Guidance Manua pdf

 

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6.   Apache Lake drawdown.  SRP must drain 25,000 AF (833 AF/day, or 416 cfs) from 

Apache Lake in September to increase storage capacity.  This constraint is 

important, because this is a considerable portion of the flow in the Arizona and 

South Canals during September. 

 

7.  Maintenance of minimum flow in the Verde River. SRP must maintain 100 cfs “plus 

orders” flow in the Verde River, per agreement with the Gila River Indian 

Community.  This constraint has minimal effect on blending considerations. 

 

8.  Maintenance of minimum flow across the Arizona Canal fish barrier.  Flow across 

the fish barrier at the head of the Arizona Canal must be maintained at 100 cfs.  This 

means that at least 20% of the flow in the Arizona Canal will always be SRP water 

during low flow.  Again, this is a minor constraint with respect to the feasibility of 

blending. 

 

9.   Maintenance of minimum flow from Apache Lake.  Flow from Apache Lake must be 

maintained at 8 cfs (~ 475 AF/month) from November 1 to May 1, per agreement 

with U.S. Fish and Wildlife.  This regulation is not important, because T&O problems 

generally occur in the late summer and fall. 

 

10.  Nitrate levels in the Arizona Canal.  Pumping from SRP wells may be limited if it 

causes elevated nitrate or salt buildup.  This constraint would not likely be important 

for the Arizona Canal, because nitrate levels never approach EPA’s MCL.   

 

The newly modified Water Exchange Agreement should give the water utilities greater 

flexibility with respect to blending.  In general, however, other constraints probably limit 

the extent to which blending could be used to achieve better water quality in the Arizona 

Canal in normal-to-wet years.  During dry years, more CAP water would be used to 

augment the SRP water supply.  COP could take advantage of this situation in dry years 

to optimize the delivery of CAP and SRP waters by using a greater proportion of SRP 

water early in the season (April-August) and more CAP water later in the season (e.g., 

September-October). 

 

5.3  MANAGEMENT OF CANALS 

 

The canal system is a major source of MIB/geosmin production. Over a ten-fold increase 

in MIB/geosmin concentrations has been detected over a distance of a few  miles of the 

canal during the summer and fall. Several species of blue-green algae, which are 

primarily distributed along the canal sidewalls, are confirmed producers of MIB.  Two in-

canal implementation strategies have been developed to prevent growth of  T&O culprit 

organisms in the canal system. One is copper treatment and the other is canal wall 

brushing.  The two approaches have been implemented primarily in the Arizona Canal. 

However, the principles and techniques involved in these treatments are applicable to 

other canals within the Phoenix water supply system, and may be further applicable for 

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other regions where major open canal systems distribute water from reservoirs or other 

surface water supply systems. 

 

Preventing and eliminating the growth of culprit organisms in the canal system will 

reduce MIB/geosmin concentrations in water entering into the WTPs.  Copper treatment 

and canal wall brushing are effective and cost-affordable tools for reducing the T&O 

problem in canals.  Brushing may be utilized as a more intensive localized algae control 

measure for known hotspots, whereas copper treatment is of greater systemic value 

since it affects a larger part of the canal system. 

 

5.3.1  Copper Treatment 

5.3.1.1 

Selection of Desired Product 

 

Two different types of copper-based algaecides, Cutrine-Plus and Earthtec, have been 

tested in the Arizona Canal. The former is a chelated elemental copper with 

triethanolamine, whereas the latter is a copper sulfate-based acidic solution (pH 0.5). 

Both are registered by the USEPA as algaecides, and the latter is certified to ANSI/NSF 

Standard 60, Drinking Water Treatment Chemicals. 

 

Both algaecides reduced the production of MIB and geosmin in the canal, but Cutrine-

Plus appeared to be more effective than the Earthtec copper.  However, application of 

Cutrine-Plus in the canal resulted in a temporary increase in chlorine demand in the 

WTPs downstream shortly after copper application. In contrast, little chlorine demand 

was observed when Earthtec was introduced.  The increase in chlorine demand was due 

to the reaction of triethanolamine residues of Cutrine-Plus with free chlorine to form 

organic chloramines.  The Earthtec product is therefore the algaecide of choice.  

 

5.3.1.2 

Treatment Dose and Duration 

 

The maximum recommended dosage of Earthtec solution is 0.2-0.4 mg/L Cu.  

Concentrations of 0.5 mg/L may result in some fish-kill. The toxicity of copper to blue-

green algae and other microalgae is most pronounced under light conditions and when 

water temperature is at least 60° F.  Therefore, it is critical to select sunny days for 

copper application, and to start application early in the day so that the treatment is 

conducted in continuous daylight.  A dosing period of 6 to 8 hours achieves satisfactory 

results. 

 

5.3.1.3 

Treatment Site and Length 

 

Copper addition should occur at the upper stretch of a canal section that experiences 

high concentrations of MIB and geosmin.  Ideally, the copper solution should be added 

into the canal at a radial gate to facilitate even distribution and rapid mixing of copper.  In 

case a radial gate is not available, a large dilution of concentrated Earthtec solution with 

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