Adapting to Climate Change: Assessing the World Bank Group ...

APPENDIX FANALYTIC WORK ON CLIMATE ADAPTATIONF3. Comparison of Analytic Models of Climate Change Impact on HydropowerStudyNepal: Khimti 160 MW run ofriverStenek ConnellFirth Colley(2011)Kafue GorgeLower750 MW station,part of a 3 dam, 3reservoir systemwith importantenvironmentalflow requirementsStenek and others2011Zambezi BasinBasinwidemodeling ofhydropower andirrigationStrzepek andothers 2011Modeling approach andissues4 GCMs*2 emissionsscenarios.A regression model relatedpast annual climate conditionsto water flows. The regressionwas then used for futureprojections.However, water flows for 1985-1994 were drastically higherthan for 1995-2006. Projectionswere made based on each ofthese differing baselines.No reliable info on snowpackcontribution to summer runoff.3 GCMs * 2 emissionsscenarios were statisticallydownscaled and fed into ahydrological model to assessfinancial and flood risk impacts.Only one realization of eachGCM was used, leading toincorrect interpretation ofclimate impact. (see note*).56 GCM/emission scenariosapplied to basin models withoutdownscaling.Findings on climate impactGCMs gave widely varyingprecipitation projections—someincreasing, some decreasing.(Basin is highly dependent onmonsoon rainfall, but monsoonsare poorly modeled.) Thesechanges were added to divergentbaselines. Hence, uncertainty wastoo great to allow quantitativeimpact assessments.Baseline IRR=21.6%IRR under climatechange=19.7±2.4%Average annual loss from droughtincreases from current $2.1 millionto $3.4 to $5 million over 2010-2039. Flood and landslide lossesare small.Almost all GCMS show areduction in precipitation; meanreduction is 20%. This is projectedto heighten the tradeoff betweenpower production and irrigation,because water availability isreduced. Power production has ahigher economic value, butirrigation provides much moreemployment.AdaptationrecommendationsBecause the plant is alreadyin place, recommendationsare no-regret, low regret, andadaptive management,emphasizing ongoingmonitoring of flows andenhancement of capacity.Model results not used toassess recommendations.A variety of no regrets andlow regrets measures wereproposed, together withcostlier ones (increasereservoir capacity). But thereis insufficient information toassess costs and benefits.Repeat analysis with a morerefined model, reassessinginvestment plans andconsidering agriculturaladaptation options.*Note: The Kafue Gorge Lower analysis compares projected outcomes for 2010-2039 under the A2 (high) andB1 (low) global emissions scenarios, finding divergent results. It concludes that the economic returns will belower under A2. However, a well-known feature of these scenarios is that the higher emissions under A2 do notnoticeably affect the overall atmospheric accumulation of CO2—and hence have little impact on the climatesystem—until the 2040s. So it is implausible that KGL performance would drastically differ between the twoscenarios. The difference appears to reflect random variation between a single realization of each scenario. Thatis, many possible weather sequences are compatible with each of the two emissions scenarios. By chance, thestudy arrived at a particularly unfavorable A2 scenario and a favorable B1 scenario. A side analysis ran 9randomly “tweaked” versions of A2, arriving at a range of possible outcomes (reported in the findings columnabove).121