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2016.05.24

Twater: A Seismic Risk Analysis Tool for Water Supply Systems

Water supply destruction following an earthquake may cause severe inconvenience to people in the disaster-affected areas, impeding their ability to carry out daily activities. Medical care, sanitation, and firefighting may also be seriously malfunctioned. Water authorities therefore urgently need a seismic risk analysis tool for estimating the likely damage in water systems and the expected loss of functionality in earthquake scenarios. Measures could then be taken to enhance seismic preparedness and emergency response in an appropriate and timely manner.


Twater is a specialized tool for scenario-based seismic risk analysis of water systems developed by the National Center for Research on Earthquake Engineering (NCREE) of the National Applied Research Laboratories (NARLabs). As a subsystem of the software program of the Taiwan Earthquake Loss Estimation System (TELES), Twater is fully integrated with a geographic information system. With its graphical user interface shown in Figure 1, Twater can simulate hazards resulting from ground shaking and ground failure, the probable number of repairs required in the distributed pipelines, and the damage status of various types of facilities (e.g. distribution reservoirs, pump stations, and water pipe bridges) in water supply systems in any earthquake scenario.

  Figure 1. Graphical user interface of Twater.

Twater has been employed in regional planning to enhance the preparedness of water supply systems against seismic hazards. Under an earthquake scenario, Twater can predict the number of breaks and leakages in water pipelines, which areas will suffer water shortages, and the cost and time required to fully restore the water supply. The amount of water required for shelters and firefighting can be estimated as well. For example, Figure 2 depicts a thematic map of the amount of water pipeline damage in each district in the Greater Taipei region under an M6.9-scenario earthquake triggered by the Sanchiao fault. This map was originally prepared, along with many other simulated results, to propose disaster reduction plans for the National Fire Agency of the Ministry of the Interior. Twater has also been employed to identify hot spots for liquefaction-induced pipeline damage. A cost-benefit analysis may be carried out accordingly for pipe replacement to reduce earthquake hazards.

Figure 2. The amount of water pipeline damage in the Greater Taipei region under an M6.9-scenario earthquake triggered by the Sanchiao fault.

With the help of Twater, the Early Seismic Loss Estimation (ESLE) service provided by NCREE was extended to all water utilities in Taiwan at the end of 2015. Emergency personnel are notified with damage estimates for water systems within a minute after the ESLE system receives an earthquake alert email from the Central Weather Bureau (CWB), Ministry of Transportation and Communications. After the Meinong earthquake on February 6, 2016, the ESLE system used the limited information in the earthquake alert email from the CWB to successfully predict that the Tainan water system would be severely damaged. Combined with other information, such as fault plane solutions and the distribution of aftershocks, a more precise set of seismic source parameters was obtained 3 hours later and the damage estimates were updated accordingly. Table 1 presents a summary of the actual and estimated numbers of damaged sections of pipeline in Tainan. The manual estimate showed high agreement with the actual damage observed. Notably, the ESLE notification successfully accelerated the initiation of emergency operations by the Taiwan Water Corporation after the earthquake.

Table 1. Estimated and actual numbers of damaged sections in water pipelines in Tainan after the Meinong earthquake on February 6, 2016.

 

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