Alyssa McCluskey, University of Colorado

1. Decision Tools to Evaluate Vulnerabilities and Adaptation Strategies to Climate Change- The Water Resource Sector-UNFCC Climate Change Impacts and Adaptations Maputo18 April 2005 Alyssa McCluskey, University of Colorado and David Yates, National Center for Atmospheric Research

2. 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

3. Effective Vulnerability and Adaptation Assessments • Defining Vulnerability and Adaptation (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

4. Effective Vulnerability and Adaptation Assessments • 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 • The assessment process requires • 1. Value • 2. Credibility • 3. Legitimacy • 4. Consistent Participation

5. Effective Vulnerability and Adaptation Assessments • V&A Assessments - 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

6. Natural Systems External Pressure 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 Managed Systems External Pressure Product, good or service Process Control Example: Agriculture Example: Wetlands

7. 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/Hydroplants/Delivery systems • Raising dam wall height • Increasing canal size • Removing sediment from reservoirs for more storage • Inter-basin water transfers • Adaptive management of existing water supply systems • Change operating rules • Use conjunctive surface/groundwater supply • Physically integrate reservoir operation system • Co-ordinate supply/demand

8. Examples of Adaptation – Water Demand • Policy, Conservation, Efficiency, and Technology • Domestic • Municipal and in-home re-use • Leak repair • Rainwater collection for non-potable uses • low flow appliances • Dual supply systems (potable and non-potable) • 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

9. Examples of Adaptation – Water Demand (continued) • Policy, Conservation, Efficiency, and Technology • Industrial • Water Re-use and Recycling • Closed cycle and/or air cooling • More efficient hydropower turbines • Cooling ponds, wet tower and dry towers • Energy (hydro-power) • Reservoir re-operation • Co-generation (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

10. 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

11. Hydrologic Implications of CC for Water Resources • Precipitation amount • Global average increase • Marked regional differences • Precipitation frequency and intensity • Less frequent, more intense (Trenberth et al., 2002) • Evaporation and transpiration • Increase total evaporation • Regional complexities due to plant/atmosphere interactions

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

14. Africa Focus – ECHAM4/OPYC

15. Africa Focus – GFDLR30

16. 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

17. Water Resource PlanningWater’s “Trade-Off” Landscape

18. 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 provide by freshwater systems

19. Freshwater Ecosystem Services Extractable; Direct Use; Indirect Use

20. Tools to use for the Assessment: Referenced Water Models Planning • WEAP21 (also hydrology) • Aquarius • SWAT • IRAS (Interactive River and Aquifer Simulation) • RIBASIM • MIKE BASIN

21. 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

22. Current Focus – Planning and Hydrologic Implications of CC • Select models of interest and available at workshop Why??? Free; deployed on PC; extensive documentation; ease-of-use • WEAP21 • SWAT • HEC suite • Aquarius

23. 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

24. 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

25. Physical Hydrology and Water Management Models(continued) • WEAP21 advantage: Seamlessly integrating watershed hydrologic processes with water resources management • Can be climatically driven

26. 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

27. 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

28. 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?

29. 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?

30. 40 60 A Simple System with WEAP21

31. 10 Unmet 30 70 An Infrastructure Constraint

32. 10 Unmet 30 70 IFR Met A Regulatory Constraint

33. 40 60 0 10 unmet Different Priorities • For 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

34. Different Preferences • For example, a center pivot operator may prefer to take water from a tributary because of lower pumping costs 30 10 0 90

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

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

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

38. 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 HYDROLOGIC context

39. What Do We Do Now?

40. Add Hydrology

41. And this is the Climate Interface

42. Integrated Hydrology/Water Management Analytical Framework in WEAP21

43. The WEAP 2-Bucket Hydrology Module Surface Runoff = f(Pe,z1,1/LAI) Sw Dw

44. One 2-Bucket Model per Land Class

45. Some Comments • The 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

46. This Last Point Leads to a Stylized Groundwater Representation

47. Some Comments • The 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

48. The WEAP21 Graphical User Interface Languages: Interface Only English French Chinese Spanish

50. WEAP’s Temporal and Spatial Scale • Time step: Daily, weekly, monthly, etc. • No routing, as 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 times steps (e.g., one month) • Smaller watersheds can apply shorter time steps (e.g., 1-day, 5-day, 10-day)