San Juan River Environmental Flows Workshop Background on 1999 Flow Recommendations for the San Juan River February 12-13, 2015

Goals of Flow Recs. and SJRIP ❖ Conserve populations of CPM and RBS ❖ Proceed with water development

7-Year Research Period ❖ Data gathered and analyzed on fish populations and habitat responses to reregulation of Navajo Dam ❖ Flow/geomorphology ❖ Geomorphology/fish habitat ❖ Flow/habitat availability

Foundation of Flow Recommendations “Mimicry of the natural hydrograph is the foundation of the flow recommendation process for the San Juan River. The flow recommendations require mimicry of statistical parameters of flow based on flow/geomorphology/habitat linkages and the statistical variability of the pre-dam hydrology rather than mimicry of each annual hydrograph. Therefore, the resulting flows will not mimic a natural hydrograph in all years, but will mimic the variation and dynamic nature of the 65-year record of the San Juan River.” Reference: 1999 Flow Recommendations for the San Juan River, page S-5

Riverware - San Juan River Basin Hydrology Model Primary modeling tool for the development of Flow Recommendations

Model Use ❖ Used 1929 to 1993 hydrology ❖ Simulates flow in the river at various gaging points ❖ Data driving the model came from USBR, BIA, NM, CO ❖ Use to evaluate the 65-year ( ) flow statistics under various depletion and reservoir management scenarios ❖ Used a post process to derive daily flows from monthly data for evaluation of the flow statistics

Hydrograph Recommendations ❖ Designed to meet conditions needed to develop and maintain habitat for CPM and RBS (handout) ❖ Provide the needed hydrologic conditions for various life stages of endangered and other native fishes

Assumption and Consequence “The underlying assumption in the flow conditions is that over a long period of time, history will repeat itself: if the conditions were met during the past 65-years, they will be met in the future. To the extent that the water supply is different in the future, then the natural condition would also be altered and the conditions of mimicry would be maintained, although the exact flow recommendation statistics may not be met.” Reference: 1999 Flow Recommendations for the San Juan River, page S-5

Flow Recommendation Elements ❖ Flow Magnitude ( e.g. 10,000 cfs) ❖ Duration (e.g. minimum of 5-days) ❖ Frequency ❖ percent of years based on record ❖ maximum number of consecutive years not meeting 97% of flow ❖ Purpose ❖ Peak flow statistics evaluated between Mar 1 and July 31 ❖ Higher flow statistics achievable only by matching Animas peak with Navajo Release

Criteria: 10,000 cfs ❖ Flow Magnitude: > 10,000 cfs ❖ Duration: 5-day minimum ❖ Frequency: ❖ 20% of years ❖ 10-year maximum duration of not meeting 9,700 cfs ❖ Purpose: ❖ Out of bank flow ❖ Generate new cobble sources and spawning habitat ❖ Increases channel/habitat complexity and island count ❖ Nutrient loading improves habitat productivity ❖ Frequency and duration based on mimicry of natural hydrograph ❖ Provides flow and habitat deemed important to CPM and RBS

Criteria: 8,000 cfs ❖ Flow Magnitude: > 8,000 cfs ❖ Duration: 10-day minimum ❖ Frequency: ❖ 33% of years ❖ 6-year maximum duration of not meeting 7,760 cfs ❖ Purpose: ❖ Bankfull discharge below Farmington is about 8,000 cfs ❖ Needed bankfull 1 year out of 3 on average to maintain channel cross-section ❖ Provides sufficient energy to move cobble and build cobble bars for spawning ❖ Research showed positive response in bluehead sucker and speckled dace abundance ❖ Flooded vegetation, low velocity habitat formed by these flows important habitat for larval RBS ❖ Mimicry of natural hydrograph important for CPM reproductive success

Criteria: 5,000 cfs ❖ Flow Magnitude: > 5,000 cfs ❖ Duration: 21-day minimum ❖ Frequency: ❖ 50% of years ❖ 4-year maximum duration of not meeting 4,850 cfs ❖ Purpose: ❖ Maintain backwaters and maintain low-velocity habitat in Reach 3 ❖ Maximize nursery habitat in the system ❖ Frequency is dependent on perturbation storm requiring flushing in about 50% of years ❖ Maintenance of Reach 3 critical because CPM spawning at RM 132

Criteria: 2,500 cfs ❖ Flow Magnitude: > 2,500 cfs ❖ Duration: 10-day minimum ❖ Frequency: ❖ 80% of years ❖ 2-year maximum duration of not meeting 2,425 cfs ❖ Purpose: ❖ Flows above 2,500 cfs cause cobble movement in higher gradient areas ❖ 10-days was thought to provide sufficient sediment movement to clean cobble ❖ Conditions to provide sufficient peak flow to trigger CPM spawning. The frequency specified represents a need for frequent spawning conditions but recognized it is better to provide for larger flow events than to force this release each year. Specified frequency represents a tradeoff.

Criteria: Baseflow ❖ Target Base Flow: 500 cfs from Farmington to Lake Powell, 250 cfs from Navajo Dam ❖ Purpose: ❖ Low stable base flows enhances nursery habitat conditions ❖ Flows between 500 and 1,000 cfs optimize backwater habitat. ❖ Selecting flows at the low end of the range increase water availability for SPR and provides capacity for storm flows to increase flows and still maintain optimum backwater areas.

Decision Tree ❖ Decision tree provides operating criteria for Navajo Dam operations to meet the flow recommendations and fulfill commitments made as part of the various Biological Opinions.

Hydrographs 344,000 AF 236,000 AF 166,000 AF 114,000 AF

Available Water = Storage + Inflow - TBF Releases - Evaporation - NIIP Diversions - Carryover Storage Spill = Inflow - (Available Space + TBF Releases + Evaporation + NIIP Diversions) Definitions Both Available Water and Spill evaluated from the current time step to the end of September Perturbation: A year in which the nursery habitat has been deteriorated by storm events to a level requiring flushing. In the absence of a direct observation, a perturbation year is any year in which there are more than 13 sediment event days between August 1 and December 31.

1. Very Dry. AW = 100,000 af 2. Very Wet. Spill = 500,000 af -Type 4 Release (344,000 af) -op spill = 500, ,000 = 156,000 -Release on nose of hydrograph -May meet 10,000 cfs criteria 3. Other. AW = 200,000 -Spill = 0 af -No perturbation -Release last year Type 1 -Bankfull 1 out of 3 years -No Release 4. Other. AW = 115,000 -Spill = 0 -Perturbation -Clean sediment from storm -Type 1 Release Case Studies

Flow Recommendation Challenges

BW area in Reach 6 was multiplied by 4 to get it on a similar scale. Reach 3-6 total is about the same in 1962 as in Total drops lower in , but it is a drier antecedent flow condition than in Reach 6 is lower than in 1962, indicating a bigger impact in Reach 6. Although Reach 6 is recovering with increased flow faster than the sum of reaches 3-6. Reach 3-6 was used because that is all the 1962 aerial photos covered.

BW area in Reach 6 was multiplied by 4 to get it on a similar scale. Reach 3-6 total is about the same in 1962 as in Total drops lower in , but it is a drier antecedent flow condition than in Reach 6 is lower than in 1962, indicating a bigger impact in Reach 6. Although Reach 6 is recovering with increased flow faster than the sum of reaches 3-6. Reach 3-6 was used because that is all the 1962 aerial photos covered.

Negative Habitat Response to 5,000 cfs Flows Relationship between backwater and low velocity habitat area, adjusted for flow at mapping, and days between 4,000 and 6,000 cfs, limited to years when flows were less than 8,000 cfs. Miller, 2005

No correlation between 2500 cfs flow days and clean cobble Mean depth to embeddedness on four cobble bars from 1995 through 2003 plotted with flow days greater than 2500 cfs Miller, 2005

2005 Recommendations ❖ Investigate the ability to obtain high peak flows (i.e. greater than 8000 and 10,000 cfs) during runoff more frequently than currently recommended ❖ As part of the above investigation, change the shape of the ascending and descending limb of the hydrograph and do not try to meet the 2,500 cfs and 5,000 cfs flow recommendations ❖ User Riverware model as the method to make the above determination