Guidance Manua pdf
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- Bu səhifədəki naviqasiya:
- Bartlett Lake 0 10 20 30 40 50 60
- Dec-00 Feb-01 Apr-01 Jun-01 Aug-01 Oct-01 Dec-01 Feb-02
- Saguaro Lake 0 20 40 60 80 100 120
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0 10 20 30 40 50 60 Aug-99 Oct-99 Dec-99 Feb-00 Apr-00 Jun-00 Aug-00 Oct-00 Dec-00 Feb-01 Apr-01 Jun-01 Aug-01 Oct-01 Dec-01 Feb-02 Apr-02 MIB, ng/L Epilimnion Hypolimnion Verde R. below Bartlett
Figure 4-3. MIB in the epilimnion, hypolimion, and outflow from Bartlett Lake. Figure 4-4. MIB in the epilimnion, hypolimion, and outflow from Saguaro Lake.
For Lakes Pleasant and Bartlett, MIB in water released from the hypolimnion during the stratification period rarely or never exceeds 10 ng/L (Figures 4-2 and 4-3). Water released from Saguaro is most often in the range of 10-20 ng/L during the summer stratification period. The higher concentrations for Saguaro occur for two reasons. First, MIB concentrations in the epilimion of Saguaro Lake are higher than in the other two reservoirs (Figure 4-4). Second, Saguaro is not as strongly stratified, as the other two reservoirs, which results in more mixing between the epilimnion and hypolimion.
Mixing of the water column occurs in Saguaro and Bartlett Lakes around mid-October, and in Lake Pleasant in November. At lake turnover, MIB levels become uniform throughout the lake, increasing the concentration of MIB released downstream. For both Bartlett and Saguaro, peak MIB concentrations in the released water occurred during October, following turnover (Table 4-3).
25 Table 4-3. Average monthly MIB concentrations over the three-year T&O study for the CAP Canal at 7 th
Street (release from Lake Pleasant and/or Colorado River water), the Verde River below Bartlett Lake, and the Salt River below Saguaro Lake. The time of thermal destratification turnover is indicated by boldfaced values.
CAP at 7th Street Verde R. below Bartlett Lake Salt River below Saguaro Lake January 0 0 4 February 0 0
March 1 1 19 April
1 2 5 May 0 0 8 June
1 2 9 July 1 3 12 August
2 2 10 September 4 8 16 October
4 13 19 November 5 2 8 December 0 1 10
MIB in the reservoirs degrades slowly after turnover, reducing the concentrations throughout the winter. Lab experiments and mass balance studies show that a typical MIB degradation rate is about 1 ng/L-day (Figure 4-5).
26 0 10 20 30 0 10 20 30 40 Incubation Time (day) Geosmin (ng/L) R L =0.81 ng/L/d R L =1.0 ng/L/d B 0 10 20 30 40 50 0 10 20 30 40 Incubation Time (day) MIB (ng/L) R L =0.90 ng/L/d R L
A
Figure 4-5. Kinetic degradation of MIB (A) and geosmin (B) in water collected at a depth of 5 m from Saguaro Lake (September 2000). Abiotic (filtered) control sample ( ¾ bioseed ( r ); sample with the added bioseed ( ¯ ). Error bars are one standard deviation. Lines represent fitted laboratory pseudo zero-order rates (R
).
Finally, the amount of MIB in SRP water depends upon which side of the system is delivering water. The timing of the Salt-to-Verde shift is important. This shift normally occurs in October (Table 4-4). Because MIB levels are normally higher in the Salt River than in the Verde River, the switch generally decreases MIB in water delivered to the Arizona and South Canals. Yüklə 0,58 Mb. Dostları ilə paylaş:
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