Snake River Wyoming Fishing Report

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Hello,

below is an update on the Bureau of Reclamation’s water operations in the upper Snake River watershed.

Thanks,
Brian

(Friday May 10, 2019)
Subject: 2019 Upper Snake River Operations Update

Purpose: The purpose of these Operation Updates is to provide information regarding Reclamation’s operations as the season progresses. The operations outlined in this update are based on the best data available at the time and are subject to change as new information becomes available. For additional information and resources, please visit our website at: https://www.usbr.gov/pn/hydromet/uppersnake/ .

Upcoming discharge changes

Milner Dam – a small amount of flow will be going by Milner Dam until Tuesday (5/14), on which date discharge at Milner Dam will go to 0 cfs. Decreased flow into the Milner pool will be stored in Lake Walcott in the short term.
· Current discharge today = 350 cfs.
· Tuesday (5/14) discharge will go to 0 cfs.

Summary

The Upper Snake reservoir system is currently 78% full (3,174,573 acre-feet out of 4,045,695 acre-feet).
The precipitation forecast for the next week looks light with some increased chances for locally varying totals next weekend 5/17-5/19. Temperatures are forecast to increase slowly over the next 5 days with a potential slight cool down late next week. Temperatures above 9,000 feet are forecasted to remain above freezing for the next 3-5 days before the forecasted cool down late next week.

Jackson Lake’s discharge was increased over the last 2 days to the current 3,000 cfs. Inflows are forecasted to increase at a fairly good rate over the next week. Outflow may be increased again next week so storage content can follow flood control requirements.

Palisades’ discharge is 12,000 cfs. This outflow is expected to stay constant into next week as the storage content tracks near the flood control requirements. Over the next week as inflows increase reservoir storage will be refilling along flood control requirements with a target of filling the reservoir in the mid- to late-June timeframe. Outflow is not expected to change soon until much higher inflows arrive in the last half of May.

Ririe’s discharge was increased to 150 cfs yesterday to manage the fill rate of the reservoir. The reservoir is anticipated to fill in the next few weeks. At that time discharge will be adjusted to pass approximately inflow levels.

Island Park’s discharge was decreased from 1,050 cfs to 950 cfs earlier this week. Outflow could change over the next few weeks to manage either wet or dry conditions to target approaching full in late May.

American Falls Reservoir’s discharge decreased from 14,000 cfs to the current 9,700 cfs this week to manage the fill of the reservoir. Outflow is not expected to change until the reservoir fills.

Minidoka’s discharge will decrease on Tuesday 5/14 to meet only irrigation demand downstream.

Milner Dam’s discharge is currently 350 cfs. Outflow will go to 0 cfs on Tuesday 5/14.

Little Wood Reservoir discharge has been slowly increasing over the last few days as the reservoir is within range of filling in the next few weeks. Additional small increases are likely next week to manage the fill rate of the reservoir.

Facility
% Full
Storage
(acre-feet)
May – July Runoff Forecast
% of Normal
Yesterday’s
Inflow
(cfs)
Estimated Outflow (cfs)
Next anticipated discharge change
Jackson Lake
77%
651,782
112%
2,580
3,000
Not scheduled
Palisades
51%
608,802
107%
12,800
12,000
Not scheduled
Ririe
93%
75,041
110%
450
150
Not scheduled
Island Park
85%
114,401
109%
1,200
950
Not scheduled
Grassy Lake
92%
13,917
–
17
0
Not scheduled
American Falls
97%
1,618,357
–
10,000
9,700
Not scheduled
Minidoka
97%
92,273
–
9,990
7,400
Not scheduled
Milner
0.5 feet below full
–
8,700
350
*River QD
Decrease to 0 cfs Tue. 5/14
Little Wood
89%
26,683
118%
520
320
Not scheduled

Reservoir levels, reservoir discharge and river flows can be monitored on the USBR Hydromet page here: https://www.usbr.gov/pn/hydromet/

The Upper Snake “teacup” diagram which provides a graphical overview of system conditions can be accessed here: https://www.usbr.gov/pn/hydromet/burtea.html

image.png

—
Brian Stevens
Water Operations Manager
Upper Snake Field Office
Middle Snake Field Office
Bureau of Reclamation
470 22nd St.
Heyburn, ID 83336