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 Change The
Water Resource Sector
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Outline

• 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 VA Assessments

• Defining VA assessment
• Often VA 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 VA 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 VA 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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Water Resources A Critical VA Sector

• Often critical to both managed and natural
  systems
• Human activity influences both systems

Managed Systems
External Pressure
Product, good or service Process Control
services
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 VA 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 VA 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 SectorWaters 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)
• RIBASIM
• 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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An Infrastructure Constraint
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A Regulatory Constraint
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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
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10

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

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90
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Example

• 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 f(Pe,z1,1/LAI)
Sw
Dw
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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
Languages Interface Only English French Chinese S
panish
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WEAPs 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 lt 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
• http//www.mara.org.za/climatecd/info.htm
• Hydrology
• http//www.dwaf.gov.za/hydrology/
• GIS
• http//www.sahims.net/gis/
• General
• http//www.weap21.org (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 www.weap21.org 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