PWS Aerial Snow Survey 2021-2022 (SS)_1.pdf

PERFORMANCE WORK STATEMENT

Aerial Snow Surveys of Upper San Joaquin Basin

December 2020

1.0 SCOPE

The objective of this contract is to acquire spatial snow depth measurements across the San Joaquin Watershed and be provided accurate spatial estimates of snow water equivalent. These surveys will be acquired through remote sensing, conducted at periodic or strategic intervals, and may span across accumulation and ablation phases of a winter season. Measurements must be robust to steep terrain, forested areas, and capture the full variability in snow dept. Data acquisition must be able to respond to changing weather, be able to deploy with short notice, and data reporting must allow Reclamation to make reservoir management decisions in near real-time. The advances in runoff forecasting made possible by remotely sensed snow surveys creates substantial benefits to Friant Division water users and the San Joaquin River Restoration Program and provides broad public benefits such as reduced flood magnitude.

2.0 BACKGROUND

The San Joaquin watershed above Millerton Lake, impounded by Friant Dam operated by Reclamation, is a high elevation watershed of California’s Sierra Nevada. On average, 70% of runoff originates from snowpack. Peak runoff is typically in May, but this can vary from April to July. The watershed produces on average 1.8 Million acre-feet of runoff (MAF), yet Millerton Lake can only impound 0.5 MAF. Annual runoff is highly variable, ranging from 0.3 MAF to 4.6 MAF, and appears to be trending toward greater variability. Ground-based snow sensors omit portions of the watershed due to land management regulations, and the terrain is rugged, extending nearly to 14,000’ elevation.

In 2020 the largest single-source wildfire burned a significant portion of the watershed, which will further reduce available snowpack data this coming winter. Prior to remote sensing of snowpack, management of snowmelt runoff has been challenged by limited forecast accuracy and slow reporting times, which results in reservoir management decision by Reclamation, and water management decisions by water users and environmental projects, to stray from optimal. Better runoff forecasting results in optimization of limited reservoir storage capacity and canal conveyance capacity, effectively “building” new storage capacity through better information.

Reclamation acquired remotely sensed snowpack information through Interagency Agreement with NASA and other methods beginning in 2017. NASA had previously been providing 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.

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.

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

Author

Title

Date

Source

Pending Pending Pending Pending

4.0 PERIOD OF PERFORMANCE — March 1, 2021 through February 28, 2022 The contract will span 12 months from date of signing, allowing flexibility in scheduling surveys. In cases of severe drought in early 2021, surveys can be rescheduled for the following winter.

5.0 TASKS — The contractor shall perform the following tasks:

1. Collect snow depth data and snow water equivalent data (SWE) across the San Joaquin Watershed above Millerton Lake. Surveys will be conducted between March 1, 2021 and June 1, 2021, and optionally between January 15, 2022 and February 28, 2022, unless the periods are otherwise extended or shortened by mutual agreement (extremely wet years may result in snow surveys into September). Reclamation will consult with 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 scheduled to start at least 72 hours into the future; the window may be rescheduled or shifted by mutual agreement.

At least one and up to three surveys are anticipated within the period of performance. The first survey will be conducted between March 1, 2021 and June 1, 2021. One optional additional survey may be conducted between March 1, 2021 and June 1, 2021; and one optional additional survey may be conducted between January 15, 2022 and February 28, 2022.

Surveys will cover at least 95% of the snow-covered terrain above 5,000’elevation within the bounds of the San Joaquin Watershed above Millerton Lake. By mutual agreement a different minimum elevation or different elevation band coverage may be set.

2. For each aerial snow survey, provide an electronic report within 72 hours of final flight completion. 72 hours is roughly the time it takes for snowmelt in the upper watershed to reach Millerton Reservoir. Receiving reports later than 72 hours reduces the time that Reclamation has to evacuate water. This results in higher flood release magnitudes and reduced opportunities for groundwater recharge.

3. iSNOBAL model output or equivalent model will be optionally provided on semi-monthly intervals from March 15, 2021 through June 15, 2021. These will quantify modeled snowpack depth, density, and snow water equivalent spatially across the watershed and tabulated by 1000’ elevation band. When aerial snow survey data is available, the model will be updated with measured snow depths. Model output at operational snow pillow sites will be shown in graphical or tabular means and comparted to snow pillow reading.

4. Coordinate semi-monthly phone meetings between Reclamation and contractor from March 1, 2021 through June 1, 2021 to consult on survey timing, weather, hydrology, and performance factors.

4.0 PERFORMANCE REQUIREMENTS SUMMARY

Task #

Task Description

Performance

Indicator

Performance

Standard

Minimum Acceptable Quality Level

1 (1 fixed and 1 optional)

Snow Depth data and Snow Water Equivalent data across San Joaquin Watershed.

March 1, 2020 through June 1, 2020.

SD and SWE at <5 meter resolution with a precision of 5 centimeters or better

Coverage of watershed’s snow-covered area

>95% of snow-covered area above 5,000’ elevation has survey data at this requisite resolution and precision

Complete survey within 15-day window, which may be scheduled with 72 hours notice

Completion rate

50% of surveys completed within the window when an uninterrupted span of 72 hours of clear skies over the watershed occurs.

(optional)

Snow Depth data and Snow Water Equivalent data across San Joaquin Watershed.

January 15, 2022 through February 28, SD and SWE at <5 meter resolution with a precision of 5 centimeters or better

Coverage of watershed’s snow-covered area

>95% of snow-covered area above 5,000’ elevation has survey data at this requisite resolution and precision

Complete survey within 15-day window, which may be scheduled with 72 hours notice

No standard N/A

Survey reporting.

Complete and transmit report within 72 hours if final flight completion

Completion rate

Maximum of one report not completed and transmitted within 72 hours of final flight completion

(optional)

Snowpack modeling and semi-monthly reporting. March 15, 2021 through June 15, 2021

Complete modeling update and report, including spatial and tabular data of snow depth, density, and SWE and reference to snow pillows

Completion rate

75% of reports completed and transmitted within ±3 days of semi-monthly interval

4 Coordination through semi-monthly phone meetings. March 1, 2020 through June 1, 2020

Consistency of availability for meetings

Minimum fraction of meetings will be scheduled and conducted

75% of scheduled meetings occur, unless otherwise cancelled by mutual agreement

5.0 DATA AND REPORTS — The contractor shall provide the following data and reports as follows:

Task #

Description

Content

Format

Medium

Delivery

2 Snow survey report

See Task #2 Deliverables below

Electronic file Contractor’s choice

Via FTP or data sharing portal

(optional)

Snow modeling report

See Task #3 Deliverables below

Electronic file Contractor’s choice

Via email, FTP, or data sharing portal

6.0 DELIVERABLES - The contractor shall submit the following reports in accordance with paragraph 5.0, “DATA AND REPORTS”:

• Snow Survey Report (Task #2) shall include:

a. Brief narrative of survey acquisition and conditions

b. Snow depth by 1000’ elevation band (table: mean, std deviation or percentiles)

c. Snow water equivalent by 1000’ elevation band (table: mean, std deviation or percentiles, total volume)

d. Tabular data broken down by HUC 10 units, broken down by four subwatersheds, and aggregated for entire San Joaquin Watershed above Millerton Lake.

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

f. Low resolution image of spatial SWE distribution

• Snow Modeling Report (Task #3) shall include:

a. iSnobal or equivalent model output

b. Brief narrative of conditions and calibration by any measures

c. Snow depth by 1000’ elevation band (table: mean, std deviation or percentiles)

a. Snow density by 1000’ elevation band (table: mean, std deviation or percentiles)

d. Snow water equivalent by 1000’ elevation band (table: mean, std deviation or percentiles, total volume)

e. Tabular data broken down by HUC 10 units, broken down by four subwatersheds, and aggregated for entire San Joaquin Watershed above Millerton Lake.

f. 50 meter geoTIFF file of snow depth and snow water equivalent

g. Low resolution image of spatial SWE distribution