The potential benefits ofGreen Water Credits

Part 1: Quantifying the role and advantages for

upstream farmers Johannes HuninkPeter Droogers

Wilco TerinkSjef Kauffman

Godert van Lynden

First: the basic principles1) Water always flows downhill2) So do sediments and nutrients It follows that land/water management upstream:

a) Can positively influence food security upstream b) Can positively influence water supply downstream

Quantifying GWC

Water Demand?

Water Consumption?

Water Supply?

Impact Changes?

Productive Use?

Soil Water Conservation impact?

Example of potential benefits

WHAT to quantify?

• Supply Biophysicial assessment

• Supply vs. Demand Cost-benefit analysis

HOW to quantify?

• Observations in field (flows, erosion)– Precipitation dominant factor

• Large scale– experimental plots not possible– a lot of experimental data is already available

• Simulation model– experimental basin in PC– multiple options can be tested– various weather conditions (dry-wet)

RIVER BASIN SOIL AND WATER CONSERVATION

Methodology

• Hydrological models as a tool to simulate the paths of water and soil movement

• Upstream-downstream interactions

Methodology

• Soil and Water Assessment Tool (SWAT)

• Physically based• Focus on water-erosion-land

management processes• Public domain• Large user-group worldwide• Successfully applied in many

other studies worldwide as well as in Kenya

Data

Elevation

Landuse

SoilsClimate

Model Reliability

Selection of GWC options

• 11 options explored• Bench terraces• Conservation tillage • Contour tillage• Fanya Juu terraces• Grass strips• Micro-catchments for planting fruit trees• Mulching• Rangelands• Ridging • Riverine protection• Trash lines

• Labor: intensive vs. extensive• Investment: low vs. high• Implementation on 20% of area ~ 100,000 farmers

Results: temporal

Results: spatial

• F.e. erosion rates may drop considerably in some areas

• Relative reduction depends on – location and – crop and land

management

Results: Spatial

targeting

Results: Key Indicators

• Upstream– Crop transpiration– Soil evaporation– Groundwater recharge– Erosion

• Downstream– Inflow Masinga– Sediment load Masinga

• Climate– dry (2005)– wet (2006)

Results: Key Indicators

Inflow Masi

nga

Sedim

ent inflow M

asinga

Crop tr

ansp

iration

Soil e

vaporation

Groundwate

r rech

arge

Erosio

n

Scenario Land use* Year MCM/y Mton/y mm/y** mm/y** mm/y*** ton/ha/y***

dry 931 1.0 335 121 16 1.2

wet 2508 4.2 308 140 128 7.9

dry 1.1% -21% 0% -1% 3% -23%

wet 1.9% -21% 0% 0% 2% -18%

dry 0.1% -1% 1% -5% 1% -2%

wet 0.1% -1% 1% -4% 0% -1%

dry 1.1% -10% 0% -1% 7% -12%

wet 0.8% -7% 0% 0% 3% -6%

dry 0.4% -21% 1% -1% 4% -23%

wet 1.3% -20% 1% 0% 2% -18%

dry 0.6% -11% 0% -1% 3% -14%

wet 0.6% -10% 0% 0% 1% -10%

dry 0.6% -8% 0% -1% 2% -8%

wet 0.6% -6% 0% 0% 1% -5%

dry 0.4% -6% 3% -12% 3% -9%

wet 0.5% -6% 2% -12% 2% -8%

dry 0.1% -4% 0% -3% 1% -4%

wet 0.0% -2% 0% -2% 0% -6%

dry 1.4% -18% 0% -1% 23% -21%

wet 1.0% -12% 0% -1% 10% -12%

dry 0.0% -5% 0% -1% 0% -5%

wet 0.0% -4% 0% 0% 0% -4%

dry 0.6% -7% 0% -3% 3% -8%

wet 0.6% -6% 1% -2% 1% -5%

*M=Maize, C=Coffee, T=Tea,A=Agricul tura l ASAL, R=Rangelands ;

** Agricul tura l areas ; *** Bas in-wide;

Baseline

Inflow Masi

nga

Sedim

ent inflow M

asinga

Crop tr

ansp

iration

Soil e

vaporation

Groundwate

r rech

arge

Erosio

n

Scenario Land use* Year MCM/y Mton/y mm/y** mm/y** mm/y*** ton/ha/y***

dry 931 1.0 335 121 16 1.2

wet 2508 4.2 308 140 128 7.9

dry 1.1% -21% 0% -1% 3% -23%

wet 1.9% -21% 0% 0% 2% -18%

dry 0.1% -1% 1% -5% 1% -2%

wet 0.1% -1% 1% -4% 0% -1%

dry 1.1% -10% 0% -1% 7% -12%

wet 0.8% -7% 0% 0% 3% -6%

dry 0.4% -21% 1% -1% 4% -23%

wet 1.3% -20% 1% 0% 2% -18%

dry 0.6% -11% 0% -1% 3% -14%

wet 0.6% -10% 0% 0% 1% -10%

dry 0.6% -8% 0% -1% 2% -8%

wet 0.6% -6% 0% 0% 1% -5%

dry 0.4% -6% 3% -12% 3% -9%

wet 0.5% -6% 2% -12% 2% -8%

dry 0.1% -4% 0% -3% 1% -4%

wet 0.0% -2% 0% -2% 0% -6%

dry 1.4% -18% 0% -1% 23% -21%

wet 1.0% -12% 0% -1% 10% -12%

dry 0.0% -5% 0% -1% 0% -5%

wet 0.0% -4% 0% 0% 0% -4%

dry 0.6% -7% 0% -3% 3% -8%

wet 0.6% -6% 1% -2% 1% -5%

*M=Maize, C=Coffee, T=Tea,A=Agricul tura l ASAL, R=Rangelands ;

** Agricul tura l areas ; *** Bas in-wide;

11 Trash lines

Baseline

1 Bench terraces

2 Conservation tillage

3 Contour tillage

4 Fanya Juu terraces and variations

5 Grass strips

6 Micro-catchments for planting fruit trees

7 Mulching

8 Rangelands

9 Ridging

10 Riverine protection

MCT

M

M

MCT

MCT

MCT

MCT

MCT

AR

M

MCTA

Results: Increase in Benefits

The potential benefits ofGreen Water Credits

Part 2:Quantifying profits for

downstream water usersPeter Droogers

Wilco TerinkJohannes Hunink

Sjef KauffmanGodert van Lynden