HRL program overview

The Healthy Rivers and Landscapes (HRL) program is an eight-year, multi-agency effort to restore aquatic habitat, provide environmental flows, and adaptively manage ecosystems across the Sacramento River watershed and the Bay-Delta estuary. HRL aims to improve ecological conditions for native fishes by coordinating habitat restoration and flow actions at a watershed scale.

HRL is proposed as part of the program of implementation for the State Water Resources Control Board’s Bay-Delta Water Quality Control Plan and reflects a broad partnership among state, federal, and local entities.

HRL Science Program

The HRL Science Program provides the scientific foundation for implementing and evaluating HRL. It investigates how restoration actions and environmental flows influence ecosystem processes, habitat conditions, and biological responses across diverse riverine and estuarine environments.

The Science Program is structured around 55 hypotheses that span tributary habitats, the mainstem Sacramento River, bypass floodplains, and tidal wetlands. These hypotheses are articulated in the overarching HRL Science Plan. Mechanisms for collecting necessary data and evaluating these hypotheses are further detailed in system- and project-level science plans.

Scientific evaluation will occur through:

• Annual reporting on data collection and early insights
• Triennial synthesis reports that integrate results across projects, special studies, and geographic scales every three years
• Ecological Outcomes and Analysis report at the end of the program that assesses the cumulative effectiveness of HRL actions

HRL data program structure and collaboration

HRL science and implementation are organized through an interagency governance structure. For HRL data engineering and data science work, key program roles include:

• Data Producers – Collect and publish datasets and metadata following shared protocols
• Central Data Team – Maintain program-level data systems, standards, and tools for analysis, modeling, visualization, and communication
• Synthesis Teams – Analyze curated data to evaluate hypotheses and generate synthesis products
• HRL Science Committee – Provide scientific oversight, prioritization, and guidance

These groups work together to support scientific research and adaptive management and ensure that HRL decisions are informed by rigorous, transparent, and reproducible science.

A whole-watershed approach

A core feature of HRL is its emphasis on integrated, system-wide science. The program links actions and outcomes across rivers, floodplains, and estuarine habitats, enabling coordinated research on:

• Habitat restoration effectiveness at multiple spatial scales
• Environmental flow benefits in individual tributaries and integrated across the whole watershed
• Species responses across life stages
• Watershed-scale ecological patterns

By uniting restoration, flow management, and interdisciplinary science, HRL seeks to develop knowledge that improves adaptive management for ecosystem resilience and supports long-term stewardship of California’s rivers and landscapes.