PWS_1.docx

PERFORMANCE WORK STATEMENT

Aerial Snow Surveys of Upper San Joaquin, Yuba, and Merced Bains March 26, 2024

1.0 SCOPE

The objective of this contract is to acquire spatial snow depth measurements and albedo measurements across three Sierra Nevada watersheds and be provided accurate spatial estimates of snow water equivalent (SWE). These surveys will be acquired through remote sensing, conducted in the spring of 2024 during the melt phase of the season. These remote measurements and SWE estimates will contribute to a Reclamation funded investigation to improve National Weather Service (NWS) runoff forecasts in California which inform multiple reservoir operations. Measurements must be robust to steep terrain, forested areas, and capture the full variability in snow depth. Data acquisition must be able to respond to changing weather, be able to deploy with short notice to capture ideal snow cover and weather conditions. The data will also be valuable for reservoir operations in those watersheds, and data reporting should be rapid enough to inform decisions in near real-time. Snow survey methods must be equivalent to or better than NASA Airborne Snow Observatory methodology.

2.0 BACKGROUND

In 2021 Congress directed Reclamation to improve runoff forecasting at its reservoirs by employing advanced snow measurement technologies in snow-dominated basins (PL 116-260, Section 1111). In response, Reclamation has developed a Snow Water Supply Forecasting Program in partnership with other agencies. Reclamation administers grants and funding to advance snowmelt runoff forecasting throughout the West, including non-Reclamation basins. A 2022 Report to Congress identified several promising snow measurement technologies, one of which is airborne lidar measurement of snow. This technology has been used in California since 2013, and at the Upper San Joaquin Watershed above Reclamation’s Millerton Lake, since 2017.

On average, the Upper San Joaquin Watershed receives about 70% of its runoff from snowpack; with the Merced Watershed about 65%, and the Upper Yuba Watershed about 60%. Snowpack serves as a natural reservoir, extending the release of water and maximizing the utility of that water. Snow can be challenging to measure, either because of the remoteness and ruggedness of terrain, or because of changing snow accumulation and melt patterns brought about by climate change, wildfire, and forest changes. Ground-based measurements have become increasingly unreliable due to maintenance challenges or because they are decreasingly representative of the basin as a whole. Better snow measurement improves runoff forecasting which results in optimization of limited reservoir storage capacity and canal conveyance capacity, effectively “rebuilding” new storage capacity through better watershed information.

Reclamation previously acquired remotely sensed snowpack information through Interagency Agreement with NASA and other methods beginning in 2017 – 2019. NASA had previously provided aerial snow survey services through the “Airborne Snow Observatory” research project of CalTech/JPL (a NASA contractor). This NASA effort ended the research phase in 2019 and completed the Technology Transfer process to a private vendor in late 2019. In 2020 and again in 2021, Reclamation contracted with a new private vendor, ASO Inc., for winter surveys. Data collection under this current effort must equal or exceed the standardized approached developed by NASA and documented in a peer-reviewed paper (See REFERENCES) and be directly comparable to previously collected data. The service provider retains responsibility for all aspects of data acquisition, airspace permission, ensuring that flight operations adhere to any applicable DOI Office of Aviation Service requirements, reporting, and transfer of data.

A 2023 grant administered by Reclamation’s Snow Water Supply Forecasting Program aims to improve runoff forecasts provided by the NWS. This contract would expand the datasets available for this investigation at three high-priority watersheds by conducting late spring aerial snow surveys in 2024.

3.0 REFERENCES — The following list of documents are required in the performance of this contract:

Author

Title

Date

Source

4.0 PERIOD OF PERFORMANCE — May 1, 2024 through June 15, 2024 (or commence upon the date of signature if later than May 1, 2024).

5.0 TASKS — The contractor shall perform the following tasks:

1. Collect snow depth data and snowpack albedo (reflectivity) across the upper San Joaquin, Yuba, and Merced watersheds (i.e. basins). One survey shall be conducted across each of the three watersheds between May 1, 2024 and June 15, 2024. Reclamation will consult with the Contractor and set a 15-day target window to accomplish a complete survey, based upon weather and hydrology, which may require multiple flights across multiple days. This window will be coordinated with Reclamation and scheduled to start at least 72 hours into the future; the window may be rescheduled or shifted by mutual agreement. This data collection may or may not include mobilization, calibration, demobilization, and other tasks associated with staging and deploying remote-sensing resources.

The area to be surveyed will include 95% of snow-covered area above 6,000’ elevation in the following basins: (A) Upper San Joaquin Watershed, Hydrologic Unit Code (HUC) 18040006, B) Upper Yuba Watershed, HUC 18020125, and C) Merced Watershed, HUC 1804008 (See FIGURE OF SURVEY AREAS).

2. Using available ground-based measurements, modeling, or other estimates of snowpack density, estimate spatial SWE for each basin. For each aerial snow survey, provide an electronic report within 72 hours of final flight completion which presents snow depth, albedo, and SWE in total and in 1000’ elevation bands. Snow depth, albedo, and SWE data shall be archived and publicly available for a period of 2-years.

6.0 PERFORMANCE REQUIREMENTS SUMMARY

Task #

Acceptable Quality Level

2b

7.0 DATA AND REPORTS — The contractor shall provide the following data and reports.

Task #

Description

Content

Format

Medium

Delivery

8.0 DELIVERABLES — The contractor shall submit the following reports in accordance with paragraph 7.0, “DATA AND REPORTS”:

· Snow Survey Report (Task #2b) shall include:

a. Brief narrative of survey acquisition and conditions

b. Snow depth by 1000’ elevation band (tabular data)

c. Snow water equivalent by 1000’ elevation band (tabular data)

d. 50-meter geoTIFF file of snow depth and snow water equivalent

e. Low resolution map image of spatial SWE distribution

f. Low resolution graphic of spatial snow surface albedo across all measured elevations

FIGURE OF SURVEY AREAS — From North to South, the Upper Yuba (purple), Merced (green), and Upper San Joaquin (orange) watersheds are shown as HUC-8 areas California.

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