A Comparison of Precipitation Downscaling Procedures | R16AC00024

Opportunity Information: Apply for R16AC00024

The grant opportunity titled "A Comparison of Precipitation Downscaling Procedures" is a Bureau of Reclamation (Reclamation) Science and Technology-funded research effort focused on improving how future rainfall is represented in hydrologic studies for small, arid-region watersheds. In these settings, precipitation can change dramatically over short distances and short time periods, and streamflow response is often dominated by the fine details of individual storms, including sub-daily behavior such as hourly rainfall intensity and timing. Because flood peaks and runoff generation in desert basins can be extremely sensitive to these storm characteristics, Reclamation is looking closely at whether the downscaled climate products it commonly relies on are adequate for practical planning and operational needs.

Reclamation notes that its climate change assessments in these types of basins typically use CMIP5 global climate model projections that have been statistically downscaled using Bias Corrected Statistical Downscaling and Bias Correction/Constructed Analog methods, referenced here as BCSD-BCCA. While these approaches are widely used and useful for many applications, the opportunity description makes it clear that the resulting precipitation datasets do not always provide the kind of event-scale realism or management-relevant information needed for studies such as flood projection, water resources appraisal, or other decision-support analyses in arid watersheds. The core purpose of the project is therefore to perform a rigorous, side-by-side comparison between BCSD-BCCA products and alternative precipitation downscaling or projection approaches, then translate those findings into practical guidance for Reclamation staff who must incorporate climate change effects into hydrologic work.

The comparison is designed to include multiple alternative methods and data sources rather than relying on a single replacement technique. In addition to BCSD-BCCA, the project will evaluate precipitation outputs derived from dynamical downscaling using Regional Climate Models (RCMs), which attempt to represent atmospheric physics at finer spatial resolution than global models. It will also consider a stochastic rainfall generator approach, which produces synthetic rainfall sequences that can be calibrated to observed statistics and then "forced" by either GCM or RCM information to reflect projected climate changes. A further approach described in the announcement uses historical precipitation records that are conditioned on signals from either GCMs or RCMs, aiming to retain observed storm structure while still incorporating projected changes. By comparing these options, the project is meant to clarify the tradeoffs between statistical methods, dynamical modeling, stochastic simulation, and conditioned historical analog approaches, especially with respect to representing storm intensity, duration, frequency, and temporal sequencing that matter for runoff and flooding.

Work under this award will be performed for two specific Arizona-region study sites chosen because they reflect active, real-world Reclamation management questions. One site is the Bill Williams River drainage to Alamo Lake, upstream of Lake Havasu, identified by the Lower Colorado Region River Operations Group as an area where improved flood projections are needed. The other site is the Upper Santa Cruz River near Nogales, Arizona, along the U.S.-Mexico border, where Reclamation has an ongoing water resources appraisal study. These two basins provide different but relevant testbeds for judging whether a downscaling method is "fit for purpose" depending on the type of study being conducted, such as flood-risk related analyses versus broader water resources planning evaluations.

The opportunity lays out three main objectives. First, it aims to evaluate the suitability of each precipitation projection method for each study type, implying that the best method may differ depending on whether the analysis is focused on floods, supply, reliability, or other planning metrics. Second, it seeks to develop a test or selection framework that can be used to choose the preferred precipitation projection method for a given application, which is essentially a decision rule or diagnostic procedure that staff can apply rather than relying on ad hoc judgment. Third, it intends to quantify how much the choice of downscaling or projection method affects Reclamation planning activities, meaning it will not only compare climate datasets in the abstract but also track how differences propagate through hydrologic modeling and ultimately change planning-relevant outputs and decisions.

Administratively, this was a discretionary funding opportunity issued by the Bureau of Reclamation under a cooperative agreement instrument, categorized under Science and Technology and other research and development, with CFDA number 15.560. The funding opportunity number is R16AC00024, and it was created on 2016-02-09 with an original closing date of 2016-02-23. The anticipated award structure was a single award (expected awards: 1) with an award ceiling of $123,000. The eligibility field is listed as "Others," indicating it was not limited strictly to state or local governments in the way some federal opportunities are, although the specific interpretation of that label typically depends on the full grants.gov posting. Finally, Reclamation states it did not solicit full and open competition for this award, citing "Unique Qualifications" as the justification, which signals that the agency intended a more targeted award approach based on the specialized expertise or capabilities required to carry out the work.

• The Bureau of Reclamation in the science and technology and other research and development sector is offering a public funding opportunity titled "A Comparison of Precipitation Downscaling Procedures" and is now available to receive applicants.
• Interested and eligible applicants and submit their applications by referencing the CFDA number(s): 15.560.
• This funding opportunity was created on 2016-02-09.
• Applicants must submit their applications by 2016-02-23. (Agency may still review applications by suitable applicants for the remaining/unused allocated funding in 2026.)
• Each selected applicant is eligible to receive up to $123,000.00 in funding.
• The number of recipients for this funding is limited to 1 candidate(s).
• Eligible applicants include: Others.

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