Undertaking risk assessments for Hong Kong reservoirs

The 2013 RARS (risk assessments for reservoir safety management) guidance was developed for the Environment Agency to provide a robust three-tiered framework for the risk analysis, assessment and management of reservoirs in the United Kingdom. The methods presented can be used to assess a reservoir's risk in its entirety, either at a qualitative level (tier 1) or more in-depth quantitative levels (tiers 2 and 3). Binnies undertook RARS assessments of reservoirs for Hong Kong's Water Supply Department. This paper identifies the limitations and challenges encountered when applying the guidance in Hong Kong, beyond its original intended purpose. It outlines the adjustments made to assess the Hong Kong service reservoirs at tier 1, and large embankment and gravity dams at tier 2. Some of the differences include (i) how the nature of loading and external threats differs due to geographical and locational differences; (ii) how consequences of reservoir failure differ due to topology, population densities and cultural differences in the reservoirs’ uses and (iii) how the reservoirs are atypical from ‘Pennine’ type UK embankment dams, from which most UK empirical methods are derived.