Islands Trust Area Groundwater Recharge Precipitation Interception Potential, 2021

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STAFF REPORT 
Z:\11 Trust Wide Services\5420 Freshwater\10 Programs (P)\GWSS\Projects\GW Recharge\PIP\FWSS_2021-06-15_VRI-Interception-Report_FINAL.docx  
*This report was updated in June 2022 to reflect changes in the Islands Trust Area Groundwater Recharge Mapping report (GW Solutions, 2021) 
Islands Trust Staff Report 1 
File:  
Date: 
FWSS-GWSS 
June 15, 2021* 
 
 
TO: Regional Planning Committee  
FROM: Alex Hedley, Watershed Ecosystems Technologist, Co-Op Student (UVic) 
William Shulba, P.Geo, Senior Freshwater Specialist 
Local Planning Services 
COPY: Islands Trust Conservancy 
SUBJECT: Islands Trust Area Precipitation Interception Potential  
   
REPORT SUMMARY 
The  purpose  of  this report is to present Precipitation  Interception  Potential maps that represent real-world 
precipitation  interception by  terrestrial  ecosystems in the  Islands  Trust  area. These Precipitation  Interception 
Potential surfaces are combined  with  groundwater  recharge  data,  to  create  a  comprehensive  groundwater 
recharge potential of the terrestrial surface for the Islands Trust area. This product was created by Islands Trust 
staff to inform  the Islands Trust Groundwater Recharge Mapping project  on  the  role  of  ecosystems  in  the 
determination of groundwater recharge potential. The successful completion of this product in concert with the 
groundwater recharge  potential  mapping informs decision-makers on  current  and  future  water  management 
strategies, supporting the Islands Trust mandate to preserve freshwater and protect watersheds.   
BACKGROUND 
Water  shortage  issues  are  an  ever-present  concern  for many  individuals  in  the  Islands  Trust  area.  In  a  survey 
conducted in 2016, more than 40% of residents indicated they have concerns about exhausting their household 
freshwater supply  (Islands Trust, 2021). Furthermore, changing precipitation patterns are projected to result in 
longer drought periods during the summer, and more intense precipitation events in the wetter seasons, resulting 
in reduced freshwater quality (Pinna Sustainability, 2020). Climate change-related issues such as sea-level rise and 
storm surge flooding are also expected to worsen the saltwater intrusion issues found on the islands (Islands Trust, 
2021). With  freshwater  concerns  abound,  actions  must be  taken to  mitigate  these water-related  issues. 
Understanding how groundwater recharge potential and Precipitation Interception Potential influence the rate of 
groundwater and freshwater resource replenishment, is a logical step towards developing plans to ease some of 
these concerns. 
 
Groundwater recharge is one of the primary factors controlling limits on groundwater withdrawal (Döll & Flörke, 
2005, as cited in Mohan et al., 2018). To determine the groundwater recharge potential of the Islands Trust area, 
multiple variables, including ground and vegetation characteristics, need to be considered (Mohan et al., 2018). 
Forest cano

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