Water Quality Parameters

Water quality measurements include chemical, physica

l and biological parameters. The following is a brief descripti

on of some commonly used parameters.

Chlorophyll

Chlor

ophyll is the pigment that allows plants, including algae, t

o convert sunlight into organic compounds through photosyn

thesis. Measuring chlorophyll a concentrations in water is a s

urrogate for an actual measurement of algae biomass. Exce

ssive amounts of chlorophyll a indicate the presence of blo

oms, which usually consist of a single species of algae - typ

ically one that is not desirable for consumption by fish and oth

er predators. Unconsumed algae sink to the bottom and deca

y, depleting deeper water of oxygen.

Suspended Minerals

Suspended minerals are a measure of the amount of sediment

moving along in a stream. It is highly dependent on the flow of

water and usually increases during and immediately after rai

n events. As the sediment settles out of the water, aquatic hab

itats are often destroyed.

Colored Dissolved Organic Carb

on

Colored dissolved organic carbon, also referred to as f

ulvic acid and humic acid, contributes to the brownish tan c

olor of a waterway. Tannins are one example of such compoun

ds. In a nutrient-poor environment, it can serve as a nutrient allo

wing for the growth of algae whereas in a nutrient-rich environ

ment, it can be given off as a byproduct from the decay of alga

e.

Turbidity

Turbidity is a measure of the amount of particu

late matter that is suspended in water. Water that has high tu

rbidity appears cloudy or opaque. High turbidity can cause i

ncreased water temperatures because suspended particles

absorb more heat and can also reduce the amount of light pene

trating the water.

Secchi Depth

Secchi depth is the depth to

which one can see into a lake and is an indication of water cla

rity. This measurement is obtained by lowering a black and wh

ite disk into the water and recording the depth at which it is n

o longer visible.

Dissolved Oxygen

Although water molec

ules contain an oxygen atom, aquatic organisms rely upon a s

mall amount of oxygen that is actually dissolved in the water.

In general, rapidly moving water contains more dissolved o

xygen than slow or stagnant water and colder water contai

ns more dissolved oxygen than warmer water. Bacteria consum

e oxygen as organic matter decays. As a result, an oxygen-defi

cient environment can develop in lakes and rivers with excess

organic material. These conditions can eventually lead to fish

kills.

Temperature

Water temperature affects the abil

ity of water to hold oxygen, the rate of photosynthesis by aq

uatic plants and the metabolic rates of aquatic organisms. Ca

uses of temperature change include weather, removal of sha

ding streambank vegetation, impoundments, discharge of co

oling water, urban storm water, and groundwater inflows to th

e stream.

pH

pH is a term used to indicate the alkalinity or

acidity of a substance as ranked on a scale from 1.0 to 14.0.

Acidity increases as the pH gets lower. A pH of 7.0 is neutra

l. Aquatic organisms differ as to the range of pH in which they

flourish.

Streamflow

Streamflow, or discharge, is the volum

e of water that moves over a designated point over a fixed peri

od of time. It is often expressed as cubic feet per second (ft3/s

ec). The flow of a stream is directly related to the amount of wa

ter moving off the watershed into the stream channel. It is af

fected by weather as it increases during rainstorms and decr

eases during dry periods, and also varies by season.

Benth

ic Macroinvertebrates

Macroinvertebrates are organisms

that are large (macro) enough to be seen with the naked eye an

d lack a backbone (invertebrate). Benthic refers to the bottom

of a waterway. Examples of benthic macroinvertebrates in

clude insects in their larval or nymph form, crayfish, clams

, snails, and worms. Most live part or most of their life cycle atta

ched to submerged rocks, logs, and vegetation. The basic pri

nciple behind the study of macroinvertebrates is that some

are more sensitive to pollution than others. Therefore, if a str

eam site is inhabited by organisms that can tolerate pollutio

n and the more pollution-sensitive organisms are missing a po

llution problem is likely.

WATER QUA

LITY PARAMETERS AND DRINKING WATER STANDARDS

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