Application of Water Evaluation and Planning (WEAP) tool for Water Resource Management

Francis Oloo & Jigme Thinley

Outline

Introduction Objectives Modeling process in WEAP Creating Scenarios in WEAP

Impact of population growth Impact of climate change

Results Conclusion

Introduction

Water is an essential resource upon which all life depends.

Even though water constitutes three quarters of the earth surface, not all this is available for human consumption.

There is a great difference in availability of water from region to region, with extreme cases in deserts

Scarcity in the amount of water calls for efficient water resource management.

Water resource management Aims at optimizing the available

natural water flows to satisfy competing needs while ensuring that quality is not compromised.

Key principles of Water Resource Management Water and sanitation sector is affected by

water use in other sectors There are potential positive and negative

impacts of all water uses There is need for a holistic view to ensure

equitable and efficient water use

Water Evaluation and Planning (WEAP)

Is a microcomputer tool for water resource planning

Implements an integrated approach, placing supply

projects in the context of demand-side issues,

quality and ecosystem preservation.

WEAP allows users to implement “what if”

analysis

WEAP tool is developed by Stockholm

Environmental Institute (USA)

Objectives

Create a simple water management system with

supply and demand nodes

Analyse optimal water use within the water

management system as a result of changing

demand and supply scenarios

Analyse the impact of population growth and

climate change on demand and supply

equilibrium

Area of Study/Demonstration Site

Weap River Basin

This is a hypothetical data set associated

with WEAP system.

Designed to aide the user in exploring

various components of WEAP

Modeling Process in WEAP

Defining the study area and time steps for analysis

Evaluation of results

Creation of future scenarios

Creation of the current Accounts

Schematic view: • consists of GIS tools that can be used to configure the

system• Icons for drainage components are used to drag and

drop components at the appropriate position

Notes:Documentation of data specifications and assumptions

Scenario Explorer:Allows the user to design and display unique outputs from various model aspects, gives a “bird’s eye” view of the model

Results view:• Allows for presentation of model outputs both in graphical and tabular format

Data view:• This is where the system data is modeled•Allows for assumptions to be made and can be dynamically linked to Excel

WEAP System Elements

Demand sites: A set of users sharing physical distribution system (geographical)

Catchments: Points created to account for precipitation, ET, runoff, irrigation and yield from agricultural and non-agricultural fields

Reservoirs: Reservoir sites on the river Stream flow gauges: points where actual

flow measurements are acquired, can be compared with simulated values

Ground water nodes: represent ground water sources and aquifers

Waste Water treatment plants

Creating system elements

• GIS layers (shapefiles and topographic maps) than can be used as geographic references for the various elements

Defining time steps

Creating Current Accounts

Key aspects to be defined include: Key assumptions in the system Demand sites in the system and the current

status of water demand Hydrology, defining the current inflows into

the system and the expected variations Supply and resources, supply nodes and

transmission links and the associated costs in running and maintaining

Water treatment plants and associated cost of treatment

Creating Current Accounts

Creating Scenarios in WEAP• The scenario explorer can be used to create new (rename) scenarios and to define the variables associated with them•Previously defined scenarios can also be deleted

Impact of population growth on water demand

In the study an assumption is made that

the population will grow uniformly at a

rate of 3.3% per annum, for the period

2010-2020

Expression builder within WEAP can be

used to calculate the interpolated

population of each year if the population

of the start year is known.

Impact of climate change on water resources

Two methods can be used to account for impact of climate change on the hydrology of the system ReadFromFile method: Used when detailed

forecasts are available and can simply be read into the system

Water Year Method: Each year is defined either as “normal”, “wet”, “very wet”, “dry”, “very dry”. The inflows of wet, very wet, dry and very dry years relative to a normal year can be defined. E.g if a wet year averagely has 25% more inflow than a normal year then a value of 1.25 will be set to the wet year relative to the normal year.

Impact of climate change on water resources

2010 2011

2012 2013

2014 2015 2016

2017 2018 2019 2020

Normal

wet very wet

wet normal

dry dry very dry

very dry

dry normal

Results

Unmet demands

Unmet demands

Ground Water Storage

Exporting the system to Google Earth

Conclusion

WEAP is a valuable tool for water resource planning and evaluation, easy to learn and use. Very useful for policy decision in water resource management.

It is possible to use GIS layers for referencing and visualization, the integration needs to be enhanced to allow for analysis and map creation

The tool has additional inbuilt modules like MODFLOW and MODPATH which should be explored