1. WEAP Water Evaluation & Planning System www.weap21.org weap@tellus.org
Overview

2. WEAP Highlights Integrated water resources planning system.
GIS-based, graphical drag & drop interface.
Basic methodology: physical simulation of water demands and supplies.
Additional simulation modeling: user-created variables and modeling equations.
Scenario management capabilities.
Links to spreadsheets & other models
WEAP is comprehensive, straightforward and easy-to-use, and attempts to assist rather than substitute for the skilled planner. As a database, WEAP provides a system for maintaining water demand and supply information. As a forecasting tool, WEAP simulates water demand, supply, flows, and storage, and pollution generation, treatment and discharge. As a policy analysis tool, WEAP evaluates a full range of water development and management options, and takes account of multiple and competing uses of water systems.

3. WEAP Capabilities Can do
High level planning and strategic analysis at local, national and regional scales
Demand management
Water allocation
Cannot do
Daily operations
Least-cost optimization of supply and demand

4. Examples of Analyses Sectoral demand analyses Water conservation
Water rights and allocation priorities
Groundwater and streamflow simulations
Reservoir operations
Hydropower generation
Pollution tracking
Ecosystem requirements

5. Selected Projects California Volta and Syr Darya China South Africa
Impacts of climate change and other stressors on ecosystem services
Volta and Syr Darya
Food and environmental security
China
Providing a basis for cooperation/negotiation between Beijing and upstream water users
South Africa
Moving towards equity in water use
WEAP has been used in both developed and developing country contexts.
We are currently entering the second year of a four year research project looking at the Sacramento/San Joaquin River Basins in California, trying to establish a transferable methodology for looking at multiple stressors, including climate change, on ecosystem services.
We are just starting a project in the Hebei province in China. This Project focuses on the planning and decision-making processes that prevent upstream-downstream conflicts from being resolved even when the advantages should be evident—a set of problems, which are fundamental to the Programme’s focal problem: the conflict over conspicuously scarce water resources. This Project is designed to provide the basis for achieving the most critical objective of the Programme: co-operation on water-related issues, and involves upstream stakeholders in Hebei Province and downstream stakeholders in Beijing, altogether about 20 counties.
Finally, we are working with IWMI in the South African basin, Olifants, a tributary to the Limpopo, in establishing a shift towards more equitable allocation of water among different populations in the basin.

6. WEAP for Vulnerability…
Alternative baseline scenarios can examine vulnerability of water supplies to different demographic, technological, & climatalogical/hydrological futures.
…& Adaptation…
Alternative policy scenarios can explore demand and supply management options for adapting to future vulnerability.
Implications for the multiple and competing demands on water systems.
Implications of policies can be evaluated (ability to meet water needs, hydropower availability, pollution loadings, costs, etc.)

7. Click and drag to create a new demand site
Schematic View
Click and drag to create a new demand site
The Schematic View is the starting point for all activities in WEAP. A central feature of WEAP is its easy-to-use “drag and drop” graphical interface used to describe and visualize the physical features of the water supply and demand system. This spatial layout is called the schematic. You can create, edit and view it in the Schematic View. GIS layers can be added to add clarity and impact. The Schematic View provides you with one-click access to your entire analysis—right clicking on any element in the schematic gives access to its data or results.

8. Data is displayed numerically and graphically
Data View
Data is displayed numerically and graphically
The Data View is the place where you create your data structures, models and assumptions in WEAP. In the Data View, the screen is divided into four panes. On the top left, a hierarchical tree is used to create and organize data structures under six major categories Key Assumptions, Demand Sites, Hydrology, Supply and Resources, Environment, and Other Assumptions. The tree is also used to select the data to be edited, which is shown on the right of the screen. For example, clicking on the “Demand Sites” tree branch on the left of the screen, will display the data for all demand sites on the right of the screen. On the top-right of the screen, a data entry table is used to edit data and create modeling relationships. The information you enter here is displayed graphically in the bottom right pane.

9. Results can be displayed in wide range of formats and scales
Results View
The Results View displays a wide variety of charts and tables covering each aspect of the system: demand, supply, costs, and environmental loadings. Customizable reports can be viewed for one or more scenarios. You can also use the “Favorites” option to bookmark the most useful charts for your analysis.

10. Favorite charts can be selected to give quick overviews
The Overviews View is used to group together “Favorite” charts (created earlier in the “Results” view) which can then be displayed on the screen simultaneously. With Overviews, you can get a birds-eye perspective on different important aspects of your system, such as demand, coverage, storage levels, environmental impacts and costs. You can create multiple Overviews, each of which can display up to 16 different Favorites.

11. Sectoral Water Demands
Irrigation
Ecosystems
Livestock
Domestic
Total
Water Demand
Mining
A demand site is best defined as a set of water users that share a physical distribution system, that are all within a defined region, or that share an important withdrawal supply point. You also must decide whether to lump demands together into aggregate demand sites (e.g., counties) or to separate key water uses into individual demand sites. You might want to define demand sites according to the following groupings:
  major cities or counties
individual user which manages a surface or groundwater withdrawal point, such as an industrial facility
irrigation districts
demands which return to a unique wastewater treatment plant
water utilities
Commercial
Industrial
Major Cities

12. Illustrative Demand Structure
SECTOR
SUBSECTOR
END-USE
DEVICE
Agriculture
Industry
Municipal
Cotton
Rice
Wheat
...
Electric Power
Petroleum
Paper
South City
West City
Irrigation
...
Cooling
Processing
Others
Single Family
Multi-family
Furrow
Sprinkler
Drip
Standard
Efficient
...
Kitchen
Bathing
Washer
Toilet
You can adapt the structure of the data to your purposes, based on the availability of data, the types of analyses you want to conduct, and your unit preferences. Note also that you can create different levels of disaggregation in each demand site and sector.
Types of disaggregation:
Ÿ         Sector: A sample sectoral partition could include agriculture, industry, urban domestic and rural domestic. The sector categories can be used flexibly to correspond to the particular problem under analysis. The example at the right has no sectoral breakdown within a demand site—the demand sites themselves each represent one sector (two each for municipal, industry and agriculture).
Ÿ        Subsector: For example, the industrial sector could be divided into industrial classifications, e.g., steel and iron, petroleum, chemistry, textile, pulp and paper, and food processing. The agriculture sector might be broken down by crop type, livestock or another appropriate subsector.
Ÿ    End-use: For example, a crop end-use might be characterized by water requirements in different soil conditions or in different locations in the study area, or different irrigation techniques. Industrial end-uses might include processing, cooling and sanitary amenities.
Ÿ      Device: For example, sprinkler, drip or flooding irrigation in agricultural sectors, or showers, toilets, and washing for domestic sectors.

13. Supplies Rivers Groundwater Diversions (e.g. canals, pipelines)
storage capacity
maximum monthly withdrawal
natural recharge
Diversions (e.g. canals, pipelines)
Reservoirs
Other (e.g. desalination)
WEAP allows users to specify several types of water sources, including surface and ground water. Other components of supply include diversions and reservoirs. Finally, other sources of water may be available, such as desalination plants or inter-basin transfers.

14. Hydrology Water-Year Method Read-from-File Method
Create a series of water year “types” from very dry through normal to very wet (5 types).
For each scenario year specify its type.
Use to examine alternative climate scenarios.
Read-from-File Method
Historical or synthetic data, imported from data files
An important aspect of modeling a water system is understanding how it operates under a variety of hydrologic conditions. Natural variations in hydrology—month to month and year to year—can have major effects on the results of your scenarios.
WEAP has three methods for projecting the surface water hydrology over the study period: the Water Year Method, Read From File Method and Expressions. These methods may be used to project the inflow to every surface and groundwater inflow point in the system for every month in the study period. This includes river and tributary headflows, surface water inflows to river reaches, groundwater, local reservoir and other local supply inflow. With Read From File, you specify the inflow for each month; with the Water Year Method, you specify the twelve months of inflow for the Current Accounts, and then specify the future sequence of wet and dry years; with Expressions, you specify the inflows via a mathematical expression.

15. Capacities, efficiencies, and other properties of power generation
Hydropower
Capacities, efficiencies, and other properties of power generation
Hydropower generation is computed from the flow passing through the turbine, based on the reservoir release or run-of-river streamflow, and constrained by the turbine's flow capacity. Maximum and Minimum Turbine Flows define the upper and lower capacity limits. When turbine flow exceeds the maximum, hydropower will only be generated up to the maximum flow. When turbine flow falls below the minimum, no hydropower will be generated. Tailwater Elevation defines the working water head on the turbine. The power generated in a given month depends on the head available, which is computed as the drop from the reservoir elevation (as computed by WEAP, using the Volume Elevation Curve and the current storage volume) to the tailwater elevation. The Plant Factor specifies the percentage of each month that the plant is running. The plant Generating Efficiency defines the generator's overall operation effectiveness (electricity generated dived by hydropower input).
Run of river hydropower can also be specified.

16. Priority Allocation of Water Resources
Supply Priorities
Demand Preferences
Allocation Order
Two user-defined priority systems are used to determine monthly allocations from local supplies and river nodes to demand sites, and for instream flow requirements.
Competing demand sites and flow requirements are allocated water according to their supply priorities. The supply priority is attached to the demand site or flow requirement. Sites can share the same priority. These are useful in representing water rights, and are also important during a water shortage, in which case higher priorities are satisfied as fully as possible before lower priorities are considered. If priorities are the same, shortages will be equally shared. Typically, you assign the highest priorities to critical demands that must be satisfied during a shortfall, such as a municipal water supply.
When demand sites are connected to more than one supply source, you can also rank their demand preferences. These are attached to transmission links.
Using the supply priorities and demand preferences, WEAP determines the allocation order to follow when allocating the water. The allocation order represents the actual calculation order used by WEAP for allocating water.

17. Network

18. WEAP System Requirements
Windows 95 or later
32 MB of RAM (64 MB suggested)
Imports from/exports to Excel and Word (not required).
Uses standard ArcView GIS “shape” files. ArcView is not required.

19. Availability
Evaluation version available at no charge (CDs available here) or download from
Full version requires license, available from SEI-Boston.
Training is needed for majority of users, available from SEI-Boston.