imp5manual3.0

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USER MANUAL FOR

IMP 5.0(Integrated Method For Power Analysis)

February 3, 2004

239 Menzies Street, Suite 210 Tel: (250) 385-0206

Victoria, BC V8V 2G6 Canada Fax: (250) 385-7737

www.powelgroup.com User Manual: 2103-1800-3.0

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Table of Contents

Page

DISCLAIMER.......................................................................................................................................................... iv

1.0 INTRODUCTION.......................................................................................................................1 1.1 Purpose of IMP 5.0 .........................................................................................................11.2 How to Obtain IMP..........................................................................................................11.3 Minimum Software Requirements...................................................................................21.4 Installation Procedure ..................................................................................................... 2

2.0 GETTING STARTED................................................................................................................32.1 Navigating Around ..........................................................................................................32.2 Creating a New Project ................................................................................................... 32.3 IMP File Formats.............................................................................................................4

2.3.1 Project File (.PRO) .................................................................................................................. 4

2.3.2 Flood Frequency File (.FFA) ................................................................................................... 42.3.3 Watershed File (.PAR) ............................................................................................................42.3.4 Powerhouse File (.PIN) ........................................................................................................... 52.3.5 Database File (.MDB).............................................................................................................. 52.3.6 Excel File (.XLS)...................................................................................................................... 52.3.7 Text File (.TXT)........................................................................................................................ 62.3.8 Filename.AES.......................................................................................................................... 62.3.9 Filename.WSC ........................................................................................................................ 62.3.10 FilenameHDY.HSP................................................................................................................ 72.3.11 FilenameHHR.HSP................................................................................................................ 7

3.0 DATA IMPORTING...................................................................................................................83.1 Using the AES Format ....................................................................................................83.2 Using the WSC Format...................................................................................................93.3 Using the HSP Format....................................................................................................93.4 Using the TXT Format..................................................................................................... 93.5 Using the XLS Format...................................................................................................10

4.0 PRECIPITATION DATA.........................................................................................................114.1 View Meteorological Stations Closest to a Selected Location ......................................114.2 View All Meteorological Stations in Canada .................................................................114.3 View Precipitation Statistics..........................................................................................114.4 View Average Annual Precipitation for a Selected Location.........................................124.5 View 24-Hour Maximum, One-in-Ten Year Rainfall for a Selected Location................ 12

5.0 WEATHER AND STREAMFLOW DATA ..............................................................................135.1 Select a Station.............................................................................................................13

5.2 Select a Period to View.................................................................................................135.3 Select Data Type ..........................................................................................................13

6.0 FLOOD FREQUENCY ANALYSIS DATA.............................................................................146.1 View and Edit Catchment Data.....................................................................................146.2 View and Edit Streambed Data.....................................................................................156.3 Estimate Stream Width ................................................................................................. 156.4 View and Edit Precipitation...........................................................................................156.5 View and Edit Observed Streamflow ............................................................................16

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7.0 FLOOD FREQUENCY ANALYSIS RESULTS......................................................................17

8.0 WATERSHED DATA..............................................................................................................188.1 View and Edit Basin Characteristics .............................................................................188.2 View and Edit Water Budget .........................................................................................188.3 View and Edit Time Constants......................................................................................208.4 View and Edit Weather Stations ...................................................................................208.5 View and Edit Meteorology ...........................................................................................21

9.0 WATERSHED RUNOFF SIMULATION ................................................................................229.1 Simulate Watershed Runoff..........................................................................................229.2 View Simulated Discharge and Watershed Conditions................................................. 229.3 Analyze Results ............................................................................................................ 22

10.0 POWERHOUSE STUDY DATA.............................................................................................2310.1 View and Edit Efficiency Curve Data ............................................................................2310.2 View and Edit Reservoir Levels .................................................................................... 2310.3 View and Edit Turbine Data ..........................................................................................24

10.4 View and Edit Penstock Data .......................................................................................2410.5 View and Edit Operating Limits..................................................................................... 24

11.0 POWERHOUSE OPERATION MODELING..........................................................................2611.1 Simulate Powerhouse Operation ..................................................................................2611.2 View Powerhouse Operation Results ...........................................................................2611.3 Analyze the Results ...................................................................................................... 27

12.0 INSTALLED CAPACITY OPTIMIZATION.............................................................................28

13.0 STREAM GEOMETRY DATA................................................................................................2913.1 View and Edit an Existing Cross-Section......................................................................2913.2 Define a New Cross-Section.........................................................................................2913.3 Delete an Existing Cross-Section .................................................................................30

13.4 View and Edit the Discharge-Rating Curve...................................................................3014.0 FISH PREFERENCE DATA...................................................................................................31

14.1 Add a New Fish and Stage ........................................................................................... 3114.2 Delete a Fish................................................................................................................. 3114.3 View and Edit Composite Fish......................................................................................31

15.0 WEIGHTED USABLE AREA ................................................................................................. 3215.1 Simulate Weighted Usable Area vs. Discharge ............................................................3215.2 View Weighted Usable Area vs. Discharge Results .....................................................32

16.0 THE FLOOD FREQUENCY MODEL.....................................................................................3416.1 Use of Climatological Data to Define Probability .......................................................... 3416.2 Definition of Rainfall Events..........................................................................................34

16.3 Probability Density Function .........................................................................................3616.4 Probability and Return Period.......................................................................................3816.5 The Flood Frequency Watershed Model.......................................................................4016.6 Flood Probability ...........................................................................................................4216.7 Evaluation of Flood Probability ..................................................................................... 4216.8 Uses for Approximate Flood Frequency Formula .........................................................4416.9 Evaluation of Flood Frequency Method ........................................................................4516.10Estimates of Climatological Parameters ....................................................................... 46

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16.11Estimates of Area Producing Runoff.............................................................................47

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17.0 THE WATERSHED MODEL METHODOLOGY....................................................................4917.1 UBC Watershed Model Meteorological Analysis ..........................................................50

17.1.1 Temperature Lapse Rate.....................................................................................................5017.1.2 Precipitation Elevation Gradients ........................................................................................ 51

17.1.3 Orographic Enhancement as Function of Elevation, Barrier Height and Temperature.......5117.1.4 Form of Precipitation ........................................................................................................... 5317.1.5 Precipitation Interception Adjustment.................................................................................. 5417.1.6 Precipitation Transposition Factors.....................................................................................54

17.2 Soil Moisture and Groundwater .................................................................................... 5517.2.1 First Priority: Impermeable Percentage - Fast Runoff Control ...........................................5517.2.2 Second Priority: Soil Moisture and Actual Evapotranspiration........................................... 5517.2.3 Third Priority: Groundwater Percolation (GWPERC) .........................................................5717.2.4 Fourth Priority: Medium Runoff...........................................................................................57

17.3 Watershed Routing.......................................................................................................5717.3.1 Fast Runoff Routing.............................................................................................................5717.3.2 Medium Runoff Routing....................................................................................................... 5817.3.3 Slow Runoff Routing............................................................................................................58

17.4 Snowmelt Formulation .................................................................................................. 5917.4.1 Forested Melt Formulation...................................................................................................6017.4.2 Open-Area Melt Formulation............................................................................................... 6017.4.3 Negative Melt Budget .......................................................................................................... 61

17.5 Calibration Considerations............................................................................................6117.5.1 Regional Precipitation..........................................................................................................6117.5.2 The Watershed Model Parameters .....................................................................................6217.5.3 Runoff Area Contributing to Floods ..................................................................................... 63

18.0 THE POWER STUDY METHODOLOGY ..............................................................................6618.1 Linear Programming Approach..................................................................................... 6618.2 The Objective Function.................................................................................................6718.3 Constraints....................................................................................................................6718.4 Operating Rules............................................................................................................ 69

19.0 BIBLIOGRAPHY.....................................................................................................................70

20.0 APPENDIX A SCREENS FROM IMP 5.0...........................................................................73

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List of Figures

Figure 16-1 Rainfall and Runoff Spectra ................................................................................36Figure 16-2 Probability Density Function, Storm Duration......................................................37

Figure 16-3 Probability Density Function, Storm Intensity ......................................................37Figure 16-4 Watershed Concept.............................................................................................40Figure 16-5 Effect of Rainfall Intensity on Time of Concentration at Pearson Creek..............41Figure 16-6 Flood Frequency Comparison .............................................................................44Figure 16-7 Estimator for Rainfall Event Intensity...................................................................46Figure 16-8 Estimator for Rainfall Event Duration ..................................................................47Figure 16-9 Estimator for Number of Rainfall Events .............................................................47

List of Tables

Table 17-1 Calibration Factors for Regional Precipitation.....................................................62Table 17-2 List of Watershed Model Parameters ..................................................................64Table 17-3 Watershed Model Parameter Values in the IMP Database.................................65

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DISCLAIMER

This manual and corresponding computer program were prepared by Powel Group, Inc. as a

result of work sponsored by Natural Resources Canada. Neither the Government of Canada nor

its ministers, officers, employees or agents nor Powel Group, Inc. nor any of their employeesmake any warranty, express or implied, or assume any legal liability or responsibility for the

accuracy, completeness or usefulness of any information, apparatus, product, or process

disclosed or represented that its use would not infringe privately owned rights.

Her Majesty the Queen Right of Canada as represented by the Minister of Natural Resources

Canada (1990-2003).

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1.0 INTRODUCTION

1.1 Purpose of IMP 5.0

The purpose of IMP is to provide a convenient tool for evaluating small-scale hydroelectric powersites. By utilizing IMP (combined with the relevant meteorological and topographical data), in

approximately one day of in-house study, an experienced user can evaluate all aspects of an

ungauged hydro site. This includes a power study, development of a flood frequency curve and fish

habitat analysis.

IMP consists of five basic components that include:

An Atmospheric Model of annual precipitation and one in ten year, 24 hour maximum rainfall.

This model consists of a database on a ten-minute latitude longitude grid and a database of

nearly 10,000 weather stations in Canada. Note: This database contains data up to 1976 and

should be used with caution, as it may not be representative of current climate conditions. To

reduce errors, more recent precipitation data should be used from stations closer to the hydro

site. In Canada precipitation data can be obtained online at: www.ec.gc.ca.

A Flood Frequency Analysis Model that uses topographic information specific to the site and

information from the Atmospheric Model to generate the flood frequency curve. This is a

knowledge-based program that incorporates hydrologic judgment to suggest site-specific

parameters.

A Watershed Model that will generate a continuous hourly or daily time series of streamflow for

an ungauged site based on daily precipitation, maximum and minimum temperature and a

description of the basin including information from the Atmosphere Model.

A Hydroelectric Power Simulation Model that determines the daily energy output for a

run-of-river or reservoir storage site based on selected generation facilities and the hydrologic

daily time series generated by the Watershed Model. An optimization routine performs a

sensitivity analysis on the results of a simulation and provides an estimate of the optimal

installed capacity from economic data.

A Fish Habitat Analysis Model to help determine the weighted usable area (WUA) of one or

more types of fish in a particular stream cross-section at a particular flow. Weighed usable

area is the area available in a stream for fish to inhabit, and is a function of discharge and

fish preference.

1.2 How to Obtain IMP

IMP 5.0 is distributed by downloading directly from the IEA Small Hydro website at www.small-

hydro.com. The downloaded software is open to the public at no cost. User registration allows

user updates by email and dissemination of news items regarding IMP 5.0 software. For

international users without sufficient access to the Internet, a low cost or free CD-ROM can be

provided.

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1.3 Minimum Software Requirements

IMP 5.0 is designed for Windows 2000 Service Pack 4 with Microsoft Office 2000 Professional

including Access 2000.

1.4 Installation Procedure

IMP 5.0 can be successfully installed on any Windows 2000 while logged in with administrative

privileges. Execute the IMP 5.0 installation kit and follow the instructions on the screen to

complete the installation.

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2.0 GETTING STARTED

The program starts with a [Browser] window that displays the four files required to run IMP 5.0.

By default, the program loads the Demo project and its related files. The Demo project has been

set up based on data from British Columbia, Canada and is distributed with IMP as a samplefile.

2.1 Navigating Around

The program provides a Menu Bar, Toolbar and Status Bar that are visible at all times and common

to all screens. The Menu Bar and Toolbar are located at the top of the screen and the Status Bar

can be found at the bottom.

The Menu Bar offers utilities to open, create and save files, as well as access user options offered

in IMP. The four main components of the Menu Bar are: File, Options, Window and Help. The [File]

menu option is used to manage the file structure in a project. The [Options] menu offers user

options to change units and user level. The [Window] menu lists the current screen and allows for

different screen arrangements. The [Help] menu links to the online help system and provides

information about the program. The Toolbar is used to navigate and access the various screens in

the program. The Status Bar provides information related to the loaded screen, activity, and the

current date and time.

2.2 Creating a New Project

The IMP package requires a project file that stores the names of the four parameter files. The

files loaded in a project are displayed in the [Browser] window. Different information is stored in

each parameter file as described above. A new parameter file can be created and saved with

the project. To load a new database file, click on [File] in the Menu Bar and select [New ProjectDatabase File] from the list of menu options. Similarly, select [New Flood Frequency File] to

load a new flood frequency file, [New Watershed File] to load a new watershed file, [New

Powerhouse File] to load a new powerhouse file. New file is loaded each time and all

information must be re-entered. A new file name can be defined when the project and files are

saved.

To make an existing file part of the loaded project, click on [File] in the Menu Bar and select

[Add File] from the list of menu options. Select the file and click on the [Open] button, keeping in

mind that the correct file extension must be selected. (i.e., To load a Flood Frequency file,

select a file name with an FFA extension.) All five files must be stored in the same directory.

To save the project, select [Save Project] from [File] in the Menu Bar. To save all files, click onthe [Save] button in the Toolbar. To create a new project, select [Save Project As] from [File] in

the Menu Bar. Define a new name for your project and click on the [Save] button. Only new

project file will be created.

It is recommended that the Demo project and the related parameter files be used as a starting

point when performing new analysis. All data can be edited and saved. Use the Windows

Explorer to copy and rename these files first, then load them in IMP or add them to your new

project.

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2.3 IMP File Formats

The IMP package requires parameter and raw data files and creates a variety of files. Five files

are required to run IMP: project file (.PRO), project database (.MDB), flood frequency file (.FFA),

watershed file (.PAR) and powerhouse file (.PIN). If one of these files is missing, some featuresin IMP will not be available. Other weather and streamflow data files are not required by IMP but

may be useful when importing streamflow and meteorological data. A detailed description of

files included and required by IMP is described in the sections that follow and sample files are

located in \IMP\Demo.

2.3.1 Project File (.PRO)

The PRO file is a project file created, edited and saved in the program. This file controls the four

files that store data for a project and the units and user level type. This file is a required input for

IMP 5.0.

2.3.2 Flood Frequency File (.FFA)

The FFA file can be created, edited, used and saved in the program. It contains all stream and

catchment parameters needed for flood frequency analysis. This file is a required input for IMP

5.0, and is in ASCII format as follows:

Line Contents

1 Watershed name

2 Units (1 = metric, 0 = English)

Catchment area (sq. km or sq.mi.)

Stream length (km or mi.)Stream slope

Catchment slope

Stream width (km or mi.)

Manning's n of streambed

Manning's n of catchment

3 Phi1 * Phi2

Area runoff / area catchment

Average rain event duration (hrs)

Average rain event intensity (mm/hr or in/hr)

Average number of rain events / year

Average snow event duration (hrs)

Average snow event intensity (mm/hr or in/hr)Average number of snow events / year

2.3.3 Watershed File (.PAR)

The PAR file is a basin parameter file created, edited and saved in the program. This file contains

all basin parameters needed to simulate streamflow from weather data. The file is in ASCII and a

title line identifying the parameter precedes each line of data. This file is a required input for IMP

5.0.

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2.3.4 Powerhouse File (.PIN)

The PIN file is a hydro plant configuration file created, edited, used and saved in the program. It

contains all project parameters needed for reservoir operations simulation. This file is a required

input for IMP 5.0 and is in ASCII in the following format:

Line Contents

1 Station name

2 Dummy variable, # reservoirs (1), unit flag (1 = metric, 0 = English)

3 Firm energy period: Start Year, Start Month, End Year, End Month

4 Dummy Variable

5 Reservoir Levels: Maximum, Minimum and Starting (m/ft)

6 Minimum operating reservoir level for each month (m/ft)

7 Maximum operating reservoir level for each month (m/ft)

8 # of points on the Stage-Storage Curve

9 Elevations for Stage-Storage Curve (m/ft)

10 Storage Volumes at each of above elevations (cms-days/cfs-days)

11 Turbine Rated Flow (cms/cfs)

12 Turbine Rated Head (m/ft)

13 Dummy variable

14 Penstock: Length (m/ft), Diameter (m/ft), Manning's n

15 Maximum operating Turbine Flow for each month (cms/cfs)

16 Minimum Downstream Flow for each month (cms/cfs)

17 Maximum Downstream Flow for each month (cms/cfs) - 0 = no limit

18 # of points on the Tailwater Curve

19 Discharges for Tailwater Curve (cms/cfs)

20 Elevations for each of the above discharges (m/ft)21 # of points on the Turbine Efficiency Curve

22 Discharges for Turbine Efficiency Curve (cms/cfs)

23 Turbine Efficiency at each of the above discharges (%)

24 # Default Turbine selected, # Default Penstock selected, Penstock

Material

Note: All monthly data begins in October (Month 1) and ends in September (Month 12).

2.3.5 Database File (.MDB)

The MDB file is a Microsoft Access 2000 database that stores information including: simulated

hourly streamflow, simulated daily and hourly reservoir operations, meteorological andstreamflow data. This file is a required input for IMP 5.0.

2.3.6 Excel File (.XLS)

The XLS file is a Microsoft Excel 2000 spreadsheet that may store meteorological and

streamflow data. This file is not required for IMP 5.0 but may be used to import data into the IMP

database.

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2.3.7 Text File (.TXT)

The TXT file is an ASCII file that may store meteorological and streamflow data. This file is not

required for IMP 5.0 but may be used to import data into the IMP database.

2.3.8 Filename.AES

The AES files contain weather data (maximum and minimum temperature as well as

precipitation depth), in a compressed format. This file has a standard file format and can be

obtained from Environment Canada in the 4 column/field format.

The AES data begins in January of the Start Year and ends in December of the End Year.

Missing data is expressed as -99999. The file is in ASCII and has the following format:

Line Contents

1 Station identifier

2 Year of data to follow (yyyy)

A Month (1-12)

B Maximum temperature for each day of this month ino

C * 10

C Minimum temperature for each day of this month ino

C * 10

D Precipitation for each day of this month in mm of water * 100

E If Month = 12 then this line exists and lists the next Year (as line 2)

Note: Lines A - E continue for each month until all data for the End Year (shown in line 1) has

been listed.

2.3.9 Filename.WSC

The WSC files contain streamflow data and can be obtained from Environment Canada. The

WSC file has a standard file format and can be used in IMP for simulation of reservoir

operations and calibration of simulated streamflow.

The WSC data usually begins in January of the Start Year and ends in December of the End

Year. The file is in ASCII and has the following format:

Line Contents

1 Station name (Start Year - End Year)

2 Streamflow for 1 period in cms

Note: Line 2 continues for each period until all data for the End Year (shown in line 1) has

been listed.

The streamflow is listed in the following fields:

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Column Contents

3-5 Line # (not including title)

21-22 Current Year

23-24 Current Month25 Period (1-3)

26-END Streamflow (cms) for each day of period

Note: Periods 1 and 2 are always 10 days, Period 3 contains the remaining # of days in the

month.

2.3.10 FilenameHDY.HSP

IMP also has the ability to read streamflow records from HSPF that are in a standard

Hydrocomp Daily Format.

The HDY file is in ASCII and each line has the following format:

Column Contents

8-9 Current Year

10-11 Current Month

12 Period (1-3)

13-END Streamflow (cms) for each day of period

Note: Periods 1 and 2 are always ten days; Period 3 contains the remaining days in the month.

2.3.11 FilenameHHR.HSP

IMP also has the ability to read streamflow records from HSPF that are in standard Hydrocomp

Hourly Format.

The HHR file is in ASCII and each line has the following format:

Column Contents

1-10 Station Name

11-12 Current Year

14-15 Current Month

17-18 Current Day20 Am, Pm flag (1,2)

21-END Streamflow (cms) for 12 hours, 5 significant figures

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3.0 DATA IMPORTING

To perform any runoff or power simulations, time series data must first be entered and stored in

the project database file. Mandatory time series data include: daily total precipitation and daily

maximum and minimum temperature. The IMP package includes sample weather and flow datafor British Columbia, Canada. Observed streamflow data is helpful during the calibration

process to compare simulated streamflow against observed streamflow. Sample files for all data

types and variety of formats is distributed with IMP.

The Data Import utility is used to import meteorological and streamflow data into the IMP

database from the following formats:

Atmospheric Environment Service (*.AES) - a predefined format that can be obtained from

Environment Canada containing weather data (maximum temperature, minimum

temperature and precipitation depth), in a compressed format. The file extension is AES. Water Survey of Canada (*.WSC) - a predefined format that can be obtained from

Environment Canada and contains streamflow data. The file extension is WSC. HSPF format (*.HSP) - a predefined format generated by Hydrocomps HSPF Model and

constraints hourly or daily streamflow records. The file extension is HSP. Generic format - a user-defined format in an ASCII file. The file extension is TXT. Excel format - a user-defined format in Microsoft Excel. The file extension is XLS.

Refer to Section 2.2 for a detailed description of each file format. Screen capture of the Data

Import utility can be found in Section 20, Screen A.2.

Click on the [Import Data] button in the Toolbar to access the Data Import utility. Data can be

imported into an existing station or a new station can be created. To import data into an existing

station, select a station from the [Station Name] drop down menu. To import data into a newstation, enter a station name in the [Station Name] drop down menu. Data can be imported from

a variety of formats described in the sections that follow.

The most convenient way to import data to IMP is to create a file in Microsoft Excel with date in

the first column and the data in the second. Create separate files for streamflow, maximum

temperature and minimum temperature. In Microsoft Excel, save the file as a space delimited

text file. Make sure that the file extension is txt. For a text file, the extension can be easily

changed in Windows Explorer. Using this procedure, the file can be imported as described in

Section 3.4.

3.1 Using the AES Format

The following AES formats are supported in IMP 5.0:

Archived Hourly - The length of the entire line must be 184 or 185 characters. See example

in \IMP5\Samples\6Charhr.AES.

Compressed Hourly - The length of the entire line must be 113 characters. See example in

\IMP5\Samples\4Charhr.AES.

Archived Daily - The length of the entire line must be 232 or 231 characters. See example in

\IMP5\Samples\6Charday.AES.

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Compressed Daily - The length of the entire line must be 139 characters. See example in

\IMP5\Samples\4Charday.AES.

IMP recognizes only a 3-digit year 'YYY' for both daily and hourly AES formats. Any line with

extra space at the beginning or end of the line will cause an error "IMP does not recognize thefile format".

1. Select the [Atmospheric Environment Service (*.AES)] option. The AES files are standard

files distributed by the Atmospheric Environment Service and do not require any additional

setup.

2. Click on the [Import] button to advance to the next step.

3. Select the file to import and click on the [Open] button.

4. Review the data and click the [Import] button or click on the [Cancel] button.

3.2 Using the WSC Format

1. Select the [Water Survey of Canada (*.WSC)] option. The WSC files are standard files

distributed by the Water Survey of Canada and do not require any additional setup.




3.3 Using the HSP Format

1. Select the [HSPF Data] option. HSPF provides standard file types for streamflow,

temperature and precipitation.


3. Select the file to import and click on the [Open] button.4. Select the type of data, units and data resolution from options provided at the top of the

window.

5. Using the [Start Import at Line Number] up and down buttons to select the line number to

start the import.


3.4 Using the TXT Format

1. Select the [Generic Format] option.



4. Select the type of data, units and data resolution from options provided at the top of thewindow.

5. Use the [Start Import at Line Number] up and down buttons to select the line number to start

the import.

6. Use the [Width of Date Column] up and down button to identify where the date ends and the

data begins.


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3.5 Using the XLS Format

1. Select the [Excel Format] option.


3. Select the file to import and click on the [Open] button.4. Select the type of data, units and data resolution from options provided at the top of the

window.

5. Use the [Start Import at Line Number] up and down buttons to select the line number to start

the import.

6. Use the [Width of Date Column] up and down button to identify where the date ends and the

data begins.


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4.0 PRECIPITATION DATA

The precipitation grid in IMP is composed of a map of Canada and maps of the provinces and

territories in Canada. The map of Canada provides access to the directory of approximately

10,000 Atmospheric Environment Stations (AES) climatological stations located throughoutCanada. The database contains data up to 1976 and should be used with caution, as it may not be

representative of current climate conditions. To reduce errors, more recent precipitation data should

be used from stations closer to the hydro site. In Canada precipitation data can be obtained online

at: www.ec.gc.ca.

To view the precipitation data of Canada click on the [View Precip Grid] button in the Toolbar.

Select the appropriate region by clicking on the [Canada], [United States] or [Other] options and

click on the [OK] button. IMP 5.0 is distributed with information for Canada only. When the

[Canada] option is selected, a map of Canada is displayed on the screen.

This is not a required feature and is included to provide guidance only. Screen capture of the

precipitation grid can be found in Section 20, Screen A.3.

4.1 View Meteorological Stations Closest to a Selected Location

Place the mouse anywhere on the map of Canada and left-click to see the list of stations closest

to the selected location. The stations are displayed as dots on the map and are also listed in the

table at the bottom of the screen. The table displays the station identification, name, latitude and

longitude.

4.2 View All Meteorological Stations in Canada

To view all meteorological stations in Canada, click on the [Plot All] button located in the topright of the screen. It may take several minutes to display all the information. The stations are

displayed as dots on the map and are also listed in the table at the bottom of the screen. Use

the horizontal and vertical scroll bars to view the stations in the table.

Click on the [Clear] button located in the top right of the screen to remove all the stations from

the map.

4.3 View Precipitation Statistics

Place the mouse anywhere on the map of the province of British Columbia and right-click to view

the average annual precipitation and 24-hour maximum, one-in-ten year rainfall for that area. The

[Precip-British Columbia] screen is displayed.

On a latitude and longitude grid of ten minutes, IMP contains the grid for both average annual

precipitation and 1:10 year, 24-hour maximum rainfall. The grid covers most of British Columbia

except for some areas in the region of Prince Rupert. This database was prepared by M.B. Danard,

a meteorological consultant to the BC Ministry of Environment, and contains data up to and

including 1976.

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The average annual precipitation and 24-hour maximum rainfall databases are not essential to

IMP; however, both the Watershed and Flood Frequency Models require the average annual

precipitation information. The Watershed Model utilizes average annual precipitation at the site

to develop a scalar factor for transposing the daily record of precipitation and maximum and

minimum temperature from the regional weather station onto the ungauged watershed. Thewatershed modeling procedure itself manages the effects of elevation on temperature and

precipitation in the watershed. The Flood Frequency Model uses the average annual

precipitation at the site to estimate rainfall event parameters from internal relationships

developed from hydrological research into the characteristics of severe floods and individual

rainfall events. Average annual precipitation can be entered in the appropriate screens.

4.4 View Average Annual Precipitation for a Selected Location

To select a location in the [Precip-British Columbia] screen, click on the map at the location of your

hydro project or enter the longitude and latitude in degrees and minutes in the labeled boxes in the

[Location] window and click on the [Go to Location] button.

Select the [Average Annual Precipitation] option in the [Data] window. The data in the [Information

Around Selection] table is updated with information for the selected location.

4.5 View 24-Hour Maximum, One-in-Ten Year Rainfall for a Selected Location

To select a location in the [Precip-British Columbia] screen, click on the map at the location of your

hydro project or enter the longitude and latitude in degrees and minutes in the labeled boxes in the

[Location] window and click on the [Go to Location] button.

Select the [10 Year Return Period, 24 hr Precip] option in the [Data] window. The data in the

[Information Around Selection] table is updated with information for the selected location.

The precipitation grid contains values at 10-minute intervals so that minutes will be rounded to the

nearest ten minutes.

The precipitation data is shown in a grid for the 24 points surrounding the selected location. In a

large basin, it is a good idea to mark the precipitation values on a topographic map at the

appropriate 10-minute intervals of latitude and longitude in order to sketch the isohyetals over

the watershed. This procedure will develop a better appreciation for the variability of the

precipitation and the potential for errors in estimates of runoff.

If there are localized cells of very high precipitation in the vicinity of the watershed, or if the

precipitation is changing rapidly over short distances, there is a high potential for significant errors inthe precipitation estimates. In these circumstances the Atmospheric Model is very sensitive to

orographic effects. When the precipitation database is in error it is usually low.

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5.0 WEATHER AND STREAMFLOW DATA

To view the streamflow and weather data available in the loaded project database, click on the

[View Weather and Streamflow Data] button in the Toolbar. Utilities below the graph can be

used to view data types for different periods of available stations. Screen captures of theweather and streamflow data features can be found in Section 20, Screens A.4 and A.4.

5.1 Select a Station

Select a station from the [Historical Data Station] drop down menu and click on the [Refresh]

button to update the graph.

5.2 Select a Period to View

To change the period to view, click on the [Starting Date] and [Ending Date] windows at the

bottom of the screen. Click the [Refresh] button to update the graph with the selected period.

5.3 Select Data Type

To view the streamflow data, click on the [Streamflow] option and select either [Observed] or

[Simulated] or both. Observed and simulated streamflow data can be compared for each

station.

To view the weather data, click on the [Weather] option and select [Max Temperature], [Min

Temperature], [Precipitation] or all. Temperature and precipitation are plotted on two separate

scales.

At least one data type must be selected at all times. If the data is not available for the selectedperiod, an error message will be displayed. Click on the [Refresh] button to update the graph

each time a different selection is made.

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6.0 FLOOD FREQUENCY ANALYSIS DATA

Simulation of average daily discharge as described in Sections 8.0 and 9.0, is not suitable for

evaluating flood peaks that might endanger the safety of a small hydro plant. These less

frequent events produce very high flood peaks in a few hours on the watersheds of interest forsmall hydro developments. To provide estimates of such floods, the Flood Frequency Analysis

Model uses a completely different technique involving additional data to describe how the

watershed and stream channel route heavy rainfall to the site.

Before using the Flood Frequency Analysis Model, it will be necessary to measure certain

parameters from a topographic map. The watershed above the penstock intake should be

delineated on the map and its area should be measured. The topographic map should also be

used to estimate representative values for the slope of the stream and the catchment. These

parameters need not be calculated with great precision since they have only a secondary effect

on the flood frequency curve. Reasonable estimates are easily obtained by inspection of a

topographic map.

To view the Flood Frequency Analysis data, click on the [Edit FFA Data] button in the Toolbar.

The [Flood Frequency Analysis Data] screen allows for viewing and editing of catchment data,

streambed data, precipitation and observed streamflow. The Flood Frequency Analysis data

will be edited in the flood frequency file loaded in the current project.

The [Parameter File Description] located at the top of the screen displays the watershed name

and the date of last change. The watershed name can be modified and saved. The name is

overwritten when the file is saved. For more detailed information on the model parameters, see

Section 16.0. Screen captures of the flood frequency analysis data can be found in Section 20,

Screens A.6 to A.9.

6.1 View and Edit Catchment Data

The [Catchment Data] tab contains information related to the basin. Click on the [Catchment

Data] tab to view and edit the basin information. The catchment area should be measured from

a topographic map. Enter the catchment area in the [Area] field using the correct units. The

units are shown in brackets and can be changed by clicking on [Options] in the Menu Bar,

selecting [Units] and clicking on either [Metric] or [English]. The selected screen must be

refreshed for the selected units to be displayed.

The watershed slope can be estimated from the topographic map by dividing the distance

across the predominant area of the watershed towards the stream by the corresponding change

in elevation. There are no units associated with the slope. Enter the slope in the [Slope] field.

The catchment parameters are used by the model to develop estimates of the routing that takes

place during storm events and the approximate water balance. However, the driving force

behind flood peaks is obviously the rainfall, which occurs during an event. Each year there are

several hundreds of rainfall events occurring in coastal watersheds. Detailed analysis of hourly

records for several stations in BC has shown that the probability distributions of duration,

intensity and annual number of events can be estimated solely from their averages.

During most floods the entire area of the catchment does not contribute to the direct runoff that

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appears in the flood peak. Runoff Area/Catchment Area is a fraction that represents this ratio.

The area, which is actually contributing to runoff usually, varies between 0.4 and 0.6 times the

drainage area, which is measured from a topographic map. On a given watershed the value is a

random variable depending upon previous precipitation. For extreme events on small, steeply

sloping catchments and in areas of very high annual precipitation (3000 mm annually) a value of1.0 is appropriate. This ratio is the most important parameter influencing flood frequency

estimates. Enter the appropriate ratio in the [Runoff Area/Catchment Area] field.

6.2 View and Edit Streambed Data

The [Streambed Data] tab contains information similar to those in the catchment. Click on the

[Streambed Data] tab to access the information provided in this screen. The length of the

stream along with its slope and the width of stream must be estimated. The stream slope can be

estimated by simply dividing the difference between high and low elevations of the watershed by

the length of the stream. Enter the length, width and slope in the appropriate fields using the

selected units.

6.3 Estimate Stream Width

The stream width for an ungauged watershed is often unknown since the site may not yet have

been visited. The program will calculate the width with an internal routine based on

morphological relationships for British Columbia to provide a first guess at the stream width. To

calculate the stream width, click on the [Estimate Width] button in the [Streambed Data] tab. The

value entered in the [Width] field will be overwritten.

6.4 View and Edit Precipitation

The [Precipitation] tab contains information specific to rain and snowmelt events. Click on the[Precipitation] tab to view the information. The Flood Frequency Analysis deals with rainfall and

snowmelt independently and then combines them to produce the overall flood frequency curve.

In most cases, this is a valid procedure.

The [Precipitation] tab contains average annual precipitation and the 10-year, 24-hour rainfall.

Enter these two numbers in the appropriate fields.

The [Estimate Event Parameters] button provides an estimate of the average rain event

duration, intensity and the number of rainfall events per year based on an empirical correlation

between annual precipitation and the values obtained from an analysis of hourly rainfall at

several stations in British Columbia. The values can then be adjusted based on other

information about the statistics of individual rainfall events or by comparing flood frequencycurves obtained from the program with those obtained from records of runoff on nearby gauged

small streams.

Snowmelt is a factor for small hydro watersheds, however, it does not contribute significantly to

rare flood peaks. The average snow event duration, intensity and annual number of snowmelt

events can be left blank.

For larger watersheds (500 sq. km and above) hydrologic simulation can be used to identify

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snowmelt. An analysis of the snowmelt time series can determine the required statistics. This

capability is not part of IMP.

6.5 View and Edit Observed Streamflow

To view, add and edit actual streamflow measurements, click on the [Observed Streamflow] tab.

The annual maximum flows are displayed in a table on the right side of the screen. This data is

used for comparison with the computed Flood Frequency Analysis values. If a discharge record

is available, the user can click on the [Retrieve Max Flows From Station] button and the

historical yearly maximums will be updated in the [Maximum Flow] table.

To add an entry to the table in the [Observed Inflow] tab, click on the [Add Entry] button. A

blank row is inserted at the bottom of the table. To delete an entry from the table in the [Observed Inflow] tab, highlight the entry by clicking

on the left hand bar of the table and then click on the [Delete Entry] button. To delete all data in the table in the [Observed Inflow] tab, click on the [Clear Entries] button.

To complete the Flood Frequency Analysis, click on the [Calculate FFA] button in the Toolbar.

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7.0 FLOOD FREQUENCY ANALYSIS RESULTS

The results of the Flood Frequency Analysis are shown in the [Flood Frequency Analysis

Results] screen. Click on the [Calculate FFA] button in the Toolbar to access the screen. Every

time the data is updated or modified in the [Flood Frequency Analysis Data] screen, the resultsare automatically recalculated when the [Calculate FFA] button is selected. The results are

saved when the project is saved.

The [Flood Frequency Analysis Results] screen displays the results in both graphical and

tabular formats. The graph in the top half of the screen shows the observed and computed

discharge. The table below the graph summarizes the results by intensity, concentration time,

discharge, return period rainfall, return period snowmelt and return period total.

For methodology for calculating flood frequency curves, please refer to Section 16.0. Screen

capture of the flood frequency analysis results can be found in Section 20, Screen A.10.

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8.0 WATERSHED DATA

The [Watershed Data] screen contains the watershed modeling parameters that describe the

watershed and the various paths which precipitation takes over land and through the soil as well

as temperature and precipitation information. To access this screen, click on the [EditWatershed Data] button in the Toolbar.

The watershed files contain the watershed modeling parameters that describe the watershed

and the various paths which precipitation takes over land and through the soil. The database

contains daily precipitation and maximum and minimum temperature values. The Watershed

Model uses these files to develop estimates of average daily runoff.

The [Parameter File Description] button located at the top of the screen displays the watershed

name and the date of last change. The watershed name can be modified and saved. The name

is overwritten when the file is saved. For more detailed information on the model parameters,

see Section 17.0. Screen captures of the watershed data features can be found in Section 20,

Screens A.11 to A.15.

8.1 View and Edit Basin Characteristics

Click on the [Basin Characteristics] tab to view and edit the characteristics required for

watershed runoff simulation. A watershed can be broken up into several sub-basins, each with

its own hypsometric (area vs. elevation) curve. For small hydro analysis there would normally be

only one sub-basin. Working from a topographic map the areas between certain intervals can be

estimated. The hypsometric curve can then be plotted from it and the elevation bands can be

defined.

The [Basin Characteristics] tab contains a [Number of Elevation Bands] slider bar and a tabledescribing each elevation band. The slider bar defines the number of elevation bands. Click to

the left or right of the slider to decrease or increase the number of elevation bands. A minimum

of one and a maximum of ten elevation bands can be defined. To update the parameters in

each band, edit the values in the table.

The elevation, area, percent of tree cover, glaciated area, percent of impermeable area and

precipitation adjustment parameter can all be edited from the table. All percentages are entered

as fractions that IMP automatically converts to a percentage.

The precipitation adjustment parameter accounts for the variation of precipitation with elevation

within the watershed. The parameters, which should be input, are fractional changes. For

example, a precipitation transposition value of 0.9 in a specific elevation band would indicatethat the desired precipitation in that band is 90 percent of the value automatically computed by

the Watershed Model.

8.2 View and Edit Water Budget

Click on the [Water Budget] tab to view and edit the water budget characteristics. The [Water

Budget] tab contains six slider bars, which are used to incrementally increase or decrease the

value for each parameter. Click on the bar to the left or right of the slider.

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Use the [Soil Moisture Loss Threshold] slider bar to edit the parameter. The soil moisture loss

threshold uses the same concept as the fast runoff soil moisture deficit control to determine the

ratio of actual evapotranspiration to potential evapotranspiration. Before groundwater flow can

occur, soil saturation must be exceeded by the threshold limit for groundwater allocation.

Use the [Fast Runoff Soil Moisture Deficit Control] slider bar to edit the parameter. The fast

runoff soil moisture deficit control parameter is the value at which 10 percent of the indicated

impermeable watershed area occurs. The indicated impermeable area occurs at the soil

moisture, which causes saturation. Between these values there is an exponential shrinkage in

the impermeable area as the watershed dries out towards the lower value of 250 mm of water

deficit in the root zone.

Use the [Threshold Limit for Groundwater Allocation] slider bar to edit the parameter. The

threshold limit for groundwater allocation establishes the daily limit allocation to the groundwater

runoff system in a day.

Use the [Depressional Storage Allocation] slider bar to edit the parameter. A value of 1.0 for the

depressional storage allocation indicates that depressional storage is not being used in the

runoff routing. A value of less than one will allocate depressional storage to represent, for

example, natural regulation by marshes or lakes within the catchment.

Use the [Deep Zone Storage Allocation] slider bar to edit the parameter. The groundwater flow

itself is split between the deep and shallow zones. The deep zone storage allocation indicates

the fraction of total groundwater, which goes to the deep zone. For example, a value of 0.5

would indicate that the groundwater is equally split between the deep and shallow components.

Use the [Initial Outflow from Deep Groundwater] slider bar to edit the parameter. The initial

outflow from deep zone groundwater specifies the base flow level, which is prevalent at thebeginning of the simulation. This deep zone groundwater outflow may take up to one year of

simulation before the effects of the initial value disappear. The parameter files distributed with

IMP contain representative values of this outflow. The value shown for the region in which a site

is located must be multiplied by the ratio of the drainage area of the ungauged hydro site to the

drainage area of the representative watershed for that hydrological region.

The importance of the initial outflow for the deep zone groundwater is different in the interior

than it is on the coast. Interior watersheds do not receive significant recharge to the deep zone

groundwater after freeze up in the fall, whereas on the coast there is a significant amount of

input during the rainy season in the winter. An interior watershed experiences its lowest runoff,

often, in late spring. At that time, a significant proportion of the total flow in the stream will be

coming from deep zone groundwater, which has finally percolated through, to the stream. Theinitial value chosen during the previous October may have significant influence on the total

amount of water that appears in the stream at that time. Thus, in analyzing the power potential

of watersheds of this type, it may be important to carry on the simulation for more than one year

to reduce the importance of assumptions about this deep groundwater outflow initialization

value. For each of these components, a different time constant governs the rate at which it

returns to the stream. Calibration between computed and observed runoff is required in each of

the hydrological regions.

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8.3 View and Edit Time Constants

Click on the [Time Constants] tab to edit the runoff component time constants. The hydrograph

shape is governed primarily by five runoff component time constants. One of them, interflow, is

not shown for editing because, for the small watersheds considered here, it behaves essentiallylike surface runoff. Use the appropriate slider bar to edit the time constants for fast rainfall

runoff, fast snowmelt runoff, upper groundwater and deep groundwater.

The values used in the parameter files for each hydrological region were obtained by

calibration. The fast runoff time constants vary from 0.1 for a 10 sq. km basin to 0.5 for a

watershed area of 1000 sq. km. Values can be interpolated for other watersheds within this

range.

8.4 View and Edit Weather Stations

Click on the [Weather Stations] tab to select weather stations for simulation. This tab displays

available and selected stations with utilities and link to other properties related to the weather

station.

To select a weather station for simulation, click on the appropriate station in the [Available

Stations] window and then click on the [Add Station] button. The selected station is displayed in

the [Stations Used in Simulation] window. Multiple stations can be used in the simulation. Add

each station separately to the [Stations Used in Simulation] window. A station must be

assigned to an elevation band, using the [Assign to Elevation Bands] button.

Click on the [Edit Station Attributes] button to view and edit the elevation and transposition

factors. Select the station from the [Station Name] drop down menu. The station elevation, rain

and snow transposition factors are shown in their respective fields. The elevation of the weatherstation is required to perform orographic transposition to watershed elevation bands. Update the

station elevation by entering a new value in the [Station Elevation] field. The rain and snow

transposition factors can be updated by entering a new value in [Rain Transposition Factor] and

[Snow Transposition Factor] fields or calculated using the [Calculate Transpositions Factors]

button.

In the [Calculated Transposition Factors] window, enter the average annual rainfall and snowfall

at the weather station and at the hydro site. Some values may be available in the database.

Click on the [Retrieve Station Data] button to load the station information from the database.

The transposition factors are calculated via mouse click in another field or when the screen is

closed by clicking on the [Close] button in the top right of the screen. The transposition factors

are saved when the watershed file is saved. The transposition factors are updated in the[Station Attributes] screen when the [Calculate Transposition Factors] window is closed.

The [View Hourly Hydrograph] button allows the user to specify an hourly precipitation pattern

for hourly streamflow simulation. The simulation computes streamflow due to snowmelt and

rainfall on a daily basis and then divides that streamflow into hourly increments. The streamflow

due to rainfall is desegregated according to the indicated hourly precipitation pattern. The

snowmelt portion is desegregated according to a diurnal temperature fluctuation. The hourly

precipitation pattern can be adjusted by sliding the hourly slider bars or by selecting one of the

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patterns determined from historical hourly weather records. To select a predefined pattern for

the coastal region, click on the [Coastal] button. To select a predefined pattern for an interior

region, click on the [Interior] button. The pattern does not need to sum to any particular number;

it is normalized by IMP. The hourly pattern is displayed graphically in the bottom graph. Click

the [OK] button to return to the previous screen.

Click on the [Assign to Elevation Bands] button to access the utility to define stations to

elevation bands. The [Weather Stations] window lists all stations selected for simulation in the

[Weather Station] tab and assigns an index to every station. Use the index to assign the

precipitation and temperature to each elevation band in the sub-basin in the [Station

Assignments] table. The index is updated by entering a new value. Click on the [Save] button to

save your assignment. A station must be assigned to an elevation band to be used in the

simulation.

8.5 View and Edit Meteorology

Click on the [Meteorology] tab to view and edit the temperature lapse rates, orographic

enhancement factors and degree-day snowmelt factors. Each value can be edited in the

appropriate field.

To complete the runoff simulation, click on the [Simulate Runoff] button in the Toolbar.

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9.0 WATERSHED RUNOFF SIMULATION

The watershed runoff simulation performs a day-by-day or hour-by-hour simulation to determine

runoff from the watershed project. Click on the [Simulate Runoff] button in the Toolbar to access

this screen. Screen captures of the watershed runoff simulation can be found in Section 20,Screens A.16 and A.17.

9.1 Simulate Watershed Runoff

Select daily or hourly simulation by clicking on the appropriate option in the [Simulation Type]

window. To change the simulation period, click on [Starting Date] and [Ending Date] windows at

the bottom of the screen. Once all the desired options have been selected, click on the

[Simulate] button to activate the simulation process.

When the simulation is complete, the simulated runoff and watershed conditions are displayed

in this screen. The Watershed Model is explained in detail in Section 17.0. The parameters can

be adjusted until the simulated flow matches the observed flow.

9.2 View Simulated Discharge and Watershed Conditions

When the simulation is complete, the simulated runoff and watershed conditions are displayed

in this screen. To view the simulated discharge, click on the [Discharge] tab at the bottom of the

screen. The graph in the top portion of the screen illustrates both precipitation and maximum

and minimum temperature for the simulation period. The bottom graph shows the simulated

streamflow over the simulation period.

Click on the [Watershed Conditions] tab to view the simulated watershed conditions. The

[Watershed Conditions] tab illustrates the deep and shallow groundwater flow and the snowpack content for all elevation bands defined in the Watershed file.

For simulation with multiple stations, click on the [Weather Data from] drop down menu to view

the precipitation and maximum and minimum temperature of different stations. The top graph is

updated with weather for the selected station.

9.3 Analyze Results

To view statistics and analyze the results, click on the [Analyze Results] button. Observed and

streamflow runoff can be compared for all values, selected months or selected years by clicking

on the appropriate option in the [Analysis Type] window below the graph. Click on the [Refresh]

button every time an option is changed and the graph is updated.

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10.0 POWERHOUSE STUDY DATA

Click on the [Edit Powerhouse Data] button from the Toolbar to view and edit the powerhouse

characteristics. The [Parameter File Description] located at the top of the screen displays the

plant name and the date of last change. The plant name can be modified and saved. Screencaptures of the powerhouse study data features can be found in Section 20, Screens A.18 to

A.22.

10.1 View and Edit Efficiency Curve Data

Click on the [Efficiency Curve] tab to specify a turbine efficiency curve available from a turbine

database distributed with IMP. Click on the [Turbine Type] drop down menu to select a turbine.

To view the efficiency curve for the selected turbine, click on the [Edit Turbines] button. The

turbine types distributed with IMP cannot be deleted, changed nor modified. Only user-defined

turbine types can be edited.

An additional turbine type can only be added to the turbine database in the Advanced Mode.

Select the [Advanced User Level] option from the [Option] menu in the Menu Bar. Click on the

[Edit Turbines] button to access the utilities. The [New Turbine] button is enabled in Advanced

Mode.

Click on the [New Turbine] button to add a new turbine, enter a turbine name and click on the

[OK] button. To add points to the turbine efficiency curve, click on the [New Entry] button. Enter

the values in the appropriate fields and click on the [Add] button. Click the [Add] button each

time you enter a new point. Click on the [Close] button to finish. The efficiency curve is

automatically sorted.

To delete an entry from a user-defined turbine efficiency curve, click on the appropriate cell inthe [Turbine Efficiency Curve] table and click on the [Delete Entry] button. At least one entry

must remain in the table.

To delete a curve, select the curve in the [Turbine Types] window and click on the [Delete

Turbine] button. Only user-defined turbine types can be deleted.

10.2 View and Edit Reservoir Levels

Click on the [Reservoir Levels] tab to set the minimum, maximum, and starting levels for the

reservoir and define the tail water and stage-storage curves.

The minimum, maximum and starting levels can be entered in the appropriate fields. Define thetail water curve by clicking on the [Tail Water Curve] button. Define the stage-storage curve by

clicking on the [Stage-Storage Curve] button.

The total flow below the powerhouse, the sum of the powerhouse discharge and the spill, may

increase tail water levels on the plant. The variation in tail water elevation with discharge

defines the tail water curve. The net head on the plant will be calculated by interpolating

between the values specified. If a single point is given, its elevation will be used for all

discharges.

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Points on the stage storage curve should cover the full range of possible reservoir storage

volumes. The program will interpolate between the points specified, therefore a minimum of two

points is required. There must be a "dead" storage pocket below the elevation of the intake. The

pocket can be small but if it is not specified, the program will not always operate properly.

The window and utilities accessed by clicking on the [Tail Water Curve] and [Stage-Storage

Curve] buttons operate similarly. Use the [Add Entry] button to add a blank row to the table and

enter appropriate values in the new row. The table is automatically sorted and the graph below

the table is automatically updated when a new data point is entered. To delete a data point from

the curve, select the point to delete and click on the [Delete Entry] button. At least one data

point must remain in the table.

Click on the [Close] button to close the window or click [Cancel] to close without saving the

data.

10.3 View and Edit Turbine Data

The [Turbine Data] tab contains the rated flow and rated head for the powerhouse. The rated

flow capacity of the powerhouse is the maximum total flow that the turbine set can pass at the

rated net head. The turbine capacity should be carefully matched to the hydraulic capability of

the penstocks. The rated head can be defined by subtracting estimated penstock losses and tail

water at the rated discharge from the maximum gross head. Under a given condition of head

and flow, the discharge through the powerhouse is calculated from the ratio of the net head to

the rated head raised to an exponent. The value of the exponent depends upon the type of

turbine and its configuration within the powerhouse. A value of 0.5 is often used as the

exponent in this discharge capacity relationship.

Enter the rated flow and rated head in the appropriate fields.

10.4 View and Edit Penstock Data

The [Penstock Data] tab enables the user to set the various penstock parameters. IMP assumes

that the penstock intake is connected directly to the reservoir. During the calculation of energy

production, the net head accounts for drawdown in the reservoir and all controlled releases are

assumed by the program to pass through the penstock and powerhouse. If there is more than

one reservoir or a reservoir that is located some distance upstream from the penstock intake,

this can be modeled by aggregating the upstream storage, selecting an appropriate stage

storage curve and defining appropriate operating rules for use of the storage during the year.

Enter the penstock length and diameter in the appropriate fields. Friction losses in the penstockare calculated in the program using the Manning's equation. The Manning's n can set by

choosing the penstock material from the [Material] drop down menu. Selecting an effective

length that reflects minor losses can incorporate additional losses due to bends and joints.

10.5 View and Edit Operating Limits

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The [Operating Limits] tab allows the user to set various reservoir levels and downstream flows.

The maximum and minimum monthly reservoir levels and the maximum monthly turbine

operating discharge control the operation of the reservoir. The reservoir levels are used by the

program as a guide for drawdown and refill in accordance with the hydrologic behavior of the

watershed.

The minimum monthly reservoir levels in each reservoir and the minimum downstream flow for

each reservoir are the essential elements when modeling powerhouse operations. These two

parameters are interrelated and should be developed with this in mind. The amount of water

that can be released on any day depends upon the water available in storage and the inflow.

The two targets can be in conflict if there is not enough water to satisfy both. If the minimum

downstream flow is too high, it may not be possible to meet the minimum monthly reservoir

levels. A workable combination of the two targets is dependent on hydrology, the live storage

volume and how it will be used to regulate the flow. Appropriate targets will develop as the user

gains experience modeling the project under study. Enter each value in the table in the

appropriate row and column. Make sure you hit [Enter] on the keyboard after each entry.

The appropriate minimum monthly reservoir levels can be determined from the volume of the

minimum downstream flow, which must come out of storage in each month. Assume the

reservoir is empty at the end of the dry season; then calculate backwards in time to determine

the levels required at each month. A similar procedure can be used to develop the minimum

monthly reservoir elevations during filling.

For reservoirs that are to operate as run-of-river, a different approach is required. These

reservoirs are always full and simply pass the inflow. Therefore, the minimum downstream flow

would be the powerhouse capacity (provided that the penstock is large enough) and the

minimum monthly reservoir level is the full supply level throughout the year.

The maximum operating turbine flows are more than a guide; they are the absolute maximum

releases through the powerhouse. If the reservoir is full and an additional release is required, it

will bypass the powerhouse and appear as spill in the simulation results.

The minimum downstream flows provide additional guidance to the program where flexibility in

operations is possible. The program will normally ensure that powerhouse flows are at least as

high as the minimum downstream flows.

To simulate the powerhouse operation, click on the [Simulate Powerhouse] button in the

Toolbar.

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11.0 POWERHOUSE OPERATION MODELING

Click on the [Simulate Powerhouse] button in the Toolbar to perform a day-by-day simulation to

determine energy production from the powerhouse project or view an existing simulated

operation. Screen captures of the powerhouse study results can be found in Section 20,Screens A.23 to A.26.

11.1 Simulate Powerhouse Operation

Prior to performing the powerhouse simulation, the simulation period, firm energy period and

streamflow source must be defined.

The simulation period depends on the available streamflow selected in the [Streamflow Source]

window. By default, the simulation period is set to the period of available streamflow. To change

the simulation period, use the [Starting Month] slider bar to set the starting date and the

[Number of Years] slider bar to define the end of the simulation period.

There may be some portion of a period of record that is known to be very important (i.e., a

period of known very low runoff or very high energy demand). This firm energy period can be

defined in the [Firm Energy Period] window. The firm energy period must fall within the

simulation period. During the simulation, the program will identify the energy produced during

this period separately. Use the [From] slider bar to set the firm energy period start date and the

[To] slider bar to set the firm energy end date.

To perform the simulation with observed streamflow, click on the [Use Observed Streamflow]

option and select the streamflow station from the [Gauge] drop down menu. To perform the

simulation with simulated inflow, click on the [Use Simulated Streamflow] option. If simulated or

observed streamflow is not available, the appropriate option box will be disabled.

The streamflow can be adjusted by indicating a correction factor that will scale all of the

streamflow values. Enter the correction factor in the [Streamflow Correction Factor] field. To use

the streamflow values without an adjustment, enter 1.

To start the powerhouse simulation, click on the [Simulate] button. The [Power Study Simulation

Results] screen is displayed when the powerhouse simulation is complete.

11.2 View Powerhouse Operation Results

To view powerhouse operation results click on the [View Existing Results] button. The [View

Existing Results] button will bypass the powerhouse simulation and provide plots of the currentpowerhouse simulation results in the [Power Study Simulation Results] screen. The powerhouse

operation results are automatically displayed when the powerhouse simulation is complete.

The tabs at the top of the screen control displays of simulated flows, reservoir levels and power

generation. Click on the [Flows] tab to display the inflow, turbine release and spill. By default, all

three flows are displayed on the graph. Click on the check boxes on the legend of the graph to

change the display. When a check box is selected, the flow type is displayed in the graph. The

[Reservoir Levels] tab displays the reservoir levels during the simulation period. The [Power

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Generation] tab displays the power generation during the simulation period.

Summary of the simulation results are displayed below the graph in the [Simulation Results]

window. These results summarize the simulation period, firm energy period, firm power and

average power. These values cannot be edited.

To return to the powerhouse simulation, click on the [Close] button.

11.3 Analyze the Results

Click on the [Frequency Analysis] button to analyze the results. The [Frequency Analysis]

screen allows the user to perform a frequency analysis for different periods and data types. The

frequency analysis can be performed on all values, selected months or selected years for inflow,

turbine release, spill, reservoir level and power generation. Select the appropriate options and

click on the [Analyze] button. The graph is updated with a frequency analysis on the selected

data. The [Statistical Results] window in the bottom right of the screen displays the average,

mode, median and frequency interval. The units vary with the data set selected in the [Analysis

Data Set] window. The mode is the value occurring most frequently in the selected data set.

Click on the [Close] button in the [Frequency Analysis] screen to return to the [Power Study

Simulation Results] screen.

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12.0 INSTALLED CAPACITY OPTIMIZATION

The Optimize Powerhouse Module performs a simple incremental analysis on the results from

the powerhouse simulation for the chosen project configuration. Click on the [Optimize

Powerhouse] button to access the [Installed Capacity Optimization] screen.

This module examines the spill, which could be captured or created if the powerhouse capacity

was changed within specified lower and upper limits. The resulting increase or decrease in

energy generation is used as the basis for calculating the marginal value and the marginal cost.

When these are equal (ratio = 1) the optimum installed capacity is indicated.

Optimizing the installed capacity may be useful in suggesting whether the powerhouse capacity

is correctly matched with the hydrologic capability of the site and the penstock dimensions. If

the powerhouse discharge capacity is limiting energy output, there will be a gradual increase in

annual energy production as powerhouse discharge capacity is increased. Penstock hydraulic

losses limit energy production if annual energy production reaches a maximum at a discharge

less than the mean annual runoff.

When the [Installed Capacity Optimization] screen is loaded the [Optimization of Installed

Capacity] table in the middle of the screen is blank. Define the discharge range for analysis in

the [Maximum] and [Minimum] fields at the top of the screen. The default discharge range is

plus or minus 50% of the discharge capacity at the rated head of the turbine selected for the

simulation. Define the cost of analysis by entering appropriate values in the [Value of Energy]

and [Cost of Capacity] fields.

Click on the [Compute] button to start the optimization.

The results are displayed in the [Optimization of Installed Capacity] table in the middle of thescreen. The optimum capacity occurs at the point where the ratio of the marginal value to the

marginal cost is 1.00. After reviewing the output, the optimum installed capacity may be

examined more closely by reducing the range of capacities and recalculating the analysis.

Results from simulating powerhouse operation for discharge, installed capacity and average

power are displayed in the [Capacity Simulated in Detail] window at the bottom of the screen.

Screen capture of the optimized powerhouse study results can be found in Section 20, Screen

A.27.

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