Scenario-based Planning

1. MRC-MDBC STRATEGIC LIAISON PROGRAMBASIN DEVELOPMENT PLANNINGTRAINING MODULE 2APPLICATION OF BASIN PLANNING PRINCIPLESPhnom Penh19-22 January 2003 Scenario-based Planning

2. Two Key Development Questions For the various potential developments being proposed within the Mekong Basin, as planners we must answer two key questions: • Which development proposals are acceptable and which are unacceptable? • Which acceptable proposals are “better” than other acceptable proposals? The answer to both questions lies in the extent to which the proposals meet Basin objectives. There is no mandate to move beyond these.

3. Basin Planning in a Nutshell

4. Scenario-based Planning • A scenario is a description of a possible specific set of future events and circumstances. It is not a forecast of the future, but rather is something that is foreseen as being possible or feasible. • We can, if necessary, attempt to estimate the likelihood or probability of occurrence of the scenario. • For BDP, a scenario is simply a set of possible future developments and water demands.

5. Why Create Scenarios? • Scenarios in BDP will used to study the results (benefits and costs) of: • events we think will happen (eg population growth, urbanisation etc) • events that might happen • events that we can make happen - such as creating development, building new structures, and operating existing structures. • These studies will enable evaluation of the desirability of possible water-based developments & will lead to evolution of development strategies.

6. Scenario-based Planning

7. Shortlists vs. Development Strategies • As the MRC basin planning process proceeds, it may be found that currently identified development proposals are not necessarily the best possible from a basin wide view. ( Refer to Article 2) • Therefore, instead of a ‘short list’ of actual projects, the BDP may identify strategic directions in which further investigation should occur, and perhaps some development principles - eg all upriver dam development is to take account of mitigation measures needed in the lower river. • Or, there may be both lists and strategies.

8. What can a Basin Model do for BDP? • MRC models simulate changes in river hydrology and floodplain inundation resulting from: • changes in demand (extractions) • building and operating dams and other river infrastructure Traps for the unwary! • The models only replicate the period of hydrological record. Is this truly representative? • Models often produce results that some interest group does not believe. How to resolve this? • The models do not help much with many decisions. • MRC will need to become skilled at making decisions with limited information.

9. What do Planners need to tell Modelers • Location of each proposed development. • Hydrological parameters of the development: • reservoir capacity; • discharge capacity; • water demands (daily / monthly); • minimum flow rules; etc. • Places on the river where outputs are needed: • junctions of critical tributaries; • national boundaries; etc. • Preferred form of outputs: • raw data; • monthly maxima, minima, and/or averages; • flow-duration curves; etc.

10. How do We Formulate Scenarios • The elements of scenarios need to be chosen as factors that the basin simulation model will accept as inputs - that is, water-based factors. • The basin model has three modules: • Rainfall - runoff. Will compute hydrology changes brought about by catchment development etc • River flows. Will compute flow changes influenced by water demands (ie water extractions) • Floodplain hydraulics. Will compute flow and water depth changes due to levees etc

11. A Sub-Basin – Current Development

12. Development Options

13. How to Build a Scenario

14. Scenario Variations

15. How do We Choose Projects for Scenarios • There are no fixed rules - but guidelines can help. • For initial trials in a basin such as the Mekong, it is suggested that projects be those already identified by national line agencies over the past 25 years, plus any identified by previous MRC consultants - eg the Mekong Basin Hydropower Strategy. • The reason for this is simply efficiency. To provide hydrology, water demand and floodplain intervention data, it is necessary to have at least some brief, pre-feasibility study done. BDP does not have the time to do its own studies.

16. How can Scenarios be Assessed? Not easily! BENEFITS TO THE COMMUNITY (the primary reason for the project) • The simulation models available only generate water outputs (flow, depth etc). Therefore a simple set of socio-economic outcomes needs to be separately calculated. EFFECTS ON THE MEKONG RIVER • Simulated by the models. (quantified changes to the river hydrology and to flood patterns ) • BUT - the models do not directly compute: environmental effects, water-sharing trade-offs, etc

17. Development of Assessment Criteria

18. Comparing Scenarios • Quantified model outputs applicable to each assessment criterion can simply be compared (and ranked) numerically. • Non-quantified results of each scenario can be ranked subjectively against each assessment criterion by knowledgable people. • However, because scenarios will have a mix of rankings against various criteria, a variety of multi-criteria analysis tools will be required.

19. Multi-Criteria Assessment Which Scenario is “best”? * Subjective, non-numerical ratings

20. Decision Making and Uncertainty Basin Planning Rule #1 - There is NEVER enough information for a guaranteed, perfect decision. Basin Planning Rule #2 - Development pressures are sufficiently strong that decisions will be made with or without a Plan. Conclusion: An interim Plan, with its decisions made under a state of uncertainty is better than no Plan. Although game theory and so on are worth knowing about, the MDBC (and other) experience is that participatory decisions involving all stakeholders, given whatever information is available, are surprisingly good decisions.