United States Department of the Interior 

FISH AND WILDLIFE SERVICE 

Sacramento Fish and Wildlife Office 

In Reply Refer to: 2800 Cottage Way, Suite W-2605 

OSESMF00- Sacramento, California 95825-1846 

2015-F-0116 

JUN - ~ 2015 

Memorandum 

To: 	 Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office, 


Bureau of Reel ation, Sacramento, California 


From: ~/IJ er M. Norris, Field Supervisor, U.S. Fish and Wildlife Service, Sacramento Fish 

and Wildlife Office, Sacramento, California 

Subject: 	 Reinitiation of Programmatic Formal Consultation for Bureau ofReclamation's 


Proposed Central Valley Project Long Term Water Transfers (2015-2024) with 


Potential Effects on the Giant Garter Snake within Sacramento Valley, California 


On May 13, 2015, the U.S. Fish and Wildlife Service (Service) received an email from the Bureau of 

Reclamation (Reclamation) requesting that the April 30, 2015 Programmatic Formal Conmltationfor the 

Bureau ofReclamation's Proposed Central Valley Project Long Term Water Transfers (2015-2024) with Potential 

Effects on the Giant Garter Snake within Sacramento Valley, California, be revised to reflect changes and 

corrections to the Conservation Measures related to cropland idling transfers within the Description 

of the Action. Reclamation also requested that the Service consider revising Term and Condition #3 

to remove the reference to buffer zones and to require a report within 60 days instead ofonce every 

month. Reclamation indicated that a report within 60 days following the approval of transfers each 

year should capture all idling transfers taking place for the year and provide the Service adequate 

assurance that conservation measures are being implemented for the various parcels being idled. 

Tbis memorandum is in response to Reclamation's November 4, 2014, request for formal 

consultation with the Service on the proposed Long-Term Water Transfer Program from 2015 to 

2024 (proposed project) which Reclamation has determined may affect, and is likely to adversely 

affect, the threatened giant garter snake (Thanmophis gigas) (snake). Your request, which included a 

biological assessment (BA), was received by the Service on November 18, 2014. This response is 

provided under the authority of the Endangered Species Act of 1973, as amended (16 U.S.C. 1531 et 

seq.) (Act), and in accordance with the implementing regulations pertaining to interagency 

cooperation (50 CFR §402). 

The federal action we are consulting on is Reclamation's approval of the transfer of water from 

willing sellers to Central Valley Project (CVP) contractors. This includes transfers that involve CVP 

water supplies or require the use of CVP or State Water Project (SWP) facilities over a 10-year 

period (2015-2024) and are subject to approval by Reclamation on an individual basis annually. 

Reclamation is requesting this consultation on behalf of the contractors that would be selling or 

buying water as part of the proposed project. For the purposes of this analysis this program will be 

referred to collectively as "long-term water transfers". Transfers will be from willing sellers 

upstream of the Sacramento-San Joaquin River delta (Delta), to buyers in the Sacramento River 

basin (north-to-north transfers), the San Francisco Bay area and to buyers that export water from 

Jennifer M. Norris
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 2

the Delta (north-to-south transfers). 

Pursuant to 50 CFR §402.12(j), you submitted a BA for our review and requested concurrence with 

the findings presented therein. The Service concurs with your findings that the proposed project 

may affect, and is likely to adversely affect the snake. The proposed project is not within designated 

or proposed critical habitat for any federally-listed species. 

In considering your request, we evaluated the following: (1) your November 4, 2014 letter initiating 

consultation and the October 2014 Long-Term Water Transfers BA, received by the Service on 

November 18, 2014; (2) your March 12, 2015 letter providing additional information regarding the 

Formal Consultation for the Proposed Long Term Water Transfers from 2015 to 2024, received by 

the Service on March 17, 2015; (3) your April 2, 2015 letter amending the project description for the 

Proposed Long-term Water Transfers Formal Consultation, received by the Service on April 8, 

2015; (4) email and telephone correspondence between the Service and Reclamation; and (5) other 

information available to the Service. A complete administrative record of this consultation is on file 

in the Service’s Sacramento Fish and Wildlife Office. 

The Service has consulted with Reclamation, both informally and formally, eight times since 2000 on 

various forbearance agreements and proposed water transfers for which water is made available in 

the Sacramento Valley by fallowing rice (and other crops), substituting other crops for rice, or 

substituting groundwater for surface supplies. Although transfers of this nature were anticipated in 

our 2004 biological opinion on the Environmental Water Account (EWA; Service File 03-F-0321), 

that program expired in 2007 and, to our knowledge, no water was ever made available to EWA 

from rice fallowing or rice crop substitution. 

As a result of discussions during consultation for the 2009 Drought Water Bank (DWB) between 

Reclamation, California Department of Water Resources (DWR) and the Service (along with 

representatives from the potential buyer and seller communities), a commitment was made to work 

together to identify long-term solutions for future water transfers. As a result, Reclamation and San 

Luis Delta Mendota Water Authority (SLDMWA) have prepared a joint EIS/EIR (Reclamation 

2014b) to analyze the effects of water transfers from water agencies in northern California to water 

agencies south of the Delta and in the San Francisco Bay Area over a 10-year period (2015-2024). 

The EIS/EIR evaluates transfers of CVP water and non-CVP water supplies that require use of 

CVP or State Water Project (SWP) facilities to convey the transferred water and are the subject of 

this programmatic consultation. Scoping has been completed for this project and all of the scoping 

information is available on Reclamation’s website at http://www.usbr.gov/mp/cvp/ltwt/. 

Subsequently, Reclamation and the Tehama Colusa Canal Authority (TCCA) prepared a joint 

Environmental Assessment/Initial Study (EA/IS) addressing potential effects of selling of water to 

TCCA members, all north of the Delta, which is also included in this biological opinion 

(Reclamation 2015). 

We have evaluated the information contained in the BAs/consultations for respective interim and 

long-term water service contracts of the south of Delta buyers (1) Westlands Water District (Service 

file 14-F-0035); (2) Cities of Avenal, Coalinga, and Huron (Service file 12-I-0652); (3) San Luis 

Water District and Panoche Water District (Service file 13-I-0073); and (4) Banta-Carbona Irrigation 

District, Broadview Water District, Byron-Bethany Water District, Del Puerto Water District, Eagle 

Field Water District, James Irrigation District, Laguna Water District, Mercy Springs Water District 

(unassigned portion), Oro Loma Water District, Patterson Irrigation District, Reclamation District # 

1606, Tranquillity Irrigation District, The West Side Irrigation District, West Stanislaus Irrigation 

District (Service file 04-I-0707) and it is our determination that the effect of these transfers on San 

Joaquin kit fox were included in those consultations. We do not anticipate additional adverse effects 
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 3

to San Joaquin kit fox or an increase in the incidental take authorized, beyond what was evaluated in 

the biological opinions for the respective interim and long-term water service contracts of the 

potential south of Delta buyers.

In addition, based on a review of the information contained in the December 15, 2008, biological 

opinion for the Coordinated Operations of the CVP and SWP, it is our determination that the 

effects of these transfers on delta smelt and its critical habitat were included in that consultation

(Service 2008). We do not anticipate additional adverse effects to delta smelt or its critical habitat, or 

an increase in the incidental take authorized, beyond what was evaluated in our December 15, 2008, 

biological opinion. 

The remainder of this document provides our programmatic biological opinion on the effects of the 

proposed project on the snake.

Consultation History

March 4, 2014 – Meeting held between the Service, DWR, U.S. Geological Survey (USGS), and 

California Department of Fish and Wildlife (CDFW) focused on draft environmental 

commitments to conserve the snake. Reclamation recommended that the environmental 

commitments for water transfers in 2014 should reflect new information published since the 

2010 biological opinion. USGS concurred that their data supported revision to the 

environmental commitments and provided refinements to the technical analysis used to 

depict areas of highly suitable habitat which likely contained snake populations. Reclamation 

asked for feedback on the draft language and agreed to modify the technical analysis used to 

depict snake priority habitat areas. 

April 21, 2014 – The Service issued Biological Opinion for the snake to Reclamation for 2014 Water 

Transfers (Reference No. 08ESMF00-2014-F-0359) (Service 2014)

November 18, 2014 – The Service received Reclamation’s request for formal consultation for the 

Proposed Long-term Water Transfers from 2015 to 2024.

February 10, 2015 – The Service requested that Reclamation provide additional information 

regarding proposed conservation measures for the snake.

March 17, 2015 – The Service received Reclamation’s memorandum with additional information 

regarding snake research and monitoring and proposed conservation measures.

April 8, 2015 – The Service received Reclamation’s memorandum amending the description of the 

proposed project to include eight additional sellers, increase the proposed transfer amounts 

of three existing sellers and adding one buyer, TCCA. Reclamation also revised total 

maximum potential transfer amount which was incorrect in the November 2014 BA.

April 23, 2015 – The Service and Reclamation met to discuss the preparation of a programmatic 

biological opinion with annual appendages and incidental take statements for the remainder 

of the program.

May 13, 2015 – The Service received Reclamation’s email requesting revisions and corrections to the 

Service’s April 30, 2015 Programmatic Biological Opinion.
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 4

Description of the Action

The proposed project consists of water transfers to CVP contractors over which Reclamation has 

approval authority, including any transfers that involve CVP water supplies or require the use of 

CVP facilities, for a 10-year period (2015-2024). These transfers may result from forbearance1

actions taken by the sellers and may include Base Supply and Project Water from willing sellers 

located upstream of the Sacramento-San Joaquin Delta (Delta). Water transfers included in the 

proposed project represent only a portion of the expected overall transfers between 2015 and 2024. 

The remaining transfers (SWP) are not dependent on Reclamation’s approval; this biological opinion

considers these transfers in the context of cumulative effects.

The proposed project consists of making up to 565,614 acre-feet (AF) of water available for transfer 

each water year (2015 through 2024) through cropland idling/shifting, reservoir releases, 

conservation measures or groundwater substitution and assumes 100 percent supply is allocated

(Tables 1 and 2). The CVP contractors identified in Tables 1 and 2 are the most likely participants 

through the duration of the proposed project. However, all CVP contractors North of the Delta

have the opportunity to participate in the proposed project, subject to Reclamation’s review and 

approval of all transfer proposals2. Annual transfer maximums authorized under the proposed 

project will not exceed the maximum transfer volume of 565,614 AF nor will the maximum annual 

cropland idling acreages, by region, exceed the values included in Table 4. 

Procedures for Appending to the Programmatic Biological Opinion

This programmatic biological opinion addresses the effects of Reclamation’s 10-year water transfer 

program and will be appended annually to include an incidental take statement that is consistent 

with the specifics of that year’s proposed transfers. Because Reclamation is proposing specific 

actions that will affect the snake in 2015, this document also issues an incidental take statement for 

2015 actions. In future years, we expect changes in the amount of anticipated take based on a 

variety of factors including willing sellers and buyers, water year type, amounts of land idled, crop 

shifting, habitat conditions for the snake and biological information from snake and habitat 

monitoring. For water transfers in years 2016-2024 (including multi-year transfers) Reclamation will 

prepare a description of the proposed action for the calendar year (sellers/buyers, conservation 

measures, etc.), provide detailed monitoring reports for the previous years actions, and submit this 

information to the Service no later than January 31 of each year. 

Additionally, Reclamation will provide to the Service for review a report containing the following:

 

1 For purposes of this BA, the term “forbear” or “forbearance” will refer to both the Base Supply and Project Water 

made available under the respective Sacramento River Settlement Contract, although, it is understood the Base Supply 

will be forborne, while the Project Water will be transferred. Base Supply and Project Water Supply are terms of art from 

the Sacramento River Settlement Contract which is available at 

http://www.usbr.gov/mp/cvpia/3404c/lt_contracts/2005_exec_cts_sac_river/index.html. Base Supply shall mean the 

quantity of Surface Water established in Articles 3 [refers to Exhibit A: Schedule of Monthly Diversions of Water] and 5 

[Constraints on the Availability of Water] which may be diverted by the Contractor from its Source of Supply each 

month during the period April through October of each Year without payment to the United States for such quantities 

diverted. Project Water shall mean all Surface Water diverted or scheduled to be diverted each month during the period 

April through October of each Year by the Contractor from its Source of Supply which is in excess of the Base Supply.

2 Guidance for preparation of water transfer proposals is revised annually to reflect how transfers would be implemented 

and includes the prescribed measures in project-specific CEQA/NEPA and section 7 documents that cover the area 

where tranfsers are proposed. The environmental commitments approved in Reclamation’s EIS/EIR and this biological 

opinion will be used to establish guidance for future water transfers proposals.
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 5

 all available information including monitoring reports from previous transfers that address 

amount and locations of fallowed lands;

 giant garter snake and habitat monitoring data; and

 environmental conditions from the previous year(s) and those expected in the coming year. 

The annual monitoring reports will include detailed information in the action area (narrative and 

GIS spatial analysis) on implementation of the conservation measures, land idling/fallowing, 

hydrologic conditions, presence/absence/not found surveys for the snake, recent reports prepared 

on the snake, implementation of the conservation measures, and any other information that is 

relevant to snake impacts and conservation. 

Reclamation proposes an adaptive approach to implementation of the water transfer program to 

ensure that prior to finalizing the water transfer agreements each year, Reclamation can make 

adjustments to the program. Adjustments would be made in response to new information about the 

status of the snake, effectiveness of conservation measures, environmental conditions, and 

population responses of the snake. By February 28 of each year Reclamation, the Service, the 

California Department of Fish and Wildlife (CDFW), and USGS meet to discuss the annual 

monitoring report, evaluate results of snake monitoring and research, evaluate the implementation 

of conservation measures and consider other relevant information. The Service, CDFW, and 

Reclamation, in consultation with USGS scientists, will identify any changes needed to snake 

conservation measures for the current year’s water transfer program to assure continued 

conservation of the snake based on the joint evaluation of the most current scientific 

information. In addition the agencies will discuss water transfers anticipated for the current year and

the extent and location of proposed crop idling (up to the stated maximum acreage).

By March 30 of each year, following the joint meeting and review of available information, the 

Service will provide additional analysis in support of an Incidental Take Statement for the current 

year’s water transfers that will be appended to this programmatic biological opinion. It is expected 

that the total amount of water transferred which results in impacts to the snake (crop idling/crop 

shifting) will not exceed what is identified in the BA; however, Reclamation anticipates that the 

location of these impacts in the landscape will shift annually based on willing sellers, water year type, 

and other uncertainties.

The Service will append this biological opinion each year over the 10-year life of the proposed action 

with an Incidental Take Statement based on the specific and current information available to 

Reclamation and the Service. The purpose of this programmatic consultation is to allow 

Reclamation to take an adaptive approach to implementation of the water transfer program due to 

the degree of uncertainty in water availability, annual farming decisions, and natural variability 

associated with snakes, their habitat, and their responses to the proposed action.
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 6

Table 1 Maximum Potential Transfer by Seller Based on 100% Supply (2015) 

Water Agency Maximum Potential 

Transfer (AF)

Sacramento River Area of Analysis 

Anderson-Cottonwood Irrigation District 5,225

Burroughs Farms 2,000

Canal Farms 1,000

Conaway Preservation Group 35,000

Cranmore Farms 8,000

Eastside Mutual Water Company 2,230

Glenn-Colusa Irrigation District 91,000

Maxwell Irrigation District ( max. transfer would be under a 75% supply scenario) 7,500

Natomas Central Mutual Water Company 30,000

Pelger Mutual Water Company 4,670

Pelger Road 1700, LLC 3,400

Pleasant Grove-Verona Mutual Water Company 18,000

Princeton-Cordora-Glenn Irrigation District 8,000

Provident Irrigation District 9,000

Reclamation District 108 35,000

Reclamation District 1004 19,675

River Garden Farms 15,000

Sutter Mutual Water Company 18,000

Sycamore Mutual Water Company 20,000

T&P Farms 1,200

Te Velde Revocable Family Trust 7,094

American River Area of Analysis 

City of Sacramento 5,000

Placer County Water Agency 47,000

Sacramento County Water Agency 15,000

Sacramento Suburban Water District 30,000

Yuba River Area of Analysis 

Browns Valley Irrigation District 8,100

Cordua Irrigation District 12,000

Feather River Area of Analysis 

Butte Water District 17,000

Garden Highway Mutual Water Company 14,000

Gilsizer Slough Ranch 3,900

Goose Club Farms and Teichert Aggregates 10,000

South Sutter Water District 15,000

Tule Basin Farms 7,320

Merced River Area of Analysis 

Merced Irrigation District 30,000

Delta Region Area of Analysis 

Reclamation District 2068 7,500

Pope Ranch 2,800

Total 565,614

Source: Reclamation 2014a
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 7

Table 2 Transfer Types by Water Agency (AF; Upper Limits) (2015)

Water Agency

April – June (AF) July –September (AF)

Groundwater 

Substitution

Cropland 

Idling/Crop 

Shifting

Stored 

Reservoir 

Release

Conservation

Groundwater 

Substitution

Cropland 

Idling/Crop 

Shifting

Stored 

Reservoir 

Release

Conservation

Sacramento River Area of Analysis 

Anderson-Cottonwood Irrigation District 2,613 2,613 

Burroughs Farms 1,000 1,000

Canal Farms 575 235 425 400

Conaway Preservation Group 21,550 7,900 13,450 13,450 

Cranmore Farms 5,140 925 2,860 1,575 

Eastside Mutual Water Company 1,067 683 1,163 1,163

Glenn-Colusa Irrigation District 12,500 24,420 12,500 41,580 

Maxwell Irrigation District 1,330 888 2,270 1,512

Natomas Central Mutual Water Company 15,000 15,000 

Pelger Mutual Water Company 2,151 939 2,670 1,599 

Pelger Road 1700, LLC 1,700 1,700

Pleasant Grove-Verona Mutual Water Co. 8,000 3,330 10,000 5,670 

Princeton-Cordura-Glenn Irrigation District 2,000 1,110 3,000 1,890

Provident Irrigation District 3,000 1,110 3,000 1,890

Reclamation District 108 7,500 7,400 7,500 12,600 

Reclamation District 1004 4,625 7,175 7,875

River Garden Farms 4,000 5,550 5,000 9,450

Sutter Mutual Water Company 6,600 11,340

Sycamore Mutual Water Company 7,500 3,700 7,500 6,300 

T&P Farms 650 330 550 560

Te Velde Revocable Family Trust 2,700 2,581 4,394 4,394 

American River Area of Analysis 

City of Sacramento 5,000 

Placer County Water Agency 47,000 

Sacramento County Water Agency 15,000 

Sacramento Suburban Water District 15,000 15,000 

Yuba River Area of Analysis 

Browns Valley Irrigation District 5,000 3,100 

Cordua Irrigation District 12,000 

Feather River Area of Analysis 

Butte Water District 2,750 5,750 2,750 5,759

Garden Highway Mutual Water Company 6,500 7,500 

Gilsizer Slough Ranch 1,500 2,400 

Goose Club Farms and Teichert Aggregates 4,000 3,700 6,000 6,300 

South Sutter Water District 15,000 

Tule Basin Farms 3,800 3,520 

Merced River Area of Analysis 

Merced Irrigation District 30,000 

Delta Region Area of Analysis 

Reclamation District 2068 2,250 2,775 2,250 4,725 

Pope Ranch 1,400 1,400 

Total (AF)

1 134,426 84,551 0 0 176,590 140,032 97,000 3,100 

1 These totals cannot be added together. Agencies could make water available through groundwater substitution, cropland idling, or a 

combination of the two; however, they would not make the full quantity available through both methods. This table reflects the total 

upper limit for each agency.

Source: Reclamation 2014a
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 8

Table 3 identifies potential buyers who may be interested in participating in the long-term water 

transfers. Not all of these potential buyers may purchase transfer water. Purchase decisions depend 

on a number of factors, including hydrology, water demands, availability of other supplies, and 

transfer costs.

Table 3 Potential Buyers (2015)

Tehama Colusa Canal Authority Member Units

Colusa County Water District

Corning Water District

Cortina Water District

Davis Water District

Dunnigan Water District

4-M Water District

Glenn Valley Water District

Glide Water District

Kanawha Water District

Orland-Artois Water District

Westside Water District

San Luis & Delta-Mendota Water Authority Participating Members

Byron-Bethany Irrigation District

Del Puerto Water District

Eagle Field Water District

Mercy Springs Water District

Pacheco Water District

Panoche Water District

San Benito County Water District

San Luis Water District

Santa Clara Valley Water District

Westlands Water District

Contra Costa Water District

East Bay Municipal Utility District

Reclamation approves transfers consistent with provisions of the Central Valley Project 

Improvement Act (CVPIA) that protect against injury to third parties as a result of water transfers. 

Several important CVPIA principles include requirements that the transfer will not violate the 

provisions of Federal or State law, will have no significant adverse effect on the ability to deliver 

CVP water, will be limited to water that would have been consumptively used or irretrievably lost to 

beneficial use, will have no significant long-term adverse impact on groundwater conditions, and will 

not adversely affect water supplies for fish and wildlife purposes. Reclamation will not approve any 

water transfer for which these basic principles have not been adequately addressed (Reclamation and 

DWR 2013).

Additional information about water rights protection and water transfers is located at 

http://www.waterrights.ca.gov/watertransferguide.pdf in a SWRCB staff document titled “A Guide 

to Water Transfers”. 
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 9

Reservoir Release

Some buyers will acquire water by purchasing surface water stored in reservoirs owned by entities

(Placer County Water Agency, Browns Valley Irrigation District, South Sutter Water District and 

Merced Irrigation District) not part of the CVP or SWP (non-Project entities) (Reclamation 2014a). 

To ensure that purchasing this water would not affect downstream users, Reclamation will limit 

transferred water from these sources to what would not have otherwise been released downstream. 

Refer to Reclamation 2014a for additional information about reservoir releases.

Cropland Idling 

Cropland idling will make available for transfer water that would have been used for agricultural 

production. Water would be available on the same pattern throughout the growing season as it 

would have been consumed had a crop been planted. The irrigation season generally lasts from 

April through October for most crops in the Sacramento Valley. 

Under the proposed project, cropland idling transfers could occur in Glenn, Colusa, Butte, Yolo, 

Solano, and Sutter Counties in the Seller Service Area. Table 4 shows the maximum acreages that 

could be idled in a year. Cropland idling transfers during a single year would likely affect less than 

the maximum acreages listed in the table. 

Table 4 Maximum Annual Rice Cropland Idling Acreages

Region Rice (acres)

Sacramento Region 49,924

Feather Region 10,769

Delta Region -

Total 60,693

Landowners could annually choose whether to idle their fields to transfer water, and landowners 

could place fields back into production the following season. The quantity of water made available 

for transfer through cropland idling would be calculated based on the evapotranspiration of applied 

water (ETAW). ETAW is the portion of applied surface water that is used by the crop and 

evaporated from the soil and plant surfaces. For rice, the estimated ETAW is 3.3 AF of water/acre 

(Reclamation and DWR 2013). 

Rice has been the crop idled most frequently in previous water transfer programs because rice is an 

annual crop that provides the largest amount of transfer water per acre. The Sacramento Valley 

contains most of California’s rice production; therefore, crop idling acquisitions are likely to take 

place in this region. See Table 5 for estimated acres of rice production ranging from a low of 

369,600 acres in 1992 to a high of 562,300 acres in 2004 with an annual average of 487,429 acres. 

No water was transferred under federal actions during any of these years.
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 10

Table 5 Estimated Sacramento Valley Rice Production (acres) from 1992-2013 by County

Year Butte Colusa Glenn Sacramento Sutter Yolo Yuba Total

Total 

Annual 

Change

1992 76,300 94,800 65,800 8,900 73,100 19,000 31,700 369,600 --

1993 79,300 112,000 74,500 10,400 81,000 21,400 31,300 409,900 40,300

1994 88,000 123,000 81,000 11,500 90,000 26,700 34,000 454,200 44,300

1995 83,000 122,000 79,000 10,300 82,000 27,000 32,000 435,300 -18,900

1996 97,000 136,000 87,000 8,800 86,000 21,600 34,000 470,400 35,100

1997 97,000 137,000 89,000 9,400 90,000 24,000 35,000 481,400 11,000

1998 88,000 121,000 83,000 9,100 91,000 20,400 37,300 449,800 -31,600

1999 102,500 135,000 88,000 9,700 104,500 30,000 39,200 508,900 59,100

2000 98,000 145,000 87,500 9,000 108,000 35,500 39,000 522,000 13,100

2001 86,800 126,300 78,300 7,800 87,700 26,000 37,100 450,000 -72,000

2002 100,000 138,500 87,500 8,200 101,700 31,500 36,000 503,400 53,400

2003 87,800 138,000 82,500 8,100 96,900 32,300 35,400 481,000 -22,400

2004 105,800 156,400 90,300 9,600 124,000 41,900 34,300 562,300 81,300

2005 96,800 145,600 87,100 7,900 101,800 29,200 33,300 501,700 -60,600

2006 99,100 145,900 87,500 3,700 106,600 28,900 33,200 504,900 3,200

2007 102,000 155,000 86,500 3,700 106,000 23,800 33,700 510,700 5,800

2008 96,500 152,000 84,700 2,500 97,300 27,300 35,200 497,500 -13,200

2009 106,400 150,400 85,700 3,120 115,300 35,900 38,000 534,820 37,320

2010 93,800 153,000 85,600 4,184 116,000 41,000 38,700 532,284 -2,536

2011 111,000 154,000 88,600 3,200 123,000 41,000 39,000 561,000 28,716

2012 93,000 157,000 86,000 5,899 119,000 40,461 39,400 540,760 -20,240

2013 104,000 164,000 80,000 8,363 117,000 33,200 37,500 544,063 3,303

Avg. 95,095 139,177 83,868 7,426 100,814 29,912 35,650 492,088 --

Source: U.S. Department of Agriculture 2015; Sacramento County Agricultural Commissioner’s annual Stock and Livestock 

Reports 2015; Yolo County Agricultural Commissioner’s 2013 Agricultural Crop Report

Groundwater Substitution

In this case, transferred water will be substituted by groundwater withdrawals to facilitate continued 

agricultural production. See the BA (Reclamation 2014a) for a description of groundwater 

substitution. 

Crop Shifting and Conservation

For crop shifting transfers, water is made available when farmers shift from growing a higher water 

use crop to a lower water use crop. Conservation transfers must include actions to reduce the 

diversion of surface water by the transferring entity by reducing irrecoverable water losses. Refer to 

Reclamation 2014a for more information. 
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 11

Transfer Quantities

Table 1 provides a list of entities that could potentially sell water for transfers in 2015. Table 2

specifies maximum quantities that each agency could make available through different transfer 

mechanisms. Adding these maximum quantities produces a total of 565,614 AF, but multiple other 

factors may limit the transfers to a smaller amount. Annual transfer maximums authorized under 

the proposed project will not exceed the maximum transfer volume of 565,614 AF nor will the 

maximum annual cropland idling acreages, by region, exceed the values included in Table 4. Refer 

to Reclamation 2014a for more information.

It is anticipated that water transfers would be implemented during critically dry years when CVP and 

SWP water service contractors’ allocations are low. Calculating a baseline for critically dry years can 

be challenging because it is difficult to determine the actions that may be taken to accommodate 

reduced water allocations. Sellers may increase groundwater pumping, increase cropland idling/crop 

shifting, or utilize a combination of pumping and cropland idling/crop shifting to address 

reductions in allocations. For example, Glenn Colusa Irrigation District estimates that about 15 

percent of rice in the service area would be idled if they were to receive 75 percent allocation from 

the CVP (Reclamation 2014a).

Consolidated Place of Use

Reclamation and DWR petitioned the State Water Resources Control Board (SWRCB) to 

temporarily consolidate the CVP and SWP places of use, and the SWRCB granted that consolidation 

in 2014. Reclamation is currently filing another petition for 2015 as the current order expires in 

April 2015. Approval of a consolidated place of use would allow transfers from CVP contractors 

contemplated in this document to SWP contractors south of Banks or Barker Slough Pumping 

Plants which are outside the CVP authorized place of use. Reclamation will not approve any CVP 

water transfers to buyers outside of the CVP place of use unless the SWRCB approves a Petition for 

Change (either through a joint petition to consolidated the CVP and SWP places of use or through 

individual petitions for change) authorizing the delivery of water outside the CVP place of use. The 

joint point of diversion authorization contained in D-1641 allows the CVP and SWP to use the 

other’s facilities to divert or convey water under certain terms and conditions, but it does not allow 

delivery of that water to outside that Project’s existing authorized place of use. Without SWRCB 

approval of a Petition for Change, CVP water could only be delivered within the CVP authorized 

place of use. 

Risk and Uncertainty

Transferring water from north of the Delta to south of the Delta would involve uncertainty and risk. 

The CVP and SWP would move this water using the Jones and Banks Pumping Plants, but the CVP 

and SWP must first meet regulatory requirements and the needs of their users. CVP and SWP 

operations are governed by the criteria contained in D-1641, the 2008 Service and 2009 National 

Marine Fisheries Service biological opinions, and all other regulatory restrictions governing 

operations. 

Buyers and sellers would typically negotiate transfers during the wet season before hydrologic 

conditions are clear. Late season precipitation could increase the amount of available water for the 

CVP and SWP and reduce or eliminate available capacity for transfers. The CVP and SWP may not 

know the capacity in advance and would not guarantee available capacity; any uncertainty regarding 

capacity would rest with the buyers and sellers.
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 12

Transfers, particularly transfers involving cropland idling, could be heavily affected by this 

uncertainty. Growers would need to idle crops at the beginning of the growing season, which 

typically occurs in April or May. The possibility exists that buyers and sellers would negotiate a 

cropland idling transfer at the beginning of April, the seller would leave fields idle, and late-season 

rains could reduce excess capacity at the Delta pumps and prevent this water from being transferred. 

This risk would typically fall on the buyers after the contracts are negotiated.

A major concern to potential buyers in the Export Service Area is the ability to deliver the 

purchased water through the Delta to the buyer’s service area. Export of the transfer water through 

the Delta is dependent on availability of capacity at the CVP or SWP pumping facilities and subject 

to other operational requirements. Available CVP and SWP capacity is severely limited due to 

operational and regulatory restrictions. The pumping window for transfers is currently July through 

September. Pumping within this window can be further reduced or expanded based on specific 

hydrologic conditions and regulatory compliance or water quality issues. Reclamation and DWR 

cannot guarantee that a specific quantity of transfer capacity would be available.

Transfer Length

Buyers and sellers may negotiate transfers that last one year or multiple years. Sellers and buyers can 

negotiate the terms of a single year transfer during the wet season and would generally finalize an 

agreement after the hydrologic conditions are understood well enough to establish available 

pumping capacity. 

Sellers and buyers could also negotiate multi-year transfers. In this type of transfer, a long-term 

agreement would generally give the buyer the first right of refusal for water that a seller makes 

available. The buyer could pay the seller a fee every year to reserve the water, whether the buyer 

uses it or not. In years where adequate capacity exists to move water through the Delta, the buyer 

would have priority to buy the water at an established price. If the buyer does not want the water in 

a year when capacity is available, the seller could negotiate a one-year transfer with another buyer.

Conservation Measures

The proposed project would incorporate conservation measures consistent with the Central Valley 

Project 2014 Water Transfers Biological Opinion (reference no. 08ESMF00-2014-FO359) and the 

Draft Technical Information for Water Transfer Proposals in 2014 (Reclamation and DWR 2013). 

Commitments that broadly restrict idling across the service area were refined to focus on cropland 

idling restrictions in areas where snakes have a high likelihoood of occurrence. Giant garter snake 

priority habitat areas have been identified by USGS and maps have been developed (Attachment A) 

for each water district using the information on habitat use, known populations, and historic tule 

marsh zones (see also USFWS 2014). The purpose of these maps is to identify areas with the 

highest probability of snake occurrence so that water transfer actions can be avoided within these 

areas. Reclamation is implementing a conservation strategy that requires water be maintained in 

areas most important to snakes and that water not be transferred from habitat priority conservation 

areas (e.g., Natomas). 

The following actions to protect snakes would be incorporated into contracts between Reclamation 

and the water sellers:
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 13

All Transfer Methods

 Carriage water (a portion of the transfer that is not diverted in the Delta and becomes Delta 

outflow) will be used to maintain water quality in the Delta.

Cropland Idling/Shifting Transfers

 As part of the approval process for long-term water transfers, Reclamation will have access 

to the land to verify how the water transfer is being made available and to verify that actions 

to protect the snake are being implemented. 

 Reclamation will provide a map(s) to the Service in June of each year showing the parcels of 

riceland that are idled for the purpose of transferring water for that year. These maps will be 

prepared to comport to Reclamation’s geographic information system (GIS) standards.

 Movement corridors for aquatic species (including pond turtle and snake) include major 

irrigation and drainage canals. The water seller will keep adequate water in major irrigation 

and drainage canals3. Canal water depths should be similar to years when transfers do not 

occur or, where information on existing water depths is limited, at least two feet of water will 

be considered sufficient.

 Districts proposing water transfers made available from idled rice fields will ensure that 

adequate water is available for priority habitat with a high likelihood of giant garter snake 

occurrence. The determination of priority habitat will be made through coordination with 

giant garter snake experts, GIS analysis of proximity to historic tule marsh, and GIS analysis 

of suitable habitat. The priority habitat areas are indicated on the priority habitat maps for 

participating water agencies and will be maintained by Reclamation. As new information 

becomes available, these maps will be updated in coordination with the Service and 

CDFW. As appropriate, map updates will be provided to the Service along with the related 

GIS data. In addition, fields abutting or immediately adjacent to federal wildlife refuges will 

be considered priority habitat. 

 Maintaining water in smaller drains and conveyance infrastructure supports key habitat 

attributes such as emergent vegetation for snake for escape cover and foraging habitat. If 

crop idling/shifting occurs in priority habitat areas, Reclamation will work with contractors 

to document that adequate water remains in drains and canals in those priority areas. 

Documentation may include flow records, photo documentation, or other means of 

documentation agreed to by Reclamation and the Service. 

 Areas with known priority snake populations will not be permitted to participate in cropland 

idling/shifting transfers. Water sellers can request a case-by-case evaluation of whether a 

specific field would be precluded from participating in long-term water transfers. These 

areas include lands adjacent to naturalized lands and refuges and corridors between these 

areas such as:

 

3 The term “adequate water” is used in the environmental commitments along with objectives of what must be 

accomplished with this water. Reclamation will review each transfer proposal to make sure that the seller meets these 

objectives. These other terms describe agricultural water conveyance and drainage facilities, and are also considered 

during review of each transfer proposal. (D. Cordova, pers. comm. 2015)
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 14

o Fields abutting or immediately adjacent to Little Butte Creek between Llano Seco 

and Upper Butte Basin Wildlife Area (WA), Butte Creek between Upper Butte Basin 

and Gray Lodge WAs, Colusa Basin drainage canal between Delevan and Colusa 

National Wildlife Refuges (NWR), Gilsizer Slough, Colusa Drainage Canal, the land 

side of the Toe Drain along the Sutter Bypass, Willow Slough and Willow Slough 

Bypass in Yolo County, Hunters and Logan Creeks between Sacramento and 

Delevan NWRs; and 

o Lands in the Natomas Basin.

 Sellers will continue to voluntarily perform snake best management practices, including 

educating maintenance personnel to recognize and avoid contact with snakes, cleaning only 

one side of a conveyance channel per year, and implementing other measures to enhance 

habitat for snakes.

 In order to limit reduction in the amount of over-winter forage for migratory birds, 

including greater sandhill crane, cropland idling transfers will be minimized near known 

wintering areas in the Butte Sink. 

 At the end of each water transfer year, Reclamation will prepare a monitoring report that 

contains the following:

o Maps of all cropland idling actions that occurred within the range of potential 

transfer activities affected by this program;

o Results of current scientific research and monitoring pertinent to water transfer 

actions; and

o A discussion of conservation measure effectiveness.

o The report will be submitted to the Service and CDFW by January 31, prior to the 

next year of potential transfers. 

 Reclamation will establish annual meetings with the Service to discuss the contents and 

findings of the annual report. These meetings will be scheduled following the distribution of 

the monitoring report and prior to the next transfer season.

 If, upon review of monitoring reports or other scientific literature, it appears that the 

proposed project is having unanticipated effects on snakes, Reclamation will initiate contact 

with the Service to discuss the information available and effectiveness of conservation 

measures. 

Action Area

The action area is defined in 50 CFR §402.02, as “all areas to be affected directly or indirectly by the 

Federal action and not merely the immediate area involved in the action.” For the proposed project, 

the action area includes those areas of California that might receive water from the long-term water 

transfer actions or areas potentially affected by the long-term water transfers because they serve as a 

site for water acquisition or conveyance (Figures 1, 2, and 3). 
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 15

The overall action area includes specific areas of analysis for each resource that may be directly or 

indirectly affected by potential water transfers. In a general sense, these areas of analysis comprise: 

(1) watersheds of rivers that may participate in cropland idling/shifting; (2) rivers used to convey 

transfer water; (3) lands that may be used for cropland idling/shifting and adjacent lands; (4) district, 

on-farm and CVP or SWP conveyance facilities; and (5) storage and conveyance facilities in areas 

that would receive water from transfers. The action area consists of the following areas and 

features:

 Major watersheds and numerous minor watersheds within the Sacramento River Basin 

consisting of the following water bodies: 

o Sacramento River from Lake Shasta to the Delta;

oNumerous small tributaries to the Sacramento River and other smaller creeks;

o Feather River, including and downstream of Lake Oroville and its tributaries the Yuba 

River, including and downstream of New Bullards Bar Reservoir, and the Bear River, 

including and downstream of Camp Far West Reservoir; and

o Middle Fork American River downstream of Hell Hole and French Meadows

Reservoirs.

 Within the San Joaquin River watershed, potentially affected water bodies in the Seller 

Service Area, specifically; 

o San Joaquin River downstream of the Merced River.

o Merced River, including and downstream of Lake McClure.

 Portions of the CVP and the SWP systems; 

 San Luis Reservoir; 

 Agricultural lands in the Sacramento Valley (Colusa, Glenn, Sutter, Butte, Solano and Yolo 

Counties) in which farmers participate in cropland idling/shifting. 
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 16

Figure 1 Action Area
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 17

Figure 2 Locations of Potential Sellers (2015)
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 18

Figure 3 Locations of Potential Buyers (2015)
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 19

Analytical Framework for the Jeopardy Analysis

In accordance with policy and regulation, the jeopardy analysis in this biological opinion relies on 

four components: (1) the Status of the Species, which evaluates the snake’s range-wide condition, the 

factors responsible for that condition, and their survival and recovery needs; (2) the Environmental 

Baseline, which evaluates the condition of the snake in the action area, the factors responsible for that 

condition, and the relationship of the action area to the survival and recovery of the snake; (3) the 

Effects of the Action, which determines the direct and indirect effects of the proposed federal action 

and the effects of any interrelated or interdependent activities on the snake; and (4) the Cumulative 

Effects, which evaluates the effects of future, non-Federal activities in the action area on the snake. 

In accordance with the implementing regulations for section 7 of the Act and Service policy, the 

jeopardy determination is made in the following manner: the effects of the proposed Federal action 

are evaluated in the context of the aggregate effects of all factors that have contributed to the 

current status of the snake. Additionally, for non-Federal activities in the action area, we will 

evaluate those actions likely to affect the species in the future, to determine if implementation of the 

proposed action is likely to cause an appreciable reduction in the likelihood of both its survival and 

recovery in the wild.

The jeopardy analysis in this biological opinion places an emphasis on consideration of the rangewide survival and recovery needs of the snake and the role of the action area in the survival and 

recovery of the snake as the context for evaluating the significance of the effects of the proposed 

Federal action, taken together with cumulative effects, for purposes of making the jeopardy 

determination.

Status of the Species

For the most recent comprehensive assessment of the range-wide status of the snake, please refer to 

the Giant Garter Snake (Thamnophis gigas) Five-year Review: Summary and Evaluation (Five-year Review, 

Service 2012). No change in the snake’s listing status was recommended in the review. Threats to 

the snake discussed in the review have continued, with loss of habitat being the most significant 

effect. While there continue to be losses of snake habitat throughout its range, to date no project 

has proposed a level of effect for which the Service has issued a biological opinion of jeopardy for 

the snake. 

Following are the nine recovery units for the snake (Service 2012): (1) Butte Basin, extending from 

Red Bluff in the north to the Sutter Buttes in the south; (2) Colusa Basin, extending from Red Bluff 

in the north to Cache Creek in the south and bounded by the Sacramento River on the east and the 

Coast Range foothills on the west; (3) Sutter Basin, extending south from the Sutter Buttes to the 

confluence of the Feather and Sacramento rivers; (4) American Basin, extending south from 

Oroville to the confluence of the Sacramento and American rivers; (5) Yolo Basin, extending from 

Cache Creek in the north to the Sacramento-San Joaquin River Delta in the south; (6) Cosumnes 

Mokelumne Basin, bordered by the City of Sacramento and the Cosumnes River to the north, Sierra 

Nevada foothills to the east, Interstate 5 to the west, and the Mokelumne River to the south; (7) 

Delta Basin, extends from just south of the confluence of the Sacramento and American rivers 

south to the Stanislaus River; (8) San Joaquin Basin, extending from the Stanislaus River in the north 

to the San Joaquin River in the south and bordered by the Coast Ranges on the west and the Sierra 

Nevadas to the east; and (9) Tulare Basin, extending from the southern San Joaquin River south to 

the Buena Vista and Kern lakebeds. The action area includes all or part of each of these recovery 

units described in the Five-year Review.
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 20

Snake Research Associated with CVP/SWP Conservation Programs

The EWA biological opinion stated that Implementing Agencies (i.e. Service, CDFW) shall develop 

a Conservation Strategy for the snake through the Ecosystem Restoration Program (ERP). The 

Implementing Agencies did not complete the Conservation Strategy through the ERP. However, 

research and monitoring have continued to support a more comprehensive approach to snake 

conservation in the Sacramento Valley. In 2009, DWR developed a snake Baseline Monitoring and 

Research Strategy to help quantify and evaluate the response of the snakes to rice land idling. Since 

2009, DWR developed fundamental information about the snake’s ecology as it relates to the 

potential impacts from rice land idling. DWR is in the third year of working with the USGS 

Western Ecological Research Center (WERC) on the study of snakes in the Sacramento Valley. The

broad objective of this research effort is to provide scientific information to the Service in support 

of identifying the effects of rice land idling for the purpose of water transfers on the snake. 

Ultimately, the goal is to design conservation measures that will avoid and minimize effects to the 

snake from rice land idling for water transfers.

Up until now the study has focused on foundational studies, including distribution analysis of the 

snake in the Sacramento Valley. USGS WERC has suggested that the probability of occurrence 

decreases as distance from historic tule marsh increases and that the intervening historic habitat also 

affects this relationship (i.e., probability of snake occurrence remains higher as you move into 

California prairie, where smaller marshes were likely, as opposed to other habitats like blue oak 

savanna or riparian forest, where snakes were historically less likely to occur) (Halstead pers. comm. 

2014).

Radiotelemetry studies conducted by USGS WERC have examined snake habitat use in several areas 

in the Sacramento Valley. At the Gilsizer Slough study site in Sutter County, snakes were located in 

rice fields 19 to 20 percent of observations, marsh habitat 20 to 23 percent of observations, and in 

canal and waterway habitat 50 to 56 percent of observations (Service 1999). At the Colusa NWR 

study site, snakes used rice field in 19 percent of observations, marsh in 20 percent of observations, 

and canals in 50 percent of observations. USGS WERC also examined a study site in the Natomas 

Basin where only rice and canal habitat was available. Once rice was emergent in the rice fields, 

snakes used rice fields 39 to 60 percent of the time and canals 40 to 61 percent of the time (Wylie 

and Casazza 2000a, 200b). Thus both rice fields and canals are important habitats for the snake. 

USGS WERC estimated the home range size of snakes at four study sites. Home range (area of 

daily activity) averages about 0.1 mile (25 hectares) in both the Natomas Basin and the Colusa NWR 

(Wylie 1998; Wylie et al. 2002a; Wylie et al. 2002b). Home range estimates for snakes near the 

restored wetlands at Colusa NWR were generally smaller than previously found at the refuge when 

the lands were managed for waterfowl and in other off-refuge study areas (Wylie et al. 2000a). It is 

believed that maintaining water in the restored wetlands and nearby habitat provided sufficient 

conditions to meet the biological requirements of the snakes; thus, individuals were less likely to 

move further distances as in previous years when conditions were drier and water was not 

maintained specifically to benefit snakes (Wylie et al. 2000a). These managed areas apparently met 

the biological needs of the snakes, thereby reducing their movements. The Badger Creek area also 

appeared to be an example of where permanent wetland and sufficient habitat reduces snake 

movements. There the home range (N=8) was estimated to be 10 to 203 acres for an area 580 acres 

in size.
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 21

USGS WERC has also estimated home range sizes for snakes and determined median home ranges 

that are generally less than 100 acres in size, demonstrating that snakes typically use relatively small 

areas, even though they are capable of moving longer distances (up to five miles in a few days). 

Home range sizes for snakes at the Gilsizer Slough study site varied from approximately five acres to 

212 acres with a median of 39.5 acres. In the Natomas Basin, home range sizes varied from 32 acres 

to 214 acres with a median of 86 acres. USGS WERC has also studied snakes at the Colusa NWR 

where home range sizes were found to be highly variable. Home range sizes estimated for year 2000 

ranged from 2.5 to 81.5 acres with a median of 42 acres and for 2001 from 7.4 to 427.5 acres with a 

median of 59.3 acres. These home ranges are about half the size of those estimated for the study 

period 1996-97 (home ranges varied from 3.2 acres to 2,792 acres with a median of 103.8 acres). 

USGS-WERC concluded that home range sizes decreased as more summer water became available 

to the snake on the refuge in the later study period. 

Restored areas that provided summer water were more effective in meeting the habitat needs of the 

snake in 2000-2001 study periods; therefore, snakes did not have to venture as far as in previous 

years to find aquatic habitat during their active period. This was also found to be true for 

monitoring conducted during 2005. Sampling of the restored areas in Colusa NWR during the 

summers of 2002 and 2003 continued to document use of the restored wetland area as the habitat 

quality improves. The aquatic component of the habitat is important because the snake forages on 

frogs, tadpoles and fish. Most of the radio-marked snakes were captured along the water’s edge of 

the wetlands (Wylie et al. 2005). USGS WERC also concluded that reduced movements indicated 

that snakes were less exposed to mortality factors such as predators and vehicles (Service 1999, 

Wylie and Casazza 2000a, Wylie et al 2002a).

Other work has centered on improving trapping techniques for the snake. The level of precision for 

trapping requires an increase in detection and capture probabilities, which USGS WERC has 

achieved in modified traps. Snake behavior is the primary cause of remaining low capture 

probabilities (Halstead pers. comm. 2014).

USGS WERC has completed a comprehensive literature review and conceptual model of snake 

ecology and conservation (Halstead pers. comm. 2014). From this information DWR will develop a 

research framework to guide the research. DWR will do this in cooperation with a technical review 

committee made of internal and external (to DWR) scientists (pers comm. Vargas 2014). 

Habitat suitability modeling is a valuable exercise to support the conservation of species about which 

little is known. It can inform conservation by defining the habitat relationships of species and 

identifying locations at which a species is likely to occur. These locations can be used to direct future 

survey effort, and identify sites suitable for establishment of reserves or repatriation of extirpated 

populations. (Halstead et. al 2010) Also, based on studies undertaken by USGS, proximity to historic 

habitat appears to be the most important variable for predicting the probability of ocurrernce of 

snakes in the Sacramento Valley at the landscape scale. The occurrence of rice agriculture, its 

supporting network of irrigation and drainage canals, and the restoration of marsh habitats currently 

provide suitable habitat throughout the area of inference. Their research demonstrates, however, 

that snakes have not been able to disperse into all suitable habitats, and are largely restricted to areas 

near locations at which they were likely historically abundant (Halstead et al. 2013). 

Due to the need for several baseline studies (including a study to improve trap design) during the 

years following the issuance of the 2009 Biological Opinion, the first year of study specifically 

addressing the relationship between idling and snakes was in 2014. According to USGS WERC, the 

2014 snake trapping effort did not occur until after many fields were dried. Therefore, there was 

limited opportunity to observe snake behavior and spatial ecology among sites with varying degrees 

of idling (Reclamation 2015). 
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 22

DWR has in place $9,000,000 of funding to support the research work to be completed by USGS 

WERC on snakes and task orders utilizing these funds are being executed to supplement the current 

knowledge of snake populations and habitat use. Most recently, five tasks orders in 2012 were 

funded to support snake research, these include:

 Distribution of Giant Garter Snake (Thamnophis gigas) and the probability the species occurs 

at a given location, in the Sacramento Valley, California.

 Assessment of Distribution of the Giant Garter Snake (Thamnophis gigas), 

in the Sacramento Valley, California; 

 Assessment of Trap Modifications to Increase Capture and Detection Probabilities of the 

Giant Garter Snake (Thamnophis gigas);

 Review and Development of a Conceptual Model of Giant Garter Snake (Thamnophis gigas) 

Ecology and Conservation, in the Sacramento Valley, California; and

 Assessment of Realized Giant Garter Snake (Thamnophis gigas) Detection and Capture 

Probabilities using Modified Floating Aquatic Funnel Traps, in the Sacramento Valley, 

California.

Central Valley Project Conservation Program (CVPCP) and Central Valley Project Improvement Act 

Habitat Restoration Program (HRP)

The Central Valley Project Conservation Program (CVPCP) was developed during the section 7 

consultation process for the implementation of CVPIA. Accordingly, the CVPCP implements 

actions to protect, restore, and enhance special status species populations and habitats affected by 

the CVP, with special emphasis on federally listed species. The CVPIA HRP was established under 

Title XXXIV, Section 3406 (b) (1) “other” of the CVPIA under the “Fish and Wildlife Restoration 

Activities” section. The HRP also implements actions to improve conditions for species impacted 

by operation of the CVP. Reclamation and the Service coordinate administration of these two grant 

programs based on the authority established in the Fish and Wildlife Coordination Act, as amended, 

16 U. S.C. Section 661 et seq of 1956; the Fish and Wildlife Act of 1956, 16 U. S. C. 742(a-j); and the 

CVPIA of 1992, Public Law No. 102-575. Title XXXIV, Section 3406(b)(1). Jointly, CVPCP and 

HRP provide financial support for research on various aspects of biology, ecology, genetics, as well 

as, habitat improvements for special status species in the Central Valley. 

One of CVPCP and HRP Priority Actions supports snake research and habitat improvements. In 

order to identify the highest priority needs to which grant funds are directed each year, CVPCP and 

HRP managers work directly with the Service to identify Priority Actions. The Service identifies 

research and habitat improvement priorities based on recovery actions identified in recovery plans 

for federally listed species and expert opinion on which CVP-impacted federally listed species having 

the greatest recovery needs and/or which species face the greatest risk of extinction. Research and 

habitat improvement proposals which most closely align with the Priority Actions receive preference 

and are more likely to be funded by the CVPCP and HRP programs. Since the inception of the 

CVPCP and HRP in the mid-1990s, research yielding information on snakes has routinely been 

identified as a top Priority Action and been funded (Table 6).
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 23

Table 6 CVPCP and HRP Funded Giant Garter Snake Grants

Year Project Funding 

($)

2014 Giant Garter Snake Environmental DNA Research –

Colusa, Sutter and Sacramento counties

149,915

2009 Giant Garter Snake Distribution/Modeling - Butte 

County

180,000

2009 Giant Garter Snake Surveys, White Slough 122,648

2008 Giant Garter Snake Habitat Restoration, Cosumnes 

Preserve, Badger Creek

142,225

2007 Giant Garter Snake Genetic Study 60,210

2007 Giant Garter Snake Surveys, Merced and Fresno Counties 157,655

2004 Giant Garter Snake Surveys Colusa NWR 88,619

2004 Giant Garter Snake Surveys San Luis NWR 237,879

2003 Giant Garter Snake Surveys Colusa NWR 70,900

2002 Giant Garter Snake Surveys at Colusa NWR 38,060

2002 Giant Garter Snake – Surveys San Luis NWR (Grasslands) 53,200

2002 Giant Garter Snake – Surveys Grasslands Water District 157,760

2001 Giant Garter Snake Monitoring 67,570

2000 Giant Garter Snake Census 38,000

1997 Giant Garter Snake – Multi-year Surveys Colusa NWR 486,500

Source: D. Cordova pers. comm. 2015

Environmental Baseline

Known snake populations within the action area occur in freshwater marsh wetland or rice land 

areas which have tight clay soils such that there is standing surface water for long periods of the 

year. 

The USGS has been conducting a study of the life history and habitat use of the snake since 1995. 

Results of these studies have provided basic understanding of the preferential habitat use by the 

snake. This information is used to define important habitat components for management of the 

snake and demonstrates that: (1) in the active summer season, snakes predominately can be found in 

aquatic habitat; (2) irrigation canals are commonly used by giant garter snakes; (3) giant garter snakes 

use active rice fields in the summer; (4) giant garter snakes are most often f ound under vegetative 

cover; and (5) in the summer, snakes are most often found under aquatic vegetative cover. (Service 

2012)

The known range of the snake in the Sacramento Valley has changed little since the 1993 listing and 

2006 Five-year review. A summary of recent surveys and sightings for each population since the 

previous status review follows (Service 2012):
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 24

Butte Basin. The northernmost locality record of the snake is found five miles west of the City of 

Chico where at least four snakes have been found (Kelly pers. comm. 2006, Gallaway in litt. 2008, 

cited in Service 2012). In 2009 and 2010, the USGS surveyed rice fields in Butte County near Butte 

Sink and found snakes near the City of Nelson and at the Butte Sink WMA (Halstead in litt. 2011, 

cited in Service 2012). Surveys in 2008 to 2010 by USGS have found snakes at several new locations 

in southwest Butte County (USGS 2011, cited in Service 2012). Two sightings of snakes were 

reported in May and October of 2011 on the south perimeter of the Thermolito After Bay just east 

of State Route 99 (R. Martin in litt. 2012, cited in Service 2012). 

Colusa Basin. USGS and USFWS NWR staff observed snakes at each of the Federal NWRs (Colusa, 

Delevan, and Sacramento) that make up the Sacramento NWR Complex (Wylie et al. 2005, 2006, 

cited in Service 2012). In addition, snakes occur outside Refuge lands in the adjacent rice 

production areas. In 2010 snakes were found in Glenn County six miles southwest of the Chico 

Water Pollution Control Plant (Swaim in litt. 2010, cited in Service 2012). Snakes were found at the 

Colusa Basin Drainage Canal near the City of Knight’s Landing by walking and trapping surveys 

from spring through summer during the years 2003, 2004 and 2006 (Wylie et al. 2008, cited in 

Service 2012). 

Sutter Basin. A trapping survey in 2005 found snakes at Gilsizer Slough (Wylie 2008, cited in Service 

2012). At the Sutter Basin Conservation Bank, Hansen (2007, cited in Service 2012) caught 37 

snakes in an investigation of snake use of surrounding ricelands. In 2007, six conservation areas in 

Yolo, Sutter, Colusa and Sacramento counties were surveyed but snakes were found only at the 

Gilsizer Slough South Conservation Bank in Sutter County (Wildlands 2008, cited in Service 2012). 

American Basin. Snakes have been observed among the rice fields in the area within and around the 

Natomas Basin where the greatest number of surveys has occurred. The Natomas Basin property 

managed by the Natomas Basin Conservancy has been monitored for snakes since 2000 and surveys 

show that snakes persist in the Basin and continue occupying both restored habitat and rice fields. 

Outside of the Basin, other areas where snakes have been found include the area immediately north 

of the Natomas Cross Canal (E. Hansen 2003a, 2004a, 2005, 2006b, 2007b, and 2008b, cited in 

Service 2012). The areas around Marysville and northward have not been comprehensively surveyed 

for snakes and their status in this region remains unknown. 

Yolo Basin. Snakes have been documented within the Yolo Bypass WA and adjacent rice lands 

within the Yolo Bypass, and at the Willow Slough Bypass in Yolo County (E. Hansen 2006a, 2007c, 

2008c, cited in Service 2012). Occurrences at Ridgecut Slough near the City of Dunnigan were also 

recently described by Wylie and Martin (2005b, cited in Service 2012). A snake was found near the 

Pope Ranch Conservation Bank south of the Yolo Bypass WA (E. Hansen 2009a, cited in Service 

2012) and in 2009, snakes were found during surveys conducted on the Conaway Ranch bordering 

Willow Slough (E. Hansen 2009b, cited in Service 2012). The population at Liberty Farms that was 

listed as extant in1993 appears to have been extirpated (Service 1993, E. Hansen 2008c, cited in 

Service 2012). Wylie and Martin (2004, 2005a, cited in Service 2012) conducted trapping surveys at 

15 locations in Solano County for two consecutive years in order to confirm historic records; they 

did not find snakes at any of the 15 locations (Wylie and Martin 2004, 2005a, cited in Service 2012). 

Cosumnes-Mokelumne Watershed. Snakes have been detected at the Badger Creek sub-unit of the 

Cosumnes River Preserve, in the southern portion of Sacramento County (Wylie et al. 1997, E. 

Hansen 2001, 2003b, E. Hansen et al. 2010, cited in Service 2012). A baseline survey conducted in 

2008 revealed a large population of snakes at the Badger Creek sub-unit area called “Snake Marsh” 

(E. Hansen et al. 2010, cited in Service 2012). 
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 25

Delta Basin. The Delta Basin includes portions of Sacramento, Yolo, Solano, Contra Costa and San 

Joaquin counties. Although the presence of snakes in this area remains unknown, suitable habitat 

for the snake is known to exist in this area (G. Hansen 1986, 1988, DWR 2010, cited in Service 

2012). No snakes were trapped or observed during a 2009 survey (DWR 2010, cited in Service 

2012). Hansen captured three snakes at White Slough WA in 2009 and four snakes (three were road 

mortalities) were photographed near Little Connection Slough (ESA in litt. 2010, cited in Service 

2012). 

San Joaquin Basin. Snakes currently occur in the northern and central San Joaquin Basin within the 

northern and southern Grassland Wetlands. Trapping surveys conducted by Hansen in 2006 and 

2007 within the Grasslands Ecological Area both south and east of the San Joaquin River and in the 

Mendota WA resulted in only 10 captures in the two year study, with the majority of snakes being 

found in the Los Banos Creek corridor between the San Joaquin River and the City of Los Banos, a 

wetland supply channel for the private wetlands in the northern reach of the Grasslands Ecological 

Area (E. Hansen 2008a, cited in Service 2012). CDFW trapped in the Volta and Los Banos WAs in 

2006 in order to monitor populations and found snakes only at the Volta WA (Sousa 2007, cited in 

Service 2012). Low numbers of snakes in the San Joaquin Valley populations places these 

populations at high risk of extirpation (Paquin et al. 2006, E. Hansen 2008a, cited in Service 2012). 

Tulare Basin. The southern San Joaquin Valley includes portions of Fresno, Kings, Tulare, and Kern 

counties. Agricultural and flood control activities are presumed to have extirpated the snake from 

this portion of its historic range in the former wetlands associated with the Buena Vista, Tulare and 

Kern lake beds (G. Hansen and Brode 1980, R. Hansen 1980, G. Hansen 1986, 1988, cited in 

Service 2012). A survey of the historic documented localities of the snake in the southern San 

Joaquin Valley was conducted by USGS in 2006 (Wylie and Amarello 2007, cited in Service 2012), 

including Buena Vista Lake bed, Fresno Slough, Kern NWR, King’s River, and North King’s River, 

resulting in no snakes. 

The giant garter snake is highly aquatic but also occupies a terrestrial niche (Service 1999; Wylie et al. 

2004a). The snake typically inhabits small mammal burrows and other soil and/or rock crevices 

during the colder months of winter (i.e., October to April) (Hansen and Brode 1993; Wylie et al. 

1996; Wylie et al. 2003a), and also uses burrows as refuge from extreme heat during its active period 

(Wylie et al. 1997; Wylie et al. 2004a). Snakes can be communal in their habits, sharing burrows 

during the colder months and when escaping extreme heat (E. Hansen 2008 pers. comm.). While 

individuals usually remain in close proximity to wetland habitats, Wylie et al. (1997) documented 

snakes using burrows as much as 165 feet (50 meters) away from the marsh edge to escape extreme 

heat; and as far as 820 feet (250 meters) from the edge of marsh habitat for over-wintering habitat.

In studies of marked snakes in the Natomas Basin, snakes moved about 0.25 to 0.5 miles (0.4 to 0.8 

kilometers) per day (Hansen and Brode 1993). Total activity, however, varies widely between 

individuals. Individual snakes have been documented to move up to 5 miles (8 kilometers) over a 

few days in response to dewatering of habitat (Wylie et al. 1997) and more than 8 miles (12.9 

kilometers) of linear aquatic habitat over the course of a few months. Estimated home ranges in the 

Natomas Basin and Colusa NWR of snakes have averaged about 0.1 mile (25 hectares) in both the 

Natomas Basin and the Colusa NWR (Wylie 1998a; Wylie et al. 2002a; Wylie et al. 2002b). Home 

range estimates for giant garter snakes near the restored wetlands at Colusa NWR were generally 

smaller than previously found at the refuge when the lands were managed for waterfowl and in other 

off-refuge study areas (Wylie et al. 2000a). Wylie hypothesized that maintaining water in restored 

wetlands and nearby habitat provided sufficient conditions to meet the biological requirements of 

the giant garter snakes; individuals were less likely to move further distances as in previous years 
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 26

when conditions were drier and water was not maintained specifically to benefit giant garter snakes 

(Wylie et al. 2000a).

Factors Affecting the Snake within the Action Area

As noted in the Giant Garter Snake Five-year Review: Summary and Evaluation (Service 2012), the overall 

status of the snake has not improved since its listing. The Colusa Basin sub-population supports a 

better documented, relatively larger, and more stable snake sub-population (Wylie et al. 2004; Wylie 

and Martin 2004); its continued healthy persistence is, therefore, extremely valuable for survival and 

recovery of the snake. Yet, the Colusa Basin sub-population continues to be impacted by past and 

present Federal, State, private, and other human activities. 

Urban and commercial development results in direct habitat loss and also may expose snakes to 

secondary effects including water pollution from urban run-off and increased vehicular mortality, 

both of which act in concert with direct habitat loss and degradation to further threaten the snake. 

Although rice fields and agricultural waterways can provide valuable seasonal foraging and upland 

habitat for the snake, agricultural activities such as waterway maintenance, weed abatement, rodent 

control, and discharge of contaminants into wetlands and waterways can degrade snake habitat and 

increase the risk of snake mortality (Service 1993). On-going maintenance of agricultural waterways 

can also eliminate or prevent establishment of snake habitat, eliminate food resources for the snake, 

fragment existing habitat, and prevent dispersal of snakes (Service 1993). 

Flood control and maintenance activities which can result in snake mortality and degradation of 

habitat include levee construction, stream channelization, and rip-rapping of streams and canals 

(Service 1993). Flood control programs are administered by the U.S. Army Corps of Engineers 

(Corps) and the Corps has typically consulted on previous projects and is expected to continue to do 

so for future projects. The ongoing nature of these activities and the administration under various 

programs, however, makes it difficult to determine the continuing and cumulative effects of these 

activities. 

Other projects affecting the environment in and around the action area include transportation 

projects with Federal, county, or local involvement. The Federal Highway Administration and/or 

the Corps have consulted with the Service on the issuance of wetland fill permits for several 

transportation-related projects within basins that affected snake habitat. The direct effect of these 

projects is often small and localized, but the effects of transportation projects, which improve access 

and therefore indirectly affect snakes by facilitating further development of habitat in the area and 

by increasing snake mortality via vehicles, are not quantifiable. 

In the final rule listing snakes as threatened (October 20, 1993, 58 FR 54053), fluctuations in rice 

production and changes in water management including reduction in water availability due to 

drought and water transfers were cited as threats to the continued existence of the snake. The 

Service concluded that these factors in combination with other threats put the Butte, Colusa, and 

Sutter Basin populations of snakes at risk of moving from the status of threatened to endangered 

(all other areas were considered to be at risk of extirpation.) In addition, the Draft Recovery Plan for the 

Giant Garter Snake (Service 1999) considers the maintenance of rice cultivation to be important to 

the continued existence of the species. In addition to restoration of wetland habitat, the Draft 

Recovery Plan proposes recovery tasks to protect rice lands, to develop methods to assure water 

deliveries to support snakes, and promote maintenance of cropping patterns that benefit the snake. 
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 27

The Five-year Review concluded that by far the most serious threats to snakes continues to be loss 

and fragmentation of habitat from urban and agricultural development and loss of habitat associated 

with changes in rice production. Although some snakes have been discovered in several southern 

populations that were thought to be extirpated, these populations remain in danger of extirpation 

because their numbers remain very low and discontinuous, and they are located on isolated patches 

of limited quality habitat. Activities such as water management that are associated with habitat loss 

are also of particular concern because they exacerbate the losses from development and from loss of 

rice production. Populations range-wide are largely isolated from one another and from remaining 

suitable habitat. Without hydrologic links to suitable habitat during periods of drought, flooding, or 

diminished habitat quality, the snake’s status will decline (Service 2012).

Sacramento Valley populations of the snake depend on agricultural croplands, leaving them 

vulnerable to wide-scale habitat loss in the event of changes in agricultural management such as 

changes in crops or fallowing large areas of rice fields (Paquin et al. 2006). Long-term fallowing can 

reduce or eliminate habitat, yet short-term fallowing can ultimately improve rice agriculture and 

associated habitat components and sustain them over the long term while reducing chemical inputs 

and discharges (J. Roberts in litt. 2011, referenced in Service 2012). When rice fields are left out of 

production there is a substantial reduction or elimination in the use of the surrounding and nearby 

water conveyance structures by snakes where water supply is dependent upon surface or ground 

water from non-adjacent or on-site sources (Service 2012). Radio tracked snakes are known to leave 

previously occupied rice land sites when fallowing is continued for more than one season (Wylie 

pers. comm. 2008, E. Hansen 2008). If rice fields are planted with a rotation crop, especially one 

that is irrigated, essential habitat components for the snake may be maintained, and the long-term 

values may be enhanced if the rice crop is made more sustainable where it otherwise might be 

eliminated (Service 2012). Fallowing fields alternately in a ‘checkerboard’ pattern may minimize the 

impacts to snakes (Service in litt. 2008, referenced in Service 2012). 

Recent studies have concluded that snakes have adapted to the mosaic of seasonal wetlands and 

upland habitats that rice cultivation mimics, and use flooded rice fields for foraging, and irrigation 

dikes for basking sites (Service 2012). Regular long-term water transfers have the potential to reduce 

significantly the amount of rice lands and the temporary and artificial wetlands they produce (Service 

2012). Impacts may be especially severe in those areas adjacent to State and Federal wildlife refuges 

which may function as the core habitat to lead recovery efforts (Service 2012). 

Habitat degradation or alteration that benefits non-native species may increase the vulnerability of 

snakes to predation. Introduced game fish such as largemouth bass (Micropterus salmoides) and catfish 

(Ictalurus species) prey upon snakes and have been responsible for eliminating many species of native 

fishes and aquatic vertebrates in the western United States (Service 2012). Brood areas free of 

predatory fish may be important in that these areas allow juvenile snakes to grow large enough to 

avoid predation by game fish (G. Hansen pers. comm. 1998). Introduced predatory fish may also 

compete with snakes for smaller forage fish (G. Hansen 1986, 1992). G. Hansen (1986) observed

that nearly all snakes captured and examined showed scars or recent injuries, presumably acquired 

during attacks by predators. R. Hansen (1980) concluded that the abundance and diversity of 

predators suggested that predation pressure probably is severe. However, predation is not believed 

to be a limiting factor in areas that provide abundant cover, high concentrations of prey items, and 

connectivity to a permanent water source (Wylie et al. 1997).
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 28

Past Water Transfer Programs

Reclamation and DWR facilitated similar transfers in water years 2009 through 2014 (see Table 7). 

For 2010 and 2011 water transfers, the Service issued a biological opinion on these transfer program 

for effects on the snake. Only federal, CVP-related, water transfers were considered in the 

biological opinion and corresponding Environmental Assessment and Finding of No Significant 

Impact in 2010 and 2011. In 2012, Reclamation did not receive any ‘north to south’ water transfer 

proposals, and in 2013, only water made available via groundwater substitution was transferred. 

Since these 2013 transfers were made available by pumping groundwater, no effect on snakes or 

snake habitat was expected (Reclamation 2014a). In 2014, Reclamation completed a biological 

assessment and the Service issued a biological opinion for effects on the snake from proposed 

cropland idling as part of 2014 water transfers (Service 2014). 

Table 7 Water Transfer Quantities 2009 to 2014 (AF) and Acreage of Rice Fallowed

Water Year

Actual Water Made Available (AF)

Crop Idling Groundwater 

Substitution

Acreage of Rice Fallowed

2009 21,045 58,881 5,946

2010 0 0 0

2011 0 0 0

2012 No Reclamation 

Water Transfers 

Proposed

No Reclamation Water 

Transfers Proposed

No Reclamation Water 

Transfers Proposed

2013 0 31,406 0

2014 40,650 10,289 15,694

Source: Reclamation 2014a, D. Cordova pers. comm. 2015 and B. Hubbard pers. comm. 2015

During the 2014 transfer season, Reclamation conducted monitoring in compliance with the 

Endangered Species Consultation on the Bureau of Reclamation’s Proposed Central Valley Project 2014 Water 

Transfers (2014 Biological Opinion). During the 2014 transfer season, 23,120.3 acres within five 

water districts were idled under the program. During the transfer season, Reclamation personnel 

monitored transfer acreage for compliance with the conservation measures of the 2014 Biological 

Opinion. Monitoring confirmed that all transfers were conducted in compliance with the 2014 

Biological Opinion (Reclamation 2014a).

Effects of the Action

The proposed project will result in fallowing a maximum of 60,693 acres of rice land each year for 

10 years if the full amount of 224,583 AF of surface water is transferred as a result of cropland

idling/crop shifting. Maximum fallowing as a result of the proposed project would be 

approximately 12.3% (60,693/492,088) of the average annual rice acreage grown in the Sacramento 

Valley from 1992 to 2012. This reduction in habitat will likely result in increased stress on snakes 

that must disperse further to find suitable habitat, a likely reduction in prey base due to less available 

habitat, the potential displacement of individual snakes, increased risk of predation on snakes, and 

the potential for reduced reproduction and recruitment. All of these factors may result in the loss of 

individual snakes through increased mortality or reduced or forgone reproduction by snakes in 

affected areas. However, Reclamation has proposed a conservation strategy that will maintain 

important snake habitat throughout the program area. Areas with known priority snake habitat 

adjacent to naturalized lands and wildlife refuges and corridors between these areas will not be 

available for transfer, ensuring that these areas are protected and that suitable habitat will be 

available to the snake.
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 29

The draft Recovery Plan for giant garter snakes concluded that maintenance of rice cultivation is 

important to the continued existence of the species. In addition, the draft Recovery Plan proposes 

recovery tasks to protect rice lands, to develop methods to assure water deliveries to support snakes, 

and to develop programs to promote maintenance of historic cropping patterns that benefit the 

snake (Service 1999). As was noted in the Drought Water Bank and Environmental Water Account 

biological opinions (Service File Nos. 08-F-1596-1 and 03-F-0321, respectfully), fallowing of rice 

fields reduces the amount and availability of habitat, including summer water for the snake. 

The proposed idling or crop shifting of up to 60,693 acres of rice fields to alternate crops which 

would occur in the action area will reduce the availability of consistently available wetland areas, 

including ricelands and canals/ditches, available each year which are important to snake populations. 

The importance of consistently available wetlands was reported in the 2005 Monitoring Report for 

the Colusa NWR that concluded that, “The management of the Colusa Refuge for snakes, which 

began with the restoration of Tract 24, has clearly benefitted the snakes in the restored wetlands and 

other habitats by maintaining and increasing stable summer water habitats for the snakes, 

maintaining connectivity among wetland habitats and carefully managing marsh vegetation.” (Wylie 

et al 2005).

The proposed idling or shifting to alternate crops of up to 60,693 acres of rice fields within the 

action area may reduce foraging success for snakes that have left their home range in search of 

shallow summer aquatic habitat due to lack of familiarity with the area, increased foraging effort 

because of more widely dispersed prey resources, increased competition for prey items with resident 

snakes or other displaced snakes, and reduced prey resources that are also dependent on rice land 

habitats. Effects associated with reduced available summer water and rice field habitat also include 

displacement of individual snakes from familiar habitat areas and result in snakes foraging over a 

wider area. Snakes may move to other areas of suitable habitat, but will encounter increased 

mortality from vehicles, exposure to temperature extremes, predation, and human disturbance while 

migrating to new areas. Dispersing snakes or snakes using a larger foraging area may displace 

resident snakes or compete for food and shelter resources with resident snakes. This will result in 

reduced survivorship and fecundity of both resident and immigrant snakes. Fallowing will also 

result in reduced prey availability by reducing the acreage of flooded rice fields which act as seasonal 

marshes in producing high numbers of tadpoles, frogs and mosquitofish for the snake to feed on (E. 

Hansen 2008, pers. comm.).

Repeated episodes of fallowing riceland may also result in reduced survivorship or fecundity when 

females are displaced from familiar retreats and basking sites. Abundant food resources are also 

essential for females to both recover body mass after giving birth and to survive the overwintering 

period when the snakes do not forage, and for young snakes which rely on smaller prey items most 

typical of rice fields. Fallowing rice fields will not only temporarily remove suitable habitat, but may 

adversely affect reproduction, recruitment, and survival of snakes. The Service estimates a 

generation time of about five years for snakes to reach maturity (D. Kelly, pers. comm. 2015).

Adverse effects from the proposed idling or shifting to alternate crops of up to 60,693 acres of rice 

fields within the action area may be greatest for juvenile snakes due to the loss of rice fields and 

wetland areas suitable for forage. Abundant food resources are also essential for females to both 

recover body mass after giving birth and to survive the overwintering period when the snakes do not 

forage. Abundant food resources are also essential to the survival of juveniles and neonates. Snakes 

typically double their weight in the first year, with rapid growth likely necessary to reach a size class 

no longer susceptible to predation by non-native predatory fish and bullfrogs. Small prey items are 

particularly important to snakes that are less than two years old because they physically cannot feed 

on larger items. Lack of small prey would inhibit growth and result in delayed sexual maturation of 
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 30

snakes, resulting in decreased births and recruitment of individuals into the population, potentially 

skewing the age structure of the population to older snakes. Juveniles and neonates also rely on 

developing sufficient body mass prior to overwintering in order to survive long periods without 

foraging. 

The proposed idling or shifting to alternate crops of up to 60,693 acres of rice fields within the 

action area may result in an increased risk of predation on individual snakes when they leave a 

fallowed field in search of a suitable location after emerging from overwintering. Rice fields provide 

cover for snakes to escape predators. Ditches, canals, and other agricultural conveyances typically 

provide limited cover in the form of emergent vegetation. Predators such as large fish, egrets, and 

herons are more prevalent in ditches and canals and are known to prey on snakes.

To the extent that reducing the available habitat can affect the likelihood of survival and 

reproduction of individual snakes if individuals are unable to assimilate in to remaining suitable 

habitat, this occurrence on a large scale may have population-level effects, particularly if the quantity 

of available habitat is reduced persistently, over time, or undergoes annual fluctuations of high 

magnitude. Should this occur, it can affect the population beyond the duration of the proposed 

project. Fallowing of land appears to reduce or eliminate snake capture success in adjacent canals 

(Wylie et al. 2004). It is unknown to what extent snakes will successfully relocate and assimilate into 

adjacent or nearby habitat when rice lands are fallowed. Trapping efforts in the “Snake Alley” area 

of the Natomas Basin have resulted in fewer snakes being trapped in years when much of the rice 

fields in this area were fallowed (E. Hansen, pers. comm. 2008). Habitat conditions in “Snake 

Alley” are similar to what is found in much of the action area in the Sacramento Valley; that is a 

matrix of agricultural fields and canals and ditches. Snakes can move considerable distances in days 

or months when resources are limited, suggesting that adult snakes may disperse widely in search of 

shallow summer aquatic habitat, such as rice, if it is not available when they emerge from 

overwintering. However, the time and effort that is expended even travelling relatively short 

distances to find suitable aquatic habitat may reduce the fecundity of female snakes who would 

otherwise be expending that effort on breeding, feeding, and other essential life functions (G. Wylie, 

pers. comm. 2008). In addition, snakes exhibit some level of site fidelity, despite their fairly large 

range (E. Hansen, pers. comm. 2008); suggesting that fallowing their habitat would result in 

additional stress on individual snakes.

The proposed conservation strategy ensures that most or all canals and waterways, which make up a 

portion of snake aquatic habitat, will remain wetted during the summer months, thereby providing 

refuge to snakes. The conservation measures, as proposed by Reclamation, will minimize the effects 

of the proposed project by providing assurances that in specific high priority snake habitat areas, as 

shown in Attachment A, conservation measures will be implemented. In other areas where high 

quality snake habitat exists and snakes are known to occursellers will be required to maintain habitat 

features (ditches, drains, conveyance structures, etc.) in an aquatic condition that can be used by 

snakes, thus providing habitat across the action area.

These measures were developed using the best available science on snake biology, habitat use and 

suitability, and known occurrences (Halstead et al 2013, Halstead 2010). The measures focus 

conservation in the most important areas for snakes, considering high quality habitat and known use 

by snakes. One of the main goals is to maintain water in canals and ditches known to be suitable for 

snakes and that represent 85% of the known snake occurrence (USFWS 2014). Maintaining water in 

drains and conveyance structures in these areas will also maintain emergent cover for snake foraging 

and escape habitat over the action area. Other measures, implemented during water conveyance 

structure maintenance, will also be important minimization measures and include cleaning only one 
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 31

side of the conveyance channel per year and when mowing allowing sufficient remaining vegetation 

to avoid direct mortality to snakes. 

Implementation of these conservation measures is expected to reduce the severity of some of the 

adverse effects described previously, such as loss or reduction of consistently available wetted areas 

and isolation of snakes in islands of idled cropland with no movement corridor to enable them to 

leave the area. By requiring crop idling/substitution to occur away from high priority habitat and 

areas with high likelihood of snake occurrence, and by maintaining movement corridors for snakes 

in areas where crop idling occurs, it is expected that snakes will be able to reach suitable habitat 

despite drying due to crop idling. However, there is some uncertainty that snakes will respond as 

anticipated, that the areas identified as priority habitat are sufficiently well distributed or have the 

capacity to maintain a large proportion of the resident snake population. These expected responses, 

while supported by science, have not been validated by monitoring. The adaptive approach 

proposed by Reclamation is important to address this uncertainty and enable Reclamation to work 

with the Service, CDFW, and snake researchers to adapt the program as new scientific information 

becomes available.

Cumulative Effects

Cumulative effects include the effects of future State, Tribal, local or private actions that are 

reasonably certain to occur in the action area considered in this biological opinion. Future Federal 

actions that are unrelated to the proposed action are not considered in this section because they 

require separate consultation pursuant to section 7 of the Act. 

Water transfers may also be made by other water contractors not included in the proposed project

considered in this biological opinion. It is estimated that up to about 86,940 AF of water could be 

made available from SWP sellers via cropland idling/crop shifting (D. Cordova pers. comm. 2015). 

After rice is harvested, fields can be flooded in the late summer to the early winter period to aid in 

the decomposition of the remaining vegetative material (rice straw). These flooded fields can 

provide important foraging and rearing habitat for snakes (Sterling and Buttner 2011). The acreage 

of rice straw decomposition is not formally tracked but some estimates have been made in recent 

years (2007 to current) and range from 270,000 acres (Miller et al 2010) and 357,000 acres on the 

high end (D. Frisk pers. comm. 2015, R. Grimes pers. comm. 2015 and Service 2006) to 100,000 

acres on the low end (D. Frisk pers. comm. 2015). It is possible that fewer acres will be flooded for 

rice straw decomposition as fewer acres of rice is grown because of decreased water allocations, 

decreased availability of groundwater, and changing market conditions for rice. 

Conclusion

After reviewing the current status of the snake, environmental baseline for the action area, effects of 

the proposed project, cumulative effects, and proposed conservation measures, it is the Service’s 

biological opinion that the Long-term Water Transfers (2015-2024) as proposed, are not likely to 

jeopardize the continued existence of the snake.

The proposed project will likely result in the loss of an unknown number of snakes as a result of 

increased mortality from temporal loss of habitat, increased competition for resources, reduced 

reproductive rates, and increased mortality from predation. We expect that crop idling and shifting 

will temporarily remove suitable snake habitat and may also reduce reproduction, recruitment, and 

survival of the snakes and these effects will extend beyond the project time frame.
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 32

However, Reclamation is implementing a comprehensive conservation strategy that is based on 

recent research that focuses on maintaining suitable habitat conditions in priority areas throughout 

the action area. Water will be maintained in areas most important to snakes and water will not be 

transferred from priority conservation areas (e.g., Natomas). In addition, Reclamation will identify 

where idling has occurred, collect and verify habitat conditions, synthesize species data and 

implement adaptive management measures to assure effective implementation of the conservation 

measures.

INCIDENTAL TAKE STATEMENT

Section 9 of the Act and Federal regulation pursuant to section 4(d) of the Act prohibit the take of 

endangered and threatened species, respectively, without special exemption. Take is defined as 

harass, harm, pursue, hunt, shoot, wound, kill, trap, capture or collect, or to attempt to engage in any 

such conduct. Harass is defined by FWS regulations at 50 CFR 17.3 as an intentional or negligent 

act or omission which creates the likelihood of injury to a listed species by annoying it to such an 

extent as to significantly disrupt normal behavioral patterns which include, but are not limited to, 

breeding, feeding, or sheltering. Harm is defined by the same regulations as an act which actually 

kills or injures wildlife. Harm is further defined to include significant habitat modification or 

degradation that results in death or injury to listed species by significantly impairing essential 

behavioral patterns, including breeding, feeding, or sheltering. Incidental take is defined as take that 

is incidental to, and not the purpose of, the carrying out of an otherwise lawful activity. Under the 

terms of section 7(b)(4) and section 7(o)(2), taking that is incidental to and not intended as part of 

the agency action is not considered to be prohibited taking under the Act provided that such taking 

is in compliance with this Incidental Take Statement. This incidental take statement does not 

authorize any incidental take of listed species resulting from related actions that are not part of or 

controllable by Reclamation, long-term water transfer water sellers, or long-term water transfer 

water purchasers, and that are not included in the project description of this biological opinion.

The measures described below are non-discretionary, and must be implemented by Reclamation so 

that they become binding conditions of any agreement, contract, grant or permit issued to the 

applicant, as appropriate, in order for the exemption in section 7(o)(2) to apply. Reclamation has a 

continuing duty to regulate the activity covered by this incidental take statement. If Reclamation (1) 

fails to assume and implement the terms and conditions or (2) fails to require the applicant to adhere 

to the terms and conditions of the incidental take statement through enforceable terms that are 

added to any agreement, contract, permit, or grant document, the protective coverage of section 

7(o)(2) may lapse. In order to monitor the impact of incidental take, Reclamation must report the 

progress of the action and its impact on the snake to the Service as specified in the incidental take 

statement [50 CFR §402.14(i)(3)].

Amount or Extent of Take for 2015

The Service anticipates incidental take of snakes will occur. The Service is unable to quantify an 

exact number of snakes that will be taken as a result of the proposed action because it is impossible 

to know how many individuals may be present in the action area. Since take is expected to result 

from effects to habitat, the quantification of habitat affected becomes a direct surrogate for the 

species that will be taken. Snakes are secretive and sensitive to human activities and individual 

snakes are difficult to detect unless they are observed, undisturbed, at a distance. Adverse effects to 

snakes are additionally difficult to quantify due to seasonal fluctuations in their numbers, random 

environmental events, or additional environmental disturbances. In instances in which the total 

number of individuals anticipated to be taken cannot be determined, the Service may use the 

amount of habitat impacted as a surrogate. Since the take of individuals anticipated will result from 
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 33

the acreage of cropland idled by the proposed action, the quantification of habitat lost as a result of 

the proposed action serves as a direct surrogate for the snakes that will be lost.

Based on our analysis presented in the Environmental Baseline and Effects of the Proposed Action sections, 

which describe how the majority of the action area, both under current and proposed land 

management, is considered to be snake habitat, we anticipate that snakes are likely to be exposed to 

adverse effects from the proposed rice field fallowing and crop shifting. The incidental take is 

expected to be in the form of harm as displaced snakes may be taken by predators or may die or 

suffer reproductive failure if they cannot successfully relocate and utilize suitable habitat on or 

adjacent to a field fallowed as a result of implementation of this water transfer program in 2015 in 

and around the 60,693 acres of rice fields that are idled or have alternative crops. 

The proposed fallowing or crop shifting on up to 60,693 acres of rice fields in 2015 will result in the 

loss of an undetermined number of individual snakes through increased mortality levels of adults 

and juveniles due to decreased prey availability and/or reduced reproduction by snakes, and 

mortality of snakes that may move out of areas subject to crop idling and shifting due to predation

Effect of the Take

In the accompanying biological opinion, the Service has determined that the level of anticipated take 

is not likely to result in jeopardy to the snake because the conservation measures, as proposed by 

Reclamation, will minimize the effects of the proposed project by providing assurances that transfers 

will not occur in areas where high quality snake habitat exists and snakes are known to occur, and 

sellers will be required to maintain habitat features (ditches, drains, canals, etc.) in a condition that 

can be used by snakes, thus providing habitat across the action area. In addition, Reclamation has 

proposed an adaptive approach to the water transfer program so that information collected through 

monitoring and research will be reviewed annually with the wildlife agencies and giant garter snake 

scientists. This approach will enable Reclamation to make adjustments to snake conservation 

measures prior to finalizing each annual transfer program.

Reasonable and Prudent Measures

Measures to avoid or minimize effects on the snake resulting from implementing long-term water 

transfers have been incorporated into the proposed project’s conservation measures. Therefore, the 

Service believes the following Reasonable and Prudent Measure is necessary and appropriate to 

minimize incidental take of the snake:

1. Subject to adaptive management as described below, all conservation measures, as described in 

the revised biological assessment and restated here in the Project Description section of this 

biological opinion, shall be fully implemented, adhered to and validated as to their 

effectiveness. Further, this Reasonable and Prudent Measure shall be supplemented by the Terms 

and Conditions below.

Terms and Conditions

In order to be exempt from the prohibitions of section 9 of the Act, Reclamation must ensure

compliance with the following terms and conditions, which implement the Reasonable and Prudent 

Measure described above. These terms and conditions are nondiscretionary.

1. For lands where cropland idling or crop shifting will occur, Reclamation shall condition the 

contracts between them and potential water sellers to include the conservation measures contained 

in the project description and the terms and conditions including access by Reclamation and Service 

personnel to said lands to validate their implementation.

2. No later than December 31, 2015, Reclamation shall submit to the Service a supplement to the 
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 34

conservation measures which will establish performance measures and metrics to evaluate their 

effectiveness. This supplement shall identify the data needed to produce estimates of change or 

trends in snake reproduction, numbers, and distribution in the action area.

3. Reclamation shall submit a compliance report to the Service’s Sacramento Fish and Wildlife 

Office sixty (60) calendar days following water transfer contract execution each year. This report 

shall detail (i) acreage and location of seller’s parcels affected by crop idling/crop substitution and 

maps of where the cropland idling or cropland shifting occurred; (ii) confirmation that, where 

appropriate, water levels are being maintained in ditches around affected fields; (iii) occurrences of 

incidental take of any snakes including an updated occurrence map based on the most recent data 

available; (iv) an explanation of failure to meet such measures, if any; and (v) other pertinent 

information. GIS shape files of the parcels that were fallowed will be in projected coordinate system 

NAD 1983 Zone 10 N.

4. At the end of each water transfer year, Reclamation will submit to the Service a monitoring 

report that contains the following: (i) maps and GIS shape files of all cropland idling or cropland 

shifting actions that occurred within the range of potential transfer activities affected under this 

program; (ii) results of current scientific research and monitoring pertinent to water transfer actions;

(iii) a discussion of conversation measure effectiveness; (iv) maps and GIS shape files indicating 

where rice was grown; (v) results of annual snake monitoring; (vi) snake detections; (vii) a 

cumulative history of the location and extent of crop idling/crop shifting; and (viii) report on water 

districts/sellers participation in voluntary best management practices. GIS shape files of the parcels 

that were fallowed will be in projected coordinate system NAD 1983 Zone 10 N. The report will 

be submitted to the Service no later than January 31 following each transfer year. Reclamation and 

the Service will establish annual meetings no later than February 28 of each year to discuss the 

contents and findings of the annual report and develop additional conservation measures if 

necessary.

Reporting Requirements

For water transfers in years 2016-2024 (including multi-year transfers) Reclamation will prepare a 

description of the proposed action for the calendar year (sellers/buyers, conservation measures, 

etc.), provide detailed monitoring reports for the previous years actions, and submit this information 

to the Service no later than January 31 of each year. By February 28 of each year, the Service will 

review the description of the proposed action and monitoring reports and meet with Reclamation 

regarding the proposed action. The annual monitoring reports will include detailed information in 

the action area (narrative and GIS spatial analysis) on implementation of the conservation measures, 

land idling/fallowing, hydrologic conditions, presence/absence/not found surveys for the snake, 

recent reports prepared on the snake, and any other information that is relevant to snake impacts 

and conservation.

CONSERVATION RECOMMENDATIONS

Section 7(a)(1) of the Act directs Federal agencies to utilize their authorities to further the purposes 

of the Act by carrying out conservation programs for the benefit of endangered and threatened 

species. Conservation recommendations are discretionary agency activities to minimize or avoid 

adverse effects of a proposed action on listed species or critical habitat, to help implement recovery 

plans, or to develop information. The Service recommends the following actions:

1. Reclamation should assist the Service in implementing recovery actions identified in the 

Draft Recovery Plan for the Giant Garter Snake (Service 1999) or any final recovery plan for the 

giant garter snake issued during the transfer action.
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 35

2. Reclamation should work with the Service, DWR, and water contractors to investigate the 

long-term response of snake individuals and local populations to annual fluctuations in 

habitat from fallowing rice fields. 

3. Reclamation should support the research goals of the Giant Garter Snake Monitoring and 

Research Strategy for the Sacramento Valley proposed in the project description of this 

biological opinion. 

4. Reclamation should work with the Service to create and restore additional stable perennial 

wetland habitat for snakes in the Sacramento Valley so that they are less vulnerable to 

market-driven fluctuations in rice production. The CVPIA (b)(1) other and CVPCP 

conservation grant programs would be appropriate for such work.

In order for the Service to be kept informed of actions minimizing or avoiding adverse effects or 

benefiting listed species or their habitats, the Service requests notification of the implementation of 

any conservation recommendations.

REINITIATION - CLOSING STATEMENT

This concludes formal consultation on the long-term water transfers from 2015 to 2024. As 

provided in 50 CFR §402.16, reinitiation of formal consultation is required and shall be requested by 

the Federal agency or by the Service where discretionary Federal agency involvement or control over 

the action has been retained or is authorized by law and: 

(a) If the amount or extent of taking specified in the incidental take statement is exceeded; 

(b) If new information reveals effects of the action that may affect listed species or critical 

habitat in a manner or to an extent not previously considered; 

(c) If the identified action is subsequently modified in a manner that causes an effect to the listed 

species or critical habitat that was not considered in the biological opinion; or 

(d) If a new species is listed or critical habitat designated that may be affected by the identified 

action. 

If you have any questions regarding this biological opinion, please contact Ken Sanchez at the 

letterhead address or (916) 414-6600.

cc:

California Department of Fish and Wildlife, Paul Forsberg, Sacramento, CA 

National Marine Fisheries Service, Bruce Oppenheim, Sacramento, CA 

California Department of Water Resources, Tom Filler, Sacramento, CA

Bureau of Reclamation, Russ Grimes, Brad Hubbard, Dan Cordova, Sacramento, CA

Attachment

GGS Priority Habitat Maps
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 36

LITERATURE CITED

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6, 2014. Available from http://www.water.ca.gov/watertransfers/ .

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_____.2010. Habitat Suitability and Conservation of the Giant Gartersnake (Thampnophis gigas) in the 

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_____.2003a. Year 2002 investigations of the giant garter snake (Thamnophis gigas) in the Middle 

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Area Flood Control Agency by Eric Hansen. February 28, 2006.
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 37

_____. 2007a. Results of year 2006 giant garter snake (Thamnophis gigas) surveys at the proposed 

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snake (Thamnophis gigas) – continuing surveys in Merced County, CA, with an extension to 

northern Fresno County. Prepared for the U.S. Fish and Wildlife Service by Eric Hansen. 

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Hansen. Dated January 1, 2009.

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Preserve. Final report submitted to the CVPCP/HRP. December 29, 2010.

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Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 38

Paquin, Melanie M, G.D. Wylie & E.J. Routman. 2006. Population structure of the giant garter 

snake, Thamnophis gigas. Conservation Genetics (2006) 7:25-36. 12 pp.

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report, U.S. Geological Survey, Biological Resources Division. 
Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 39

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Basin: 1998-1999. Unpublished report. U.S. Geological Survey, Biological Resources 

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Anastasia Leigh, Regional Environmental Officer, Mid-Pacific Regional Office 41

ATTACHMENT A

GIANT GARTER SNAKE PRIORITY HABITAT MAPS