Engineers and operators have determined that an adequate amount of water has been released from Lake Granby, so we'll get back to filling the reservoir. We've kept the reservoir at lower levels to leave room for the finale of our forecasted runoff and to prevent the need for sudden large releases downstream.
We are going to decrease releases gradually, which limits environmental disruptions. We will cut flows back 200 cfs per day until we reach an outflow of 1,000 cfs, which will be early next week. Then we'll determine whether outflows should be reduced more.
With this reduction in releases, Lake Granby's elevation should begin to rise noticeably in the next week.
2011 RUNOFF UPDATE
Tuesday, June 28, 2011
Sunday, June 26, 2011
Record inflow on North Fork of Colorado River
Yesterday's flow of 995 cfs on the North Fork of the Colorado River broke an all-time record, according to records kept by the USGS since 1953.
The previous record was 976 cfs on June 30, 1957. As it turns out, we've been comparing this year's snowpack to 1957 for some time.
Our models suggest there's still plenty of gas in the tank in terms of snowpack, so record-level flows are likely to continue for another day or two.
The North Fork of the Colorado River discharges into Shadow Mountain Reservoir.
The previous record was 976 cfs on June 30, 1957. As it turns out, we've been comparing this year's snowpack to 1957 for some time.
Our models suggest there's still plenty of gas in the tank in terms of snowpack, so record-level flows are likely to continue for another day or two.
The North Fork of the Colorado River discharges into Shadow Mountain Reservoir.
Wednesday, June 22, 2011
Weekend forecast: Peaking rivers, some records
A cocktail of increased temperatures on top of big snowpack may swell area rivers over the weekend.
The Colorado Basin River Forecast Center recently put out a forecast expecting peaks on all of the high-elevation watersheds in their area this weekend. The center based its forecast on current cool temperatures, which have prevented snowmelt, along with predicted upcoming high temperatures that would kickstart more runoff.
If you had a bird's eye view, the CBRFC's forecast would have you seeing simultaneous peaks in several Upper Colorado basin rivers: the Fraser, Williams Fork, Upper Colorado into Granby, and Blue into Dillion.
The Colorado River at the Cameo gage (between De Beque and Palisade) may have its second peak, possibly higher than the one we saw June 7.
The center is most concerned about Northern Utah, Northwestern Colorado and Southwestern Wyoming. A few streams in Utah and Wyoming, for example, are expected to hit record flows. The forecast also stated that flooding is occurring and will likely continue to occur along rivers where there's still high-elevation snow.
The CBRFC does not forecast Northern Water's East Slope tributaries, but we expect the climate to have similar effects on our snowpack.
The Colorado Basin River Forecast Center recently put out a forecast expecting peaks on all of the high-elevation watersheds in their area this weekend. The center based its forecast on current cool temperatures, which have prevented snowmelt, along with predicted upcoming high temperatures that would kickstart more runoff.
If you had a bird's eye view, the CBRFC's forecast would have you seeing simultaneous peaks in several Upper Colorado basin rivers: the Fraser, Williams Fork, Upper Colorado into Granby, and Blue into Dillion.
The Colorado River at the Cameo gage (between De Beque and Palisade) may have its second peak, possibly higher than the one we saw June 7.
The center is most concerned about Northern Utah, Northwestern Colorado and Southwestern Wyoming. A few streams in Utah and Wyoming, for example, are expected to hit record flows. The forecast also stated that flooding is occurring and will likely continue to occur along rivers where there's still high-elevation snow.
The CBRFC does not forecast Northern Water's East Slope tributaries, but we expect the climate to have similar effects on our snowpack.
Saturday, June 18, 2011
Willow Creek inflow record shattered, with more to come
After 57 years of tracking Willow Creek Reservoir stats, we've now hit an amazing new inflow record.
Some background: in the Western U.S., April through July are considered the snowmelt months, so official streamflow forecasts (and thus runoff records) are based on that four-month period.
Until now, Willow Creek Reservoir's inflow record was in 1986, when the April through July runoff totaled 85,600 acre feet, which is 168 percent of the official average of 50,800 acre feet. That sounded like a lot until yesterday, when we tabulated the inflow since April 1 as 87,100 acre feet. And we still have six weeks to go!
Our latest forecast anticipated a total of 110,000 acre feet of inflow to Willow Creek by July 31. If it materializes, this would be 216 percent of the official average. And the Colorado Basin River Forecast Center expects even more than we do.
The peak inflow rate (in daily average) this year was 1,652 cfs on June 7. This wasn't quite a record, but anything more than 1,500 cfs is notable for Willow Creek. This date of peak inflow was about two weeks later than usual (about May 24); late peaks often come hand-in-hand with larger-than-normal snowpacks.
This staggering runoff quantity raises questions about what kind of runoff we should expect from neighboring watersheds - especially above Lake Granby. While we don't expect as high an inflow to Granby, our latest forecast anticipates 175 percent of average, which would be another one for the record books.
It's disconcerting to drive past Granby, which is 20 feet below full, and see the surrounding dry sagebrush - if you know how high snowpack is in Rocky Mountain National Park and along the Gore Range.
That snowpack may seem remote and unassuming, but looks are deceiving. Stay tuned.
Some background: in the Western U.S., April through July are considered the snowmelt months, so official streamflow forecasts (and thus runoff records) are based on that four-month period.
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Willow Creek Reservoir |
Our latest forecast anticipated a total of 110,000 acre feet of inflow to Willow Creek by July 31. If it materializes, this would be 216 percent of the official average. And the Colorado Basin River Forecast Center expects even more than we do.
The peak inflow rate (in daily average) this year was 1,652 cfs on June 7. This wasn't quite a record, but anything more than 1,500 cfs is notable for Willow Creek. This date of peak inflow was about two weeks later than usual (about May 24); late peaks often come hand-in-hand with larger-than-normal snowpacks.
This staggering runoff quantity raises questions about what kind of runoff we should expect from neighboring watersheds - especially above Lake Granby. While we don't expect as high an inflow to Granby, our latest forecast anticipates 175 percent of average, which would be another one for the record books.
It's disconcerting to drive past Granby, which is 20 feet below full, and see the surrounding dry sagebrush - if you know how high snowpack is in Rocky Mountain National Park and along the Gore Range.
That snowpack may seem remote and unassuming, but looks are deceiving. Stay tuned.
Wednesday, June 15, 2011
Too soon to say that rivers have peaked
There has been much in the news this week about our rivers being past their peak flows for the season.
Not so fast!
The high elevation portions of our watersheds melted next to nothing during the month of May. They're just now getting started. While temperatures may continue to play nice, there's every chance that a couple of days of warmth could cause surprise surges in streamflow.
Don't believe us? Take a look at the 1957 hydrographs - a year with a giant snowpack (but not as big as this year's) and a cold May. That year, the peak runoff didn't happen until the very end of June. Here's Middle Boulder Creek at Nederland as an example.
Not so fast!
The high elevation portions of our watersheds melted next to nothing during the month of May. They're just now getting started. While temperatures may continue to play nice, there's every chance that a couple of days of warmth could cause surprise surges in streamflow.
Don't believe us? Take a look at the 1957 hydrographs - a year with a giant snowpack (but not as big as this year's) and a cold May. That year, the peak runoff didn't happen until the very end of June. Here's Middle Boulder Creek at Nederland as an example.
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| BODMIDCO - this year (red) vs. 1957 (green) |
Monday, June 13, 2011
Granby releases to increase today
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| Spillway at Lake Granby as seen from below |
The increases in outflows will be evident at the downstream USGS gage.
Note that releases from the outlet valves will continue at approximately 410 cfs. The combined release from the valves and from the spillway will be approximately 500 cfs.
Wednesday, June 8, 2011
Adams Tunnel diversions decreasing
When we expect gigantic runoff, we prefer to keep the Adams Tunnel running full blast, because every acre foot diverted to the East Slope creates room for another acre foot of runoff. With that, we lower the possibility of having to make higher releases out of Lake Granby.
But we have two things working against us. First, East Slope reservoirs are nearly full, and soon we won't have empty space available for Adams Tunnel diversions.
Second, the water rights system limits our options. Northern Water holds decrees for Big Thompson River water, and when those rights come into priority, we are obligated to use that water, not West Slope water, to fill our East Slope reservoirs and make water deliveries.
Yesterday our East Slope decree came into priority and operators reduced tunnel diversions by 40 cfs. Today, even more East Slope water became available and tunnel diversions went down an additional 125 cfs.
The amount of East Slope water available to our decree varies from day to day and depends on streamflow and other water users' demands. To keep up to date, you can monitor Adams Tunnel diversions as we move through the warm season.
But we have two things working against us. First, East Slope reservoirs are nearly full, and soon we won't have empty space available for Adams Tunnel diversions.
Second, the water rights system limits our options. Northern Water holds decrees for Big Thompson River water, and when those rights come into priority, we are obligated to use that water, not West Slope water, to fill our East Slope reservoirs and make water deliveries.
Yesterday our East Slope decree came into priority and operators reduced tunnel diversions by 40 cfs. Today, even more East Slope water became available and tunnel diversions went down an additional 125 cfs.
The amount of East Slope water available to our decree varies from day to day and depends on streamflow and other water users' demands. To keep up to date, you can monitor Adams Tunnel diversions as we move through the warm season.
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Willow Creek backing off after three near-record peaks
The past several days have brought three peak events on Willow Creek: 1,748 cfs on May 30 and again on June 3, and 1,761 cfs on June 8.
But it's not over yet. The snowpack at the top of Willow Creek Pass normally peaks in late April, but it's the beginning of June and we still have more snow up there than the average peak, despite the fact it's been melting. The forecast calls for cooler weather, which means snowpack will continue to melt - but at a slower, much more manageable rate. Flows are retreating today and will likely hold steady or decline slightly in the next few days. But keep an eye on the skies and thermometers: We are still vulnerable to additional peaking events if there's a rainstorm or stretch of hot weather.
Our records show that the maximum observed inflow to Willow Creek Reservoir was a daily average of 1,857 cfs on May 24, 1984. In comparison, this year's three peak flow rates occurred for just a few minutes each; our maximum daily average for 2011 so far was yesterday at 1,652 cfs.
So while we don't have a flow rate that's going into the record books, we're still on track to smash the previous record for the total volume of runoff: 85,300 acre feet from April 1 to July 31 in 1957. This year's inflows are already 64,600 acre feet, and we still have seven weeks to go!
As the elevation in Willow Creek Reservoir continues to rise, we will pump water into Lake Granby if necessary to help keep Willow Creek Reservoir outflows at or below 1,300 cfs.
But it's not over yet. The snowpack at the top of Willow Creek Pass normally peaks in late April, but it's the beginning of June and we still have more snow up there than the average peak, despite the fact it's been melting. The forecast calls for cooler weather, which means snowpack will continue to melt - but at a slower, much more manageable rate. Flows are retreating today and will likely hold steady or decline slightly in the next few days. But keep an eye on the skies and thermometers: We are still vulnerable to additional peaking events if there's a rainstorm or stretch of hot weather.
Our records show that the maximum observed inflow to Willow Creek Reservoir was a daily average of 1,857 cfs on May 24, 1984. In comparison, this year's three peak flow rates occurred for just a few minutes each; our maximum daily average for 2011 so far was yesterday at 1,652 cfs.
So while we don't have a flow rate that's going into the record books, we're still on track to smash the previous record for the total volume of runoff: 85,300 acre feet from April 1 to July 31 in 1957. This year's inflows are already 64,600 acre feet, and we still have seven weeks to go!
As the elevation in Willow Creek Reservoir continues to rise, we will pump water into Lake Granby if necessary to help keep Willow Creek Reservoir outflows at or below 1,300 cfs.
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Wednesday, June 1, 2011
Testing may increase Willow Creek releases
Willow Creek releases may be incrementally increased over the next few days for the purpose of testing safe channel capacity below the reservoir.
Northern Water is coordinating closely with area property owners. If you have questions, please contact Noble Underbrink at the Farr Pump Plant at 970-627-3406.
Northern Water is coordinating closely with area property owners. If you have questions, please contact Noble Underbrink at the Farr Pump Plant at 970-627-3406.
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