Water Quality 101: Water Temperature
By: Bryan Duggan
Tribal Water and Environmental Specialist
Last month we talked about Total coli form bacteria as a water quality
parameter which is being tested for by the Tribe’s Land Resources and
Environmental Service’s (LRES), Water Quality Monitoring Program (WQMP).
This month I would like to bring our attention to another important water quality
parameter; water temperature.
The temperature of a body of water is very important for water quality.
Many of the physical, biological, and chemical characteristics of a creek are
directly affected by temperature. For example, water temperature influences the
amount of oxygen that can be dissolved in water, the rate of photosynthesis of
plants, metabolic rates of animals, and the sensitivity of aquatic organisms to
toxic wastes, parasites, and diseases.
At the start of this month the LRES, WQMP personnel installed
approximately 29 water temperature data loggers within the Reservation Creeks,
reservoirs, and a few of the Coquille Forest streams currently being monitored for
water quality. This is part of the WQMP yearly effort to record and understand
water temperature trends on Tribal lands.
A data logger is an electronic device that records information over a period
of time for later reference. It contains a sensor to receive the temperature
information, a computer chip to store it, and a battery to keep them both running.
It is the intent of the WQMP to capture the 7 day average temperatures of
Tribal waters over the seasonally warm summer months. This information
provides Tribal resource managers with an assessment of tribal water conditions
and a point from which to maintain or improve management actions. After the
warm months are over the data loggers will be collected and the information
stored in them will be transferred to a computer for analysis.
One of the most common and indirect ways that humans have influenced
the temperature of streams on Tribal lands is through the cutting down of trees
and other riparian vegetation that helped to provide shade for the creeks, thus
exposing the water to direct sunlight.
Another factor that may affect water temperature is the temperature of the
air above the water. The extent of this influence has a great deal to do with the
depth of the water; a shallow stream is more susceptible to changes in
temperature than a deep river would be. Therefore, increasing global average
temperatures will have a significant affect on the future quality of water on the
Reservation.
A change in water temperature can affect the general health of the aquatic
organisms thus changing the health of the stream’s ecosystem. For example,
temperature influences the amount of oxygen that can be dissolved in water;
more gas can be dissolved in cold water than in warm water. Animals, such as
salmon and trout, which require high levels of dissolved oxygen can only thrive in
cold water. Increased water temperature can also cause an increase in the
photosynthetic rate of aquatic plants and algae. This can lead to increased plant
growth and algal blooms, which can be a further burden on the need for
dissolved oxygen within the system and consequently harmful to the local
ecosystem.
Water temperature also influences the metabolic rates of aquatic
organisms; after a significant thermal threshold has been crossed certain aquatic
organisms which were originally adapted to cool coastal streams will disappear.
Table 1 lists the optimal temperature ranges of some selected aquatic organisms.
Water temperatures outside the optimal range for a stream or river can cause
organisms to become stressed, lowering their resistance to pollutants, diseases,
and parasites.
Table 1: Optimal Temperature Ranges for Aquatic Organisms
Organism
Temperature Range (°F)
Salmon & Trout
41 – 68
Smallmouth bass
41 – 82
Blue gill
41 – 77
Caddisfly larvae
50 – 77
Mayfly larvae
50 – 77
It is the Tribe’s intent to create a salmon and trout fishery within the
Empire Reservation waters but several factors must be addressed in order to
sustain and justify these efforts. The most crucial of these factors is water quality,
and particularly water temperature. A 1997 Biological Assessment of Tarheel and
4th Creeks identified water temperature and sediment loading as the two all
important factors limiting resident trout population numbers in the Reservation
waters.
During the summer of 2006, the Tribe’s WQMP placed temperature data
loggers within all creeks and reservoirs on the Reservation and recorded
extremely high temperatures, ranging between 58 and 74 degrees (graph 1).
These high temperatures are lethal to salmonids. Both reservoirs and all four
creeks on the reservation are relatively shallow and so it is unlikely that thermal
stratification is occurring at a grand enough scale to allow cold water refuge for
significant numbers of salmonid species. This thermal “pollution” is common for
our Reservation waters and can ultimately be addressed by encouraging the
growth of proper riparian vegetation cover, which the Tribe is currently seeking to
do.
75
7 Day Average Temperatures, 2006
WQ18 - Tarheel Creek Above Reservoir
Degrees Farenheit
70
65
60
55
Spawning
Rearing
Migration
7-day min
7-day max
50
6/6 6/13 6/20 6/27 7/4 7/11 7/18 7/25 8/1 8/8 8/15 8/22 8/29 9/5 9/12
While improving water temperature throughout the Reservation will be no
easy task, improving stream side shade quantity in the Reservation riparian
areas will contribute to lower temperatures and improve the water quality for
salmonids and the Tribe alike. Therefore the water temperature data collected
today and years to come will help LRES in our efforts to restore not only optimal
water temperature but also improve biodiversity in the water bodies of all Tribal
lands. So if you come across a small 4-5 inch device attached to some rebar or a
buoy within the creeks or reservoirs, please do not disturb them these are the
data loggers working for the Tribe. If you happen to see one out of the water,
please contact Bryan Duggan at the Tribal Administration office with a location.