Green Water Credits Use of quantitative tools to evaluate potential Green Water Credits options Peter Droogers Wilco Terink Johannes Hunink Sjef Kauffman Godert van Lynden

Blue and Green Water

Example of potential benefits

Introduction

CONCEPTS BIOPHYSICAL ANALYSIS

Tools and Information Understand current water resources Understand past water resources Options for future - technical - socio-economic - policy oriented Trend Past Today Future Observations Remote Sensing Analysis Statistics Models ? ? change

Quantification GWC Water Demand? Water Consumption? Water Supply? Impact Changes? Productive Use? Soil Water Conservation impact?

GWC Proof Observations in field (flows, erosion) – Precipitation dominant factor Large scale – experimental plots not possible Simulation model – experimental basin in PC – multiple options can be tested – various weather conditions (dry-wet)

Tool Selection Physical detail lowhigh Spatial scale field system basin continent Podium STREAM SLURP WSBM SWAT WEAP IQQM SWAP AquaCrop

SWAT and WEAP SWAT (Soil and Water Assessment Tool) Supply analysis Physical Based Impact soil-water-conservation measures Detailed farm management analysis Public domain User friendly interface WEAP (Water Evaluation And Planning systems) Demand analysis Conceptual based Benefit – Costs analysis Detailed upstream-downstream interactions Public domain Very user friendly interface

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 Data sets required: – Digital Elevation Model (DEM) – Climate – Land use and management – Soils – Streamflow – Reservoirs

Data Sources locally- sourced locally- sourced non- RS non- RS global public-domain global public-domain Remote Sensing Remote Sensing Land Cover Streamflow Operations Climate LAI Soils Topography Socio-Economic Groundwater

Data Elevation Landuse Soils Climate

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: Key Indicators Upstream – Crop transpiration – Soil evaporation – Groundwater recharge – Erosion Downstream – Inflow Masinga – Sediment load Masinga Climate – dry (2005) – wet (2006)

Results: Key Indicators

Results: Spatial

OVERALL BENEFIT-COST ANALYSIS

WEAP Tool Impact of changes in water-soil dynamics on: – upstream rainfed improved production – downstream hydropower domestic water supply irrigation Benefit-cost analysis Integrations tool: WEAP

WEAP Tool

WEAP: Validation

Results: Reduction in water shortage

Results: Increase in hydropower

Results: Increase in Benefits

Results: Benefit-Cost Analysis 20% of area ~ 100,000 smallholders

DISCUSSIONS, CONCLUSIONS

Conclusions GWC beneficial for: – upstream – downstream Analysis tools: – SWAT: (upstream) supply – WEAP: (downstream) demand Steps – Understand current situation – Explore options GWC – Biophysical component – Socio-economics – Institutional – Financial

Discussion / conclusions Smaller focus area – current study: 1.8 million ha total; 0.5 million ha rainfed Definition of GWC options – effectiveness of implementation Convincingness of current approach – Rainfed farmers – Downstream beneficiaries Monitoring system

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