Water quality is becoming an increasingly important part of hydrologic data collection programmes. The rapidly expanding utilization of the water resource coupled with an increased use of surface and ground water for the disposal of waste products has created a complex measurement and interpretation problem for hydrologists. The complexity of the problem is immediately apparent in reviewing the voluminous literature on water quality which has appeared in recent years. A review of published literature on analytical methods for water analysis made in 1969 (Fishman and Robinson, 1969) listed 664 methods which had been developed in a two-year period, 1967-68.
2.1.2.1 Selection of water-quality parameters
Any design for a water-quality network faces the immediate question : What parameters should be included in the measurement programme that will provide a broad base of information for general use ? About sixty chemical, physical, and biological properties are pertinent to various uses. (See Table 2.1.) It must follow that the design or plan for measurement selected willbe flexible so that the selected or key parameters measured will lead logically from one level of activity to the next higher as measured by parameter diversity.
The following parameters are recommended for measurement in hydrologic water- quality networks.
Chemical parameters : Physical parameters : Biological parameters : dissolved solids colour biological diversity dissolved oxygen turbidity coliform.
hardness temperature
alkalinity radioactivity
nitrate odour
phosphate. P H
sediment.
All of the parameters recommended for inclusion in the water-quality network are per- tinent to three or more uses of water: i.e., domestic, industrial, and irrigation. They are all relatively simple standard determinations which can be made with a minimal amount of equipment.
Description of different systems characteristics
TABLE 2.1 Tests of water to define water quality for various uses
Property or Property or
I. (A) Tests for determining potability or pollution of water for domestic and related uses.
2. (B) Test for determining probable suitability of water for industrial use.
3. (C) Tests to determine the general suitability of water for agricultural uses.
4. (D) Tests that provide data for studies in the natural sciences (a use of data that does not involve a
use of the water).
5. (E) Tests pertinent to three or more uses of data.
Clremica1 parameters. Dissolved substances include both inorganic and organic com- pounds, dissolved gases, and radioisotopes. Dissolved inorganic substances include the commonly occurring mineral constituents such as calcium, magnesium, sodium, and potassium. Salts of these elements in varying concentrations determine the fitness of water for a wide range of municipal, industrial, and agricultural uses. Although normally considered to be a physical property, p H is a measure of hydrogen ion concentration and is an important water-quality parameter.
The chemical parameters, dissolved solids, hardness, and alkalinity, are major water- quality indicators and are useful in making regional comparisons.
Dissolved gases in water include oxygen, carbon dioxide, nitrogen, hydrogen sulphide, methane, ammonia. Of these, dissolved oxygen is the most important and is used as an index of dissolved gases for network design purposes.
Physical parameters. Of the physical properties temperature, colour, odour and turbidity are the most significant. Others include density and viscosity. Non-soluble, particulate substances in streams include inorganic sediments, natural organic materials (coal particles, leaves, and other plant debris), and municipal and industrial wastes. Of these, the municipal wastes decompose relatively quickly and diminish relatively rapidly below their point of entry. Their effects on water quality bear mostly on the dissolved constituents and biota. They are taken into account in the measurement of corresponding parameters and consequently the hydrologic network for particulate materials will be organized to describe mostly inorganic sediments.
Biological parameters. Biological diversity in a stream community is illustrated by such plant and animal organisms as bacteria, fungi, algae, diatoms, mosses, flowering plants, protozoa, worms, insects, snails, mussels, and fish.
Within the hydrologic network (including benchmark and vigil stations) there is a need to know the extent of highly diversified biological systems within the basin as a baseline for comparison with conditions after a stream is affected to some degree by the works of man.
2.1.2.2
Stations in the hydrologic network may be operated at several levels of effort. In the early stages, measurements indicated in the foregoing section willbe prevalent. As data are collected, analytical studies made, and knowledge increased, the emphasis may change.
These changes may result in an expansion of effort to specific parts of the water-quality regime such as the chemical, physical, or biological, for better definition of variability and a corollary increase in frequency of sampling. This would require additional levels of effort where anomalous situations may be found due to certain environmental conditions.
Variability of the measured parameters willdetermine the level of effort required to define the causative factors. Extreme variations in dissolved solids would require a detailed examination of individual ions to determine the cause and relate the variability to a specific or general terrane characteristic. Rapid fluctuations in turbidity would lead logically into a sediment programme to determine quantities of suspended material, particle size, and mineral composition. Two additional levels of measurement are planned and illustrated in Table 2.2.
After the range in concentration has been determined and its relation to the terrane documented, the level of effort could be reduced to the initial general surveillance level.
Because streamflow varies considerably within a year, and from year to year, the con- centration of dissolved and suspended solids varies accordingly. The observation of water quality will also emphasize time-series measurements.
Level of efort within the network
Description of diflerent systems characteristics
TABLE 2.2 Level of measurement effort within the water-quality network
Level I
SURVEILLANCE
Level 11 INTENSIVE
Level 111 PROJECT
Chemical parameters:
Dissolved solids SiO,, Ca, Mg, Na, K, SO,, C1, F, B, Fe, M n
Li, Se, Br, I, S, SO, AI, As, Cr, Cu, Pb Hardness Ca, Mg, Fe, M n Ba, Sr, AI
Alkalinity (Acidity) HCO,, CO,, OH, H+, Buffering capacity. Immediate,
H!W4 potential, free acidity
Nitrate NH,, NO, Organic nitrogen
Phosphate HPO,, HZPO4
Physical parameters: Cliemical:
Colour Chloroform extracts, Infrared spectre of chloroform ether insolubles, extract and neutrals
water solubles
Odour weak acid-odour
bases-amines neutral strong acids
PH See ‘Alkalinity’
Turbidity To sediment network Radioactivity
Temperature
Biological parameters:
Biological diversity
Sr9”, Ra, U
Bacteria, fungi, algae, bryophyta, protozoa, nematoda, Pisces
B. coli Str. Faecalis Virus
Dissolved oxygen Biochemical oxygen
There is a certain relationship between levels of measurement effort and frequency of measurement. Because the intensity of water-quality problems may not be equal in all areas, certain measurements may be made at different levels of frequency, monthly, daily or continuous. For example, the time-series measurement of biological parameters may be on a different frequency schedule than those involving chemical and physical parameters.
The hydrologic factors which influence biological diversity are slightly different than those which influence quality. For example, the nature of the stream-bed community is largely determined by the following factors :
1. The velocity of the water;
2. The size, nature, and stability of the stream-bed;
3. Physical character of the water;
4. Chemical nature of the water;
5. The presence of stream-bank vegetation.
The sampling frequency for measuring biological diversity might be on a seasonal basis in order to obtain data applicable to a wide range of environmental factors.
Conversely, dissolved oxygen might be measured at several frequency levels during a particular time period. During the colder months when water temperatures are low and dissolved oxygen solubility is high, samples might be obtained at monthly intervals. In the spring and summer when the water is warm and the solubility of oxygen low and when there is increased biological activity either producing or consuming dissolved oxygen in the water, the sampling frequency required to define the environmental influences might be daily or even continuous.
The sampling in the water-quality network would be determined by the parameter variation and would not be imposed by fiat. A n increase in variability in one or two parameters requiring an increase in measurement and sampling frequency would not require a complementary increase of the same order of magnitude in the other parameters.
2.1.2.3
At the present time at least two different types of automatic water-quality sensing systems are available for water pollution studies. One type utilizes potentiometric sensors. In its basic form, it meets the needs of a simple in situ recording system that can be easily expanded to meet more complex data requirements. The second type uses resistance-type sensors for in situ monitoring in remote locations where only battery power is available.
Automated systems for recording water-quality parameters
2.1.2.4 Systems using potentiometric sensors
The heart of a typical potentiometric sensor system is a programmed, servo-drive unit (Fig. 2.1). It is designed to accept a maximum of ten channels of input from potentiometric sensors (dissolved oxygen, p H , etc.) and to automatically programme these inputs into a recording device. The unit consists of a measuring circuit for each channel, a programmer, a solid-state amplifier, and the drive unit.
Each channel has an individual, interchangeable measuring circuit to accommodate the variable inputs from the sensors. These circuits are precision resistor networks for voltage adjustments; thus, each circuit has individual span and zero adjustments. Circuits, up to the maximum ten channels, can easily be added to the system in the field. The ten circuits share a single amplifier.
Potentiometric sensors may determine water temperature, wet and dry bulb air tem- peratures, specific conductivity, dissolved oxygen, oxidation-reduction potential, p H , turbidity, sunlight intensity, wind velocity, and wind direction. The outputs of these sensors are linearly proportional to the variable being measured and are automatically compensated for temperature variations.
Description of different systems characteristics
t
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2.1.2.5 Systems using resistance-type sensors
Several data sensors of the resistance type exist. Among them are sensors for water tem- perature, wet and dry bulb air temperatures, specific conductivity, and soil moisture.
2.1.3 Lakes, impoundments and estuaries
Lakes and impoundments together represent an enormous volume of fresh water io storage. These two types of surface-water bodies are similar in that their water retention times are relatively long. The estuaries, because of their great volumes of water available for cooling and waste assimilation and their usefulness as shipping lanes, have become centres of population and industry.
The importance of the quantitative and qualitative control of these water bodies is increasing as the ratio of available water to water need decreases. General quality degrada- tion follows eutrophication in lakes and reservoirs and salt encroachment from increased waste loading and fresh-water diversion have already affected certain estuaries significantly, and can be expected to affect others. Systematic collection and interpretation of hydrologic data are required to explain the nature and magnitude of the natural controls in such water systems, and to predict their trends in the variety of environments involved.
2.1.3.1 Eutrophication of lakes
Eutrophication of lakes is usually associated with the growth of large amounts of aquatic plants. These plants, grown in small amounts are beneficial. In large amounts they may seriously impair the quality of the water.
The cause of overabundance of aquatic plants seems to be excessive fertilization by dissolved nutrients.
The problems of eutrophication are not limited to lakes, but are important in rivers, harbours, and estuaries. What will be said about lakes willapply in some respects equally to these other surface waters. The areas and effects of eutrophication may be summarized as follows.
1. Water supplies : increased cost of treatment, taste and odours, colours, 2. Recreation: loss of boating, swimming, fishing, loss of property value, 3. Agriculture: toxicity, aquatic weed growth, clogged irrigation canals.
1. Domestic and industrial wastes (phosphorus and nitrogen);
2. Urban drainage;
3. Agricultural runoff (phosphorus and nitrogen from fertilizers);
4. Natural runoff;
5. Lake sediments;
6. Atmosphere (mainly phosphorus and nitrogen from rainfall);