water quality conditions monitored at zorinsky lake

water quality conditions monitored at zorinsky lake

Zorinsky Lake
Water Quality Conditions
based on Monitoring Conducted by the Omaha District
WATER QUALITY CONDITIONS MONITORED AT ZORINSKY LAKE
SUMMARY OF NEAR-DAM WATER QUALITY CONDITIONS
Monitored in Zorinsky Lake from May through September during the 5-year period 2006 through 2010
Monitoring Results
Parameter
Detection
Limit
No. of
Obs.
Max.
State WQS
Criteria(B)
No. of WQS
Exceedances
Percent WQS
Exceedance
Mean(A)
Median
Min.
Pool Elevation (ft-msl)
0.1
26
1110.7
1110.5
1108.9
1115.0
-----
-----
-----
Water Temperature (ºC)
0.1
394
21.7
21.8
12.4
29.4
32(1)
0
0%
Dissolved Oxygen (mg/l)
0.1
394
5.3
5.9
0.1
12.7
≥5
104
30%
Dissolved Oxygen (% Sat.)
0.1
372
60.9
70.7
1.0
153.4
-----
-----
-----
1
382
470
494
291
633
2,000(3)
0
0%
0.1
373
7.8
7.9
6.7
8.7
≥6.5 & ≤9.0(1)
0
0%
Turbidity (NTUs)
1
372
38
13
0
3000
-----
-----
-----
ORP (mV)
1
382
252
258
-136
504
-----
-----
-----
Secchi Depth (in.)
1
25
36
27
12
95
-----
-----
-----
Alkalinity, Total (mg/l)
7
50
134
131
100
170
>20
0
0%
Ammonia, Total (mg/l)
0.02
50
-----
0.1
n.d.
2.7
11.1(4,5), 1.87 (4,6)
0, 1
0%, 2%
Chlorophyll a (ug/l) – Field Probe
1
323
23
18
1
112
10(7)
227
70%
Chlorophyll a (ug/l) – Lab
1
25
30
29
2
85
10
18
72%
Hardness, Total (mg/l)
0.4
5
129.2
131.0
120.0
139.0
-----
-----
-----
Kjeldahl N, Total (mg/l)
0.1
50
1.2
1.1
n.d.
4.5
-----
Nitrogen, Total (mg/)
0.1
50
1.3
1.2
n.d.
4.8
Nitrate-Nitrite N, Total (mg/l)
0.02
50
-----
0.03
n.d.
Phosphorus, Total (mg/l)
0.02
50
0.09
0.07
Phosphorus-Ortho (mg/l)
0.02
50
-----
Suspended Solids, Total (mg/l)
4
30
Aluminum, Dissolved (ug/l)
25
Antimony, Dissolved (ug/l)
Arsenic, Dissolved (ug/l)
Specific Conductance (umho/cm)
pH (S.U.)
Thermal Stratification (°C)
Monitored on 10-Aug-2010
Dissolved Oxygen Levels (mg/l)
Monitored on 10-Aug-2010
pH Levels (SU)
Monitored on 13-Jul-2010
Turbidity Levels (NTU)
Monitored on 12-Jun-2008
After a Significant Runoff Event
HISTORIC WATER QUALITY TRENDS MONITORED AT ZORINSKY LAKE
Water Quality Standards Attainment
(2)
(1)
(7)
-----
-----
(7)
30
60%
0.40
100(3)
0
0%
n.d.
0.54
0.05(7)
39
78%
n.d.
n.d.
0.19
-----
-----
-----
-----
6
n.d.
55
-----
-----
-----
5
-----
n.d.
n.d.
333
750(5), 87(6)
0, 1
0, 20%
6
5
-----
n.d.
n.d.
n.d.
88(5), 30(6)
0
0%
3
5
-----
3
n.d.
4
340 , 16.7
0
0%
Beryllium, Dissolved (ug/l)
0.5
5
-----
n.d.
n.d.
n.d.
130(5), 5.3(6)
0
0%
Cadmium, Dissolved (ug/l)
0.5
5
-----
n.d.
n.d.
n.d.
7.7(5), 0.3(6)
0
0%
Chromium, Dissolved (ug/l)
2
5
-----
n.d.
n.d.
10
739 , 96
0
0%
Copper, Dissolved (ug/l)
2
5
-----
n.d.
n.d.
2
17(5), 11(6)
0
0%
Lead, Dissolved (ug/l)
2
5
-----
n.d.
n.d.
n.d.
87(5), 3.3(6)
0
0%
Mercury, Dissolved (ug/l)
0.05
5
-----
n.d.
n.d.
n.d.
0
0%
Mercury, Total (ug/l)
0.05
5
-----
n.d.
n.d.
n.d.
0.77(6)
0
0%
Nickel, Dissolved (ug/l)
3
5
-----
n.d.
n.d.
60
588(5), 65(6)
0, 1
0%
Selenium, Total (ug/l)
2
5
-----
2
n.d.
2
,5
0
0%
Silver, Dissolved (ug/l)
1
5
-----
n.d.
n.d.
n.d.
5.5(5)
0
0%
Thallium (ug/l)
6
5
-----
n.d.
n.d.
n.d.
1,400(5), 6.3(8)
0
0%
Zinc, Dissolved (ug/l)
3
5
-----
n.d.
n.d.
n.d.
147
0
0%
Microcystin, Total (ug/l)
0.05
25
-----
n.d.
n.d.
0.64
20(9)
0
0%
Acetochlor, Total (ug/l)(C)
0.05
15
-----
n.d.
n.d.
1.00
-----
-----
-----
Alachlor, Total (ug/l)
0.05
10
-----
n.d.
n.d.
n.d.
760(5), 76(6)
0
0%
0.05
25
0.27
0.30
n.d.
0.70
330 , 12
0
0%
Metolachlor, Total (ug/l)(C)
0.05
25
-----
n.d.
n.d.
0.50
390(5), 100(6)
0
0%
Pesticide Scan (ug/l)(D)
0.05
-----
-----
-----
(C)
Atrazine, Total (ug/l)
(C)
1
(5)
(8)
(5)
(6)
1.4
(5)
20
(3,5)
(6)
(5,6)
(5)
(6)
Acetochlor
5
-----
n.d.
n.d.
1.00
-----
-----
-----
Atrazine
5
-----
n.d.
n.d.
0.35
330(5), 12(6)
0
0%
Profluralin
1
-----
0.48
0.48
0.48
-----
-----
-----
ZORINSKY LAKE WATER QUALITY
MONITORING SITES
ZORINSKY LAKE IS EXPERIENCING
EUTROPHICATION
Eutrophication: The process by which
a lake acquires a high concentration
of nutrients, especially phosphates and
nitrates, that promote excessive growth
of algae. As the algae die and compose,
high levels of organic matter and the
decomposing organisms deplete the
water of available oxygen, which can
stress and cause the death of other
organisms, such as fish. Eutrophication
is a natural, slow-aging process for a
lake, but human activity can greatly
speed up the process as is the case in
Zorinsky Lake.
• The Omaha District is currently
investigating management tools,
such as hypolimnetic withdrawal
(i.e., low-level releases), that can be
implemented to reduce the impacts
of eutrophication on Zorinsky Lake
and enhance water quality.
• A watershed and water quality
management plan has been
developed by a multi-agency work
group and is being implemented
by the City of Omaha to protect
and enhance water quality in
Zorinsky Lake.
NOTES ON THE SUMMARY
OF NEAR-DAM WATER QUALITY CONDITIONS
n.d. = Not detected.
(A)
Nondetect values set to 0 to calculate mean. If 20% or more of
observations were nondetect, mean is not reported. The mean
value reported for pH is an arithmetic mean (i.e., log conversion
of logarithmic pH values was not done to calculate mean).
(B)
(1) General criteria for aquatic life.
(2) Use-specific criteria for aquatic life. (3) Agricultural criteria for surface waters.
(4) Total ammonia criteria pH and temperature dependent.
Criteria listed are calculated for median pH and
temperature values.
(5) Acute criteria for aquatic life.
(6) Chronic criteria for aquatic life.
(7) Nutrient criteria for aquatic life.
(8) Human health criteria.
(9) Nebraska utilizes the World Health Organization
recommended criterion of 20 ug/l microcystins in recreation
water for impairment assessment.
Note: Many of Nebraska’s WQS criteria for metals are hardness
based. As appropriate, listed criteria were calculated using the
median hardness.
(C)
Immunoassay analysis.
(D)
The pesticide scan (GCMS) includes: acetochlor, alachlor,
ametryn, atrazine, benfluralin, bromacil, butachlor, butylate,
chlorpyrifos, cyanazine, deethylatrazine, deisopropylatrazine,
dimethenamid, diuron, EPTC, ethalfluralin, fonofos, hexazinone,
isophenphos, metolachlor, metribuzin, pendimethalin, phorate,
prometon, prometryn, propachlor, propazine, simazine, terbufos,
triallate, and trifluralin. Individual pesticides were not detected
unless listed under pesticide scan.
*A highlighted mean value indicates use impairment based on State of
Nebraska 2010 and Draft 2012 Section 303(d) impairment assessment
criteria. The following use impairment criteria apply to growing season
(May - September) mean concentrations: Chlorophyll a = 10 ug/l, Total
Nitrogen = 1mg/l, Total Phosphorus = 0.05 mg/l.