Potential Scenarios
Water Evaluation And Planning (WEAP) was developed by Stockholm Environment Institutes (SEI) for integrated water resources planning, which operates on the basic principle of water balance, together with demand priorities and supply preferences (Yates et al., 2005). As a scenario generation tool, WEAP simulates water demand, supply, streamflow, and storage and the generation, treatment, and discharge of pollution (SEI, 2001). As a policy analysis tool, WEAP evaluates a wide range of water management options, taking into account multiple and competing uses of water (SEI, 2001).
References:
Stockholm Environment Institute. (2001). WEAP: Water evaluation and planning system-user guide. Boston, USA
Yates D., Sieber J., Purkey D. and Lee A.H. (2005). WEAP21 – A Demand, Priority, and Preference-Driven Water Planning Model: Part 1, Model Characteristics. Water International, 30(4), 487- 500.
Scenarios for the Seven Crater Lakes
WEAP Schematic of the Seven Crater Lakes in San Pablo City
Based on the Current Accounts, possible future scenarios revolving around the two major sectors of the lake, aquaculture and tourism, were simulated for the years 1997 to 2030.
The first scenario is the Business-As-Usual (BAU) scenario, in which all factors considered in the model were held constant at the latest record except for the barangay population, which will increase based on the growth rates projected by NEDA (2020) and CIA (2021) for 2020-2025 and 2025-2030, respectively, and the number of cages, which will increase at a rate based on LLDA's 2022-2023 fish cage record.
The second scenario considered the strict implementation of the 10% aquaculture (AQC) surface restriction (SA) indicated in the Fisheries Code over the seven lakes and populations. The 10% of the lakes’ surface area was computed based on information from the San Pablo City Government website (2022). The number of cages and production annually were calculated based on the stocking density provided by the San Pablo City Agriculture Office of 3,500 fish per 10x10x5 cubic meter cage, which was held constant from 2024 to 2030.
The third scenario involves the tourism activities and strategies of SPC LGU for each lake alongside population growth and unregulated fisheries. The interventions for lakes Bunot, Calibato, Mohicap, Palakpakin, and Yambo were based on the DMPs developed by LLDA, while the strategies and corresponding activities for Sampaloc and Pandin Lake were based on the 2015-2020 SPC TMP. In the WEAP model, the establishment of additional tourist-related establishments and activities around and within the lakes was indicated by an increase in tourists based on the pre-pandemic tourism rate from (2018-2019) while the addition of accommodations and food services was signified by the 10% annual increase of their current number.
Lastly, the fourth scenario combined Scenarios 2 and 3, combining population growth, strict implementation of RA 8550, and SPC LGU's tourism plans for the future.
Key Findings:
Strict implementation of the 10% fish cage area restriction in Sampaloc Lake reduces the increasing rate of BOD, maintains the levels of NH3 and IPO4, and reduces the TSS over the duration of the forecasted period
