Fall weather has finally arrived at Lees Ferry. This is the time of year that we experience the best weather of the year with cool mornings and warm afternoons. The sun has started to lay over to the south which is really evident with the decreasing sunlight in the deep canyon of Glen Canyon; the shade is starting to really alter the amount of sunlight that enters the canyon with certain stretches of river being in the shade most of the day. It is often the sunlight that triggers our fish to feed so knowing when and where to be on the river is critically important to a successful fishing day.
September started off with a bang with most of the guides describing the fishing as “off the charts”. This almost always happens in early September which is a result of the high water of summer and the fish being in a feeding mood. When the water drops Sept 1st, the fish are still in close to shore and in a feeding mood. The fishing has slowed as the month has progressed with some days being better than others. Usually the fishing will improve from now into October. One thing to know: Usually the fishing is better on the weekends due to the lower water but this has not been the case of late, we have actually had better fishing on the weekdays in the higher water.
El Nino came through in the end and provided the Lake Powell drainage with a good snowpack. The lake rose over 30 feet. Lake elevation is higher than it has been since 2012. The high inflow will also stir up nutrients that will show up in the river next winter and spring.
Just because you caught fish in a certain spot in years past, don’t think that you are going to experience the same success again. The river is a living creature and fishing changes daily. It is our sincere desire that everyone have a great trip to the Ferry. Be sure to stop by the shop to see the flies that are currently working. The flies frequently change on a daily basis – sometimes it seems like hourly – and LFA guides let everyone at the shop know the top producing flies and how to use them. We are anxious to share this knowledge with you – even where to fish!
There is an ongoing aquatic food base study that has taken place over the past couple of years. The purpose of this study is multifaceted and is studying the relationship of flows on food production, taking inventories of and monitoring populations of aquatic insects and invertebrates that live in the river and other very important aspects of the aquatic food base. I believe that this is by far the most important study that has ever been conducted on this river. Previously, hundreds of millions of dollars were spent studying sediment while ignoring the aquatic food base and resource. Common sense dictates that fish, birds and animals do not live off dirt or sand. The aquatic food base and habitat are the foundation for all that lives in the Colorado River. One of the long-term goals of the food base study is to determine how to enhance the populations and production of aquatic insects in the river which will benefit native fish, trout, and migratory bird populations. This is a study and a goal that we can all embrace!
Quagga mussels (see http://nas.er.usgs.gov/queries/factsheet.aspx?speciesid=95 ) have become established in Lake Powell and we are now seeing some in the river below the dam. Their arrival happened sooner than I expected. So far, there has not been a major infestation and there is some thought by experts that they will not become very well established in the river due to the current. Remember to dry waders and boots before using them in any other body of water. Also, private boats should drain all water from the boat and live-wells as soon as you exit the river. We all need to do our part to limit the transport of this and all invasive species.
The fish have been holding deep in this area for the last couple of years and it appears that they are still deeper than normal which makes it tough to get out far enough to reach them. Hopefully, the fish will begin to move into the shallower water soon.
Spin fishing continues to be productive. Many of the fish are in the deeper water and it is much easier to get down to them with spinning gear than fly gear.
Glen Canyon Dam / Lake Powell
The operating tier for water year 2016 was established in August 2015 as the Upper Elevation Balancing Tier. The April 2016 24-Month Study established that Lake Powell operations will be governed by balancing for the remainder of water year 2016. Under balancing, the contents of Lake Powell and Lake Mead will be balanced by the end of the water year, but not more than 9.0 maf and not less than 8.23 maf shall be released from Lake Powell. Based on the most probable inflow forecast, this July 24-Month Study projects a balancing release of 9.0 maf in water year 2016. Reclamation will schedule operations at Glen Canyon Dam to achieve as practicably as possible the appropriate total annual release volume by September 30, 2016.
In July, the release volume will be approximately 950 kaf, with fluctuations anticipated between approximately 11,500 cfs during the nighttime and 19,500 cfs during the daytime and consistent with the Glen Canyon Operating Criteria (Federal Register, Volume 62, No. 41, March 3, 1997). The anticipated release volume for August is 900 kaf with daily fluctuations between approximately 10,000 cfs and 18,000 cfs. The expected release for September is approximately 700 kaf with daily fluctuations between approximately 8,500 cfs and 14,500 cfs.
In addition to daily scheduled fluctuations for power generation, the instantaneous releases from Glen Canyon Dam may also fluctuate to provide 40 mega-watts (mw) of system regulation. These instantaneous release adjustments stabilize the electrical generation and transmission system and translate to a range of about 1,200 cfs above or below the hourly scheduled release rate. Under system normal conditions, fluctuations for regulation are typically short lived and generally balance out over the hour with minimal or no noticeable impacts on downstream river flow conditions.
Releases from Glen Canyon Dam can also fluctuate beyond scheduled releases when called upon to respond to unscheduled power outages or power system emergencies. Depending on the severity of the system emergency, the response from Glen Canyon Dam can be significant, within the full range of the operating capacity of the power plant for as long as is necessary to maintain balance in the transmission system. Glen Canyon Dam typically maintains 30 mw (approximately 880 cfs) of generation capacity in reserve in order to respond to a system emergency even when generation rates are already high. System emergencies occur fairly infrequently and typically require small responses from Glen Canyon Dam. However, these responses can have a noticeable impact on the river downstream of Glen Canyon Dam.
Inflow Forecasts and Model Projections
The April to July 2016 water supply forecast for unregulated inflow to Lake Powell, issued on July 1, 2016, by the Colorado Basin River Forecast Center, projects that the most probable (median) unregulated inflow volume will be 6.72 maf (94 percent of average based on the period 1981-2010). The forecast increased by 2,200 kaf since last month. There is still uncertainty regarding the runoff and resulting inflow to Lake Powell through the end of the water year.
As determined in the August 2015 24-Month Study, and documented in the 2016 Annual Operating Plan, Lake Powell’s operations in water year 2016 will be governed by the Upper Elevation Balancing Tier. Because the April 2016 24-Month Study projected the end of water year elevation at Lake Powell to be above 3,575 feet and the end of water year elevation at Lake Mead to be below elevation 1,075.0 feet, Lake Powell operations shifted to balancing (Section 6.B.4 of the 2007 Interim Guidelines) for the remainder of water year 2016. Under balancing, the contents of Lake Powell and Lake Mead will be balanced by the end of the water year, but not more than 9.0 maf and not less than 8.23 maf shall be released from Lake Powell.
Based on the current forecast, the July 24-Month Study projects Lake Powell’s end of water year 2016 elevation to be near 3,612 feet with approximately 12.97 maf in storage (53 percent capacity). Projections of elevation and storage still have significant uncertainty at this point in the season, primarily due to uncertainty regarding runoff and the resulting inflow to Lake Powell. Under the minimum probable inflow scenario, updated in April, the projected end of water year elevation and storage are 3585 ft and 10.35 maf (43 percent capacity), respectively. Under the maximum probable inflow scenario, updated in April, the projected end of water year elevation and storage are 3622 ft and 14.01 maf (58 percent capacity), respectively. Modeling of projected reservoir operations based on the minimum and maximum scenarios will be updated again in August.
Upper Colorado River Basin Hydrology
The Upper Colorado River Basin regularly experiences significant year to year hydrologic variability. During the 16-year period 2000 to 2015, 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 3 out of the past 16 years. The period 2000-2015 is the lowest 16-year period since the closure of Glen Canyon Dam in 1963, with an average unregulated inflow of 8.51 maf, or 79 percent 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 2000-2015 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. The water year 2015 unregulated inflow volume to Lake Powell was 10.174 maf (94 percent of average), which, though still below average, was significantly higher than inflows observed in 2012 and 2013 (45 percent and 47 percent of average, respectively). Under the current most probable forecast, total water year 2016 unregulated inflows to Lake Powell is projected to be 9.90 maf (92 percent of average), and ranges from a minimum probable inflow of 6.86 maf (63 percent of average) and maximum probable inflow of 11.13 maf (103 percent of average).
At the beginning of water year 2016, total system storage in the Colorado River Basin was 30.3 maf (51 percent of 59.6 maf total system capacity). This is nearly the same as the total storage at the beginning of water year 2015 which began at 30.1 maf (50 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 2014. 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 2016 total Colorado Basin reservoir storage is approximately 30.5 maf (51 percent of capacity). The actual end of water year storage may vary from this projection, primarily due to uncertainty regarding this season’s runoff and resulting reservoir inflow. Based on the April minimum and maximum probable inflow forecasts and modeling the range is approximately 27.6 maf (46 percent of capacity) to 31.4 maf (53 percent of capacity), respectively.