1. Lake Spokane 2012 Nutrient Monitoring Data
Meghan Lunney
Aquatic Resource Specialist
Spokane River and Lake Spokane
DO TMDL Advisory Committee Meeting
May 22, 2013

2. Lake Spokane Monitoring Stations
Map of Lake Spokane. Shows 6 lake stations. Point out Suncrest, TumTum, and three zones within the lake. Picked three stations within each zone to show 2012 water quality conditions.
Riverine
Transitional
Lacustrine

3. Discrete Depth Sampling Stations
Lake Spokane Sampling Station and Discrete Depth
LL0
LL1
LL2
LL3
LL4
LL5
Depths
0.5 5
B-1 15 20 10 30
At each depth samples were analyzed for:
Nitrate plus nitrite
Total persulfate nitrogen (TN)
Soluble reactive phosphorus (SRP)
Total phosphorus (TP)
Chlorophyll a (chl)
At each station profiles were completed of:
Water temperature
Dissolved oxygen pH
Conductivity
Avista modified sampling procedure for 2012:
Discrete depth instead of composite sampling, provides better signature for what the parameters are doing.
Removed alkalinity, chloride, dissolved organic carbon, total dissolved solids, and total organic carbon
**Secchi Disc Depth, phytoplankton, and zooplankton also collected at each station

4. Long Lake Dam Inflows: 2001, 2010, 2011, 2012, and 2013
Hydrograph that shows flows from 2001, 2010, 2011, and 2012 (inflows to Long Lake Dam).
2001: Low flow, high temp year hot & dry summer. Used as the 7Q10, worst case scenario for CEQUAL-W2 model.
2010: Similar to 2001, but had a late runoff event, then temps warmed up quick. So quick it had an effect on the carp population in Lake Spokane.
2011: High flow year, lots of precip and snow pack up until July. Better year than 2012, so much water at three different events, flushed out the whole system. TP never really had time to settle out.
2012: High flow year, up until June. Then summer was very hot and very dry.
2013: Not as much water as 2011 and 2012, higher than normal temps in April and May. Snowpack virtually gone by May 10.
2010
2001

5. 2012 LL5 Profiles
LL5 riverine station. Doesn’t really stratify that much as shown in temp & DO profiles.
Temp & DO: not much stratification and DO looks great!
pH can be a measure of respiration of algae, CO2 lowers pH.
Cond. Can be an indicator of surface/groundwater with: surface water = lower conductivity groundwater = higher conductivity.
Also, can show interflow layer.

6. 2012 TP and SRP Concentrations (mg/L) at LL5 (May through October)
TP lower than 20 ppb. Really good!
SRP high in September, start to release more water out of Post Falls (per our License requirement), might flush out all the macrophytes upstream and start mixing water column?
September and October is usually when Lake Spokane sees blue-green algae blooms occurring.
TP Concentrations
SRP Concentrations

7. 2012 LL3 Profiles
Temp & DO: starting to see stratification at LL3, DO still looks great!
Can see peak of DO in epilimnion in August, algae is hanging out doing photosynthesis. Then at interflow layer ~9-15m, production upstream is pulled into interflow, water sinks and DO sags.
pH can be a measure of respiration of algae, CO2 lowers pH.
Cond. Can be an indicator of surface/groundwater with: surface water = lower conductivity groundwater = higher conductivity.
Also, can show interflow layer.

8. 2012 TP and SRP Concentrations (mg/L) at LL3 (May through October)
Spike in TP and SRP in bottom water would lead to believe its reflective of internal loading. But usually happens when there are anoxic condtions, and DO was on the order of 7mg/L or so. ???
End spike in TP might be related to mixing, lake turning over and de-stratifying.
TP Concentrations
SRP Concentrations

9. 2012 LLO Profiles
Typical lake characteristics with stratification set up.
High DO in epilimnion, DO sags in interflow zone, and lower DO in hypolimnino.

10. 2012 TP and SRP Concentrations (mg/L) at LL0 (May through October)
High internal loading in August and September, high TP, high SRP. Water hasn’t mixed in hypolimnion, set amount of DO and in anoxic conditions SRP released.
TP Concentrations
SRP Concentrations

11. Volume Weighted Water Column TP Concentrations from 2012 Monitoring
2012 Sampling Event
Volume-weighted Water Column TP (µg/L)
LL0
LL1
LL2
LL3
LL4
LL5
May 23-24
18.6
16.2
21.1
15.8
15.3
June 5-6
15.5
17.3
18.2
19.6
15.4
16.9
June 25-26
9.9
10.5
12.4
13.1
11.0
9.7
July 10-11
10.0
10.9
12.1
13.2
9.0
July 24-25
13.6
10.3
15.1
19.5
42.0
11.9
August 6-7
16.3
14.9
16.1
16.6
17.8
August 20-21
21.0
14.4
19.2
17.7
16.8
September 10-11
17.0
14.3
12.8
17.6
14.6
September 25-26
9.1
8.2
8.1
11.3
October 15-16
13.8
8.3
32.4
Mean
14.5
13.0
13.4
18.0
17.1
Summer Mean (Jun-Sep)
14.1
12.6
13.7
15.9
Different way to look at the TP . Relates more to how Ecology looked at the lake using the CE-QUAL-W2 model.
Volume weighted for each station. B/c volume weighted you don’t see the peak TP concentrations. If high TP usually in bottom water, which has a very small volume.
Volume weighted TP not so different between stations. LL3/LL4 tend to have higher TP, seeing more production/and or interflow zone.

12. Minimum Hypolimnetic DO in Lake Spokane below 15 m Compared to Summer Mean Inflow TP Before and After Wastewater Phosphorus in 1977
Another way to measure progress over time.
Takes data collected by Patmont from , prior to the 90% TP removal was put into place by the City of Spokane Wastewater Treatment Plant. Shows super high TP, and corresponding VERY low DO concentrations in hypolimnion.
City put in the TP reduction secondary treatment, lowered TP and raised the minimun DO concentrations.
, shows low TP and much improved DO concentrations in hypolimnion (lower than 15 m).

13. QUESTIONS?