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The potential benefits of Green Water Credits. Part 1: Quantifying the role and advantages for upstream farmers. Johannes Hunink Peter Droogers Wilco Terink Sjef Kauffman Godert van Lynden. First : the basic principles. Water always flows downhill So do sediments and nutrients
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The potential benefits ofGreen Water Credits Part 1: Quantifying the role and advantages for upstream farmers • Johannes Hunink Peter Droogers Wilco Terink Sjef Kauffman Godert van Lynden
First: thebasicprinciples • Wateralwaysflowsdownhill • So do sediments and nutrients Itfollowsthatland/watermanagementupstream: • Can positivelyinfluencefoodsecurityupstream • Can positivelyinfluencewatersupplydownstream
Quantifying GWC Impact Changes? Water Consumption? Soil Water Conservation impact? Productive Use? Water Demand? Water Supply?
WHAT to quantify? • Supply Biophysicialassessment • Supply vs. Demand Cost-benefitanalysis
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)
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 Soils Climate
Selection of GWC options • 11 options explored • Bench terraces • Conservation tillage • Contour tillage • FanyaJuu 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: 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)
The potential benefits ofGreen Water Credits Part 2: Quantifying profits for downstream water users Peter Droogers Wilco Terink Johannes Hunink Sjef Kauffman Godert van Lynden