Famosa Slough Water Quality

A periodic monitoring program measures the health of the water in Famosa Slough. Since 2002, the water in the Slough and in the water treatment basins have been sampled and analyzed for several important indicators of water quality. The sampling is done twice each month before dawn. Measurements are made either on site or in a laboratory using highly precise and accurate digital instruments.

While there are dozens of potential pollutants that influence the quality of water, the major concerns in a wetlands area are the ones listed below. For each parameter, there is a fairly narrow range that is healthful for plants and animals.

The water is regularly sampled at five sites. Two are at the treatment ponds by the south parking lot. Three are along the perimeter of the Slough. These sites are marked on the Slough map by the numerals 1 to 5. If you click on these numbers, you can view the point where water is sampled.

In addition to these parameters, occasional measurements of chlorine and bacteria counts have been made. As these were found to be within a safe range and of limited concern to the health of the Slough, they are not regularly monitored.

The data below (last updated in January 2008) is based on approximately 80 individual sample days and over 3,700 individual measurements made in the past five years. The high and low value, mean, and standard deviation of the measurements are given.

Temperature

Temperatures in the Slough and pond waters vary greatly both within daily and yearly cycles. The shallow waters are impacted directly by sunlight during the day and have a much greater temperature range that do the source waters from the ocean. The high temperatures of the Slough limit its use by many species of animals that thrive in the ocean. Water temperatures higher than 35 °C are harmful to most aquatic life.

Temperature (deg C°)
	Site 1	Site 2	Site 3	Site 4	Site 5
Min	7.6	7.3	7.3	5.3	10.4
Max	24.2	22.1	24.9	24.4	26.8

Dissolved Oxygen

The amount of oxygen in the water is probably the most important component of water quality to healthy wetlands. Without oxygen, few aquatic organisms can survive. The dissolved oxygen in the Slough waters is at a minimum just before the sun rises and peaks during the day when aquatic plants are producing oxygen. For most fish, dissolved oxygen should be above 3.5 mg/L for most of each day.

Dissolved Oxygen (DO mg/L)
	Site 1	Site 2	Site 3	Site 4	Site 5
M	2.3	3.0	3.2	3.0	2.9
StdD	1.65	1.68	1.47	1.69	2.21
Min	0.5	0.7	0.6	0.5	0.2
Max	8.9	9.0	6.5	8.5	9.6

pH

The pH of a liquid measures how acidic or alkaline it is. The scale of pH runs from the most acidic (0) to most alkaline or basic (14). Most aquatic life requires a pH between 6 and 9 to remain healthy.

pH
	Site 1	Site 2	Site 3	Site 4	Site 5
M	7.73	7.62	8.41	8.24	8.32
StdD	0.38	0.37	0.33	0.41	0.36
Min	6.91	6.91	7.62	7.38	7.18
Max	8.38	8.37	8.96	9.27	9.04

Salinity

Different plant and animal species have adapted to different levels of salinity. Seawater is typically 33 parts of salt per 1,000 of water (or ppt). The salinity of the Slough will often drop significantly below this value because of the mixing of San Diego River water or runoff from the adjoining watershed. Most animal species in the Slough can tolerate the normal shifts in salinity.

Since they contain mostly rainwater or residential water runoff, the treatment pond water salinity is usually less than 2 ppt. As a consequence, completely different species of animals and plants live there than in the Slough. The salinity of fresh water is more usually measured as its conductivity or conductance—a measure of its ability to conduct electricity.

Salinity (ppt)
	Site 1	Site 2	Site 3	Site 4	Site 5
M	1.3	2.2	29.3	27.8	29.4
StdD	0.6	1.6	5.5	6.3	4.9
Min	0.0	0.0	3.1	0.5	2.4
Max	2.5	13.4	34.8	35.4	35.2

Turbidity

Turbidity is a measurement of the amount of suspended materials in water. It can be caused by organic or inorganic substances. At the Slough, the most usual cause of high turbidity is fine silt and sediment that runs into it from the adjoining watershed. During a storm or high wind, the bottom sediments of the Slough are stirred up and increase the turbidity. The second major cause of increased turbidity is algae growth. Most Slough resident life forms are tolerant of high turbidity.

Turbidity (FAU)
	Site 1	Site 2	Site 3	Site 4	Site 5
M	23.1	42.0	15.2	16.4	7.9
StdD	16.8	44.0	13.5	15.3	8.0
Min	5	3	0	0	0
Max	95	250	76	82	55

Nitrogen and Phosphorous

A major concern is the buildup of nutrients (primarily nitrogen and phosphorus) in wetlands. These nutrients cause a harmful condition called eutrophication—a condition in an aquatic ecosystem where high nutrient concentrations stimulate blooms of algae. While the algae are not directly harmful to other life, they creates secondary problems that hurt the usefulness of the Slough to animals. Algae cloud the water and block sunlight, causing underwater grasses to die. Because these grasses provide food and habitat for aquatic animals and birds, spawning and nursery habitat is destroyed and waterfowl have less to eat when grasses die off. Also, when the algae die, their decomposition uses up oxygen in the water. Dissolved oxygen is essential to most organisms living in the water such as fish and crabs. Without these sources of food, many birds will not visit.

A healthful range for nitrogen in the form of nitrate is less than 2.0 mg/L, for nitrite less than 0.01 mg/L and for phosphate less than 2.0 mg/L. The data tables show the dramatic increase in water quality between Sites 1 and 2.

Nitrates (mg/L)
	Site 1	Site 2	Site 3	Site 4	Site 5
M	1.82	0.57	0.88	0.96	1.17
StdD	1.80	1.38	0.84	1.35	1.40
Min	0.0	0.0	0.0	0.0	0.0
Max	6.8	7.1	2.9	5.7	5.9

Nitrite (mg/L)
	Site 1	Site 2	Site 3	Site 4	Site 5
M	0.015	0.003	0.003	0.003	0.002
StdD	0.043	0.009	0.003	0.004	0.001
Min	0.000	0.000	0.000	0.000	0.000
Max	0.357	0.078	0.011	0.028	0.023

PO4 (mg/L)
	Site 1	Site 2	Site 3	Site 4	Site 5
M	1.33	0.84	0.31	0.23	0.25
StdD	0.88	0.51	0.42	0.23	0.17
Min	0.0	0.0	0.0	0.0	0.1
Max	4.8	3.1	2.6	1.1	0.7