Grand Clarity Adaptive Management Annual Report 2016

Grand Lake Adaptive Management Committee

Contents

Contents

Background & Purpose of the Report ______1 2016 Adaptive Management Process ______2 1. Adaptive Management Committee Representatives ______2 2. Meetings ______2 2016 Operational Plan ______4 1. Operational Scenarios______4 3. Water quality modeling ______5 4. Plan selection ______8 Clarity & Shadow Mountain Water Quality ______10 1. Summary of clarity and operations relative to clarity ______10 2. Shadow Mountain Reservoir Water Quality Summary ______12 3. Water Quality and Operations Summary ______16 4. Goals Assessment and Water Quality Indicators ______17 Plan vs. Observed ______18 1. Operations ______18 2. Water Quality (Model vs. Observed) ______19 Lessons Learned & Recommendations ______22 1. Lessons learned ______22 2. Recommendations ______22 Appendices ______24

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Figures

Figures

Figure 1 - Adaptive Management Process ...... 2 Figure 2 - 2016 Proposed Operational Scenarios, Adams Tunnel Deliveries ...... 4 Figure 3 - 2016 Proposed Operational Scenarios, Farr Pumping ...... 5 Figure 4 - Water quality model runs summary (best values shown in green) ...... 6 Figure 5 - Modeled Shadow Mountain Reservoir Residence Time ...... 6 Figure 6 - Modeled Shadow Mountain Reservoir Bottom Dissolved Oxygen ...... 7 Figure 7 - Modeled Shadow Mountain Reservoir Chlorophyll a ...... 7 Figure 8 - Modeled Grand Lake Clarity Secchi Depth ...... 8 Figure 9 - 2016 Final Operational Plan ...... 9 Figure 10 - Grand Lake Jul-To Date Average Secchi and Farr Pump Flows ...... 10 Figure 11 - Grand Lake Jul-To Date Minimum Secchi and Farr Pump Flows ...... 10 Figure 12 - Grand Lake Average Secchi, Farr Pump Flows and Inflows ...... 11 Figure 13 - Shadow Mountain Reservoir and Grand Lake Average Secchi, Farr Pump Flows and Inflows 11 Figure 14 - Shadow Mountain Buoy - Temperature ...... 12 Figure 15 - Shadow Mountain Mid Buoy - Temperature ...... 12 Figure 16 - Buoy – Dissolved Oxygen ...... 12 Figure 17 - Shadow Mountain Mid Buoy – Dissolved Oxygen ...... 12 Figure 18 - Shadow Mountain Dam Buoy – Dissolved Oxygen % ...... 12 Figure 19 - Shadow Mountain Mid Buoy – Dissolved Oxygen % ...... 12 Figure 20 - Shadow Mountain Dam Buoy – pH ...... 13 Figure 21 - Shadow Mountain Mid Buoy – pH ...... 13 Figure 22 - Shadow Mountain Dam Buoy – Specific Conductivity ...... 13 Figure 23 - Shadow Mountain Mid Buoy – Specific Conductivity ...... 13 Figure 24 - Shadow Mountain Dam Buoy – Turbidity ...... 13 Figure 25 - Shadow Mountain Mid Buoy – Turbidity ...... 13 Figure 26 - Shadow Mountain Dam Surface DO (2012-2016) ...... 14 Figure 27 - Shadow Mountain Mid Surface DO (2012-2016) ...... 14 Figure 28 - Shadow Mountain Dam Surface DO % (2012-2016) ...... 14 Figure 29 - Shadow Mountain Mid Surface DO % (2012-2016) ...... 14 Figure 30 - Shadow Mountain Dam Bottom DO (2012-2016) ...... 14 Figure 31 - Shadow Mountain Mid Bottom DO (2014-2016) ...... 14 Figure 32 - Shadow Mountain Dam Surface pH (2012-2016)...... 15 Figure 33 - Shadow Mountain Mid Surface pH (2014-2016) ...... 15 Figure 34 - Shadow Mountain Dam Surface Temperature (2012-2016) ...... 15 Figure 35 - Shadow Mountain Dam Surface Temperature (2014-2016) ...... 15 Figure 36 - Clarity Goals and Water Quality Indicators Summary ...... 17 Figure 37 - Adams Tunnel Diversion - Plan vs Observed ...... 18

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Figures

Figure 38 - Farr Pumping - Plan vs. Observed ...... 18 Figure 39 - Modeled Meteorological Conditions vs. Observed ...... 20 Figure 40 - Actual vs. Modeled Farr Pumping and Average Grand Lake Clarity ...... 21

Table 1 - Upper River Undepleted Flows ...... 19 Table 2 - Shadow Mountain Reservoir Water Quality - Predicted vs. Observed ...... 20

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Pg. 01 Background & Purpose of the Report

Background & Purpose of the Report

In January 2016, the U.S. Department of the Interior Bureau of Reclamation (Reclamation), Northern Colorado Water Conservancy District (Northern Water), Grand County Board of Commissioners (Grand County), Northwest Colorado Council of Government (NWCCOG) and Water Conservation District (River District) entered into the Grand Lake Clarity Stakeholders’ Memorandum of Understanding (Clarity MOU) (APPENDIX A).

In this Clarity MOU, the parties agreed to establish an adaptive management process to implement the Grand Lake Clarity narrative standard:

“The highest level of clarity attainable, consistent with the exercise of established water rights, the protection of aquatic life, and protection of water quality throughout the Three system”.

Further, the parties agreed to implement clarity goals to guide the adaptive management process. The annual Clarity Goals for Grand Lake from July 1 through September 11 are an average Secchi depth of 3.8 meters and a minimum Secchi depth of 2.5 meters.

The Clarity Goals and the adaptive management approach were subsequently endorsed by the Water Quality Control Commission (WQCC) in April, 2016 and the Clarity Goals were adopted as Goal Qualifiers. In the May 9, 2016 Statement of Basis and Purpose (APPENDIX B) the WQCC stated that “The Division will assess consistency with the adopted narrative standard by monitoring whether the Proponents continue to implement the adaptive management process described in their Memorandum of Understanding and will review clarity measurements. Evaluation of the Goal Qualifiers will be accomplished by reviewing annual reports and summarizing progress at the Basin Issues Scoping Hearing.”

The Clarity MOU also requires the preparation of an annual report to summarize what was learned about Colorado-Big Thompson (CBT) Project operational approaches to meet the Clarity Goals, and resultant effects on water quality and on clarity in Grand Lake.

This report meets the reporting requirements of the Clarity MOU and the Water Quality Control Commission.

The next Colorado Basin Issues Scoping Hearing is scheduled for October 10, 2017.

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Pg. 02 2016 Adaptive Management Process

2016 Adaptive Management Process This section describes how the Adaptive Management process was carried out in 2016.

1. Adaptive Management Committee Representatives

The Adaptive Management Committee (AMC) comprises representatives of Reclamation, Northern Water, Grand County, NWCCOG and the River District. A list of the representatives that attended the meetings in 2016 is included in APPENDIX C.

Section V.C. of the Clarity MOU, describes the process for developing an operational plan and for the adaptive management phase during the July through September 11 period. This process is illustrated in Figure 1.

ACTIVE ADAPTIVE MANAGEMENT Planning Grand Lake Clarity Critical Period Jul-Sep 11

Jun Jul Aug Sep Operational •weekly •weekly •weekly Annual Plan meetings meeting meetings through Report Sep 15

Figure 1 - Adaptive Management Process

Section V.C. of the Clarity MOU specifies that operational scenarios along with corresponding water quality model runs shall be presented to the Adaptive Management Committee.

2. Meetings

In accordance with the Clarity MOU, the Adaptive Management Committee met on June 1, 2016 to review operational scenarios and corresponding water quality model runs. Reclamation prepared three operational scenarios. Northern Water contracted Hydros, Inc. to prepare water quality model runs of all three operational scenarios.

Based on comments provided by the Adaptive Management Committee at the June 1, 2016 meeting, Reclamation selected one operational plan, out of the three proposed and announced its Revised Operational Plan on June 15, 2015.

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Pg. 03 2016 Adaptive Management Process

The Adaptive Management Committee provided comments to Reclamation by June 17, 2016. Reclamation released its Final Operational Plan on June 21, 2016.

The Adaptive Management Committee began weekly conference calls on July 7, 2016 and continued to meet weekly until September 15, 2106.

The Adaptive Management Committee held three debriefing meetings on September 15, 2016, September 22, 2016 and November 17, 2016. These meetings focused on discussion of possible improvements to the process, lessons learned and recommendations for following years.

A schedule of all the meetings is included in Appendix D. Meeting materials, notes and plans are compiled in Appendices E and F.

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Pg. 04 2016 Operational Plan

2016 Operational Plan This section summarizes operational plans that were considered by Reclamation; results of the water quality modeling effort to simulate each plan; and the final plan that was selected.

1. Operational Scenarios

Three scenarios were considered in 2016: Low and Steady, 4-week No Pump and Pulse Pumping (Figure 2 and Figure 3).

The “Low and Steady” option consisted of maintaining a constants flow of 250 cfs at the Adams Tunnel. The “4-week No Pump” option consisted of a pumping interruption from August 14 until September 11.

The “Pulse Pumping” consisted of operating Adams Tunnel diversions with a pulsing pattern, turning the diversions on and off every few days to meet water demands with flows ranging from 225 cfs to 550 cfs.

Figure 2 - 2016 Proposed Operational Scenarios, Adams Tunnel Deliveries

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Pg. 05 2016 Operational Plan

Figure 3 - 2016 Proposed Operational Scenarios, Farr Pumping

3. Water quality modeling

All three operational scenarios were modeled using the Three Lakes CE-QUAL-W2 Model developed by Hydros, Inc. Operational modeling assumed 2013 meteorological conditions based on a long-term weather outlook that indicated warmer and wetter than average conditions. The Hydrology was assumed to be similar to 2009 with an average amount and timing of runoff. Operations used came from Reclamation’s operational scenarios. No Windy Gap Pumping was modeled and a high volume of Willow Creek Pumping was assumed. Granby Reservoir was assumed to be full.

Operational scenarios were compared using water quality metrics referenced in the Clarity MOU. The simulation covered May 1 through September 11. Modeling outputs were intended to be used for comparative analysis, not with the intent to predict clarity and water quality in an absolute sense, since the modeling relied on assumptions that were likely going to be inaccurate to some extent.

Model outputs are summarized in Figure 4, Figure 5, Figure 6, Figure 7 and Figure 8.

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Pg. 06 2016 Operational Plan

Jul-Sep 11

(m)

Jul-Aug

Farr Farr DO (mg/L) DO

Pumping Pumping (mg/L) DO

Min SMR Bottom Bottom SMR Min

Min SMR Surface Surface SMR Min

Peak Chl a (ug/L) a Chl Peak Min GL Secchi (m) Secchi GL Min Scenario (af) Start Date Secchi GL Avg Pulse Pumping 5797 07/18 5.5 2.5 5.2 0 17.6

4-week No 07/18 10852 4.9 3.1 5.5 1.5 19.3 Pump

Slow and 23651 07/10 4.0 2.7 5.8 5.2 10.5 Steady Figure 4 - Water quality model runs summary (best values shown in green)

Figure 5 - Modeled Shadow Mountain Reservoir Residence Time

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Pg. 07 2016 Operational Plan

Figure 6 - Modeled Shadow Mountain Reservoir Bottom Dissolved Oxygen

Figure 7 - Modeled Shadow Mountain Reservoir Chlorophyll a

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Pg. 08 2016 Operational Plan

Figure 8 - Modeled Grand Lake Clarity Secchi Depth Model runs indicated that it is important to maintain water quality in Shadow Mountain Reservoir, to prevent dissolved oxygen depletions at the bottom of the reservoir, and to minimize the total flows to Grand Lake through the connecting channel in order to optimize clarity in Grand Lake.

4. Plan selection

Comments from the AMC on the proposed operational scenarios are documented in Appendix F.

On June 21, 2016 Reclamation announced that the Low and Steady plan (Figure 9) was selected as the Final Operational Plan. Under this plan, a constant flow of 250 cfs would be maintained at the Adams Tunnel. This operation was anticipated to start once native inflows to Grand Lake had dropped enough so as not to impact project yield. The start date of pumping was changed to July 1, instead of July 10. At the time the plan was formulated, water was expected to spill out of Granby Reservoir. An earlier start of pumping would therefore be required to take advantage of available storage space in East Slope reservoirs and to protect project yield.

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Pg. 09 2016 Operational Plan

Adams Tunnel Figure 9 - 2016 Final Operational Plan

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Pg. 10 Grand Lake Clarity & Shadow Mountain Water Quality

Grand Lake Clarity & Shadow Mountain Water Quality This section describes observed water quality in Shadow Mountain Reservoir and clarity in Grand Lake during the 2016 adaptive management season (Jul-Sep 11).

1. Summary of clarity and operations relative to clarity

Grand Lake Secchi, Jul-To Date Average

with Farr Pumping flows

06/09/16 08/24/16 06/05/16 06/13/16 06/17/16 06/21/16 06/25/16 06/29/16 07/03/16 07/07/16 07/11/16 07/15/16 07/19/16 07/23/16 07/27/16 07/31/16 08/04/16 08/08/16 08/12/16 08/16/16 08/20/16 08/28/16 09/01/16 09/05/16 09/09/16 09/13/16 09/17/16 09/21/16 09/25/16 09/29/16 10/03/16 0.0 06/01/16 1200 1.0 1000 2.0 800 3.0 600

4.0 400 Secchi (m) Secchi 5.0 200 (cfs)Flow 6.0 0 GL Jul-To Date Average Jul-Sep 11GL Avg Goal Farr Pump

Figure 10 - Grand Lake Jul-To Date Average Secchi and Farr Pump Flows

Grand Lake Secchi, Jul-To Date Minimum

with Farr Pumping flows

08/28/16 09/25/16 06/05/16 06/09/16 06/13/16 06/17/16 06/21/16 06/25/16 06/29/16 07/03/16 07/07/16 07/11/16 07/15/16 07/19/16 07/23/16 07/27/16 07/31/16 08/04/16 08/08/16 08/12/16 08/16/16 08/20/16 08/24/16 09/01/16 09/05/16 09/09/16 09/13/16 09/17/16 09/21/16 09/29/16 10/03/16 0 06/01/16 1200 1 1000 2 800 3 600

4 400 Flow (cfs)Flow Secchi (m) Secchi 5 200 6 0 GL Jul-To Date Minimum GL Jul-Sep 11 Minimum Goal Farr Pump

Figure 11 - Grand Lake Jul-To Date Minimum Secchi and Farr Pump Flows

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Pg. 11 Grand Lake Clarity & Shadow Mountain Water Quality

Grand Lake Daily Average Secchi with Farr Pumping and Inflows

06/08/16 06/15/16 06/22/16 06/29/16 07/06/16 07/13/16 07/20/16 07/27/16 08/03/16 08/10/16 08/17/16 08/24/16 08/31/16 09/07/16 09/14/16 09/21/16 09/28/16 10/05/16 0.00 06/01/16 1400 1.00 1200 2.00 1000 3.00 800 4.00 600

5.00

Flow(cfs) Secchi(m) 6.00 400 7.00 200 8.00 0 GL Avg Farr Pump North + East Inlets (cfs)

Figure 12 - Grand Lake Average Secchi, Farr Pump Flows and Inflows

Shadow Mountain and Grand Lake Daily Average Secchi with

Farr Pumping and Inflows

06/08/16 06/15/16 06/22/16 06/29/16 07/06/16 07/13/16 07/20/16 07/27/16 08/03/16 08/10/16 08/17/16 08/24/16 08/31/16 09/07/16 09/14/16 09/21/16 09/28/16 10/05/16 0.00 06/01/16 1400 1.00 1200 2.00 1000 3.00 800 4.00 600

5.00

Flow(cfs) Secchi(m) 6.00 400 7.00 200 8.00 0 GL Avg SM Avg Farr Pump North + East Inlets (cfs)

Figure 13 - Shadow Mountain Reservoir and Grand Lake Average Secchi, Farr Pump Flows and Inflows

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Pg. 12 Grand Lake Clarity & Shadow Mountain Water Quality

2. Shadow Mountain Reservoir Water Quality Summary

Figure 14 - Shadow Mountain Dam Buoy - Temperature Figure 15 - Shadow Mountain Mid Buoy - Temperature

Figure 16 - Shadow Mountain Dam Buoy – Dissolved Oxygen Figure 17 - Shadow Mountain Mid Buoy – Dissolved Oxygen

Figure 18 - Shadow Mountain Dam Buoy – Dissolved Oxygen % Figure 19 - Shadow Mountain Mid Buoy – Dissolved Oxygen % Page | 12

Pg. 13 Grand Lake Clarity & Shadow Mountain Water Quality

Figure 20 - Shadow Mountain Dam Buoy – pH Figure 21 - Shadow Mountain Mid Buoy – pH

Figure 22 - Shadow Mountain Dam Buoy – Specific Conductivity Figure 23 - Shadow Mountain Mid Buoy – Specific Conductivity

Figure 24 - Shadow Mountain Dam Buoy – Turbidity Figure 25 - Shadow Mountain Mid Buoy – Turbidity

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Pg. 14 Grand Lake Clarity & Shadow Mountain Water Quality

Figure 26 - Shadow Mountain Dam Surface DO (2012-2016) Figure 27 - Shadow Mountain Mid Surface DO (2012-2016)

Figure 28 - Shadow Mountain Dam Surface DO % (2012-2016) Figure 29 - Shadow Mountain Mid Surface DO % (2012-2016)

Figure 30 - Shadow Mountain Dam Bottom DO (2012-2016) Figure 31 - Shadow Mountain Mid Bottom DO (2014-2016) Page | 14

Pg. 15 Grand Lake Clarity & Shadow Mountain Water Quality

Figure 32 - Shadow Mountain Dam Surface pH (2012-2016) Figure 33 - Shadow Mountain Mid Surface pH (2014-2016)

Figure 34 - Shadow Mountain Dam Surface Temperature (2012-2016) Figure 35 - Shadow Mountain Dam Surface Temperature (2014-2016)

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Pg. 16 Grand Lake Clarity & Shadow Mountain Water Quality

3. Water Quality and Operations Summary

During runoff, as Secchi monitoring started on June 8, average clarity in Grand Lake was at 4.0 m. As runoff into Grand Lake began to taper off, clarity in Grand Lake increased and reached its greatest depth for the season during the second and third weeks of June at 5.1 m.

Farr Pumping started on June 29th, a couple of days before the anticipated date based on the Final Operational Plan (July 1) but 10 days earlier than had been modeled. Clarity in Grand Lake responded to the onset of pumping with a decline in clarity; by Jul 7, average clarity had dropped to 3.5 m. It further declined to 3 m by July 13 after pumping was increased on July 5 from about 400 cfs to about 800 cfs. On Jul 16, pumping was cut back to about 400 cfs to meet a constant 250 cfs flow at the Adams Tunnel in accordance with the Final Operational Plan. In effect, the Low and Steady operation started two weeks later than was modeled and about a week later than anticipated in the Final Operational Plan. When the Low and Steady operation started, and following the reduction in pumped flows, clarity began to slightly improve although the rate of improvement was minimal. Average clarity in Grand Lake went from 3 m on Jul 13 to 3.8 by Aug 3 (equivalent to an improvement rate of 4 cm per day over 21 days).

After Aug 3, clarity began to decline in response to the development of an algae bloom in Shadow Mountain Reservoir evidenced by elevated pH values during that time (Figure 20, Figure 21, Figure 32 and Figure 33) and increased surface dissolved oxygen ( Figure 16, Figure 17, Figure 26 and Figure 27).

At the Aug 8 AMC meeting, a change in operation was requested by AMC members. Northern Water, Grand County, NWCCOG and the River District requested that Reclamation consider modifying the pumping pattern to allow for larger flushing flow through Shadow Mountain Reservoir to curb the algae bloom in Shadow Mountain Reservoir and the corresponding decline in Grand Lake clarity. Reclamation agreed to the proposed change in operation, and on Aug 22 pulsed flows were doubled, in an attempt to destabilize the water column in Shadow Mountain Reservoir. However, in order to maintain Reclamation’s goal of 250 cfs outflows at the Adams Tunnel, the interval between pumping pulses went from about 9-12 hours before the change in operation to about 2 days after operations were changed.

The larger pulses of flow through Shadow Mountain had a notable effect on Shadow Mountain Reservoir water quality. The flows largely disrupted the thermal stratification near the Dam and to some extend at mid- reservoir site as well (Figure 14 and Figure 15). pH levels also responded to the pulsing events and dropped sharply when the pumps were on, but climbed back up to levels well above 8 when the pumps were off. This indicates that although the modified operation likely had an effect on algal productivity, the beneficial impacts were short-lived once the pumps were turned off. Two days of no pumping were long enough for algal productivity to resume. Clarity in Grand Lake continued to decline during the modified operation until Sep 5 when the average clarity reached 2.4 m.

Modified operations may have prevented greater degradation of clarity in Grand Lake and of water quality in Shadow Mountain Reservoir but were insufficient to lead to notable improvement.

After Sep 5, clarity started to increase, possibly as a result of the seasonal cooling of temperatures and a natural decline in algal productivity in Shadow Mountain Reservoir.

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Pg. 17 Grand Lake Clarity & Shadow Mountain Water Quality

4. Goals Assessment and Water Quality Indicators

Clarity goals (3.8 m average and 2.5 minimum during Jul through Sep 11) were not met in 2016. The Jul-Sep 11 average clarity was 3.2 m and the minimum clarity was 2.4 m.

The running average Grand Lake clarity fell below the 3.8 m threshold starting Jul 6 and remained below 3.8 m for the rest of the season. The 2.5 m threshold was crossed on Sep 4, when the average clarity reached its minimum for the season at 2.4 m.

Bottom dissolved oxygen in Shadow Mountain Reservoir levels never dropped below the 3 mg/L threshold during Jul- Sep 11.

Surface pH exceeded the threshold of 8 starting Aug 5 and remained elevated for most the season until Sep 5.

Surface dissolved oxygen saturation mostly remained above the 100% threshold for the entire Jul-Sep 11 period.

Trigger Exceeded? Date Trigger Exceeded

Grand Lake Clarity Running Average 3.8 Yes (3.2 m) 07/06-09/11 Jul-To Date (m) Grand Lake Clarity Running Minimum 2.5 Yes (2.4 m) 09/04-09/11 Jul-To Date (m) Shadow Mountain Surface DO 100% Yes 07/01-09/11 (% saturation) Shadow Mountain Surface pH 8 Yes 08/05-09/05

Shadow Mountain Bottom DO (mg/L) 3 No NA Figure 36 - Clarity Goals and Water Quality Indicators Summary

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Pg. 18 Plan vs. Observed

Plan vs. Observed The following graphs display daily flows for the Adams Tunnel and Farr Pumping as anticipated in the Final Operational Plan and as observed.

1. Operations

Figure 37 - Adams Tunnel Diversion - Plan vs Observed

Figure 38 - Farr Pumping - Plan vs. Observed

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Pg. 19 Plan vs. Observed

Farr Pumping started on June 29th, a couple of days before the anticipated date based on the Final Operational Plan (July 1) but 10 days earlier than had been previously modeled (using the water quality model). Early Adams Tunnel diversions started about a week earlier than planned and extended a week later than planned.

In effect, the Low and Steady operation started two weeks later than was modeled (using the water quality model) and about a week later than anticipated in the Final Operational Plan.

2. Water Quality (Model vs. Observed)

This section summarizes observed clarity and water quality data relative to modeled results. It should be noted that the water quality modeling results for the Low and Steady options used slightly different operational inputs from those assumed in the Final Operational Plan. Specifically, the pumping and Adams Tunnel diversions in the Final Plan assumed a start date of Jul 1, whereas the operation used in the water quality modeling assumed a start date of Jul 10 (Figure 40).

Hydrology and meteorological assumptions turned out to be a good fit for 2016 conditions. 2009 was used to prepare the daily hydrology inputs to the model while 2013 meteorological data were used.

Table 1 shows that the hydrology was well predicted with observed values within 10% of the predicted values. The timing of runoff was slightly off and runoff peaked earlier than assumed in the model run. Observed air temperature was also well predicted using 2013 data as shown in Figure 39.

Table 1 - Upper Colorado River Undepleted Flows Period Forecast Actual Difference Apr-Jul (af) 215,100 231,480 -7% Aug – Sep 11 (af) 18,000 16,520 +9%

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Pg. 20 Plan vs. Observed

Historical Max

Historical Min

Figure 39 - Modeled Meteorological Conditions vs. Observed Observed water quality in Shadow Mountain Reservoir and Grand Lake clarity well also well anticipated by the water quality model as shown in Table 2 and Figure 40. The departure in clarity between observed and modeled data in the early part of July is a direct effect of the timing difference in the pumping onset between the model and what happened. Pumping started end of June whereas the model has assumed a start date of July 10. Because pumping started earlier, there was not enough time to realize the post-runoff improvement in clarity that results from gradual settling of particles brought in by the inflows. The model showed a greater improvement in clarity with predicted Secchi reaching about 6.5 m whereas the greatest clarity observed in 2016 was 5.1 m. There was also a tapering off the clarity mid June as a result of a warming event that caused a second runoff peak and brought in additional particles into Grand Lake. After the initial onset of pumping, both the model and observed data show a two-week transition time during which clarity in Grand Lake sharply declined, after which equilibrium in the system was reached until late summer. Seasonal patterns of algal productivity emerge then both in the modeled results and observed data and both time series lined up very well.

These results show the usefulness of the modeling tool in supporting operational decision and its ability to predict water quality reasonably well, provided that assumptions used in the modeling line up well enough with observed inflows, operations and meteorology. These results also emphasize the importance and sensitivity of clarity to initial conditions in the system (i.e. post-runoff) and to the timing of the pumping onset.

Table 2 - Shadow Mountain Reservoir Water Quality - Predicted vs. Observed Metric (7/1-9/11) Predicted Actual Min SMR Top DO (mg/L) 5.8 >7 Min SMR Bottom DO (mg/L) 5.2 >6 Peak SMR Chla (ug/L) 10.5 10.7

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Pg. 21 Plan vs. Observed

Farr Start Modeled

Figure 40 - Actual vs. Modeled Farr Pumping and Average Grand Lake Clarity

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Pg. 22 Lessons Learned & Recommendations

Lessons Learned & Recommendations 1. Lessons learned

1. Earlier response is needed when triggers are exceeded or when a downward trend in water quality indicates triggers are likely to be exceeded. 2. The DO % saturation trigger of 100% needs to be reviewed as it was not a helpful indicator of water quality issues in 2016 3. When possible, it is desirable to maximize early season (post-runoff) clarity to improve the seasonal average. 4. Clarity is sensitive to the timing of runoff and of the onset of pumping; these factors should be considered in the development of operational plans. 5. Initial clarity conditions are important to consider in the pursuit of the Jul-Sep 11 average clarity goal. 6. 8 appears to be a reasonable threshold for pH. 7. The water quality model should be used more by the AMC in evaluating potential changes to operations.

2. Recommendations

1. Water Quality Model: a. Use water quality model to inform operational decisions during the adaptive management season (Jul- Sep 11) b. Consider the sensitivity of clarity to timing of runoff and pumping onset in the development of operational scenarios 2. Operational Modeling a. Document all assumptions used for operational forecasting/modeling so that these assumptions can be tracked through the season and deviation from the plan/forecast can be identified. These deviations can help explain unexpected changes in water quality/clarity and may be useful for updating revisions to the water quality model. b. Clearly identify where/when there is and is not operational flexibility. 3. Planning meeting a. Presentations of the operational runs should include (for each run) elevations/content curves for Granby Reservoir, Carter Lake and Horsetooth Reservoir, as well a superimposed graph of both Adams Tunnel and Granby Pump canal flows on the same graph. These elevations/content graphs should also include target elevations such as boat ramps, hydropower, use of old Carter Lake outlet etc...Water quality graphs should also include for each run: pumped flows along with water quality targets, all on the same graph. All graphs should have sufficient resolution on the date/time axis to allow an easier read of the timing of operations (weekly date stamps at a minimum, daily would be desirable). All graphs should be plotted using the same period (May-Sep, or Jul-Sep11)

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Pg. 23 Lessons Learned & Recommendations

b. Presentation of operational scenarios: show for each plan the Adams Tunnel and Farr Pump on the same graph. c. Work on better integration of hydrology/operations and water quality presentations. d. Agenda: Include a 15-min break so that stakeholders can visit with AMC members before the “recommendations” agenda item. Include a Questions and Answers (Q&A) session after the “recommendations” agenda items. Q&A should limited to questions and comments, not recommendations for BOR. 4. Stakeholder requested inclusion of several new charts during the season: Granby DO profiles, inclusion of DO standards for Shadow Mountain Reservoir. While it is true that these are useful indicators of water quality dynamics in the C-BT system, this information goes beyond the thresholds defined in the clarity MOU. It poses the question of the scope of the weekly reports and whether these reports are starting to depart from their purpose as defined in the clarity MOU. 5. Weekly Reports: a. Add conference call information to the reports. b. Include commentary from Field Logs in weekly report when available. c. Consider photo-documentation options: photo-documentation could be provided by GCWIN when taking Secchi readings. This could be done with pictures of the water and/or pictures of the Secchi disc submersed in water at fixed depth. This concept may be piloted for a year to evaluate how useful it would be. The utility of the photos will be re-evaluated at the end of 2017. d. Horsetooth and Carter Reservoir levels data should be presented in a more meaningful manner. Significant elevation thresholds should be added to the graphs as well as historical average in order to provide context. e. Meteorological data were not useful in the way they were presented. Graphs will be revised to include boxplots or some other representation of historical data for context. f. Include better demand tracking information in the reports. g. Presentation of operational scenarios: show for each plan the Adams Tunnel and Farr Pump on the same graph. h. Include charts with daily average for Shadow Mountain Reservoir (pH, DO, Temp) i. Evaluate averaging depth for the assessment of triggers j. DO % Sat: change chart to daily average and use daily average for triggers for consistency with Hydros analysis that was used to derive the 100% trigger. Evaluate what averaging depth should be used. k. Include clarity forecast in reports: include a chart that shows needed clarity onward in order to meet the 3.8 average goal as season progresses. 6. Monitoring a. Evaluate whether buoy profiles can start at 0.5 m instead of 1m b. Evaluate options to monitor chlorophyll a in Shadow Mountain Reservoir and Grand Lake 7. Documentation: At key decisions points, provide clear documentation and explanations of why decisions are made.

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Pg. 24 Appendices

Appendices A. Clarity MOU B. Statement of Basis and Purpose C. Adaptive Management Committee Representatives D. Meeting Schedule E. Compilation of weekly meeting reports and notes F. Operational Plans and Comments

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