Research to Continue Investigation of Hydrometeorological Prediction and the Application of Using Quantitative Precipitation Forecast Capabilities to Inform Reservoir Operations

Description

THIS IS A TWO-PHASE PROCESS. PLEASE SEE FULL ANNOUNCEMENT FOR PERTINENT DEADLINES. The U.S. Army Corps of Engineers (USACE) has been engaged in a research and development effort called Forecast-Informed Reservoir Operations (FIRO) to conduct research into quantitative precipitation estimation to improve weather forecast skill and to develop a better understanding of the balance between water availability, flood risk management, ecosystem and social benefits at multi-purpose reservoirs. Given reduced supplies, changed hydrologic conditions, and technological advances, some adjustments to the current reservoir operating procedures may be possible to optimize the goals of maintaining flood control while bolstering water availability for downstream users and the environment (e.g., to support recovery of endangered and threatened fish). Modern observation and prediction technology can be used to reduce flood risk by supporting decisions of greater reservoir level drawdown in advance of storms. Such technology can also be used to improve water availability by permitting more storm runoff to be retained for water supply while also enhancing flood risk reduction objectives. Current scientific research has yielded improvements in understanding the processes which affect the formation, intensification and duration of significant rainfall events in the western U.S., which are predominantly atmospheric river (AR) events. This research includes atmospheric reconnaissance (AR recon) missions using U.S. Air Force Hurricane Hunter aircraft as well as National Oceanic and Atmospheric Administration aviation resources. Data collected from these missions has led to meaningful gains in forecast skill for the global weather modeling community, as well as for specialized models that have been developed for the western U.S. Recent research has demonstrated the value of AR recon not only in the western U.S. but also in the Gulf of Mexico and along the eastern U.S. seaboard. Since August of 2014, the USACE has actively participated in a multi-agency, multi-discipline research and development effort to investigate how FIRO approaches might be safely and appropriately applied at reservoirs that it manages. In what is now called Phase I of FIRO, this initial effort led to the development of an effective process to determine if weather forecast skill for a reservoir is adequate to safely incorporate forecast information in reservoir operations. This was demonstrated at an initial pilot reservoir, Lake Mendocino, in the Russian River watershed in northern California, a dam that supports a climate-change-vulnerable region, where atmospheric river type storms are the cause of both flooding and provider of water supply. FIRO Phase I consisted of five years of investigation and development of a viability assessment process, concluding with a final viability assessment for Lake Mendocino. In FIRO Phase II, conducted from 2019 thru 2023, the FIRO viability assessment process was applied to three additional basins where ongoing FIRO activity is occurring at various stages: 1) in the Santa Ana River basin of southern California, where a FIRO final viability assessment is nearing completion for Prado Dam, and initial investigations into Seven Oaks Dam have begun, 2) in the Yuba-Feather system in the Central Valley of California, where the Oroville and New Bullard’s Bar dams, operated in tandem, will have a final viability assessment completed by the end of the year, and 3) at Howard Hanson Dam on the Green River of Washington, where a steering committee is being formed to conduct a FIRO viability assessment there. Additionally, in FIRO Phase II a screening process was envisioned to assess FIRO suitability at a screening level. This tool was iteratively designed, evaluated, and tested across the 85 dams of the USACE’s South Pacific Division (SPD). The FIRO Screening Process is designed to provide a means of assessing FIRO suitability across the entire portfolio of USACE dams nationwide. Program Description/Objective: At its core, FIRO is a management strategy that uses data from watershed monitoring and modern weather and water forecasting to help water managers selectively retain or release water from reservoirs in a manner that reflects current and forecasted conditions. FIRO’s utilization of modern technology can optimize the use of limited resources and represents a viable climate change adaptation strategy. With the start of FIRO Phase III in 2023, ERDC-CHL now seeks to conduct a five-year effort to: 1. Assess and Improve Forecast Skill for Multiple Flooding Storm Types FIRO is not viable at reservoirs where forecasts of extreme precipitation and associated floods do not have adequate skill. Although meteorology has largely struggled to improve quantitative precipitation forecasts (QPF), FIRO Phases I and II have found that atmospheric rivers are the key storm type in the west coast flood season (fall/winter). Additionally, FIRO research has found that there is adequate skill to support FIRO operations at all of the tested pilot reservoirs in Phases I and II. Research to improve forecasts have benefitted from focusing on the storms that predominantly produce the precipitation at these reservoirs, i.e., atmospheric rivers. FIRO viability has also been favored by the fact that watersheds along the west coast are relatively short and steep, leading to short travel times for water released from a dam to move beyond flood prone areas. AR forecast skill at lead times of even just a few days is often sufficient for FIRO to be viable at many reservoirs. FIRO viability in other regions nationally, where other very different storm types dominate flooding, will hinge on the forecast skill for these storms and on the watershed sizes and travel times for water released from dams. Slopes are likely much shallower and thus water travel times longer in places like much of the southeast and Great Plains. Also, convection, a frequent storm type in many parts of the country especially in the summer, is notoriously difficult to predict accurately, while the track and intensity of landfalling tropical storms/hurricanes can also be difficult to predict, including whether or not they stall (e.g., hurricanes Harvey and Florence). Studies have found that forecast skill for extreme daily precipitation is best in the west (due to ARs) followed by New England, and suggests the need for improvement in QPF for these storm types may be needed for FIRO to be viable. Precipitation prediction skill is tied to the dynamical processes in the major storm types, and to the models and forecast tools that have been developed to predict them. As with atmospheric rivers in the west, a key to identifying the causes of errors in predictions of extreme precipitation in these storm types is understanding the meteorological attributes of the storms that make them capable of producing the extreme precipitation. This also leads to fruitful research pathways for improving these predictions. By analogy, the hydrology differences in regions affected by these storms need to be considered. Improved QPF and other meteorological and hydrological forecast data and tools have proven to be immensely valuable to water managers where FIRO has been tested in Phases I and II. Providing water managers, decision makers, senior leaders and the public with information from these improved forecast products has been critical to the successful application of FIRO to date. Research and development of more effective and efficient means of conveying information from these data sources to a variety of audiences through the use of configurable and customizable portals and/or dashboards is an additional area of focus that is requested in this effort. In order to aid the nationwide screening assessment (see item 6 below), the USACE is interested in assessing basin-scale hydrometeorological predictability (e.g. QPF skill) using a common suite of simplified and practical metrics. Metrics of meteorological predictability will provide necessary information in assessing the practicality of FIRO in watersheds outside of regions where ARs, predictable out to multi-day lead times, are the primary forcers of reservoir inflow. Finally, a key recommendation from FIRO Phases I and II is that water control manual updates include attributes that allow for expedited increases in reservoir operations flexibility (i.e., the size of the FIRO Buffer Pool) as precipitation (and inflow) forecast skill improves. This is referred to as “FIRO 2.0” and represents a potentially efficient way to enhance reservoir operations over time, while also motivating continuing improvement in forecast skill and use of that skill to deal with increasingly extreme weather and water events anticipated to be characteristic of the future. 2. Completion of Final Viability Assessments at Reservoirs Started in Phase II Some efforts from Phase II will not be complete at the end of Phase II in FY23 and will therefore need to be carried to completion in Phase III including: · Final Viability Assessment for New Bullards Bar and Oroville reservoirs to be completed in 2024 · Viability assessment for Howard Hanson Dam. The workplan will be developed in 2023 with the Preliminary Viability Assessment in 2024 and Final Viability Assessment in 2025 · Viability assessment for Lake Sonoma which was added in 2022 as a sibling dam to Lake Mendocino in the Russian River Valley · Viability assessment for Seven Oaks Dam which was added in 2022 as an upstream dam to Prado Dam. 3. Conduct Full Viability Assessment of System of Dams in the Willamette River Basin Phase III will assess two major systems of dams (representing at least 8 dams in each system), for which coordination across several dams in an entire larger watershed is required. The first of these will be the Willamette watershed system, with its 14 reservoirs, where atmosph

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