Water, forests and
footprints –
finding the right
scale for
sustainability
Prof. Kevin Bishop
Uppsala University
& Swedish...
Deforestation widely blamed for water problems
Less than 4% forest in Blue Nile
Will more trees help?
Or will they “steal”...
Green-Blue Water sees
forests as consumers of water
65 %

35 %
M.Falkenmark March 09
Plynlimon – Hydrologist Heaven
Documented how forests took water
– at the the 2 km2 catchment scale
My own background
Digging in small
catchments –
Miss a
bigger
picture?

©Bill Waterson
Hydrology and Forests in the Blue Nile:
What can be learned from half a century of observations and
community perception f...
Popular Perception vs Science
Popular hopes for reforestation:
– Increase dry-season flow
– Decrease erosion

But science ...
Interdisciplinary PhD Thesis: Half a century
of quantitative and qualitative observations
• A dozen catchments
have over 4...
Some large declines in forest area
1957 Landcover
16% Forest = Green

2000
2% Forest
120
100

y = 0.0008x + 0.3844

4.5
4
3.5
3
2.5
2
1.5
1
0.5
0

3

Peakflow (m 3/s)

140

Baseflow (m /year)

Statistical an...
Community Perception: A complex
understanding of the forest-water relationship
Deforestation influence on streamflow:
Revisting what has science “proven”
Deforestation

Total flow
usually increases

Pe...
Watershed Mass Balance

Evaporation
+
Transpiration (ET)

Precipitation (P)

Runoff (Q)

11/14/2013

13
Are Forests Good for Water Resources?

14
The Hydrologic Cycle: Trees remove water
at one point, return it to the region
The Forest-Water Debate: Supply vs. Demand-Side

Demand-side:
Increasing forest cover reduces runoff
Ecosystems subtract...
Recycled ET

Ocean

Annual

40%

60%

Summer

60%

40%

Source data generously
provided by Michael Bosilovich, NASA

Balti...
Average Estimated Precipitation in Major River Basins
by Source (1948-1997)
120
100
80
60
40
20
0

200
150

150

100

100
...
Much Precipitation is Recycled Evaporation:
East African over 50% of rain from trees

Should Egypt be more concerned about...
The Forest Water Yield Debate:
A Question of Scale
• All Agree: Trees Increase Evapotranspiration
– Demand-side View: Redu...
What is Forest ET’s impact on precipitation??
Forest and wetland cover are the two most efficient
methods for promoting ev...
Conclusions

• Forest cover important role for
the global hydrologic cycle.
• Increasing forest cover increases
regional p...
Remember
Recycling!

M.Falkenmark March 09
Are forests good for water and food
security in Ethiopia?

Swedish Ministry of Foreign Affairs as
Project on global food s...
Two MSc Students to the
Koga Irrigation Dam
Two PhD Students from
Centre for Natural Disaster Science
New Interdisciplinary research initiative
by the Swedish Governm...
Water, forests and footprints – finding the right scale for sustainability by Kevin Bishop
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Water, forests and footprints – finding the right scale for sustainability by Kevin Bishop

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In his presentation Kevin Bishop tried to unfold how forests impact water partitioning at different scales. At a local catchment scale, a removal of forests usually increases the total flow, always increases the peak flows, and can increase as well as decrease the base flow. Although there exists some ambiguity regarding the role of forests, all scientific studies confirm that forests have larger evapotranspiration (ET) than most other land uses. (Evapotranspiration is the sum of evaporation and plant transpiration from the Earth's land surface to atmosphere) However, there are studies that consider impacts of forests on water availability for annual mass balances at the local watershed level misleading. More at www.siani.se

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Water, forests and footprints – finding the right scale for sustainability by Kevin Bishop

  1. 1. Water, forests and footprints – finding the right scale for sustainability Prof. Kevin Bishop Uppsala University & Swedish Univ. of Agricultural Sci.
  2. 2. Deforestation widely blamed for water problems Less than 4% forest in Blue Nile Will more trees help? Or will they “steal” water?
  3. 3. Green-Blue Water sees forests as consumers of water 65 % 35 % M.Falkenmark March 09
  4. 4. Plynlimon – Hydrologist Heaven Documented how forests took water – at the the 2 km2 catchment scale
  5. 5. My own background Digging in small catchments – Miss a bigger picture? ©Bill Waterson
  6. 6. Hydrology and Forests in the Blue Nile: What can be learned from half a century of observations and community perception for water management? Solomon Gebreyohannis Addis Ababa University and Swedish University of Agricultural Sciences
  7. 7. Popular Perception vs Science Popular hopes for reforestation: – Increase dry-season flow – Decrease erosion But science suggests… While Peak flows and erosion will decrease Total flow will probably decrease Dry season flows will probably decrease, (but site-specific information needed)
  8. 8. Interdisciplinary PhD Thesis: Half a century of quantitative and qualitative observations • A dozen catchments have over 40 years of daily flow data. • Remote imagery exists for land use/land cover change analysis • Community perception will be used help in the analysis. *= Flow gauge
  9. 9. Some large declines in forest area 1957 Landcover 16% Forest = Green 2000 2% Forest
  10. 10. 120 100 y = 0.0008x + 0.3844 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 3 Peakflow (m 3/s) 140 Baseflow (m /year) Statistical and Modeling Analyses: No obvious deforestation impact 80 60 40 20 y = 0.0321x - 17.17 0 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 Peakflow (m^3/sec) Baseflow (m^3/yr)
  11. 11. Community Perception: A complex understanding of the forest-water relationship
  12. 12. Deforestation influence on streamflow: Revisting what has science “proven” Deforestation Total flow usually increases Peakflow always increases Baseflow sometimes increases sometimes decreases Region-specific data needed to know response
  13. 13. Watershed Mass Balance Evaporation + Transpiration (ET) Precipitation (P) Runoff (Q) 11/14/2013 13
  14. 14. Are Forests Good for Water Resources? 14
  15. 15. The Hydrologic Cycle: Trees remove water at one point, return it to the region
  16. 16. The Forest-Water Debate: Supply vs. Demand-Side Demand-side: Increasing forest cover reduces runoff Ecosystems subtract from the water budget Strong observational basis (<2 km2) Supply-side: Increasing forest cover positively impacts precipitation and runoff Sometimes labeled the “romantic” or even mythological view Limited empirical evidence Regional Modeling is the best evidence
  17. 17. Recycled ET Ocean Annual 40% 60% Summer 60% 40% Source data generously provided by Michael Bosilovich, NASA Baltics SON Balatic JJA DJF Water Recycling Modelled at Regional Scales MAM 160 140 120 100 80 60 40 20 0
  18. 18. Average Estimated Precipitation in Major River Basins by Source (1948-1997) 120 100 80 60 40 20 0 200 150 150 100 100 50 50 0 DJF MAM JJA 200 0 DJF MAM JJA SON 150 300 250 200 150 100 50 0 100 50 0 350 300 250 200 150 100 50 0 DJF MAM JJA SON DJF MAM JJA SON HUB Mississippi 500 400 300 200 100 0 300 100 200 50 100 0 GTR 400 150 SON SON Tibet 200 DJF MAM JJA SON Baltics Siberian MacKenzie DJF MAM JJA DJF MAM JJA SON 0 DJF MAM JJA CAT SON Source data generously provided by Michael Bosilovich, NASA. Highlighting indicates Terr_shr > Oc_shr. DJF MAM JJA Amazon SON Note: local share included in terrestrial share.
  19. 19. Much Precipitation is Recycled Evaporation: East African over 50% of rain from trees Should Egypt be more concerned about deforestation of the Congo that dams on thd Blue Nile?
  20. 20. The Forest Water Yield Debate: A Question of Scale • All Agree: Trees Increase Evapotranspiration – Demand-side View: Reduces runoff – Supply-side View: Recycles Water, Increases Rain • View point depends on Scale – Demand at Small Scale – Supply at Large Scale
  21. 21. What is Forest ET’s impact on precipitation?? Forest and wetland cover are the two most efficient methods for promoting evapotranspiration (ET) Only oceans can evaporative as effectively - 90% of ocean evaporation falls back on the ocean Cropland exhibits comparatively low evaporative efficiency Land conversions to agriculture will reduce precipitation Between 2000-2005, global forest cover has decline by 3% (Hansen et al 2010) Suggests a 4.7-5.3% decline in global precipitation
  22. 22. Conclusions • Forest cover important role for the global hydrologic cycle. • Increasing forest cover increases regional precipitation and runoff . • Global impact of forest cover does not rule out local demand. • Trans-boundary impacts of local decision-making about forests. • Forest provide ecosystem services beyond biomass
  23. 23. Remember Recycling! M.Falkenmark March 09
  24. 24. Are forests good for water and food security in Ethiopia? Swedish Ministry of Foreign Affairs as Project on global food security 24
  25. 25. Two MSc Students to the Koga Irrigation Dam
  26. 26. Two PhD Students from Centre for Natural Disaster Science New Interdisciplinary research initiative by the Swedish Government Climate Adaptation = Disaster Mitigation

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