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Article from Arizona Water News: Historically Dry Winter Means Lake Mead May Be Closer To Shortfall

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Waterbaby

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Staff member
NOAA report said La Nina is weakening and we *may* return to Enso Neutral - I suspect not in time to save this year, however. Perhaps we will get at least some rain this summer - provided NOAA is accurate.
 

Waterbaby

Moderator
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Waterbaby, is there any chance they might do a Grand Canyon "flush" to add water to Lake Mead?

I don't think so, though it appears they plan to release 9.0 instead of the 8.23maf - so they are going to draw down Powell to help Mead even with no snow in the mountains to fee Powell --- see the snip below from the USBR February 2018 forecast for Lake Powell:

Inflow Forecasts and Model Projections

The April to July 2018 water supply forecast for unregulated inflow to Lake Powell, issued on February 2, 2018, by the Colorado Basin River Forecast Center, projects that the most probable (median) unregulated inflow volume will be 3.4 maf (47 percent of average based on the period 1981-2010). The projected water year 2018 inflow is 6.1 maf (56 percent of average). At this early point in the season, there is still significant uncertainty regarding this year’s water supply. The April-July forecast ranges from a minimum probable of 2.11 maf (29 percent of average) to a maximum probable of 6.5 maf (90 percent of average). There is a 10 percent chance that inflows could be higher than the current maximum probable forecast and a 10 percent chance that inflows could be lower than the minimum probable forecast.

Based on the current forecast, the February 24-Month Study projects Lake Powell elevation will end water year 2018 near 3,603 feet with approximately 12.0 maf in storage (49 percent of capacity). Note that projections of elevation and storage for water year 2018 have significant uncertainty at this point in the season. Projections of elevation and storage using the minimum and maximum probable inflow forecast, updated in January, are 3,591 feet (10.9 maf, 45 percent of capacity) and 3,628 feet (14.7 maf, 60 percent of capacity), respectively. Under these scenarios, there is a 10 percent chance that inflows will be higher, resulting in higher elevation and storage, and 10 percent chance that inflows will be lower, potentially in lower elevation and storage. The annual release volume from Lake Powell during water year 2018 is projected to be 9.0 maf under the minimum, most, and maximum probable inflow scenarios. There is a chance that inflows could be higher or lower, potentially resulting in releases greater than 9.0 maf or as low as 8.23 maf in water year 2018. The minimum and maximum probable scenarios will be updated again in April.

Upper Colorado River Basin Hydrology

The Upper Colorado River Basin regularly experiences significant year to year hydrologic variability. During the 18-year period 2000 to 2017, however, the unregulated inflow to Lake Powell, which is a good measure of hydrologic conditions in the Colorado River Basin, was above average in only 4 out of the past 18 years. The period 2000-2017 is the lowest 18-year period since the closure of Glen Canyon Dam in 1963, with an average unregulated inflow of 8.76 maf, or 81percent of the 30-year average (1981-2010). (For comparison, the 1981-2010 total water year average is 10.83 maf.) The unregulated inflow during the 2000-2017 period has ranged from a low of 2.64 maf (24 percent of average) in water year 2002 to a high of 15.97 maf (147 percent of average) in water year 2011. In water year 2017 unregulated inflow volume to Lake Powell was 11.9 maf (110 percent of average), the fourth year to be above average. Under the current most probable forecast, the total water year 2018 unregulated inflow to Lake Powell is projected to be 6.1 maf (56 percent of average).

At the beginning of water year 2018, total system storage in the Colorado River Basin was 32.9 maf (55 percent of 59.6 maf total system capacity). This is an increase of 2.7 maf over the total storage at the beginning of water year 2017 when total system storage was 30.2 maf (51 percent of capacity). Since the beginning of water year 2000, total Colorado Basin storage has experienced year to year increases and decreases in response to wet and dry hydrology, ranging from a high of 94 percent of capacity at the beginning of 2000 to a low of 50 percent of capacity at the beginning of water year 2005. One wet year can significantly increase total system reservoir storage, just as persistent dry years can draw down the system storage. Based on current inflow forecasts, the current projected end of water year total Colorado Basin reservoir storage for water year 2018 is approximately 29.3 maf (49 percent of total system capacity). The actual end of water year 2018 system storage may vary from this projection, primarily due to uncertainty regarding this season’s runoff and reservoir inflow. Based on the January minimum and maximum probable inflow forecasts and modeling, the range of end of water year 2018 total system capacity is approximately 28.0 maf (47 percent of capacity) to 32.7 maf (55 percent of capacity), respectively
 

Trix

Well-Known Member
Help may be on the way! Today's Weekly Planner at weather.com shows that the more normal storm track flowing in a more southerly direction toward the southern Rockies and hitting Colorado pretty good. Southern California also getting some relief.
https://weather.com/maps/planner
 
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