Monitoring:Monitoring

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Model Application: Temperature

Model Application: Point/Nonpoint Nutrient Loadings

Model Application: Eutrophication

Model Application: Temperature and Dissolved Oxygen

Data Required to Support Reservoir Water Quality Modeling

Assuming that reservoir water quality monitoring will include the effects of nutrients and primary production on other water quality variables, e.g., dissolved oxygen (DO), the following types of data are required:

  • Boundary conditions
  • Initial conditions
  • Site description/geometry/bathymetry
  • Parameters (e.g. coefficients)
  • In-pool/release observations (for calibration/verification)

Boundary Conditions

The types of boundary conditions required for reservoir water quality models consist of the following:

  • Inflowing tributaries
  • Other non-point source runoff
  • Point source loadings
  • Outflows
  • Meteorology
  • Sediment fluxes (for older models)

Tributary monitoring needs are shown in the table below. The variables shown in the "more complete" list are in addition to the minimum list. Variable groupings are for convenience only.

Minimum More Complete Frequency
Q = Flow Rate
T = Temperature
C= Conductivity
DO = Dissolved Oxygen
pH
TDS = Total Dissolved Solids
→ (Enough samples to correlate to C)
D or C
D or C
D or C
TOC = Total Organic Carbon DOC or POC = Dissolved or Particulate Org. Carbon W
SRP = Sol. Reactive Phosphorous
TP = Total Phosphorous
TDP = Total Dissolved P
TIP = Total Inorganic P
→ (i.e. total reactive and acid-hydrolyzable P)
DIP = Dissolved Inorganic P
→ (can get organic forms from these)
W
W

W
NO2+NO3-N = nitrite and
nitrate nitrogen
TKN = Total Kjeldahl N W
NH4-N = Ammonium N Filtered TKN
TSS = Total Suspended Solids
ISS or VSS = inorganic or volatile suspended solids
→ (These are not critical unless turbidity and its
impacts are of concern. SS do affect P partitioning
in some models, light, and water density)
Chl a = chloryphyll a
ALK = alkalinity
Si = dissolved silica
W
W
W



W
W
W
Note: D = daily, W = weekly or on that order, C = continuous recording

In Pool/Release Observations

Observations are required from within the reservoir pool and preferably in the release for model calibration and verification. One study period (e.g. a year) is typically used for calibration, and another period (e.g. another year with completely different hydrology ) is used for verification. Some in-pool observation profiles should be taken at frequent depth intervals (e.g., one meter), while others can be less detailed. Depth intervals for the less detailed profiles (i.e., grab samples for chemical analysis) should be detailed enough to characterize sharp gradients in concentration. One in-pool station should be near the dam (about several hundred meters from dam) and over the channel. Two or more stations should be placed at other locations, e.g., mid pool and headwaters.

Release temperature and DO should be monitored (primarily for selective withdrawal verification) daily, as a minimum, at conventional dams; hourly recordings are preferred at peaking hydropower dams.

In-pool profile monitoring needs are shown below. Again, the variables shown in the "more complete" list are in addition to the minimum list. Variable groupings are for convenience only.

In-Pool Profiles
Minimum Necessary More Complete
In-situ
T, DO, C, pH at about 1.0 meter
intervals depending on depth.
Need to characterize sharp gradients.
None
Samples for chemical analysis (depth intervals can be less frequent than those for in-situ)
Chl a algal biomass (dry) and type
TOC DOC or POC
SRP TDP
TP TIP
DIP
→ (can get organic forms from these)
NO2+NO3-N TKN
NH4-N Filtered TKN
light trans (e.g. Secchi depth) TDS (enough samples to correlate to C, cond.)
TIC = Total Inorganic Carbon or CO2
ALK
Si
TSS, ISS, or VSS
dissolved (i.e. reduced) Fe
total Fe
dissolved (i.e. reduced) Mn
total Mn
total dissolved sulfide
SO4 = sulfate
FeS = iron sulfide

Notes:

  1. TDS important only if concentrations are high enough to affect water density or impact water supply uses.
  2. Fe, Mn, S, FeS, and SO4 important if concerned about the affect of anoxia on the release of these problem constituents from bottom sediments and possible release to the downstream environment.

Reference

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