Willow Creek to stay steady for now

Operators cut back releases from Willow Creek Reservoir early yesterday and now the reservoir's elevation is at 8,117 feet.

For now we plan to adjust the release rate as needed to maintain this elevation, so you can expect to see it there until May, when runoff starts getting heavy.

Willow Creek Reservoir drawdown nears completion

Our initial drawdown on Willow Creek Reservoir will conclude sometime today or tomorrow when the reservoir reaches elevation 8,117 feet (normal full elevation is 8,123 feet). Operators will hold the reservoir at this elevation indefinitely by matching releases to inflows. Inflows in recent days have been approximately 15 cfs. The forecast is calling for cold and snow, so the little bit of melting we saw on Monday will subside until our next warm spell.


Click here for current Willow Creek Reservoir releases 

And so we begin...

Many of our mountain-area stream gages are frozen or too hard to get to, which makes it difficult to spot the first signs of spring snowmelt.

However, one of our favorite year-round gages has started to show sure signs of melting snow: the gage on Middle Boulder Creek at Nederland.

You can see from the gage image here that the jagged, mostly flatlined trace gave way to a wave-like and up-trending pattern in recent days. Warm daytime temperatures and cold nighttime temperatures create the cyclical pattern. This is the unmistakable signature of snowmelt in the mountains.

And so we begin.

Last throes of winter

While college students enjoy spring break skiing, water resources managers are watching for the first signs of spring runoff.

Upper Colorado SnoWatch page

Runoff follows a predictable sequence. Our low-elevation SNOTEL sites reach their peak accumulation and start to melt during the last week of March, while our highest-elevation sites continue accumulating snow until the first week of May. Willow Creek Reservoir receives its highest inflow during the last week of May, but our other watersheds typically peak during the first week of June.

Our West Slope watersheds start to show snowmelt at least a couple of weeks before our East Slope watersheds. This is counterintuitive since the West Slope watersheds are at a higher elevation. But solar radiation is a big driver of snowmelt activity, and West Slope watersheds have more southerly and westerly exposures than the East Slope.

Examples of low-elevation sites to watch are Stillwater Creek and Phantom Valley, both located in watersheds tributary to Lake Granby. Our Upper Colorado SnoWatch page tracks the action if you want to see it for yourself.

Northern Water forecast: Above-average runoff

Northern Water issued its second 2011 streamflow forecast on March 7. It anticipates above-average seasonal runoff throughout our district collection and service areas. This is in stark contrast to the dry conditions on the eastern plains.

We compute forecasts for eight basins, all of which either directly supply the C-BT and/or Windy Gap projects or provide native water supplies for Northern Water constituents. Updated forecasts will be published in April and May.

We began developing our streamflow forecasting program in 1999. At first, our forecasting tools were used to provide estimates of supply and demand to the Board as they set the quota allocation in April each year. Now, using customized technologies and tools we developed in-house, we also compute short-term streamflow forecasts to support operational decision-making for our West Slope Collection System.

Releases from Willow Creek start March 10

To prepare for spring runoff and peak inflows, we normally evacuate water from Willow Creek Reservoir in April, but because inflows to the reservoir have been much higher than usual, we need to release water now.

The releases will begin mid-morning tomorrow, March 10. The initial release rate is 100 cfs and releases will likely continue through the end of March.

Digging out the Willow Creek Pump Canal in 2008

Under normal circumstances, we would pump the water over to Lake Granby. But it’s early and the canal that carries water to Lake Granby is filled with snow. We could dig out the canal, but that doesn’t make a lot of sense when we consider this year’s likelihood that Lake Granby will spill – meaning it will be so full we’ll need to make controlled releases.

So we are going to evacuate Willow Creek Reservoir by releasing water through the outlet into Willow Creek. From there, the water will flow into the Colorado River.

If you want to keep up-to-date, the State of Colorado maintains Web pages with real-time release information and reservoir elevations.

An interesting side fact: Wintertime inflows to Willow Creek Reservoir have been higher for the last few years, and we speculate that it’s related to the massive beetle kill in the watershed.