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Watershed Planning within a Quantitative Scenario Analysis Framework
Published on: July 24, 2016
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Protecting environmental flows to achieve long-term water security
C Alvarez-Garreton1, J P Boisier2, M Billi3
1Center for Climate and Resilience Research CR2, FONDAP 15110009, Santiago, Chile.
Journal of Environmental Management
|December 12, 2022
Summary
Chile
Area of Science:
- Hydrology and Water Resource Management
- Environmental Law and Policy
- Ecosystem Services
Background:
- Water allocation schemes are critical for long-term water security at the catchment scale.
- Inadequate protection of environmental flows (e-flows) can lead to extreme water scarcity and management failure.
- Chile's water law, updated in 2005, mandates e-flows not exceeding 20% of mean annual streamflow, a limit lower than in many other countries.
Purpose of the Study:
- To develop a diagnostic approach for assessing the compatibility of water allocation schemes with long-term water security.
- To evaluate water scarcity risks and the adequacy of protected environmental flows in Chilean basins.
- To propose steps for achieving water security through improved water management.
Main Methods:
- Analyzed water scarcity risks and safeguarded environmental flows (e-flows) in 277 Chilean basins.
- Calculated water stress indices (WSIs) under two scenarios: maximum legal withdrawals (WSImax) and actual allocated uses (WSIalloc).
- Compared Chile's e-flow protection levels with those in six other countries.
Main Results:
- Chile's legal e-flow limits (≤20% of mean annual streamflow) are lower than international standards (20%-80%).
- WSImax values range from 80% to 100% across all Chilean basins, indicating extreme water scarcity risk if maximum legal withdrawals are exerted.
- While 70% of basins show low actual water scarcity risk (WSIalloc <40%), 18% exceed 100% allocation, surpassing legal and physical limits.
Conclusions:
- Chile's current water law inadequately links e-flows, water allocation, and water security, risking long-term scarcity.
- Legal e-flow provisions are insufficient to meet environmental needs and protect against extreme water scarcity.
- Recommendations include defining tolerable water scarcity risks, establishing measurable basin indices (like WSI), and setting compatible maximum water use limits.
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