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These were then used as input to the SWATmodelling.‣ a lower groundwater recharge rate isexpected (Fig.4).30Results from the scenario analysisAfter the model was calibrated and validated inthe baseline simulation (R 2 >0.90 NS=0.44), itenabled us to apply the scenarios after havingparameterized them (that is convertingconcepts into numbers used by the model).However uncertainties present in the baselinesimulation are reflected into scenarios output:the scenario on irrigation changes is notcommented here because of uncertaintiesembedded in the cropping pattern andpractices.Some of the results can be summarized as inthe following Tab.1.Baseline A2 diff %Precip mm 829 928 12ET mm 469 539 15Surf.runoff mm 177 219 24Water Yld mm 334 365 9Sediment load t/ha 12.4 28.9 132water inflow reserv mm 261 444 70water outflow reserv mm 141 177 26sed.inflow reserv t/ha 0.6 1.9 253sed.outflow reserv t/ha 0.02 0.02 27Tab. 1 Summary results of the A2 climatechange scenarioThe climate scenario impact results indicatethe following:‣ a doubling in the sediment load;‣ the sediment inflow into the TB dam isexpected to increase three times whilethe sediment outflow will remain more orless stable. This will lead to a greatincrease of the siltation rate and areduced life-time of the dam;Relative Change (%2520151050-5-10Baseline to A2IPCC SRES Scenarios ComparisonPrecipitationSurface RunoffGW RechargeWater YieldAETBaseline to B2Fig.4 Change in water balancecomponents from baseline to A2 and B2The other simulated scenarios lead to thefollowing conclusions.‣ the simulated spread of SRI leads to anexpected 6% saving of the river basinwater yield, accompanied by an overallincrease of around 20% of rice yield;‣ the simulated sewage treatment scenarioshowed that a 50% reduction fromsewage discharge can be expected inboth N and P contribution to the overallriver pollution.Even if the model was calibrated only for thehydrology, scenarios simulations areconsidered reliable since:• climate change simulation are based onhydrology except for erosion;• calculated actual erosion rate is inagreement with measured siltation rate inthe Tungabhadra dam (since monitoredsediment transport is missing);• water saving due to SRI diffusion scenariois based on changes in irrigation and thenmostly on hydrology;• sewage treatment scenario is obtained onsimple point source load calculations.allowing higher yields, less seeds requirementand less water for irrigation.STRIVER POLICY BRIEF / ISSUE NO. 7 6
Management implications‣ It is necessary to put larger efforts inplanning effective monitoring activities:more frequent water quality sampling, alarger selection of parameters to bemeasured, namely phosphorus, ammoniaand suspended solids.‣ The actual high level of erosion andincrease in simulated trend in the futuredue to climate change suggest that erosioncontrol should gain a high priority in nextfuture landscape management policy.‣ Investment in improved sewage treatmentin urban and rural areas will significantlyreduce the nutrient load to the river andcan dramatically decrease the level ofpathogens in surface water.‣ Active policies must be undertaken with adeeper effort to help the diffusion of newtechniques in rice cropping (SRI) thatroved to play a relevant role in savingwater resources.Fig.4 The Tungabhadra Dam. Public domain. Courtesy of Wikipedia users (http://www.wikipedia.com).STRIVER POLICY BRIEF / ISSUE NO. 7 7
Page 3: Why physical models?In the Tungabha
Page 8: The STRIVER Policy and Technical Br

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