WEAP-MODFLOW Tutorial - BGR

WEAP-MODFLOW Tutorial - BGR
Management, Protection and Sustainable
Use of Groundwater and Soil Resources in the Arab Region
WEAP-MODFLOW Tutorial
September 2012
WEAP-MODFLOW Tutorial
Version 2
Authors
M. Huber (geo:tools)
M. Al-Sibai (ACSAD)
With participation of
J. Al Mahameed (ACSAD)
A. Abdallah (ACSAD)
O. Al Shihabi (ACSAD)
I. Jnad (ACSAD)
J. Wolfer
J. Maßmann (BGR)
Online available at
http://www.bgr.bund.de/IWRM-DSS
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Content
1
Introduction ........................................................................................................................ 4
2
MODFLOW Model................................................................................................................ 5
2.1 Model Area – “Main River Basin” ........................................................................................ 5
2.2 Mathematical Model ........................................................................................................... 6
3
Create and link a WEAP-model based on MODFLOW data ..................................................... 8
3.1 Create a new WEAP – Area ................................................................................................. 9
3.2 Start LinkKitchen................................................................................................................ 10
3.3 Set the WEAP Area’s Boundary ......................................................................................... 11
3.4 Add Catchment and Groundwater Nodes to the Schematic ............................................. 13
3.5 Add Rivers to the Schematic.............................................................................................. 16
3.6 Set the Model Runtime in WEAP ....................................................................................... 17
3.7 Define Catchment and Groundwater in the Linkage File .................................................. 18
3.8 Define Rivers in the Linkage File........................................................................................ 21
3.9 Set the FLOW-STAGE-WIDTH relationship ........................................................................ 25
3.10
Send Linkage File Data to WEAP.................................................................................... 26
3.10.1 Send catchment areas to WEAP .................................................................................... 26
3.10.2 Send groundwater recharge to WEAP........................................................................... 27
3.11
Link WEAP and MODFLOW............................................................................................ 28
4
WEAP-hydrology in linked models – Rainfall-Runoff ........................................................... 31
4.1 Add Runoff links to the Schematic .................................................................................... 31
4.2 Assign catchments and Landuse Classes to the Linkage File. ............................................ 32
4.3 Data input in WEAP ........................................................................................................... 34
4.3.1
Enter precipitation ........................................................................................................ 34
4.3.2
Enter ETRef .................................................................................................................... 35
4.3.3
Enter Kc.......................................................................................................................... 35
4.3.4
Enter Runoff- and Infiltration fractions ......................................................................... 35
4.3.5
Run the model and browse the results ......................................................................... 35
5
Common tasks ................................................................................................................... 36
5.1 Abstraction for irrigation ................................................................................................... 36
5.1.1
Add irrigation abstraction by demand site .................................................................... 36
5.1.2
Add irrigation abstraction to a Landuse Class ............................................................... 37
5.2 Changes in Land Use .......................................................................................................... 39
5.2.1
Urbanization .................................................................................................................. 39
5.2.2
Irrigation growth ........................................................................................................... 40
5.3 Domestic water supply from well fields ............................................................................ 41
5.4 Artificial groundwater recharge ........................................................................................ 43
5.5 Climate Change.................................................................................................................. 45
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1 Introduction
The present tutorial intends to illustrate the idea of the dynamic link between WEAP and MODFLOW.
The techniques presented are kept as simple as possible in order to make you familiar with the
necessary steps for building up a WEAP model that is linked to MODFLOW and to give you an
introduction to solving common water management problems.
The first part will guide you through building a WEAP model based on the data stored in a MODFLOW
model (“Hard Data approach”). Despite this approach is not recommended in general, as flexibility is
lost and many of WEAP’s powerful modelling options are not available, it might be useful in case
measured data (e.g. precipitation) used to build and calibrate the existing MODFLOW model is
unavailable for whatever reason.
The second part focusses on building and linking a model that makes use of WEAP’s internal
functions to model groundwater recharge and surface runoff.
In the last part, you will learn how to cope with various challenges typical to modellers like
implementing artificial recharge or changes in land use.
Before you start with the tutorial, be advised to have downloaded the associated shape files
(Catchment.shp, Landuse.shp, Wellfields.shp) and the csv-file (InputData.csv).
This tutorial refers to WEAP Version 3.001 (Sep 2012) and LinkKitchen Version 1.00 (Sep 2012).
It is based on the WEAP-MODFLOW-Tutorial by BGR/ACSAD (2009) and includes contributions by M.
Al-Sibai (Chapter 2).
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Introduction
2 MODFLOWModel
The MODFLOW model used in this tutorial was designed with the intention to make many planning
options possible (dams, irrigation) and to remain easy to understand. It is a modification of the
original GMS-Tutorial model and in the following named “Main River Basin”.
2.1 ModelArea–“MainRiverBasin”
The Main River basin encompasses 783 square kilometres. It is located in a semi-arid climate, with
precipitation only in the winter months. Most of this precipitation is lost by evapotranspiration. The
aquifer consists of fractured crystalline bedrock and alluvial fills in the valleys, its saturated thickness
varies between 35 m in the South to about 53 m in the North.
Groundwater flow is towards the spring, the Main River and its 2 tributaries. The spring represents
the headflow of the Main river, with an average monthly discharge of about 320 000 m³. In the
north, outside the model area the Main River finally drains into a reservoir lake with a constant water
level of 304.8 m a.s.l.
The topography gradually decreases from South (353 m.a.s.l) to North (335 m.a.s.l).
Elevation
dem
Value
High : 353.331146
Low : 334.447601
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MODFLOW Model
2.2 Mathematical Model
GRID: The model consists of one layer (1 unconfined aquifer, 60-80m layer thickness, 35m – 50m
saturated thickness) with 88x70 cells. The cell sizes vary in width and height between 200 m to 1200
m (see figure below)
BOUNDARY CONDITIONS: Specified-Head boundary in the North (Reservoir Lake level). All other
boundaries are No-Flow boundaries (see figure above).
HYDRAULIC CONDUCTIVITY: The 4 hydraulic conductivity zones for the model are shown in the
figure below. The hydraulic conductivity of the aquifer varies between 100 m/day along the river
valley to 40 m/day towards the basin boundary.
0 m/d
0 - 0.0015 m/d
0-0.003 m/d
0 - 0.0011 m/d
0 - 0.0013 m/d
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MODFLOW Model
RECHARGE: 5 different recharge zones have been defined. The values in the zones ranging from 0 to
0.0015 m/d (see figure above).
ADDITIONAL PACKAGES: The spring was modelled as 2 DRAIN-cells (pink in the figure above) and the
rivers as RIVER-cells (blue in the figures above).
INITIAL HEAD: The initial head ranges from 306 – 327 m.a.s.l. resulting in a depth to water table of 25
to 36 m (see figures below).
Starting Heads:
Depth to groundwater table
The Model has been built and run on transient state in order to cover two years of recharge
variation. It consists of 24 monthly stress periods, which contain 3 equal time steps each. The final
balance (see figure below – units in m³ or m³/d) shows that the model is almost balanced or close to
steady state, with recharge as the main inflow and river leakage as the main outflow fraction.
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MODFLOW Model
3 CreateandlinkaWEAP-modelbasedonMODFLOWdata
At the beginning, you will create a new WEAP Area and design the Schematic for it. The necessary
tasks are:
•
•
•
•
•
Create a new WEAP area
Set the area’s spatial boundaries
Load background layers
Digitize 4 rivers
Add 5 catchment and 5 groundwater nodes
The result will look similar to the image below.
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Hard-Data-Approach
3.1 Create a new WEAP – Area
1. In the Main Menu in WEAP, go to Area → Create Area. In the following dialog, create a new
Area, which is initially blank and give it the name: “DSS-Tutorial”:
2. Click “OK” and ignore the following dialog (“Area boundary”) by clicking on “Cancel”. The
model should look like below:
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Hard-Data-Approach
3.2 Start LinkKitchen
LinkKitchen is a GIS-alike tool designed to assist the setup of the Linkage Shapefile without the need
of further GIS- and Spreadsheet-software. It provides all necessary functionality for producing the
linkage file and for its attribution. Furthermore, it allows direct parameterization of the WEAP-model
based on linkage file’s attributes.
If you are not yet familiar with the use of LinkKitchen, please read its User Manual before you
continue with the tutorial.
Remain WEAP open and start LinkKitchen in parallel.
At start-up, you are prompted to select the one of your WEAP
models which you want to work on. Select DSS-Tutorial and
confirm the dialog by click on OK.
In the following dialog, LinkKitchen prompts for the location of the
MODFLOW model and the Linkage File. Browse for the MODFLOW
model that comes with the Tutorial data and select the Namefile.
As a linkage file does not yet exist, select to create a new Linkage
File.
Once you confirm with OK, all MODFLOW files will be copied to
the WEAP-Area’s standard directory.
LinkKitchen produces the Linkage File as well as two other
shapefiles in the background. Those will be used during the next
steps.
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Hard-Data-Approach
3.3 Set the WEAP Area’s Boundary
Your LinkKitchen User Interface will show an empty grid that represents the geometry of your
MODFLOW model. This is the linkage File.
Switch back to WEAP (don’t close LinkKitchen).
Right-click into the Layer-pane and select Add Vector Layer
from the context menu.
Browse to your WEAP Area directory/SHAPE/ and select
the file MF_Domain_trans_modify_5f_drain.shp. This file
was created at start-up and represents the spatial
boundary of the MODFLOW model. You will use this file to
define the area’s boundaries.
Remove all other layers (Major Rivers, States, Country,
Ocean) except MF_Domain_trans_modify_5f_drain.shp.
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Hard-Data-Approach
Right-click into the Layer-pane and select Set Area
Boundaries from the context menu.
Draw the green rectangle (the area boundary) around the
complete extent of the black rectangle (the MODFLOW
model’s extent) and confirm by click on OK.
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Hard-Data-Approach
3.4 Add Catchment and Groundwater Nodes to the Schematic
It is assumed, that MODFLOW is the only source of information about the model area. Catchments
and Groundwater nodes are thus delineated by zones of equal recharge rate. You will use
LinkKitchen to delineate the Catchment and Groundwater zones in WEAP.
1. Switch to LinkKitchen and browse to the MODFLOW-Layer Recharge SP1 in the MODFLOW
Viewer. Click the Preview-Button to show the recharge zones.
2. Click the Make Snapshot-button to save the preview-image permanently to disc. The
image appears in the List of Layers as a regular Background Layer.
3.
At this stage, the recharge zones are saved as a JPEG-image-file in the WEAP-area directory. The file
doesn’t store any information besides a different colour for each zone.
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Hard-Data-Approach
4. Switch back to WEAP and load the file “Recharge_SP1.jpg” as a background raster layer to
the Schematic.
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Hard-Data-Approach
In the MODFLOW model, five zones of different recharge are defined. You will take these zones as
blueprints for the delineation of WEAP-Catchments and groundwater nodes.
1. Drag and drop one Catchment and one Groundwater node for each recharge zone onto the
schematic.
2. Connect the Groundwater and Catchment nodes by infiltration links.
Catchment node name
connection
groundwater node name
C_East
infiltration link
GW_East
C_MainCentral
infiltration link
GW_MainCentral
C_MainLower
infiltration link
GW_MainLower
C_MainUpper
infiltration link
GW_MainUpper
C_West
infiltration link
GW_West
NOTE: It is good practice to add the prefix “C_” before the catchment’s name and the prefix “GW_”
before groundwater nodes in order to avoid getting confused by identical names of groundwater
nodes, catchments and demand sites.
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Hard-Data-Approach
3.5 Add Rivers to the Schematic
1. Add the file MF_River_trans_modify_5f_drain.shp (located in the folder SHAPE in the area
directory) to the Schematic and give it a solid blue colour.
2. Drag and Drop river nodes onto
the Schematic and digitize each river,
in flow direction, on top of the blue
area. The rivers’ names are Main
River, East River and West River. East
River and West River are tributaries
to Main River.
3. A fourth River needs to be digitized in addition to the three rivers. In
MODFLOW, it is represented by two drain cells upstream of Main River. That
River is named Spring.
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Hard-Data-Approach
3.6 Set the Model Runtime in WEAP
In order to ensure, the WEAP calculation correlates correctly with the MODFLOW model, adjust the
WEAP time steps and the starting month according to the MODFLOW stress periods (here: October
1999 – September 2001).
This is done using the General menu item → Years and Time Steps
Initially you won’t use any WEAP internal model to calculate surface runoff, groundwater recharge
and irrigation demand, therefore choose in
Data View → Demand Sites and Catchments → Advanced
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Hard-Data-Approach
3.7 Define Catchment and Groundwater in the Linkage File
Switch back to LinkKitchen and see how it reflects the changes you made in WEAP. The Nodes you
added to the Schematic are now visible in LinkKitchen’ s Branch Viewer. During the following steps,
you will relate cells of the Linkage File to Catchments, Groundwater Nodes and Rivers.
As you have the recharge zones loaded in the background, you will use these zones as stencils for
selecting cells. Use LinkKitchen’s selection-tools (s. LinkKitchen User Manual) to select cells
corresponding to recharge-zones. The thus selected cells are then attributed with the name of the
catchment as defined in WEAP.
The procedure of attributing groundwater nodes is identical.
1. Select all cells located in the green area (C_Main Upper).
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Hard-Data-Approach
2. Highlight C_MainUpper in the Branch-Viewer and click Add Attribute to Linkage File. This will write
the Branch’s name to the linkage file.
3. Highlight GW_MainUpper and click Add Attribute to Linkage File.
3. Repeat Steps 1 and 2 for the other Catchments
4. Highlight the Parent-Branch Catchments and look at the Linkage File Preview:
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Hard-Data-Approach
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Hard-Data-Approach
3.8 Define Rivers in the Linkage File
In WEAP, a river is defined as a “chain” of reaches, sections between inflow or outflow nodes. Any
river reach requires to have a representation in the Linkage File.
There are two different ways to assign river reaches to the Linkage File. The method to choose
depends on how accurate you digitized the rivers in the WEAP Schematic beforehand. If the WEAPrivers are digitized very accurately with no overlaps of the river lines out of the blue river cells, you
should opt for method 2. If the rivers are digitized only roughly around the river cells, choose the first
method. Both methods are described in the following section.
Simplistic → Method 1
Accurate → Method 2
Method 1:
The procedure to assign river reaches to Linkage File cells is similar to the procedure to assign
Catchments except that you start from Information you get from MODFLOW rather than from an
overlay shapefile.
1. In the MODFLOW-Viewer, browse to the Layer IsDrain and click select. The drain cells represent
the river Spring in WEAP.
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Hard-Data-Approach
2. Highlight the River-branch Below Spring Headflow in the Branches-Viewer and click Add Attribute
to Linkage File.
The two drain cells are now linked to the WEAP river reach Below Spring Headflow.
3. Browse to the layer IsRiver in the MODFLOW Viewer to select River cells.
4. Use LinkKitchen’s selection-tools to sub-select those cells corresponding to the WEAP-rivers.
E.g. Click and hold the Alt-Key while drawing a rectangle around West River in order to select from
selected river cells.
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Hard-Data-Approach
5. Highlight the River-branch Below West River Headflow in the Branches-Viewer and click Add
Attribute to Linkage File.
6. Repeat the last two steps for all other river reaches.
The preview of the river-attribution should show an image similar to the image below:
Save the Linkage File to disc by clicking on the Write Linkage File button
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Hard-Data-Approach
Method 2:
You can make WEAP “guess” the river reaches and drains in accordance to your digitizing rivers in the
Schematic. In order to make this procedure work, it is necessary to link WEAP and MODFLOW first.
Continue with the next chapter and once you are about to link with MODFLOW, click the Guess River
Point Linkages and Guess Drain Cell Linkages – Buttons (Chapter 3.11).
Note: it is good practice to save the linkage file frequently in order to not lose your edits. The file is
overwritten every time you save it.
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Hard-Data-Approach
3.9 Set the FLOW-STAGE-WIDTH relationship
In order to allow WEAP to calculate river-related functions correctly, you need to assign a parameter
called “Flow-Stage-Width relationship”. This parameter (or set of parameters) describes the physical
properties of a river and its riverbed and is the basis for WEAP to calculate groundwater-riverinteractions. If you set up a WEAP-model based on the information from a MODFLOW model, it is
likely that the required information about rivers is missing.
LinkKitchen provides a rather pragmatic method to assign the Flow-Stage-Width relationship with
standardized parameters.
1. Switch to LinkKitchen and highlight the River Reach Spring, Below Spring Headflow.
2. Click the - Command to open the Flow-Stage-Width-Dialog. The following Window shows nine
images of rivers of various sizes. Left-click on the top left image (this one should come closest to a
spring).
LinkKitchen will produce a Flow-Stage-Width-curve based on parameters stored with the image (see
the LinkKitchen manual for further details).
3. Click the WEAP-button to send the curve to WEAP and check the result.
Supply and Resources → River → Below Spring Headflow → Reaches → Physical → Flow Stage Width
Note that the curve can be changed in WEAP using the Flow-Stage-Width-Wizard.
Repeat steps 1-3 for all other Rivers.
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Hard-Data-Approach
3.10 Send Linkage File Data to WEAP
In the currently used approach, you use the initial MODFLOW model inputs in WEAP rather than any
of the WEAP built-in models for calculating groundwater recharge. The groundwater recharge
retrieved from MODFLOW will be entered as input in WEAP instead.
Data View → Supply and Resources → Groundwater → Natural Recharge.
As a second obligatory parameter you need to enter catchment areas in WEAP
Data View → Demand Sites and Catchments → Landuse → Area
Both parameters are calculated by LinkKitchen and can be sent automatically to the correct inputposition in WEAP.
3.10.1 Send catchment areas to WEAP
Catchments’ areas are calculated by LinkKitchen and can be sent to WEAP by a single mouse-click:
1. Highlight the Catchments – parent branch and click the WEAP-button on the top toolbar
2. Switch to WEAP and browse to Data View → Demand Sites and Catchments → Landuse → Area
If the area’s units are not yet defined, you need to select
hectares as the area unit in order to make the entries visible.
The area distribution should look similar to the following:
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Hard-Data-Approach
3.10.2 Send groundwater recharge to WEAP
The procedure to send natural recharge to WEAP is similar to sending catchment areas.
1. Highlight the Groundwater – parent branch and click the WEAP-button on the top toolbar
2. Switch to WEAP and browse to
Data View → Supply and Resources → Groundwater → Natural Recharge.
Note: LinkKitchen calculates all recharge-values as million m³ which is the default scale for natural
recharge in WEAP. Check and change the scale if necessary!
General → Units → Groundwater: change the scale to Million m³.
The recharge values should look like:
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Hard-Data-Approach
3.11 Link WEAP and MODFLOW
After having entered the required data in both the Linkage File and WEAP, you are now ready to link
both models. This is done by:
•
•
Loading the linkage shapefile to WEAP
Set up the linkage in WEAP
Load the linkage shapefile to the WEAP schematic:
Add Vector Layer → select the linkage file (linkage.shp)
From the top menu, select:
Advanced → MODFLOW Link → MODFLOW Name File → MODFLOW/trans_modify_5f_drain.mfn
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Hard-Data-Approach
Choose your linkage shapefile and assign the respective attribute fields for Row and Column,
Groundwater, River Reach and Catchment (this should be correct by default).
If you have not yet assigned river reaches (because you opted for Method 2 in chapter 3.8), you
should now click on Guess River Point Linkages and Guess Drain Cell Linkages.
Click on the results-command and look at the result outputs like the groundwater levels (Supply and
Resources → Groundwater → MODFLOW → Cell Head) etc.
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Hard-Data-Approach
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Hard-Data-Approach
4 WEAP-hydrologyinlinkedmodels–Rainfall-Runoff
In the previous exercise, you entered groundwater recharge directly into WEAP as “Natural
Recharge” and delimited the catchments according to recharge zones in MODFLOW.
In the following exercises, the catchment names remain the same, but they correlate to different
spatial regions (surface water catchments). The Catchments are furthermore subdivided into Landuse
classes in order to reflect various water needs.
In addition, surface-runoff links are assigned to the catchment nodes (from the catchment to the
river).
In this chapter, WEAP will calculate the groundwater recharge based on its internal Rainfall Runoff
(simplified coefficient method) model.
4.1 AddRunofflinkstotheSchematic
In order to let WEAP calculate surface runoff, you need to add runoff-links from catchments to rivers
in the WEAP Schematic. Drag and drop a runoff-link from each Catchment Node to its corresponding
River.
Catchment
Runoff link to
Headflow yes/no
C_MainUpper
Main River
No
C_West
West River
Yes
C_East
East River
Yes
C_Central
Main River
No
C_Main Lower
Main River
No
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Rainfall-Runoff-Model
4.2 Assign catchments and Landuse Classes to the Linkage File.
1. Add Sub-branches to each of the Catchments.
In the Data-View: right-click on the Catchment → Add → type the name of the sub branch as specified
in the table below:
Catchment
Landuse class
C_East
unirrigated
C_East
urban
C_MainCentral
unirrigated
C_MainLower
unirrigated
C_MainLower
urban
C_MainUpper
forest
C_MainUpper
irrigated
C_MainUpper
pasture
C_MainUpper
shrub
C_West
forest
C_West
pasture
C_West
unirrigated
2. Switch to LinkKitchen and load the two files Catchment.shp and Landuse.shp as Overlays.
3. Set Layer Catchment to be selectable
4. Set Layer Catchment’s Label to “Catchment”
5. Right click into C_MainUpper and click on Select Cells from Overlay
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.
Rainfall-Runoff-Model
6. Highlight C_MainUpper in the Branch Viewer and click Add Attribute to selected Cells.
7. Highlight GW_MainUpper in the Branch Viewer and click Add Attribute to selected Cells.
Repeat steps 5-7 for the other Catchments and Groundwater nodes.
8. Set Layer Landuse selectable and assign Landuse-Classes to the Linkage File. The procedure is
similar to steps 5-7.
9. Send the Area data to WEAP
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Rainfall-Runoff-Model
4.3 Data input in WEAP
Additional inputs at catchment level are precipitation and reference evapotranspiration (ETref). Crop
coefficients (Kc) are entered at Landuse class level. These inputs are read into WEAP using the
ReadFromFile-function. The file from which to read data is named INPUT_DATA.csv. Copy the file into
the TimeSeries-Folder in the WEAP area-directory.
4.3.1 Enter precipitation
1. In the Data View, select C_MainCentral and activate Climate → Precipitation.
2. Click on the arrow besides the data-entry box and select the ReadFromFile Wizard.
3. Open the file \TimeSeries\INPUT_DATA.csv
4. In the lower pane, select the data column Precipitation and click Finish.
5. Repeat steps 2-4 for the other Catchments
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Rainfall-Runoff-Model
4.3.2 Enter ETRef
ETRef is entered the same way as precipitation but with the data column [ET].
4.3.3 Enter Kc
Go to Landuse – Kc and enter Kc values for each Landuse Class the same way as precipitation and
ETRef.
Landuse Classes Irrigated and unirrigated retrieve values from the same data column (unirrigated).
(For details on the Rainfall Runoff (simplified coefficient method)-model, see WEAP-help and FAO
Irrigation and Drainage Paper No. 56 “Crop Evapotranspiration”).
4.3.4 Enter Runoff- and Infiltration fractions
The total runoff volume can be fractioned to surface runoff and groundwater recharge:
Supply and Resources → Runoff and Infiltration → from catchment (C_...) → to …→ Runoff Fraction
Enter a value of 50% for each link.
4.3.5 Run the model and browse the results
The result below shows the calculated recharge- and runoff-flows from C_MainLower.
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Rainfall-Runoff-Model
5 Commontasks
The following part of this tutorial will give you some workarounds for dealing with common modeling
challenges. It does make no claim to be complete nor does it pretend to show the one-and-only
solution for any of the problems presented. But you might use some of the shown approaches as the
starting point for your own modeling work.
The descriptions hereafter are reduced to the basic implementations and parameter setting. If you
want to visualize the impacts of each task on the system, you should apply the changes on scenarios
and compare the results with the reference.
5.1 Abstractionforirrigation
There are multiple ways to introduce irrigation abstraction. The two most commonly applied ways
are:
1. Define a Demand Site and enter the abstracted water directly
2. Let WEAP calculate irrigation demand based on climate and crop parameters
For the former, there is no need to care about the climate or what types of crop are grown. This
method is easier to implement but very inflexible when it comes to build scenarios. The later requires
more data to enter but gives better performance for future planning.
The following chapters will show both approaches.
5.1.1 Add irrigation abstraction by demand site
1. Drag and drop a new demand site onto the Schematic View and name it “Irrigation”.
2. Drag and drop a transmission link from groundwater GW_MainUpper to the new demand site
"Irrigation".
3. Enter the water abstraction for irrigation under:
Data→ Demand sites and catchments → irriga@on → water use → Annual water use
The irrigation demand is 30 million m3 per year. As water is needed only during the months of May
and June, the annual irrigation is fractioned with the percentage (40%) in May and (60%) in June. This
is entered at
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Common Tasks
Data→ Demand sites and catchments → irrigation → water use → Monthly Varia@on
Using the Monthly Time Series Wizard.
4. As WEAP needs to know from which cells to abstract water from, you need to update the Linkage
File with that information. It is assumed, that water is abstracted from wells located all over the
irrigated area.
Switch to LinkKitchen and highlight the Landuse Class C_MainUpper/Irrigated in the Branch Viewer.
5. Click the Select Attributed Cells-Button.
6. Highlight Demand Site Irrigation and click Add Attribute to Linkage File. Now, every cell located
within the Landuse Class “Irrigated” supplies Demand Site Irrigation.
7. Save the Linkage File to disc and go back to WEAP.
8. Re-load the Linkage File if necessary and run WEAP. Browse the results
5.1.2 Add irrigation abstraction to a Landuse Class
Modelling irrigation demand by a WEAP-internal model requires a connection from groundwater to
the catchment. Further specifications, like from which cells to withdraw water and on which cells to
apply water, are defined in the Linkage File.
The water demand is controlled by the crop parameter Kc and by the climate parameters
precipitation and ET. WEAP will calculate water demand, if the plant evapotranspiration is higher
than precipitation.
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1. Drag and drop a transmission link from GW_MainUpper to
C_MainUpper
2. Set the demand priority to 1
3. Switch the irrigated Landuse Class to irrigated:
Demand Sites and Catchments→C_MainUpper→Irrigation→Irrigated = 1
4. Run the model and evaluate the results in the results view.
E.g. Land class inflows and
outflows:
You can see irrigation
takeing place during the
months May and June
when ET is high and
precipitation is low.
Although precipitation
remains low during July and
August, there is no need to
irrigate as the crops are
already harvested.
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5.2 Changes in Land Use
The purpose of this exercise is to investigate the impact of changes in land use on the groundwater
recharge. In order to emphasize the changes, the total runtime of the model is extruded to 10 years.
General →. Years and @me steps → last year of scenarios = 2009
Land use 2000
Land use 2010
5.2.1 Urbanization
Storyline: Urban areas grow towards extending over the entire catchment areas of C_East and
C_MainLower until 2010. Infiltration vanishes and the entire precipitation runs off the rivers.
1. Let WEAP repeat time-dependant data each year (precipitation, ET, Kc):
Chose “cycle”option
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2. Increase the surface runoff fraction from 50% in the year 2000 to 100% in 2009 and reduce the
fraction for groundwater recharge accordingly:
Supply and Resources → Runoff and Infiltra@on → from C_MainLower → Runoff Frac@on
Supply and Resources → Runoff and Infiltration → from C_E ast→ Runoff Frac@on
To interpolate the yearly fractions use the functions Interp(2009, 100) and Remainder(100).
Runoff Fraction (monthly)
100
to GW_MainLower
to Catchment Inflow Node 5
95
90
85
80
75
70
65
% share
60
55
50
45
40
35
30
25
20
15
10
5
0
Oct Feb Jun Oct Feb Jun Oct Feb Jun Oct Feb Jun Oct Feb Jun Oct Feb Jun Oct Feb Jun Oct Feb Jun Oct Feb Jun Oct Feb Jun
1999 2000 2000 2000 2001 2001 2001 2002 2002 2002 2003 2003 2003 2004 2004 2004 2005 2005 2005 2006 2006 2006 2007 2007 2007 2008 2008 2008 2009 2009
5.2.2 Irrigation growth
Land use class unirrigated is changed to be irrigated from the year 2001 onward.
1. Add transmission links from the groundwater to the catchment for the catchments C_MainUpper,
C_MainCentral and C_West.
2. Within these catchments, set the land use classes unirrigated and irrigated to be irrigated (1)
3. Define an irrigation fraction of 75% (= overirrigation)
4. Run the model and browse the results
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5.3 Domestic water supply from well fields
In this chapter, you will introduce two domestic demand sites (City1 & City2), which are supplied by
local well fields. You need to make entries in both WEAP and the Linkage File for this to work.
1. Drag and drop two Demand Sites (City 1 and City 2) onto the Schematic.
2. Add a Transmission link from GW_MainUpper to City 1 and another transmission link from
GW_MainLower to City 2.
3. Set the Annual Water Use Rate for both Cities to 20 Million m³.
4. Set the Consumption to 100%: Demand Sites and Catchments → Water Use →Consump@on
5. Switch to LinkKitchen and load the overlay-layer Wellfields.shp which indicates the location
of the two wellfields.
6. Select all cells of the top wellfields first and assign City 2 to the selected cells. Repeat the step
with the second wellfield. The preview should look like:
7.
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Save the Linkage File and reload it
Common Tasks
into WEAP if necessary.
8. Run WEAP and browse for Cell-Head-results (Map-View)
The result shows a significant cone of depression around the cells you defined as Demand Site
“City2”.
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5.4 Artificial groundwater recharge
Modelling artificial recharge (e.g. injection wells) is similar to modelling abstraction. The only
difference is that water is not consumed by the demand site but returned to a groundwater node.
The location of the injection is defined by the demand-attribute in the Linkage File.
1. Add a Demand Site “Artificial Recharge” to the Schematic and set Annual Water Use Rate to
20 Million m³; set Consumption to 0%
2. Add a Transmission link from Main River to the new Demand Site and a Return Flow Link
from the Demand Site to groundwater GW_MainLower
3. Switch to LinkKitchen and link some cells to Demand Site ArtificialRecharge. The preview
should look similar to the image below:
4. Save the Linkage File and go back to WEAP
5. Browse to the Cell-Head-results
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Injecting water has a similar effect on the groundwater table as withdrawal but in the opposite
direction. The effects of withdrawal and artificial recharge are visualized in the Map Window and as
3D-chart (s. images below left and bottom). Image below right shows the annual flows as calculated
by WEAP.
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5.5 Climate Change
The possible impacts of climate change on surface runoff, groundwater levels and spring flow are (at
a simplistic glance on that complex subject) driven by changes in the parameters precipitation and
evaporation.
In order to visualize the impacts of climate change, create a new scenario “Climate Change” and
change the following parameters for every single catchment:
•
•
ETRef → Growth(3%)
Precipitation → Growth (-3%)
Run WEAP and browse to the result for groundwater storage.
The comparison of the two scenarios climate change and reference shows the effect of climate
change on groundwater storage over time
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Common Tasks
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