Regional Hydrologic Modeling to Support Water Allocation and Streamflow Management Across Diverse Watersheds in California

Benjamin Bowes; John Riverson

In recent years, numerous watersheds across California have experienced exceptionally dry conditions warranting state-of-emergency protections to ensure adequate, minimal water supplies for critical purposes. Given the increasing anthropogenic demand for water, the need to protect natural ecosystems, and the uncertainty in near- and long-term climate, there is a critical need for hydrological modeling and analysis tools that support comprehensive decision making and management of water supply, demand, and instream flow needs. This presentation will discuss some of the challenges surrounding sustainable water use and supply and introduce models and tools being developed for the State Water Resources Control Board Supply and Demand Unit for watersheds across California. A key component of supply and demand management is a robust watershed hydrology simulation platform. These hydrology models are built using the EPA’s Loading Simulation Program in C++ (LSPC) with a regionally consistent configuration and calibration approach; the models form the basis for short-term forecasting of available surface water and support decisions regarding water allocation to water rights holders. Several models throughout the state are being developed simultaneously, providing a unique opportunity to evaluate similarities and differences between the models and the watersheds being represented. During model development, there is a focus on specific functional flow components — the ecological building blocks of a healthy river — such as wet season peak flows and dry season baseflows. Using the models developed with this approach, the Supply and Demand Unit has a robust, consistent basis for evaluating management scenarios and informing decision making for surface water allocation.

Predicting Ecological Uplift in Urban Stream Restorations Using Data-Driven Watershed Modeling

Wuhib Bayou; Zhuping Sheng

Ecological uplift remains difficult to achieve in stream restoration projects, particularly in urban and urbanizing watersheds where cumulative watershed-scale stressors often overwhelm localized channel interventions. This study presents a data-driven watershed modeling framework to predict ecological uplift potential using nonlinear stressor–response relationships derived from long-term biological monitoring data, with ecological condition represented by the Benthic Index of Biotic Integrity (BIBI). Machine-learning models were trained using watershed-scale predictors encompassing land use, habitat condition, and water-quality stressors to identify dominant controls, interaction effects, and threshold responses influencing biological outcomes. Results indicate that watershed-scale factors—especially impervious cover, riparian condition, and conductivity-related stressors—exert stronger control on ecological outcomes than individual in-stream restoration measures alone, limiting uplift under channel-focused interventions.

Water Quality and Ecological Risks in Artisanal Gold Mining Ponds: Implications for Watershed Management in the Peruvian Amazon

Adenka Muñoz; Manuel Velazquez Ramirez; Pedro Nascimento Herbay; John Ramirez-Avila

Artisanal and small-scale gold mining (ASGM) has cleared nearly 122,000 hectares of forest in the southern Peruvian Amazon, leaving behind abandoned ponds that now cover about 30% of the degraded landscape. These ponds function as sinks for organic matter and toxic contaminants, posing significant risks to watershed health and community well-being. This study assessed water quality and ecological conditions in mining ponds within the Native Community of San Jacinto, Madre de Dios, during both rainy and dry seasons from 2019 to 2021. Sampling followed official protocols, and results were analyzed using diversity indices (Shannon-Wiener, BMWP) and compared against Peruvian environmental quality standards, the Canadian Environmental Quality Guidelines (CEQG), and World Health Organization (WHO) thresholds. Dissolved oxygen levels were consistently below standards for natural lakes, while thermotolerant coliform counts exceeded permissible limits, indicating sewage contamination. Arsenic concentrations in sediments surpassed CEQG values in both seasons, and mercury exceeded limits during the dry season. Mercury levels in fish muscle ranged from 0.2 mg/kg to 7.9 mg/kg, with several species exceeding WHO limits for human consumption. Aquatic community diversity results underscore the ecological role of these ponds and their importance for watershed restoration planning. Overall, findings highlight an urgent need for integrated watershed management strategies to mitigate contamination, protect aquatic ecosystems, and explore sustainable uses for degraded areas in the Amazon.

Designing Resilient Urban Rivers: Integrating Flood Control, Ecology, and Access

Ben Murphy; Greg Dorolek; Brian Stephens-Hotopp

Cities across the country are rethinking their relationship to urban rivers, moving beyond hardened channels and single-purpose flood control toward integrated, living systems that restore ecological function while supporting recreation, development, and climate resilience. Denver’s River Mile—currently the largest and most complex river restoration and redevelopment effort in the city’s history—illustrates both the opportunities and the challenges of this next generation of watershed-based design.

Led by Calibre Engineering in partnership with the Mile High Flood District, The River Mile transforms a heavily modified reach of the South Platte River into a connected riparian corridor that lowers flood risk, improves water quality, and expands public access and recreation opportunities.

The project is the first riverine system in the nation to earn WEDG (Waterfront Edge Design Guidelines) verification, reflecting its holistic approach to habitat restoration, stormwater management, and community interface. Key strategies include adaptive hydraulic modeling to reduce base flood elevations and remove more than 150 acres from FEMA flood zones; re-meandering and naturalization of channel geometry; integrated wetland and riparian plant communities; and a park and trail network that reconnects neighborhoods to the river.

This session will share lessons learned from planning through implementation, including permitting complexities, stakeholder coordination, balancing restoration goals with adjacent development pressures, and sequencing improvements to maintain river function during construction. Attendees will gain insight into how multidisciplinary, WEDG-based design approaches can create resilient, ecologically functional urban rivers that advance watershed health, long-term community value, and adaptive riverfront infrastructure.