Streamlined eco-engineering approach helps define environmental flows for tropical Andean headwaters

Applying the environmental flows concept to human-altered lotic ecosystems continues to face many practical challenges and barriers. Here, we modify a previously proposed framework, the Eco-Engineering Decision Scaling, for application to part of the water supply system of Quito, Ecuador. Specifically, we used feedback from engineers and water managers to develop a common set of metrics for defining flow-ecology relationships and assess managed-flow impacts on stream ecology. At 12 sites over 3 years, we collected flow and benthic invertebrate data (taxonomic richness, taxa important for fish, functional feeding groups, and water quality-sensitive taxa) during wet and dry seasons. We then used these data to identify flow thresholds (relative to unmanaged flows) where flow withdrawal caused visible ecological impacts. For this system, reduction of flow to 20% of the annual median was detrimental to benthic communities, while reductions to 40% of the annual median flow caused a variety of responses in the system. A trade-off analysis of weighted metrics showed that a 50% benthic fauna richness could be sustained if dry season flows were maintained between 28% and 40% of the unmanaged median annual flow. This study provides a roadmap for bridging between eco-engineering theoretical frameworks and the adoption of the environmental flows concept as actionable management thresholds

Designing eco-friendly water intake portfolios in a tropical Andean Stream Network

A In view of the rapid proliferation of water infrastructures worldwide, balancing human and ecosystem needs for water resources is a critical environmental challenge of global significance. While there is abundant literature on the environmental impacts of individual water infrastructures, little attention has been paid to their cumulative effects in river networks, which may have basin-to-global impacts on freshwater ecology. Here we developed a methodological framework based on Pareto frontier analysis for optimizing trade-offs between water withdrawal and ecological indicators. We applied this framework to a mountainous Ecuadorian headwater river network that is part of a continental water transfer for supply and demand management to optimize ecological conditions and the operation of 11 water intake structures used to provide potable water to the city of Quito. We found that the current water intake configuration has an important effect on the total length of fifth-order stream sections (65% reduction compared to premanaged condition) and isolates 70.9% of the headwater stream length. The Pareto frontier analysis identified water intake portfolios (i.e., different combinations of intake sites) that decreased ecological impacts by 7.8% points (pp) and 13.0 pp for connectivity and stream order change, respectively, while meeting Quito's water demands. Additional portfolios accounting for monthly variability in water demand and resources further decrease the ecological impact up to 9.6 pp in connectivity and 13.4 pp in stream order. These eco-friendly portfolios suggest that adaptive management at basin level may help optimize water withdrawal to fulfill urban demands while preserving ecological integrity