To supplement historic data and help determine the quality of the Shasta River and Klamath River water in the reach between Iron Gate Dam and Hamburg, sampling surveys were conducted from the summer of 1981 through the spring of 1983. The 13 stations shown as study stations in Plate 1 were sampled periodically to determine seasonal and diel variations. Several supplemental stations where historic data are available or which were sampled during the study are also shown in Plate 1. Measurements were made to deter- mine the chemical, physical, and biological characteristics of this important water resource. The following sections present information on the water quality measurements, sampling procedures, and analytical methods.

The suitability of water for beneficial use is determined by its quality, which can be divided into three categories: chemical, physical, and biological. historically, chemical and physical characteristics have been of primary concern, but increased emphasis on environmental concerns has promoted greater interest in biological quality, which is more costly and difficult to determine.

Precipitation, as it reaches the earth, is an excellent solvent. It contains dissolved gases, such as carbon dioxide and oxygen, but normally contains few dissolved solids. As water passes through the hydrologic cycle, either on the surface or through the ground, it dissolves minerals from the materials it contacts. The amount and type of minerals dissolved reflect the composition of these materials and the hydrologic conditions governing the rate of water movement. Often, more salts and pollutants are added by sewage, industrial wastes, and irrigation return flows. These dissolved substances can determine water's suitability for various beneficial uses.

An indication of the overall chemical quality can be obtained by determining and summing the concentrations of individual ions in a water. A measure of the total dissolved solids (TDS) can also be obtained by filtering a water sample, drying it, and weighing the residue. A third technique measures the electrical conductivity (EC) of the water sample, as that value can be related to the ionic content of the water. Ions commonly found in natural waters and most often looked for in laboratory analysis include calcium, magnesium, sodium, potassium, bicarbonate, carbonate, sulfate, chloride, and boron. Each of these is important to one or more beneficial uses.

Another important chemical factor is pH, which is a measure of the water's acidity (hydrogen ion content). The pH scale ranges from 0 to 14, with a value of 7 being neutral. Most natural waters have a pH in the 6.5 to 8.5 range, while an acid, such as lemon juice, has a pH of about 2, and household ammonia has a pH of about 12.

Alkalinity is a measure of a water's ability to withstand changes in pH and is due to the carbon dioxide, bicarbonate, and carbonate equilibrium in the water. This buffering is important because it dampens pH fluctuations that might occur due to waste discharges or intense algal growth. It also serves as a source of inorganic carbon for plant growth.

Water contains varying amounts of certain elements which are essential to biologic productivity and are referred to as nutrients. Such metals as iron, copper, molybdenum, etc., are needed in trace amounts and are called micronutrients. Carbon, nitrogen, and phosphorus are needed in larger quantities and are referred to as macronutrients. The two elements most often considered limiting to primary productivity in aquatic systems (if there were more of that element present there would be more growth) are nitrogen and phosphorous.

Nitrogen is found in water in the form of nitrate, nitrite, and ammonium ions, ammonia gas, or as part of nitrogen-bearing organic compounds. Most aquatic plants can use nitrate, ammonia, and perhaps simple organic nitrogen compounds.

Phosphorus is found in water as orthophosphates, polyphosphates, and organic phosphorus. Most forms are converted in nature to orthophosphates by bacterial action or hydrolysis, and this is the form used by organisms. Both orthophosphate and total phosphorus levels are often included in nutrient determinations.

Dissolved oxygen (DO) is one of the most important components measured in water, as it is essential to aquatic plant and animal life. The amount of oxygen that dissolves in water is primarily a function of water temperature, air pressure (altitude), and dissolved mineral concentration. Natural aeration and oxygen from plant photosynthesis are the two most important sources of oxygen in surface waters. Dissolved oxygen is used in respiration by aquatic organisms and by biochemical demands created by decomposing organic materials. To maintain a healthy aquatic environment, DO levels should be near saturation for cold water systems and above 5 milligrams per litre (mg/L) for warm water systems.

Temperature and turbidity are important physical characteristics of water. Temperature greatly influences the suitability of a water for its beneficial use. The metabolisms of aquatic organisms respond to the temperature of their environment. (As a general rule, metabolic activity will approximately double with each 10' C increase in temperature, to the limit of the organism's range of tolerance.) Temperature also affects the solubility of gases and other substances in water, water density, and its viscosity. These factors are of great importance in aquatic environments.

Turbidity is the second important physical water quality characteristic often measured. Turbidity, or cloudiness, of water is caused by suspended matter, organic and inorganic, which obstructs the passage of light through the water. Highly turbid waters are unsightly and may pose a hazard for swimmers or other recreationists. As light penetration is restricted in turbid waters, turbidity can reduce biologic productivity and limit types of plants that can exist.

Another measure of suspended matter in water is the suspended solid determination. it usually correlates with turbidity but is a better measure of the sediment being transported by a stream.

Although observations were made of many organisms during this investigation, only benthic macroinvertebrates were sampled and evaluated. The numbers and assemblage of benthic organisms are excellent indicators of the general health of a stream--its productivity and its water quality. Unlike fish, which can escape adverse conditions through their mobility, benthic organisms cannot, making bottom life forms especially suited for studies aimed at determining long-term aquatic conditions.

Water samples were collected during this study from near the center of flow at each station. At low flows, samples were usually collected by wading, while at higher flows, samples were collected from bridges or by sampling from the river bank. Most samples were collected in plastic buckets. Temperature, PH, DO, and EC measurements were usually made at the time of each visit, while water samples were collected for analysis at the Department's laboratory at Bryte.

Temperatures were measured with standard field thermometers whose calibrations had been checked in the laboratory. During some diel surveys, maximum-minimum thermometers were also placed in the river to verify the temperature variations measured during sampling visits.

Field pd was determined by using Hellige comparators with appropriate indicator solution and disk. Laboratory pH's were also run on selected samples with a calibrated glass electrode-type pH meter.

Dissolved oxygen levels were measured at the time of sampling using the modified Winkler technique. Field kits use fixing reagents in powdered form.

Electrical conductivity was measured on portable Beckman solubridges that had been checked on known solutions. Selected samples that were sent to the laboratory also had EC determinations made for quality control and to better define the TDS-EC relationship.

Turbidity samples were measured with a Hacli Model 2100A turbidimeter which is a nephelometer-type instrument.

Samples for standard mineral (chemical) analysis were collected in sample-rinsed plastic bottles and transported to the Bryte laboratory for analysis. Table 2 lists the standard methods used at that laboratory.

Trace metal samples were collected in plastic buckets or dipped directly from the river. Special acid-rinsed bottles were used for sampling. Double-distilled nitric acid was added to reduce the pH to 3 and the samples were transported to the laboratory.

Table 2. Analytical Methods for Water Quality Parameters

Parameter	Method
Electrical Conductivity	Beckman Wheatstone Bridge
Total Hardness	EDA - Titrimetric - AWWA
Sodium	Flame Photometric - AWWA
Potassium	Flame Photometric - AWWA
Sulfate	Gravimetric - AWWA
Chloride	Argentometric AWWA
Boron	Carmine - AWWA
Arsenic	Silver Diethyl AWWA
Barium	Atomic Absorption Spectrophotometric
Cadmium	Atomic Absorption Spectrophotometric
Chromate	Atomic Absorption Spectrophotometric
Copper	Atomic Absorption Spectrophotometric
Iron	Atomic Absorption Spectrophotometric
Lead	Atomic Absorption Spectrophotometric
Manganese	Atomic Absorption Spectrophotometric
Zinc	Atomic Absorption Spectrophotometric
Mercury	Cold Vapor Atomic Absorption - EPA
Dissolved Nitrate	Brucine - AWWA
Total-Ammonia	Distillation and Nesslerization - AWWA
Total Organic Nitrogen	Digestion and Nesslerization - AWWA
Dissolved Phosphate	Stannous Chloride - AWWA
Total Phosphorus	Stannous Chloride, Sulfuric Nitric Acid Digestion - AWWA

Nutrient (nitrogen and phosphorus series) samples were collected in plastic bottles and held in portable ice chests for delivery to the laboratory. When storage was to exceed 48 hours, samples were frozen and stored in a freezer.

Benthic invertebrate samples were collected with hand-held kick screens (9.5 mm mesh) or Surber samplers (0.363 mm mesh). They were preserved in formalin until delivered to the laboratory. Appendix E contains more detailed information on the methods of sampling and preservation.