce with dense plant cover 21.1.2014

18 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 on 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 21.1.2014

19 Pristine Impacted 21.1.2014

20 DOWNSTREAM CHANNEL CONTROLS

21 CONCLUSIONS • Peatland hydrology measurements often difficult to carry out 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) • •

Thank you for your attention 22 EC 7FP , Academy of Finland, VALUE DP , MMM, EAKR, MVTT , Renlund, Thule, Vapo Oy, etc 21.1.2014