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Water Supply Outlook
National Weather Service Portland OR
400 PM PST Tuesday June 6 2023

...OREGON WATER SUPPLY SUMMARY AS OF JUNE 6TH 2023...

The water supply forecast for the summer of 2023 is above average
for almost all Oregon watersheds. Spring precipitation resulted in
major increases in streamflow and reservoir storage statewide,
especially for central and eastern Oregon, areas previously impacted
by multi-year drought.

Precipitation so far this water year (Oct 2022 - May 2023) is
slightly below average for the Cascades, along with most of western
and north-central Oregon. Water year precipitation is above average
for eastern, central, and portions of southwest Oregon. Spring
precipitation, March through May, was notably above average for most
of Oregon, helping to boost mountain snowpack and spring and summer
water supply volumes.

Despite recent improvements, drought impacts remain for portions of
the state. Drought declarations from the Oregon Governor`s Office
are in effect for Crook, Deschutes, Grant, Harney, Jefferson, Lake,
Sherman and Wasco counties.

Refer to the sections below and links provided for details regarding
precipitation, temperatures, seasonal climate outlooks, reservoirs,
streamflow, and water supply forecasts.

This is the final water supply summary of the season. Updates will
resume in January 2024.

PRECIPITATION AND TEMPERATURES ACROSS OREGON

Precipitation for the 2023 water year thus far (Oct 2022 - May 2023)
ranges from 70 to 110 percent of average in Oregon, with most of the
state being below average. However, spring precipitation, March
through May, was above average for most of the state and resulted in
major increases in streamflow, reservoir storage, and summer water
supply forecasts. Temperatures through most of the winter and spring
were below average.

May precipitation was above average for central and eastern Oregon
and below average for western and northern Oregon. May temperatures
were 1 to 3 degrees above average, with periods of hot weather in
mid and late May.

Details on precipitation and temperatures:

NOAA NWS - Northwest River Forecast Center
www.nwrfc.noaa.gov/water_supply/wy_summary/wy_summary.php

NOAA NWS - California-Nevada River Forecast Center (Klamath basin)
www.cnrfc.noaa.gov/water_resources_update.php

Westwide Drought Tracker Precipitation & Temperature graphics
wrcc.dri.edu/wwdt/index.php?region=or SNOWPACK ACROSS OREGON

PRECIPITATION AND TEMPERATURE OUTLOOK

The Climate Prediction Center produces monthly and seasonal
outlooks, in which there is a weighing of the odds of near normal,
above normal, or below normal temperatures and precipitation.

The June outlook shows an enhanced likelihood of above-average
temperatures, especially for the northern half of Oregon. The
outlook also shows a slightly enhanced likelihood of above-average
precipitation for most of the state, especially for eastern Oregon.

The big message for the July through September outlook is an
enhanced likelihood of above-average temperatures. Precipitation
amounts during this time are typically not significant in terms of
water year totals and are likely to be a little below average.

Visit www.cpc.ncep.noaa.gov for more about seasonal outlooks.

RESERVOIRS

Reservoir storage increased greatly in April and May for most
irrigation reservoirs across the state. Several reservoirs that were
at or near record low storage in late winter are now full or near
full.

Owyhee Reservoir, the largest irrigation project in the state, had
observed storage on June 5th of about 571,000 acre-feet, an increase
of about 60,000 acre-feet from a month ago. This represents 80
percent of capacity and is 107 percent of average for this time of
year.

Reservoir data is provided by the Natural Resources Conservation
Service, the Bureau of Reclamation, and the US Army Corps of
Engineers.

Additional reservoir information:

www.nwd-wc.usace.army.mil/nwp/teacup/willamette/
www.usbr.gov/pn/hydromet/select.html www.wcc.nrcs.usda.gov/basin.html

OBSERVED STREAMFLOW

Observed runoff so far this water year has been above average for
southeast and central Oregon, near average for northeast Oregon
basins and western Oregon coastal watersheds, and below average
elsewhere.

Runoff in May was above average for most of the state but near-
average for much of western Oregon. Several rivers in central and
eastern Oregon had flooding due to rapid snowmelt along with periods
of rain.

Visit waterwatch.usgs.gov for details on observed streamflow. Runoff
data is also available at www.nwrfc.noaa.gov/natural/index.html at
water year and monthly time scales for several locations in Oregon.

WATER SUPPLY SEASONAL FORECASTS

Water supply forecasts for April-September runoff volume are above
average for most Oregon watersheds, with only a smattering of near
or below average forecasts around the state. Forecasts are notably
high for central and east-central Oregon, ranging from 150 to 300
percent of average, and even higher for a few small watersheds.

The forecast for the Columbia River at The Dalles, which is a good
index of conditions across the Columbia Basin, is 90 percent of
average for April-September, an decrease of 3 percent from a month
ago.

Details on basin-scale water supply forecasts:

NOAA NWS - Northwest River Forecast Center www.nwrfc.noaa.gov/ws/

NOAA NWS - California-Nevada RFC Klamath basin)
www.cnrfc.noaa.gov/water_resources_update.php

USDA Natural Resources Conservation Service
www.wcc.nrcs.usda.gov/wsf/

$$