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ESTIMATION OF THE OPTIMAL GUIDE CURVE FORA RESERVOIR, CASE STUDY COPA DAM, BOYACÁ1. SANABRIA J ., 2. SANTOS G., 3. SIERRA F.,. 4. GERALD A. CORZO cuelaing.edu.co ps://www.un-ihe.org/https://www.escuelaing.edu.co/

INTRODUCTIONESTIMATION OF THE OPTIMAL GUIDE CURVE FOR A RESERVOIR, CASESTUDY COPA DAM, BOYACÁThe objective of the study is the understanding of the guide curve calculation for thereservoir management releases in order to improve the storage usage which can be usedfor multi-objective purposes.La Copa reservoir, located in the upper Chicamocha river basin in Colombia was originallybuilt with the objective of mitigating floods over the valley. An irrigation district was latterestablished, with the objective of supplying water to farmers.This study presents the analysis and optimization of operational rules to minimize thelikelihood of floods and shortages for the irrigation district considering the uncertainty inthe hydrological system.2011 Flooding Conditions DownstreamLa Copa Dam2

ESTIMATION OF THE OPTIMAL GUIDE CURVE FOR A RESERVOIR, CASESTUDY COPA DAM, BOYACÁGENERAL LOCATION110000011200001140000Located in Boyacá - Colombia, La Copareservoir was built in 1993 to supply thedemands of USOCHICAMOCHA irrigationsystem in the Chicamocha river basin.1140000 1120000Inundation Area: 326 Km21120000Total Storage: 70 Hm3Sources: Esri, HERE, Garmin, Intermap,increment P Corp., GEBCO, USGS,FAO, NPS, NRCAN, GeoBase, IGN,Kadaster NL, Ordnance Survey, EsriJapan, METI, Esri China (Hong Kong),(c) OpenStreetMap contributors, and theGIS User CommunityStorage for irrigation: 34.5 Hm3Storage for flooding: 5 Hm3ConvencionesLaguna 500000La Copa ReservoirEmbalse 100000RASk.tif1100000High : 2541.8202.5510110000015Sources: Esri, HERE, Garmin, Intermap, increment PCorp., GEBCO, USGS, FAO, NPS,GeoBase,LowNRCAN,: 2533.91IGN, Kadaster NL, Ordnance Survey, Esri Japan,METI, Esri China (Hong Kong), (c) OpenStreetMapKilometerscontributors, and the GIS User AlineamientoCommunity, Sources:20Esri, Garmin, USGS, NPS11200001100000ValueSources: Esri, HERE, Garmin, Intermap,increment P Corp., GEBCO, USGS,FAO, NPS, NRCAN, GeoBase, IGN,Kadaster NL, Ordnance Survey, EsriJapan, METI, Esri China (Hong Kong),3

PROBLEM DESCRIPTION1. Flooding Boundary 2011yearESTIMATION OF THE OPTIMAL GUIDE CURVE FOR A RESERVOIR,CASE STUDY COPA DAM, BOYACÁ12. Dam Release (HowellBunger Valves)3. Detail Dam Embankment4. General View BoundaryReservoir Extent2344

PROBLEM DESCRIPTIONESTIMATION OF THE OPTIMAL GUIDE CURVE FOR A RESERVOIR, CASESTUDY COPA DAM, BOYACÁOperation of a reservoir must address one or more objectives, those are mainlyrelated to flood control and water supply. While flood control objective requires themost storage capacity available in the reservoir for high runoff volumes, water supplyobjective requires the reservoir to be as full as possible in order to provide the waterdemands.Thus, a methodology was developed aimed to find and optimized guide curve takinginto account both flood control and water supply objectives.Trough a case study, a reservoir simulation model was constructed for a either acritical wet year and a critical dry year. In order to select the appropriate set point forthe case study, a set of methodologies where tested and compared.The releases calculated by the decision scheme for the suitable set point werehydrodynamically modelled downstream to validate the reduction of the flood risksfor the wet year.5

PROBLEM DESCRIPTIONESTIMATION OF THE OPTIMAL GUIDE CURVE FOR A RESERVOIR, CASESTUDY COPA DAM, BOYACÁGuide curve is the Setpoint to bereached by the decision scheme atany time step of the simulationperiod.Operation rules are the constraintsin the simulation model e.g (fullbank discharge downstream)Basin partially instrumented, a dailyinflow discharges are constructedusing semi-distributed model.Flow Chart of the Operational Water Management Simulation in the Reservoir6

ESTIMATION OF THE OPTIMAL GUIDE CURVE FOR A RESERVOIR, CASESTUDY COPA DAM, BOYACÁCOMPONENTS IN THEOPTIMIZATION PROBLEM Objective Function: Minimize the sum of the excess and shortage volumes expected in theyear.OF 𝑚i𝑛 (𝑉𝑒𝑥𝑐𝑒𝑠𝑠 𝑉𝑠ℎ𝑜𝑟𝑡𝑎𝑔𝑒 ൯ Decision Variables: For the case study are the releases from the dam Constraints: Physical and environmental restrictive conditions for the variables in thereservoir:Operational Zone: Maximum and minimum water levelsBankfull Discharges: Maximum downstream flows before floodingMinimum Discharge: Echological flow in the stream Setpoint as a guide curve: Calculated by using different methodologies7

DECISION SCHEMESMODELLED DS based in the comparison of guidecurve level (setpoint) from theactual month with respect to thereservoir level at end of theprecedent month. DS based in the comparison of guidecurve level (setpoint) from theactual month with respect to thereservoir level at the beginning ofthe precedent month. DS for the reservoir water levelprediction at the end of the actualmonth by using both maximumrelease and the maximum bankfulldischarge downstream.ESTIMATION OF THE OPTIMAL GUIDE CURVE FOR A RESERVOIR, CASESTUDY COPA DAM, BOYACÁGuide curveE.g. For February, the purpouse is conservation, given that the level at thebeggining of the precedent month is lower than the level at the actual monthDead ElevationSpillwayMax LevelSelected GCWet year operationMaximum DischargeMinimum DischargeE.g. For April, the purpouse is flood control, given that the level at thebeggining of the march is lower than the level at the actual monthDecision Scheme for Maximum Discharges in Hec-ResSim8

PHYSICAL PROCESSESMODELLEDESTIMATION OF THE OPTIMAL GUIDE CURVE FOR A RESERVOIR, CASESTUDY COPA DAM, BOYACÁHydrological SimulationThe dam inflow daily discharges werecalculated with an Hec-Hms hydrologicalmodel.Reservoir ProtocolOperation (GuideCurves Testing)2D Hydrodinamical FloodTesting DownstreamThe reservoir operation was simulatedwith HecResSim model.The downstream river condition for themanaged releases was tested with HecRas 2DAdapted From Stream Corridor Restoration, 2001.9

HYDROLOGIC MODELLINGESTIMATION OF THE OPTIMAL GUIDE CURVE FOR A RESERVOIR, CASESTUDY COPA DAM, BOYACÁAcontinuoussemi-distributedhydrological model was created forthe basin in the year 2011, whichwas an abnormal rainy.SMA (Soil Moisture Accounting) lossmethodology was selected.The model was calibrated with dailydischarge measurements.La Reforma Discharge StationThe upstream dam catchment is partially instrumented, the calibrated model allows to estimatethe daily discharges in the whole upstream reservoir catchment.10

HYDRAULIC MODELLINGESTIMATION OF THE OPTIMAL GUIDE CURVE FOR A RESERVOIR, CASESTUDY COPA DAM, BOYACÁTo understand the effects of the criticaldischarges, a 2D hydraulic model wasbuilt downstream the dam.Hec-Ras 2D Model was executed for the45 days analysis period, where peakdischarges occurred.River flood conditions were observeddownstream the dam.Flooding Conditions Modelled Downstream Dam withoutOperation11

RESERVOIR OPERATIONMODELLINGESTIMATION OF THE OPTIMAL GUIDE CURVE FOR A RESERVOIR, CASESTUDY COPA DAM, BOYACÁZone Flood ControlThe output discharges from thehydrological model were used todesign the reservoir operationmodel.Conservation ZoneHec-ResSim ReservoirManagement Software was used totest the reservoir guide curvesperformance.A set of different guide curves werecreated using differentmethodologies.Hec-ResSim SchematicHec-ResSim Results12

GUIDE CURVECONSTRUCTIONESTIMATION OF THE OPTIMAL GUIDE CURVE FOR A RESERVOIR, CASESTUDY COPA DAM, BOYACÁMETHODOLOGIES FOR GUIDECURVE CONSTRUCTION Using the guide curvesoftware calculation CEH-ECI(2008) Calculating the awaiting andreserve volumes required ineach month using statisticalanalysis Using optimization methodsMES Guide CurveMontecarlo method𝑉𝑓 𝑉𝑖 𝐴 𝐷 𝑁 0.0864Where,𝑉𝑓 𝑅𝑒𝑠𝑒𝑟𝑣𝑜𝑖𝑟 𝑣𝑜𝑙𝑢𝑚𝑒 𝑝𝑟𝑒𝑐𝑒𝑑𝑒𝑛𝑡 𝑚𝑜𝑛𝑡ℎ 𝑀𝑚3𝑉𝑖 𝑅𝑒𝑠𝑒𝑟𝑣𝑜𝑖𝑟 𝑣𝑜𝑙𝑢𝑚𝑒 𝑎𝑡 𝑡ℎ𝑒 𝑒𝑛𝑑 𝑜𝑓 𝑡ℎ𝑒 𝑎𝑐𝑡𝑢𝑎𝑙 𝑚𝑜𝑛𝑡ℎ 𝑀𝑚3𝐴 𝑀𝑒𝑎𝑛 𝑚𝑜𝑛𝑡ℎ𝑙𝑦 ��� 𝑚𝑒𝑎𝑛 𝑟𝑒𝑙𝑒𝑎𝑠𝑒𝑠 𝑎𝑡 𝑡ℎ𝑒 𝑎𝑐𝑡𝑢𝑎𝑙 𝑚𝑜𝑛𝑡ℎ𝑠𝑁 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑚𝑜𝑛𝑡ℎ 𝑑𝑎𝑦𝑠The given equation is a regressive calculation of the monthly volumes needed to ensurethe required releases of the reservoir.The objective is the calculation of the volumen at the end of the previous month to supplythe monthly demands using the affluences and the expected volume at the end of themonth.13

GUIDE CURVECONSTRUCTIONESTIMATION OF THE OPTIMAL GUIDE CURVE FOR A RESERVOIR, CASESTUDY COPA DAM, BOYACÁMETHODOLOGIES FOR GUIDECURVE CONSTRUCTIONDead ElevationSpillway Using the guide curvesoftware calculation CEH-ECI(2008)Maximum leve Calculating the awaiting andreserve volumes required ineach month using statisticalanalysis Using optimization methodsMES Guide CurveMontecarlo methodGuide Curve CEH-ECICG (EAAB-ESP, 2008) is a software which has capabilities in guide curve construction formonthly reservoir operation by using historic hydrological series (precipitation, discharges,evaporation and infiltration) and basic information from the reservoir as elevation, volume andboundary areas.14

ESTIMATION OF THE OPTIMAL GUIDE CURVE FOR A RESERVOIR, CASESTUDY COPA DAM, BOYACÁGUIDE CURVECONSTRUCTIONMETHODOLOGIES FOR GUIDECURVE CONSTRUCTION𝑞𝑖,𝑗 𝑋ഥ𝑗 𝜌𝑖,𝑗 1 𝑆𝑗𝑞𝑖,𝑗 1 𝑋ത𝑗 1 𝑍𝑖,𝑗 𝑆𝑗 1 𝜌𝑖,𝑗 1𝑆𝑗 12Where: Using the guide curvesoftware calculation CEH-ECI(2008) Calculating the awaiting andreserve volumes required ineach month using statisticalanalysis Using optimization methods𝑋ഥ𝑗 : Mean historic discharges for month j under consideration.𝑋ത𝑗 1 : Mean historic discharges for month j-1 under consideration.𝜌𝑖,𝑗 1 : First order correlation coefficient between the values in succesive months.𝑆𝑗 : Standard deviation for the historical discharges in j month.𝑆𝑗 1 : Standard deviation for the historical discharges in j-1 month.𝑞𝑖,𝑗 : Discharges at j month of the year i for the generated discharge sequence.𝑞𝑖,𝑗 1 : Discharges at j-1 month of the year i for the generated discharge sequence.𝑍𝑖,𝑗 : Random variable normally distributed applied to the j month for the i year.Thomas & Fiering ModelMES Guide CurveMontecarlo methodHistoric discharge records can be extended using the principle of presistence which indicatesthe high probability of low flow followed by a low flow due to the storage effect.15