GAZOS CREEK WATERSHED FACT SHEET

WATERSHED DESCRIPTION

Square Miles : 16 square miles

Location : Located in southern San Mateo County , just south of the town of Pescadero and between Butano and Big Basin Redwoods State Parks , and Ano Nuevo State Reserve.

Major Tributaries and Subwatersheds : The main creek consists of three forks. Tributaries include Old Womans Creek and Slate Creek and several unnamed tributaries.

Features : The three forks of Gazos Creek drop down steep narrow canyons through redwood-Douglas fir and tanoak forest. The lower 2.5 to 3.0 miles of Gazos Creek is well-vegetated with riparian species such as willow, white alder, oak, bay laurel and understory plants such as stinging nettle, berry bushes, poison oak. Surrounding the riparian zone, the landscape includes rolling grassland hills, coastal scrub and agricultural lands. A lagoon with public access adjacent to Highway One is present at the mouth of the creek.

Land Use within the Watershed : Current land uses within the watershed include rural residential, timber harvest, public park land, and grazing and agriculture. From the late 1860's through the turn of the century, Gazos Creek watershed was logged in a boom or bust fashion utilizing steam donkey engines and oxen.

During this time, the majority of the watershed was heavily cut, primarily by clearcutting. Today, only fragments of residual old growth stands remain within Gazos Creek watershed. Several residual old growth trees are nestled on the steep slopes of the headwaters of the North Fork . Land ownership is public (California State Parks) and private including two land trusts (Sempervirens Fund and Peninsula Open Space Trust).

WATER QUALITY INFORMATION

Water Quality Assessment (State Water Resources Control Board)

Gazos Creek Main Branch - 10 miles unknown. Limited information available; Problem sources unknown.

Beneficial Uses

The California Regional Water Quality Control Board identifies ten beneficial uses for Arana Creek ( Water Quality Control Plan , Region 2, 1995):

Municipal and Domestic Supply (includes uses in community systems and domestic use from individual water systems)

Agricultural Supply

Water Contact Recreation (includes all recreational uses involving actual body contact with water)

Warm Fresh Water Habitat

Cold Fresh Water Habitat

Wildlife Habitat

Preservation of Rare and Endangered Species (e.g. coho salmon and steelhead trout)

Fish Migration

Fish Spawning

AQUATIC RESOURCES

Historic and current coho salmon stream (less than 50 adult population)

Historic and current steelhead trout stream
(approximately 50+ adult population)

California Red-legged frog (status confirmed)

MONITORING RESULTS SUMMARY

July - December 1998

Description of Water Quality Monitoring Program

The Gazos Creek Watershed Monitoring project was initiated in August 1997. Fifteen to twenty volunteers have collected weekly data at three sampling sites in the watershed since September 1997. Additionally, volunteers also collect macroinvertebrate bioassessment information and stream flow measurements during the dry season. Monitoring sites include (1) Mountain Camp (formerly known as Villa Cathay), 2) South Fork, and 3) Slate Creek and a streamflow monitoring site at the junction of Cloverdale and Gazos Creek Roads.

Currently the Gazos Creek Watershed monitoring program is funded by:

California Department of Fish and Game's Salmon and Steelhead Restoration Account

National Fish and Wildlife Foundation

Sempervirens Fund

The intent of the monitoring program is to provide data that pertain to the water quality objectives set by the State Water Quality Control Board (1994) and to the anadromous fisheries present in Gazos Creek. It should be noted that this baseline data should not be considered conclusive in identifying degradation within the watershed, but rather provides information on trends within the watershed.

Monitoring Results and Trends

See the Glossary for further description of each of the monitored parameters summarized below.

Temperature

Water temperature is reported in degrees Celsius. Temperature is one of the most important water quality parameters and has direct affects on water chemistry and the functions of aquatic organisms. Temperature influences the dissolved oxygen content of the water; the rate of photosynthesis by algae and other aquatic plants; the metabolic rates of organisms; the sensitivity of organisms to toxic wastes, parasites and diseases; and the timing of reproduction, migration and aestivation of aquatic organisms.

The water temperature for the three sites was 6.2 ° C (site 4, August). Sites 1-3 maintained very similar temperature averages of 11.8 ° C, 11.9 ° C, and 12.1 ° C, respectively. In terms of steelhead habitat, water temperatures are within the acceptable range during the various life stages, although these temperatures are slightly higher than optimal.

Dissolved Oxygen

Dissolved oxygen (DO) refers to the amount of oxygen dissolved in water. The dissolved oxygen concentration in water can directly affect reproduction, incubation, changes in species, and death of adult and juvenile fish and other organisms.

In general, DO values for the three sites were acceptable for both salmonid juvenile growth and reproductive-larval phases. Dissolved oxygen values for the four sites ranged from. 7.8-12.0 mg/l. The high of 12.0, recorded at site 1, coincided with the coldest day (5 December) during this six-month period. The average values for sites 1-3 were 9.8 mg/l, 9.6 mg/l, 9.5 mg/l, and 9.5 mg/l, respectively. A low DO value of 7.8 mg/l was recorded at site1 on 11 September; it is unclear what factors may have caused this low reading.

Turbidity

Turbidity is a measure of the amount of suspended particles in the water. Watersheds in general have a natural turbidity level with inputs from natural erosion, organic decay and algae.

For the majority of the sampling events, the turbidity levels were within acceptable ranges (State Water Quality Control Board 1994). To date, turbidity levels recorded since 1997 at the three sites are generally very low. The range in turbidity at the three sites was 0 Jackson Turbidity Units (JTU) to 50 JTU. Site 1 maintained the lowest turbidity measurements averaging 2.5 JTU overall. Sites 2 and 3, had slightly higher turbidity readings of 5 JTU.

Elevated turbidity readings were measured on July and 24 October at all three sites indicating recent rain activity. It is unclear why turbidity was higher on 17 July, but the increase may be related to recent activity in the channel conducted by the County of San Mateo (Entrix 1998). On 24 October, over 1 inch of rain was recorded in nearby Pescadero watershed; increases in turbidity was probably related to this rain activity.

pH

pH is a measure of how acidic or basic (alkaline) the water is. As the pH increases, water becomes more acidic and as water become more basic, the pH increases. At the extreme ends of the pH scale, (2 or 13) physical damage to gills, exoskeleton, and fins occurs. Changes in pH may also alter the concentrations of other substances in water to a more toxic form. In fresh water, increasing temperature decreases pH.

The three sites in Gazos Creek exhibited a range of 7.0 to 8.0 pH. All sites averaged a pH value of 7.5. These values are within the range of acceptable water quality parameters.

Total Dissolved Solids or Conductivity

Conductivity or total dissolved solids is a measure of the ability of the water to conduct electrical current. Conductivity will vary with water source and can give us the ability to see different water sources (i.e., rain water, agricultural runoff, municipal waste water) as well as narrow down sources of pollution. There are no water quality objectives for conductivity for water bodies in the Central Coast Region. Generally, potable water in the US ranges between 30 to 1500 Us/cm and irrigation supply water ranges exceed 750 Us/cm.

Conductivity values within the monitoring sites vary primarily due to seasonal changes in the water table. The range of conductivity within the three sites was 250 Us to 450 Us. The measurements were highest during September and October, presumably when the water table was lowest. As rainfall and runoff increased in the early winter, conductivity rates decreased correspondingly. These conductivity values are within the acceptable range of potable water as determined by the US Environmental Protection Agency (San Francisco Estuary Institute 1997).

Macroinvertebrate Survey

CWC is currently transitioning into utilizing the new California Department of Fish and Game and US Environmental Protection Agency protocols for conducting macroinvertebrate and rapid bioassessment procedures. A summary of the 9 November sampling effort is summarized in Table 5. Volunteers sorted and identified the sample in January 1999 and, due to time constraints, were only able to identify macroinvertebrates to the order or family level. It is important to note that the sample size was relatively small, perhaps due to the late collection date of the sample (9 November).

The length of the riffle measured was 45 feet; three transects were sampled within this reach. In general, parameters measured indicated that optimal to suboptimal habitat is present within the reach. Exceptions to this were excessive sediment deposition and a slightly impaired right bank (due to the close proximity of Gazos Creek Road ). It is suspected that more sediment is present in the channel due to the log jam removal project by San Mateo County and subsequent restoration (Entrix 1998).

The results indicate that the macroinvertebrate assemblage at this site is relatively pollution intolerant and therefore the condition of the creek is good. The protocol requires that the macroinvertebrates are identified to family or even genus level. It is important to note that this is a very time-consuming process and requires extended effort of several trained volunteers. CWC is currently trying to find ways to minimize the volunteer labor required to process the sample because it is unrealistic to ask our volunteers to dedicate so much time at this juncture.

Stream Flow

From July 11, 1998 to November 6, 1998, ten streamflow data sets were collected at the site. Discharge values ranged from a high of 7.10 cfs on July 11, 1998 to a low of 2.27 cfs on October 9, 1998.

Recommendations

To date, water quality data within Gazos Creek has been excellent. Recommendations for 1999 include a transition from water quality monitoring to an emphasis on physical and biological monitoring. CWC recognizes that there are sedimentation and erosion problems due to historic and current land use practices; we will try to address these problems more directly in 1999. Physical monitoring will be emphasized during summer of 1999. Longitudinal profiles, cross sections, pebble counts and streamflow will be prioritized when the dry season begins. Macroinvertebrate sampling will also continue biannually. Phase II Restoration of Gazos Creek (Entrix 1998) is also scheduled to occur at selected sites during summer-fall 1999. CWC hopes to incorporate monitoring of some of these sites as well.

For the advent of 1999 streamflow data collection, CWC will hold a one-day streamflow training for volunteers. A Quality Assurance/ Quality Control (QA/QC) simultaneous data collection will also be coordinated with a California Department of Fish and Game fisheries biologist.