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Decision Tools to Evaluate Vulnerabilities and Adaptation Strategies to Climate Change The Water Resource Sector PowerPoint PPT Presentation

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Decision Tools to Evaluate Vulnerabilities and Adaptation Strategies to Climate Change The Water Resource Sector. Outline. Vulnerability and adaptation with respect to water resources Hydrologic implications of climate change for water resources Topics covered in a water resources assessment

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Decision Tools to Evaluate Vulnerabilities and Adaptation Strategies to Climate Change The Water Resource Sector

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Decision Tools to Evaluate Vulnerabilities and Adaptation Strategies to Climate ChangeThe Water Resource Sector

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  • Vulnerability and adaptation with respect to water resources

  • Hydrologic implications of climate change for water resources

  • Topics covered in a water resources assessment

  • Viewing water resources from a services perspective

  • Tools/models

  • WEAP model presentation

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Effective V&A Assessments

  • Defining V&A assessment

    • Often V&A is analysis, not assessment

    • Why? Because the focus is on biophysical impacts, e.g., hydrologic response, crop yields, forests, etc.

  • However, assessment is an integrating process requiring the interface of physical and social science and public policy

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Effective V&A Assessments (continued)

  • General questions

    • What is the assessment trying to influence?

    • How can the science/policy interface be most effective?

    • How can the participants be most effective in the process?

  • General problems

    • Participants bring differing objectives/ expertise

    • These differences often lead to dissention/ differing opinions

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Effective V&A Assessments (continued)

  • To be valuable, the assessment process requires

    • Relevancy

    • Credibility

    • Legitimacy

    • Consistent participation

  • An interdisciplinary process

    • The assessment process often requires a tool

    • The tool is usually a model or suite of models

    • These models serve as the interface

    • This interface is a bridge for dialogue between scientists and policy makers

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State of System

Little Control

of processes

Water Resources – A Critical V&A Sector

  • Often critical to both managed and natural systems

  • Human activity influences both systems





Product, good or service

Process Control


Example: Agriculture

Example: Wetlands

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Examples of Adaptation – Water Supply

  • Construction/modification of physical infrastructure

    • Canal linings

    • Closed conduits instead of open channels

    • Integrating separate reservoirs into a single system

    • Reservoirs/mydroplants/delivery systems

    • Raising dam wall height

    • Increasing canal size

    • Removing sediment from reservoirs for more storage

    • Interbasin water transfers

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Examples of Adaptation – Water Supply(continued)

  • Adaptive management of existing water supply systems

    • Change operating rules

    • Use conjunctive surface/groundwater supply

    • Physically integrate reservoir operation system

    • Coordinate supply/demand

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Examples of Adaptation – Water Supply (continued)

  • Policy, conservation, efficiency, and technology

    • Domestic

      • Municipal and in-home re-use

      • Leak repair

      • Rainwater collection for nonpotable uses

      • Low flow appliances

      • Dual supply systems (potable and nonpotable)

    • Agricultural

      • Irrigation timing and efficiency

      • Lining of canals, closed conduits

      • Drainage re-use, use of wastewater effluent

      • High value/low water use crops

      • Drip, micro-spray, low-energy, precision application irrigation systems

      • Salt-tolerant crops that can use drain water

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Examples of Adaptation – Water Supply (continued)

  • Policy, conservation, efficiency, and technology (continued)

    • Industrial

      • Water re-use and recycling

      • Closed cycle and/or air cooling

      • More efficient hydropower turbines

      • Cooling ponds, wet towers and dry towers

    • Energy (hydropower)

      • Reservoir re-operation

      • Cogeneration (beneficial use of waste heat)

      • Additional reservoirs and hydropower stations

      • Low head run of the river hydropower

      • Market/price-driven transfers to other activities

      • Using water price to shift water use between sectors

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Tools in Water Resource V&A Studies

  • Hydrologic models (physical processes)

    • Simulate river basin hydrologic processes

    • Examples – water balance, rainfall-runoff, lake simulation, stream water quality models

  • Water resource models (physical and management)

    • Simulate current and future supply/demand of system

    • Operating rules and policies

    • Environmental impacts

    • Hydroelectric production

    • Decision support systems (DSS) for policy interaction

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Tools in Water Resource V&A Studies (continued)

  • Economic models

    • Macroeconomic

      • Multiple sectors of the economy

      • General equilibrium – all markets are in equilibrium

    • Sectoral level

      • Single market or closely related markets (e.g., agriculture)

    • Firm level

      • Farm-level model (linear programming approach)

      • Microsimulation

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Hydrologic Implications of Climate Change

  • Precipitation amount

    • Global average increase

    • Marked regional differences

  • Precipitation frequency and intensity

    • Less frequent, more intense (Trenberth et al., 2003)

  • Evaporation and transpiration

    • Increase total evaporation

    • Regional complexities due to plant/atmosphere interactions

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Hydrologic Implications of Climate Change (continued)

  • Changes in runoff

    • Despite global precipitation increases, areas of substantial runoff decrease

  • Coastal zones

    • Saltwater intrusion into coastal aquifers

    • Severe storm-surge flooding

  • Water quality

    • Lower flows could lead to higher contaminant concentrations

    • Higher flows could lead to greater leaching and sediment transport

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Africa Example – ECHAM4/OPYC

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Africa Example – GFDLR30

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What Problems Are We Trying to Address?

  • Water planning (daily, weekly, monthly, annual)

    • Local and regional

    • Municipal and industrial

    • Ecosystems

    • Reservoir storage

    • Competing demand

  • Operation of infrastructure and hydraulics(daily and sub-daily)

    • Dam and reservoir operation

    • Canal control

    • Hydropower optimization

    • Flood and floodplain inundation

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The Water Resource SectorWater’s “Trade-Off” Landscape

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Water Resources from a Services Perspective

  • Not just an evaluation of rainfall-runoff or streamflow

  • But an evaluation of the potential impacts of global warming on the goods and services provided by freshwater systems

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Freshwater Ecosystem Services

Extractable; Direct Use; Indirect Use

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Tools to Use for the Assessment: Referenced Water Models

  • Planning

    • WEAP21 (also hydrology)

    • Aquarius

    • SWAT

    • IRAS (Interactive River and Aquifer Simulation)


    • MIKE 21 and BASIN

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Referenced Water Models (continued)

  • Operational and hydraulic

  • HEC

    • HEC-HMS – event-based rainfall-runoff (provides input to HEC-RAS for doing 1-d flood inundation “mapping”)

    • HEC-RAS – one-dimensional steady and unsteady flow

    • HEC-ResSim – reservoir operation modeling

  • WaterWare

  • RiverWare

  • MIKE11

  • Delft3d

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Current Focus – Planning and Hydrologic Implications of Climate Change

  • Select models of interest

    • Deployed on PC; extensive documentation; ease of use

    • WEAP21

    • SWAT

    • HEC suite

    • Aquarius

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Physical Hydrology and Water Management Models

  • AQUARIS advantage: Economic efficiency criterion requiring the reallocation of stream flows until the net marginal return in all water uses is equal

    • Cannot be climatically driven

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Physical Hydrology and Water Management Models (continued)

  • SWAT management decisions on water, sediment, nutrient and pesticide yields with reasonable accuracy on ungauged river basins. Complex water quality constituents.

    • Rainfall-runoff, river routing on a daily timestep

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Physical Hydrology and Water Management Models (continued)

  • WEAP21 advantage: seamlessly integrating watershed hydrologic processes with water resources management

    • Can be climatically driven

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Physical Hydraulic Water Management Model

  • HEC-HMS watershed scale, event based hydrologic simulation, of rainfall-runoff processes

    • Sub-daily rainfall-runoff processes of small catchments

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Overview WEAP21

  • Hydrology and planning

  • Planning (water distribution) examples and exercises

  • Adding hydrology to the model

  • User interface

  • Scale

  • Data requirements and resources

  • Calibration and validation

  • Results

  • Scenarios

  • Licensing and registration

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Hydrology Model

  • Critical questions

    • How does rainfall on a catchment translate into flow in a river?

    • What pathways does water follow as it moves through a catchment?

    • How does movement along these pathways impact the magnitude, timing, duration, and frequency of river flows?

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Planning Model

  • Critical questions

    • How should water be allocated to various uses in time of shortage?

    • How can these operations be constrained to protect the services provided by the river?

    • How should infrastructure in the system (e.g., dams, diversion works) be operated to achieve maximum benefit?

    • How will allocation, operations, and operating constraints change if new management strategies are introduced into the system?

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A Simple System with WEAP21

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10 Unmet



An Infrastructure Constraint

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10 Unmet




A Regulatory Constraint

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10 unmet

Different Priorities

  • For example, the demands of large farmers (70 units) might be Priority 1 in one scenario whereas the demands of smallholders (40 units) may be Priority 1 in another

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Different Preferences

  • For example, a center pivot operator may prefer to take water from a tributary because of lower pumping costs





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  • How much water will the site with 70 units of demand receive?

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Example (continued)

  • How much water will be flowing in the reach between the Priority 2 diversion and the Priority 1 return flow?

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Example (continued)

  • What could we do to ensure that this reach does not go dry?

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What Are We Assuming?

  • That we know how much water is flowing at the top of each river

  • That no water is naturally flowing into or out of the river as it moves downstream

  • That we know what the water demands are with certainty

  • Basically, that this system has been removed from its hydologic context

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What Do We Do Now?

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Add Hydrology

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And this is the Climate Interface

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Integrated Hydrology/Water Management Analytical Framework in WEAP21

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The WEAP 2-Bucket Hydrology Module

Surface Runoff =




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One 2-Bucket Model per Land Class

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Some Comments

  • The number of parameters in the model is fairly limited and is at least related to the biophysical characteristics of the catchment

  • The irrigation routine includes an implicit notion of field level irrigation efficiency

  • Seepage can only pass from the lower bucket to the river, not the other way

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This Last Point Leads to a Stylized Groundwater Representation

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Some Comments

  • The geometry of the aquifers in question is representative, not absolute

  • The stream stage is assumed to be invariant in this module

  • Although the “water table” can fluctuate, it ignores all local fluctuations

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The WEAP21 Graphical User Interface


Interface Only





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WEAP’s Temporal and Spatial Scale

  • Time step: daily, weekly, monthly, etc.

  • No routing, because all demands satisfied within the current time step

  • Time step at least as long as the residence time of period of lowest flow

  • Larger watersheds require longer time steps (e.g., one month)

  • Smaller watersheds can apply shorter time steps (e.g., 1-day, 5-day, 10-day)

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Some Ideas onCatchment Size

  • Small: < 100 km2

  • Medium: 100 to 1,000 km2

  • Large: 1,000 to 10,000 km2

  • Very large: 10,000 to 100,000 km2

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Data Requirements

  • Prescribed supply (riverflow given as fixed time series)

    • Time series data of riverflows (headflows) cfs

    • River network (connectivity)

  • Alternative supply via physical hydrology (watersheds generate riverflow)

    • Watershed attributes

      • Area, land cover . . .

    • Climate

      • Precipitation, temperature, windspeed, and relative humidity

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Data Requirements(continued)

  • Water demand data

    • Municipal and industrial demand

      • Aggregated by sector (manufacturing, tourism, etc.)

      • Disaggregated by population (e.g., use/capita, use/socioeconomic group)

    • Agricultural demands

      • Aggregated by area (# hectares, annual water-use/hectare)

      • Disaggregated by crop water requirements

    • Ecosystem demands (in-stream flow requirements)

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Example Data Resources

  • Climate


  • Hydrology


  • GIS


  • General

  • (resources)

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Calibration and Validation

  • Model evaluation criteria

    • Flows along mainstem and tributaries

    • Reservoir storage and release

    • Water diversions from other basins

    • Agricultural water demand and delivery

    • Municipal and industrial water demands and deliveries

    • Groundwater storage trends and levels

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Modeling Streamflow

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Reservoir Storage

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Looking at Results

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WEAP21 – Developing Climate Change and Other Scenarios

  • The scenario editor readily accommodates scenario analysis, e.g.,

    • Climate change scenarios and assumptions

    • Future demand assumptions

    • Future watershed development assumptions

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Licensing WEAP

  • Go to and register for a new license (free for government, university, and non-profit organizations in developing countries)

  • Register WEAP under Help menu and select “Register WEAP”

  • Login