chaophraya final

7/29/2019 Chaophraya Final

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Hydrological Modeling for Upper Chao

Phraya Basin Using HEC-HMS

UNDP/ADAPT Asia-Pacific First Regional Training Workshop

Assessing Costs and Benefits of Adaptation: Methods and DataMarch 11-14, 2013

Dr. Dilip K. Gautam

RIMES, AIT Campus, Bangkok


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Hydrological Model

A model is a simplified representation of reality.

A mathematical model consists of series of equations defining the system

we are dealing with. The function of model is to convert the given input

into an output.

A hydrological model is the mathematical representation of the responseof a catchment system to hydrologic events during the time period under

consideration.

Hydrological phenomena are extremely complex, highly non-linear and

highly variable in space and time. A model is needed to predict the watershed runoff for the design and

management of water resources utilization and flood control projects.


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Classification of Hydrological Models


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Hydrological Model Outputs for

Climate Change Impact Assessment

Simulated flow peaks, volumes and hydrographs atthe outlets of subbasins and the points of specialinterest such as reservoirs, weirs or other hydraulic

structures Simulated long flow sequences for water budget and

drought analyses

Simulated extent of flooded areas for differentprecipitation events and various antecedent basinconditions


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Hydrologic processes that need to

be captured by the model

Single-event precipitation-runoff transformation

Continuous precipitation-runoff transformation

Snow accumulation and melt

Interception, infiltration, soil moisture accounting

Evapotranspiration

Regulated reservoir operation


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HEC-HMS

US Army Corps of Engineers, Hydrologic Engineering

Centers Hydrologic Modeling System software

Designed to simulate both single event and continuous rainfall-runoff process

Simulates precipitation-runoff and routing processes, both

natural and controlled

HEC-HMS uses a separate model to represent eachcomponent of the runoff process including:

runoff volume;

direct runoff (overland flow and interflow);

baseflow;

channel routing.


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HEC-HMS representation of watershed runoff


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Key Components of Model Runoff Volume models: separate infiltration from

pervious surface, runoff from impervious surface,compute the direct runoff volume

Direct Runoff models: transform direct runoff volumefrom excess precipitation into fast component of flow

Base Flow models: compute slow subsurface drainage

component Routing models: compute flow attenuation and

translation over channel

Reservoir models: f low regulation


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Data Required

Digital Elevation Model (DEM), land use, soiltypes and other physiographic data

Precipitation, temperature data

Evaporation/evapotranspiration data

Discharge, Water level and Rating curve data

Channel and reservoir hydraulic data

Generated sequence of meteorological data

representing various scenarios of future climate


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Upper ChaoPhraya Basin,

Thailand

Catchment Area

= 105553 sq. km.


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Dams and Reservoirs

Bhumibol dam in the Ping River (Storage 13462 MCM)

Sirikit dam in the Nan River (Storage 9510 MCM)

Kwae Noi dam in Kwae Noi River (Storage 766 MCM)

Kiew Kor Mha dam in Wang River (Storage 171 MCM)

Kiew Lom dam in Wang River (Storage 112 MCM)


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Data preparation using HEC-GeoHMS

Delineate catchment and river network

Obtain catchment characteristics data (area, slope etc)

Make Thiessen polygon

Obtain Thiessen weights

Prepare basin file


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Data preparation using HEC-DSSVue

Time series data (rainfall, discharge etc.)

Pair data (elevation-storage)


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Model Setup

Basin model

Meteorological model

Time series data

Pair data

Control specification


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Meteorologic model

Precipitation

Evapotranspiration

Snowmelt : not applicable for upper Chao Phraya


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Precipitation methods

Gauge weights : selected for upper Chao Phraya

Inverse distance

Gridded precipitation

Frequency storm

SCS storm

Specified Hyetograph

Standard project storm


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Evapotranspiration methods

Monthly Average : selected for upper Chao Phraya

Priestley-Taylor

Gridded Priestley-Taylor


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Snowmelt methods

Gridded temperature index

Temperature index


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Control Specifications

Simulation start date/time

Simulation end date/time

Time interval


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Model Calibration

Finding optimal parameter values

Minimizing difference between simulated f lowand observed flow

Objective functions

Peak weighted RMS error Percent error peak

Percent error volume

RMS log error

Sum of absolute residuals

Sum of squared residuals

Time weighted error


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Search Algorithms

Nelder Mead

Univariate Gradient


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The Basin Model
http://c/Program%20Files%20(x86)/HEC/HEC-HMS/3.5/HEC-HMS.exe


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Simulated Hydrograph at Basin OutletR2 = 0.71 BIAS = 6.7 % NS = 0.71


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Conclusions

Semi-distributed physically based deterministichydrological models are powerful tools for assessingclimate change impact on water resources.

Continuous modeling approach could be taken toassess the impact on flow volume.

Care should be taken to interpret the results as thereare lots of uncertainties in the model inputs,

parameters and structure of the model. Uncertaintiesassociated with climate models will also be carriedover.


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Thank You !

Dr. Dilip K. Gautam, Senior Hydrologist, RIMES

E-mail: [email protected]

Website: www.rimes.int
mailto:[email protected]:[email protected]

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