Description
ESFAFC
High water in the Kuskokwim River region will continue over the next
few days. Conditions are expected to become favorable for water
levels to gradually recede over the weekend and into the middle of
next week.
Locations:
* Communities across the lower Kuskokwim River and its tributaries,
including, but not limited to: Kwethluk, Bethel, Oscarville,
Napaskiak, Napkiak, Kasigluk, Nunapitchuk, and Atmauluak.
Hydrologic Concerns:
* High water in the Kuskokwim and other area rivers (e.g. Kwethluk
River, Johnson River, etc) may inundate low-lying areas in the
aforementioned communities, nearby fish camps, and other lowlands.
Details/Analysis [What's causing this?]:
* Rainfall: The Kuskokwim River basin, from the mouth at Kuskokwim
Bay upstream to the headwaters in the Alaska Range and Kilbuck
Mountains, has received approximately 150 to 200 percent of normal
rainfall this summer (June to August). These rains have continued
into September, with nearly the entire basin near or exceeding 200
percent of rainfall, with much of that rainfall occurring over the
last few days.
* Persistent High Water: This heavy rainfall has resulted in
anomalously high water levels being routed down from the Upper
Kuskokwim to the Lower Kuskokwim. The river gages at McGrath and
Crooked Creek are near or exceeding record levels for this time of
year. The water levels at these stations have crested in the last
week, suggesting that the water inflow to the lower Kuskokwim
Communities may be on the decrease soon.
* Compounding Factors: In addition to the recent rainfall and
elevated river levels, strong coastal winds brought several feet of
surge to the coast, causing elevated water levels near the mouth of
the Kuskokwim River. This effectively reduces the slope of the
river, slowing drainage and resulting in water becoming backed up.
* Forecast Thoughts: A shift in the weather pattern will bring
conditions favorable for water levels to decrease. Northerly winds
will increase Saturday and continue into early next week to 20 to
30 kt, with higher gusts possible at times, and bring cooler and
drier air to the region. Precipitation will be sparse and generally
light. Additionally, tidal models indicate a slight negative surge
along the coast due to the multi-day period of strong northerly
winds, potentially assisting drainage of water from the lower
Kuskokwim River.
Look Ahead:
* After a period of weather conditions favorable for receding water,
confidence is growing that another strong Bering Sea storm will
affect western Alaska late next week (Sept 23-26). A return to
southerly winds and higher coastal water in conjunction to heavy
rainfall may exacerbate river conditions once again, particularly
on the smaller tributaries such as the Kwethluk and Johnson Rivers.
However, details remain uncertain at this time as confidence is low
in storm track and intensity. Fortunately, natural tidal cycles in
Bethel and the rest of the lower Kuskokwim favor lower tides than
usual for this timeframe which may offset any additional water or
surge.