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Water Supply Outlook
National Weather Service Portland OR
205 PM PST Thursday June 6 2024

...OREGON WATER SUPPLY SUMMARY AS OF JUNE 6TH 2024...

The water supply forecast for the summer of 2024 is near average for
most Oregon watersheds, with some notable exceptions. Water supply
forecasts are below average for far-northeast Oregon and some
watersheds in southwest and south-central Oregon. Water supply
forecasts are above average for most of southeast Oregon, including
the Owyhee basin. There were not major changes in seasonal water
supply forecasts compared to a month ago.

Precipitation so far this water year (Oct 2023 - May 2024) is near
average for most of the state but above average for far-southwest
and far-southeast Oregon and below average for south-central and far-
northeast Oregon. Temperatures for the water year thus far are above
average for most of Oregon except near-average for north-central and
southeast Oregon.

This is the last update for the season. Refer to the sections below
and links provided for additional details and updates through the
summer regarding precipitation, seasonal climate outlooks,
reservoirs, streamflow, and water supply forecasts.


PRECIPITATION AND TEMPERATURES ACROSS OREGON

Precipitation for the 2024 water year thus far (Oct 2023 - May 2024)
ranges from 80 to 110 percent of average in Oregon. The lowest
values relative to normal are in far-northeast Oregon and the
Klamath basin, and the highest are in southeast Oregon. May
precipitation was below average for south-central, southeast, and
far-northeast Oregon, above average for northwest and north-central
Oregon, and near normal elsewhere.

Temperatures for October through May were 1 to 3 degrees above
average for almost all of Oregon, except near normal for the
Columbia basin portion of north-central Oregon and much of southeast
Oregon. May temperatures were 1 to 5 degrees below normal statewide
except for near normal in far-southwest Oregon.

Details on precipitation and temperatures:

NOAA National Weather Service - 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

As of June 5, mountain snowpack is completely melted for all but a
few high elevation sites. Peak seasonal snowpack in the early spring
was generally near average statewide.

Additional snowpack information:

NOAA National Weather Service - Northwest River Forecast Center
www.nwrfc.noaa.gov/snow/

USDA Natural Resources Conservation Service
nwcc-apps.sc.egov.usda.gov/imap/


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.

ENSO conditions are ENSO neutral as of early summer and are likely
to transition to La Nina by autumn 2024. ENSO conditions have
minimal impact on summer conditions but will likely have a major
influence on the upcoming fall and winter.

The outlook for June through August is for an enhanced likelihood of
above-average temperatures and below-average precipitation
statewide.

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


RESERVOIRS

Reservoir storage for irrigation reservoirs across the state is
generally above average, with most reservoirs completely or mostly
filled as of early June. The main exceptions are reservoirs in
southwest Oregon, where reservoir storage ranges from 55 to 75
percent of capacity. Flood control reservoirs in western Oregon are
also completely or mostly filled as of early June.

Owyhee, located in southeast Oregon, is the largest irrigation
reservoir in the state. It has observed storage of about 713,000
acre-feet, which is 100 percent of capacity and 134 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
most watersheds statewide, particularly so for watersheds in central
and southweast Oregon. The only areas with below-average runoff are
south-central and far-northeast Oregon.

May runoff was generally near average statewide, except above
average for some watersheds in western Oregon and below average for
far-northeast and south-central Oregon.

Visit waterwatch.usgs.gov for details on observed streamflow. Runoff
data is 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 near to
below average for most of the state, except for above-average
forecasts for southeast Oregon watersheds.

The forecast for the Columbia River at The Dalles, which is a good
index of conditions across the Columbia Basin, is 77 percent of
average for April-September.

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/

$$