A water security case study for Central Cebu, Philippines
Rising water demand and saltwater intrusion are straining Central Cebu's water supply. In 2006, a traditional Integrated Water Resources Management (IWRM) approach was implemented to ensure a reliable municipal supply. This case was later analyzed using the CRIDA methodology to assess its benefits for adaptation planning under uncertain futures.
Контекст
Central Cebu is an archipelago with a tropical monsoon climate, centered around the highly urbanized Cebu City. Growing water demands and increasing water degradation due to saltwater intrusion are stressing the water supply system in the region. Water resource management in the region has traditionally been short-term, but changing conditions require long-term planning and broader collaboration across cities and municipalities.
Действия
The renewed analysis that expanded the 2006 IWRM analysis for the Central Cebu region started of with CRIDA Step 1. The goal was established: a reliable, affordable water supply for Central Cebu by 2030. The main performance metric was unmet demand, with a target of zero at 97% reliability. Key drivers included population growth and climate change impacts, such as reduced precipitation and higher temperatures. A water balance model was used to assess the risk of saltwater intrusion and system vulnerability to changes in demand and climate.
In CRIDA Step 2: Vulnerability Assessment, the Stress Test and Level of Concern Analysis were used to assess the system’s sensitivity to climate change. The Stress Test identified climate conditions under which the system would fail to meet demand, while the Level of Concern Analysis evaluated the risk of future climate changes based on data plausibility and uncertainty. Results showed that the system is more sensitive to demand changes than climate variability, with increased inter-annual variability posing a potential risk to surface water sources.
These findings recommended adaptive strategies to manage uncertainties. CRIDA Step 3 entailed the listing of adaptation strategies, which were subsequently compared during the 4th Step. Adaptation strategies included using surface water sources like Lusaran and Mananga Dams, groundwater wells within and outside MCWD, and desalination plants of various scales. All actions were evaluated for their climate resilience, flexibility, and economic feasibility and ranked, and less viable options got eliminated. In the case of the Cebu study, the economically beneficial pathway initially outperformed others, even under extreme climate scenarios, making it a no-regret option. This approach ensures flexibility and climate resilience without over- or under-investing.
A textbook example of a CRIDA implementation ends with Step 5, the institutionalization of the decision. Since this case study was more of a theoretical exercise, the authors formulated recommendations to decisionmakers during the last step. They recommended starting with a flexible Phase I strategy, monitoring climate conditions, and transitioning to more robust measures in Phase II if needed, while considering financial feasibility and demand reduction options.
Outcomes
This study demonstrated that CRIDA offers significant advantages over traditional IWRM in water supply planning for Central Cebu, Philippines. Unlike IWRM, which relies on observed climate data and a single net present value analysis, CRIDA incorporates climate uncertainties and provides flexible strategies through adaptation pathways. This approach allows for adjustments as climate data improves, offering a more robust and adaptable framework. CRIDA’s use of vulnerability assessments and multiple climate scenarios helps decision-makers plan for future uncertainties, making it a more effective and dynamic method for long-term water resource planning.
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