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

UNFCC Climate Change Impacts and Adaptations Maputo18 April 2005Alyssa McCluskey, University of Colorado and David Yates, National Center for Atmospheric Research

OutlineVulnerability and Adaptation with respect to water resourcesHydrologic implications of climate change for water resourcesTopics covered in a water resources assessmentViewing water resources from a services perspectiveTools/ModelsWEAP Model Presentation

Effective Vulnerability and Adaptation Assessments Defining Vulnerability and Adaptation (V&A) AssessmentOften V&A is Analysis not AssessmentWhy?? Because the focus is on biophysical impactse.g. hydrologic response, crop yields, forests, etc.However, Assessment is an integrating processRequiring the Interface of physical and social science and Public Policy

Effective Vulnerability and Adaptation Assessments General QuestionsWhat 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 ProblemsParticipants bring differing objectives/expertiseThese differences often lead to dissention/differing opinions The assessment process requires1. Value2. Credibility3. Legitimacy4. Consistent Participation

Effective Vulnerability and Adaptation Assessments V&A Assessments - An Interdisciplinary process

The Assessment process often requires a toolThe tool is usually a model or suite of modelsThese models serve as the interfaceThis interface is a bridge for dialogue between scientists and policy makers

Water Resources A Critical V&A SectorOften Critical to both Managed and Natural SystemsHuman Activity Influences Both SystemsManagedSystems

External PressureProduct, good or service

Process ControlExample: AgricultureExample: Wetlands

Examples of Adaptation Water SupplyConstruction/Modification of physical infrastructureCanal liningsClosed conduits instead of open channelsIntegrating separate reservoirs into a single systemReservoirs/Hydroplants/Delivery systemsRaising dam wall heightIncreasing canal sizeRemoving sediment from reservoirs for more storageInter-basin water transfersAdaptive management of existing water supply systemsChange operating rulesUse conjunctive surface/groundwater supplyPhysically integrate reservoir operation systemCo-ordinate supply/demand

Examples of Adaptation Water DemandPolicy, Conservation, Efficiency, and TechnologyDomestic Municipal and in-home re-useLeak repairRainwater collection for non-potable useslow flow appliancesDual supply systems (potable and non-potable)AgriculturalIrrigation timing and efficiencyLining of canals, Closed ConduitsDrainage re-use, Use of wastewater effluentHigh value/low water use cropsDrip, micro-spray, low-energy, precision application irrigation systemsSalt tolerant crops that can use drain water

Examples of Adaptation Water Demand (continued)Policy, Conservation, Efficiency, and TechnologyIndustrialWater Re-use and RecyclingClosed cycle and/or air coolingMore efficient hydropower turbinesCooling ponds, wet tower and dry towers

Energy (hydro-power)Reservoir re-operationCo-generation (beneficial use of waste heat)Additional reservoirs and hydropower stationsLow head run of the river hydropowerMarket/price-driven transfers to other activitiesUsing water price to shift water use between sectors

Tools in Water Resource V&A StudiesHydrologic Models (physical processes)Simulate river basin hydrologic processesExamples - Water Balance, Rainfall-Runoff, lake simulation, stream water quality modelsWater Resource Models (physical and management)Simulate current and future supply/demand of systemOperating rules and policies Environmental impactsHydroelectric productionDecision Support Systems (DSS) for policy interaction

Hydrologic Implications of CC for Water Resources Precipitation amountGlobal average increase Marked regional differences

Precipitation frequency and intensityLess frequent, more intense (Trenberth et al., 2002)

Evaporation and transpirationIncrease total evaporationRegional complexities due to plant/atmosphere interactions

Hydrologic Implications of CC for Water Resources (continued)Changes in runoffDespite global precipitation increases, areas of substantial runoff decreases

Coastal zonesSaltwater intrusion into coastal aquifersSevere storm-surge flooding

Water qualityLower flows, could lead to higher contaminant concentrationsHigher flows could lead to greater leaching and sediment transport

Africa Focus ECHAM4/OPYC

Africa Focus GFDLR30

What Problems are We Trying to Address??Water Planning (daily, weekly, monthly, annual)Local and regionalMunicipal and industrialEcosystemsReservoir storage Competing demand

Operation of infrastructure and hydraulics (daily and sub-daily)Dam and reservoir operationCanal controlHydropower optimizationFlood and floodplain inundation

Water Resource PlanningWaters Trade-Off Landscape

Water Resources from a Services PerspectiveNot just an evaluation of rainfall-runoff or streamflow

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

Freshwater Ecosystem ServicesExtractable; Direct Use; Indirect Use

Tools to use for the Assessment: Referenced Water ModelsPlanningWEAP21 (also hydrology)Aquarius

SWAT

IRAS (Interactive River and Aquifer Simulation)

RIBASIM

MIKE BASIN

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

Current Focus Planning and Hydrologic Implications of CCSelect models of interest and available at workshop Why??? Free; deployed on PC; extensive documentation; ease-of-useWEAP21SWATHEC suiteAquarius

Physical Hydrology and Water Management ModelsAQUARIS advantage: Economic efficiency criterion requiring the reallocation of stream flows until the net marginal return in all water uses is equalCannot be climatically driven

Physical Hydrology and Water Management Models (continued)SWAT management decisions on water, sediment, nutrient and pesticide yields with reasonable accuracy on ungaged river basins. Complex water quality constituents.Rainfall-runoff, river routing on a daily timestep

Physical Hydrology and Water Management Models (continued)WEAP21 advantage: Seamlessly integrating watershed hydrologic processes with water resources managementCan be climatically driven

Physical Hydraulic Water Management ModelHEC-HMS watershed scale, event based hydrologic simulation, of rainfall-runoff processesSub-daily rainfall-runoff processes of small catchments

Overview WEAP21Hydrology and PlanningPlanning (water distribution) examples and exercisesAdding hydrology to the modelUser interfaceScaleData Requirements and ResourcesCalibration and ValidationResultsScenariosLicensing and Registration

Hydrology ModelCritical questionsHow 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?

Planning ModelCritical questionsHow 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?

A Simple System with WEAP21

An Infrastructure Constraint

A Regulatory Constraint

Different PrioritiesFor example, the demands of large farmers (70 units) might be Priority 1 in one scenario while the demands of smallholders (40 units) may be Priority 1 in another

Different PreferencesFor example, a center pivot operator may prefer to take water from a tributary because of lower pumping costs3010900

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

Example (continued)How much water will be flowing in the reach between the Priority 2 diversion and the Priority 1 return flow?

Example (continued)What could we do to ensure that this reach does not go dry?

What Are We Assuming?That we know how much water is flowing at the top of each riverThat no water is naturally flowing into or out of the river as it moves downstreamThat we know what the water demands are with certaintyBasically, that this system has been removed from its HYDROLOGIC context

What Do We Do Now?

Add Hydrology

And this is the Climate Interface

Integrated Hydrology/Water Management Analytical Framework in WEAP21

The WEAP 2-Bucket Hydrology ModuleSurface Runoff =f(Pe,z1,1/LAI)SwDw

One 2-Bucket Model per Land Class

Some CommentsThe number of parameters in the model are fairly limited and are 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

This Last Point Leads to a Stylized Groundwater Representation

Some CommentsThe geometry of the aquifers in question are representative, not absolute

The stream stage is assumed to be invariant in this module

While the water table can fluctuate, it ignores all local fluctuations

The WEAP21 Graphical User InterfaceLanguages:Interface OnlyEnglishFrenchChineseSpanish

WEAPs Temporal and Spatial ScaleTime step: Daily, weekly, monthly, etc.No routing, as all demands satisfied within the current time stepTime step at least as long as the residence time of period of lowest flowLarger watersheds require longer times steps (e.g., one month)Smaller watersheds can apply shorter time steps (e.g., 1-day, 5-day, 10-day)

Some Ideas onCatchment SizeSmall

Data RequirementsPrescribed supply (riverflow given as fixed time series)Time series data of riverflows (headflows) cfsRiver network (connectivity)

Alternative supply via physical hydrology (watersheds generate riverflow)Watershed attributesArea, land cover . . .ClimatePrecipitation, temperature, windspeed, and relative humidity

Data Requirements (continued)Water demand dataMunicipal and industrial demandAggregated by sector (manufacturing, tourism, etc.)Disaggregated by population (e.g., use/capita, use/socio-econ group)Agricultural demandsAggregated by area (# hectares, annual water-use/hectare)Disaggregated by crop water requirementsEcosystem demands (in-stream flow requirements)

Example Data ResourcesClimatehttp://www.mara.org.za/climatecd/info.htmHydrologyhttp://www.dwaf.gov.za/hydrology/GIShttp://www.sahims.net/gis/Generalhttp://www.weap21.org (resources)

Calibration and ValidationModel evaluation criteriaFlows along mainstem and tributariesReservoir storage and releaseWater diversions from other basinsAgricultural water demand and deliveryMunicipal and industrial water demands and deliveriesGroundwater storage trends and levels

Modeling Streamflow

Reservoir Storage

Looking at Results

WEAP21 Developing Climate Change and Other ScenariosThe scenario editor readily accommodates scenario analysisClimate change scenarios and assumptionsFuture demand assumptionsFuture watershed development assumptionsEtc.

Licensing WEAPUser Name: UNFCCC, Mozambique WEAP Workshop Registration Code: 1031200517844 License Expires : 10/31/2005 (after which saving data will be disabled)After 6 months you will need to 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

WEAP Hands-On TrainingTwo sets of exercisesGeneral WEAP without hydrology WEAP with hydrology/climate (LATEST AND GREATEST)We will be training on the latest version with hydrology and climate. Follow along or enter the data along with me!

We are going to look at water resources, there are also economic based models that complement these.

Economic ModelsMacro EconomicMultiple sectors of the economyGeneral Equilibrium - all markets are in equilibriumSectoral levelSingle market or closely related markets (e.g. Agriculture)Firm levelfarm-level model (linear programming approach)microsimulation

These next couple slides look at the vulnerability of hydrology to climate change.

A change that appears most likely is that global average precipitation will increase as global temperatures rise. Evaporation will increase with warming because a warmer atmosphere can hold more moisture. This capacity is governed by the exponential Clausius-Claperyon equation, which states that for an increase in air temperature by one degree Celsius the water-holding capacity of the atmosphere is increased by about seven percent.

For example, Trenberth et al. (2003) hypothesized that, on average, precipitation will tend to be less frequent, but more intense when it does occur, implying greater incidence of extreme floods and droughts, with resulting consequences for water storage. Their arguments are based on the premise that local and regional rainfall rates greatly exceed evaporation rates and thus depend on the convergence of regional to continental scale moisture sources. They surmise that rainfall intensity should increase at about the same rate as the increase in atmospheric moisture, namely 7% K1 with warming. This means that the changes in rain rates, when it rains, are at odds with the 1%2% K1 for total rainfall amounts as discussed previously. The implication is that there must be a decrease in light and moderate rains, and/or a decrease in the frequency of rain events, as found by Hennessey et al (1997). Thus, the prospect may be for fewer but more intense rainfallor snowfallevents. This slide looks at how the vulnerability of hydrology to climate change affects water resources.Source: Nigel Arnell

Different climate change models paint different pictures of annual runoff different responses.

Source: Nigel ArnellThis is looking at changes in annual runoff in 2050 as % change compared to 1961-1990.

More relative runoff in the north with less relative runoff in the south.The ECHAM4 shows a relative decrease in runoff along the western coast in southern Africa.Source: Nigel Arnell

This is looking at changes in annual runoff in 2050 as % change compared to 1961-1990.

The GFDLR30 shows again more relative runoff in the north but not the same relative decreases in runoff in the south.

Here we are looking at the assessment of water resources.When we look at water resources planning we are looking at how to balance demand from ag, industry, domestic, nature and recreation. Not only are we talking about quantity, but also quality, timing of the flow and regulations involved.We want to emphasize its not just about runoff want to look at how much water comes from a watershed what does that water do how does it provide services for the different uses including municipal, industry, biodiversity, etc. How is the system managed and regulated?

Here is an example showing what services a watershed provides.

You have upper rivers, lower rivers, a delta, and a bay. An example would be an upper river can provide water for power generation among other services. It can also help to mitigate floods and droughts and provide erosion control while a bay cannot provide those services.

WEAP21 http://WEAP21.org Aquarius http://www.fs.fed.us/rm/value/docs/aquadoc01.pdf SWAT http://www.brc.tamus.edu/swat/ IRAS http://www.cfe.cornell.edu/research/urbanwater/project%20description/General/IRAS.HTM RIBASIM http://www.wldelft.nl/soft/ribasim/ (river basin model)MIKE BASIN http://www.dhisoftware.com/mikebasin/Download/

HEC http://www.hec.usace.army.mil/ WaterWare http://www.ess.co.at/WATERWARE/ RiverWare http://cadswes.colorado.edu/riverware/

These are the models we will talk more about. The focus for this workshop is planning and hydrology not hydraulics. These models are free, have good documentation, and are fairly easy to use.

We will be providing you with the WEAP model. The other models you can get via the web.Aquarius is an optimization model that uses perfect foresight.

The graphic represents a frontier curve for optimization.

The model is driven by aneconomic efficiency operational criterion requiring the reallocation of stream flows until the netmarginal return in all water uses is equal. This occurs by systematically examining, using anonlinear optimization technique, the feasibility of reallocating unused or marginally valuablewater storage and releases in favor of alternative uses. Because water-system components can beinterpreted as objects of a flow network, the model considers each component as an equivalentnode or structure in the programming environment as well.

SWAT addresses simple management issues, with more focus on the supply side. It lightly touches on the demand side of water management modeling.

Model ObjectivePredict the effect of management decisions on water, sediment, nutrient and pesticide yields with reasonable accuracy on large, ungaged river basins. Model ComponentsWeather, surface runoff, return flow, percolation, ET, transmission losses, pond and reservoir storage, crop growth and irrigation, groundwater flow, reach routing, nutrient and pesticide loading, water transfer. WEAP21 has many advantages. While its main purpose is a river basin model that looks at supply, demand, and infrastructure, it also has a hydrologic model that can determine runoff along with irrigation cropwat type modeling capabilities. This will be our model of focus.HEC models are looking more at hydraulics, modeling sub-daily

These models are used to get runoff used for for flood studies, urban flooding, etc.

The Hydrologic Modeling System is designed to simulate the precipitation-runoff processes of watershed systems. Now going to be moving on to the WEAP modelNow breaking down the two main components of a water resources river basin model such as WEAP which includes hydrology and planning.

Given a set of parameters specific to a catchment, these are questions the hydrology model answers.

We now put human factors into the model that will affect the way the catchment utilizes water.These are some questions that can be analyzed/answered using WEAP.

How the planning model works some supply with a demand.

The next few slides show how water is distributed and tracked in the WEAP21 model.

Legend:Red Circle = Demand SiteBlue Line = River (arrow points downstream- value at the top in blue represents the headflow of the river)Green Line = Transmission Link (brings water from supply to demand)Black Line = Represents where the water is flowing and how much

This slide 100 units of water coming in via headflow of the river, 40 units are pulled from the river to meet the demand, leaving 60 units to continue downstream

Here there is an infrastructure constraint on the transmission link (maximum allowed is 30 units)

100 units of water supplied via the headflow of the riverWhile the demand site is asking for 40 units, it will only receive 30 units because of the constraint on the transmission link.This leaves 70 units to continue downstream

Here there is a minimum flow requirement downstream of 70 units of water.

There is no constraint on the transmission link, but the flow requirement has a higher priority than the demand site.

100 units supplied as headflow, 1 priority is downstream flow requirement of 70 units, which leaves only 30 units for the demand site. The demand site is unmet by 10 units.

This example shows the priority system in WEAP21.

Each demand site is given a priority (represented in the schematic by the black number in the red circle). Higher priorities receive water before lower priorities. The water will be distributed equally among demand sites of the same priority.

In the schematic the small holder demand has the higher priority. Since there is only 100 units of water supplied, the large farmers demand is unmet by 10 units.If the large farmer had a higher priority then the small holder would only receive 30 units (a 10 unit deficit).This example shows the supply preference in WEAP21

We just saw how a demand will have a priority in the overall system. If a demand site is connected to more than one supply source, it can have a preference on which supply source it prefers more.

For example, the demand site in the schematic is connected to two different supply sources (two rivers). It prefers to receive as much water as possible from river 1 (30 units of headflow). Since River 1 can only supply 30 units, the demand site will receive its remaining 10 units from river 2 (100 units of headflow).

Preferences can vary due to water quality issues, cost issues, political issues, etc.The orange line represents a 20 unit return flow from the 40 unit demand site.

Here we have flow requirements on each river that have the highest priority. The 40 unit demand has a higher priority than the 70 unit demand. The 40 unit demand prefers water from river 1 (30 unit headflow) over water from river 2 (100 unit headflow).

The 40 unit demand site receives 10 units from river 1 (20 units on river 1 goes to the flow requirement). The 40 unit demand site also receives 30 units from river 2. River 2s flow requirement will be met by the 20 unit return flow. Therefore, the 70 unit demand site will receive all 70 units from river 2.

Not just a rainfall runoff model -

The 40 unit demand site took 30 units from river 2, the 70 unit demand site took 70 units from river 2.

There will be no flow between priority 2s demand site and priority 1s return flow.We could put a flow requirement on that reach.

We could implement demand side water saving strategies.What happens if we dont know the headflow of the rivers or the exact amount demanded from the demand sites. What type of data do we know?

We now gather data on the hydrologic components so that we can calculate the headflows in WEAP. We also gather data on what crops are being grown so that we can calculate the agricultural demands.What do we know now?

We added hydrology.

Hydrology is impacted by climate change temperature, relative humidity, precipitation, how pasture, vegetables irrigation demands are going to change.

This is the background for the training portion this is the framework of using catchments in WEAP watershed produces runoff water is distributed to different uses.

The full catchment is divided into 4 sub-catchments.

This represents how WEAP translates precipitation into surface runoff, interflow, and baseflow.

This is a stylized limited parameter hydrologic model.We are computing a watershed mass balance in a stylized way we will be going through these parameters in the example and if you want more details you can read the supporting papers.

Runoff from the upper storage occurs as direct, surface, and interflow, while baseflow originates only from the lower storage. P = PrecipitationEt = EvapotranspirationPe = Effective PrecipitationSw = Upper storage capacity (Root zone)Dw = Lower storage capacity (Deep water zone)Z1 = average, long-term relative storage in the root zone (percentage of total available capacity; % of Sw)Z2 = average, long-term relative storage in the deep water zone (percentage of total available capacity; % of Dw)

Each separate land class is analyzed with the 2 bucket model (ie, there will be parameters associated with each land class Sw(Root Zone Water Capacity) = 400 mm for trees, 300 mm for grass, and 350 mm for pasture.) Model uses a predictor/corrector to solve continuous water balance algorithm

You set the upper and lower thresholds this implies the irrigation efficiency. The further apart the thresholds, the more irrigation is required.

When in irrigated setting the system may take water out of groundwater then you have a stylized groundwater module in WEAP

WEAP also allows for modeling the interactions of surface water and groundwater.WEAP has an integrated user interface where you can drag and drop objects onto your schematic and click on each object to find the information/data associated with the object.You can calibrate and validate the model by gathering this type of information.You can look at streamflow as part of your validation and calibration process.Here is an example of a calibration; looking at modeled versus observed streamflow. We want to make sure that our modeled releases mimic what the observed data shows.

The results section in WEAP is very user friendly. You can slice-and-dice your data in a number of different ways. You can export it directly to Excel.