Guidance Manua pdf

 

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Canals should be intensively monitored every week from early June to late November, 

when water temperature is higher than 70

o 

F (21

o 

C).  Intensive monitoring ensures the 

detection of rapid increases in MIB and geosmin concentrations in the water, which can 

change within a period of days.  At other times of the year, monthly samplings are 

recommended because MIB and geosmin concentrations are more stable.  Sampling 

sites should be no more than 3-4 miles apart to ensure accurate detection of the canal 

section that is producing MIB/geosmin. At known MIB/geosmin-producing canal sections 

upstream of WTPs, such as the Arizona Canal stretch between 24

th

 Street and 29

th

 

Avenue, sampling sites should be more closely spaced (1-1.5 miles).  

 

4.2  MEASUREMENT PARAMETERS 

 

Based upon three years of monthly and intensive monitoring an array of water quality 

parameters were selected that should be monitored in the future to provide immediate 

guidance on MIB or geosmin control options and data for predicting likely MIB or 

geosmin trends two to six weeks in advance.  Physical observations yield important 

clues regarding  interpretation of the data and for management.  The presence of 

stagnant water, the presence of algae mats, the “sniff test,” and other observations in the 

field are needed for these purposes.  A field sampling sheet is attached as Appendix A. 

Specific field and laboratory parameters and the recommended sampling frequency are 

presented in Table 4-2 and briefly discussed. 

 

 

Table 4-2.  Sampling frequency and water quality parameters to be measured (June-December) 

 

Monitoring Site 

Sampling 

Frequency 

 

Water Quality Parameters 

 

  

Terminal Lakes 

1x-2x per month  Field: Depth profiles of temp, DO; Secchi 

disk depth 

Lab (Epi- and hypolimnion samples): MIB, 

geosmin, chlorophyll a, conductance (two 

500 mL glass bottles), algae identification 

Rivers 

CAP Canal 

Arizona Canal (up to 

10 locations during 

the T&O season) 

South Canal 

Water Treatment 

Plants 

Approximately 

weekly 

Field: temperature 

 

 

Lab: MIB, geosmin, nitrate, chlorophyll a, 

specific conductance (two 500 mL glass 

bottles), algae identification 

 

 

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Temperature: Temperature is a good predictor of potential T&O episodes.  Temperature 

profiles in the reservoirs are also needed to determine whether the reservoirs are 

stratified.   

 

Dissolved oxygen: Dissolved oxygen is another useful indicator of stratification in the 

reservoirs.  During summer stratification, DO levels drop, often to near zero in the 

hypolimnion.  Increasing DO levels in the hypolimnion are a good indication (sometimes 

better than temperature) that the reservoir is beginning to destratify. DO levels are 

measured using a DO meter with a long submersible cord. It is not necessary to 

measure DO in the canals or the water treatment plants. 

 

Specific conductance: Specific conductance is useful in determining the source of water 

within the canals.  A large change in specific conductance over a short period (a week or 

two) generally indicates a change in source water.  Specific conductance is related to 

total dissolved solids (TDS).  The TDS of the Verde River system (300-500 mg/L), Salt 

River system (1000-1400 mg/L), and CAP system (600-900 mg/L) are quite different but 

can vary from year to year depending upon dilution from watershed snowpack or 

monsoon rainfall. 

 

Nitrate: Algae growth is often limited by nitrogen, so this nutrient can be useful  in 

predicting when algae are likely to grow.  Nitrate is a very good indicator of well water 

inputs.  Background nitrate nitrogen concentrations in surface water are usually < 0.1 

mg/L; but may increase to > 0.5 mg/L when well water is being pumped into the canals. 

 

Algae: Producers of MIB/geosmin are primarily blue-green algae belonging to the 

taxonomic family Oscillatoriaceae, a group of microscopic filamentous organisms that 

are common to fresh waters (Figure 4-1).  Algae in the reservoirs are collected using a 

submersible Kemmerer sampler that is triggered to collect samples at specific depths.  

Periphyton samples can be collected using a periphyton sampler developed for this 

project (Appendix B) or by grab samples from canal walls or shoreline. 

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MIB Producers 

Phormidium sp

. 

Pseudanabaena sp. 

 

Geosmin Producers 

Oscillatoria agardhii 

Oscillatoria splendida 

 

Figure 4-1. Blue-green algae producers of MIB and geosmin belonging to the taxonomic family 

Oscillatoriaceae. 

 

An estimate of periphyton  biomass on canal walls and lake plankton can be determined 

by extracting an aliquot of periphyton sample in 100% acetone at 4

0 

C in the dark for 48 

hours and then measuring for chlorophyll  a absorbance at 664 nm with a 

spectrophotometer (American Public Health Association et al., 1999). 

 

The Interactive Taxonomic Guide (CD-ROM) developed for this project enables one to 

identify a potential producer, but confirmation of production requires validation by GC/MS 

analysis of the isolated organism.  Generally, production of MIB/geosmin increases with 

increase in producer biomass.  However, since periphytic producers usually represent 

only a small fraction of the total algal biomass, biomass estimates (chlorophyll  a) are of 

limited value in predicting MIB/geosmin production, especially in the reservoirs.  In the 

Arizona Canal, MIB concentrations typically became elevated when chlorophyll  a values 

exceed 10 mg/m

2

. 

 

Although many species of blue-green algae are present in the reservoirs and canals, not 

all species within a given genus, or even strains within a species produce MIB and 

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