Wetland Profile: Chorro Creek

Published 10/30/2004

LOCATION

County

San Luis Obispo

USGS Quadrangle

Morro Bay South, San Luis Obispo

Descriptive Location

Chorro Creek drains the Chorro Creek watershed, the northern half of the Morro Bay watershed, and flows through the Morro Bay Salt Marsh into the bay.

Longitude & Latitude

-120°50'28" W, +35°20'26" N

Component Names

Chumash Creek, Dairy Creek, Pennington Creek, San Bernardo Creek, San Luisito Creek, Walters Creek, Unnamed Tributaries

OWNERSHIP, MANAGEMENT & LOCAL AUTHORITIES

Management Authorities	Source
Management
California State University	3
San Luis Coastal Resource Conservation District	4

Group Name	Website	Source
Local Interest Groups
Morro Estuary Greenbelt Alliance	http://www.coastal.ca.gov/publiced/ directory/resdirectory/m_orgs/morro estuarygreenbelt.html	1
The Morro Coast Audobon Society	http://www.morrocoastaudubon.org/	2

LAND USE

On Site Use	Source
Agriculture	5, 6, 7, 8, 9, 10
Open Space	7, 11, 12, 13, 14, 15, 16, 17, 18, 19
Recreation	9, 11, 20
Rural Lands	6

Historic On Site Use	Source
Agriculture	5, 7, 8, 10, 21
Native American Use	7, 10, 20, 21
Open Space	9, 11, 17, 18, 19
Public Facilities	9
Recreation	11

Adjacent Use	Source
Agriculture	3, 5, 6, 7, 8, 9, 12, 13, 15, 17, 18, 19, 22, 23, 24, 25
Open Space	1, 7, 10, 13, 14, 15, 16, 17, 18, 19, 20, 26
Public Facilities	10, 20, 22, 23, 24, 25
Recreation	12, 16, 18, 19, 20
Residential Rural	13
Residential Single-Family	12
Rural Lands	22, 23, 25

Historic Adjacent Use	Source
Agriculture	5, 8, 10, 17, 22, 23, 24, 27
Native American Use	20
Open Space	1, 17, 18
Public Facilities	22, 23
Rural Lands	22, 23, 27

Comments	Source
Comments
Lower 1 mile of creek is in public ownership	5
Adjacent agriculture=grazing	19
Onsite and adjacent uses include general agriculture and viticulture	8
Seasonal flooding disturbances and yearly fire protection management affect the Flats area	2
Agriculture=grazing	3
Cattle grazing; some rural and urban development	25
Historic agriculture=grazing	7

HYDROLOGY

Tributary Influence	Influence	Source
Tributary Influence
Chorro Reservoir		5
Chumash Creek	400 acres	3
Dairy Creek	Little or no flow in dry season	15, 24
East Branch	Feeds into reservoir; substantial sediment load	28
Gibson Reservoir	49 acre ft capacity	7
Intermittent Stream 1		22
Intermittent Stream 2		22
Johnson Reservoir	30 acre ft capacity	7
Las Tablas Creek		18
Pennington Creek	975 acre ft/yr, Little or no flow in dry season	24, 29
Perennial Stream 1		22
San Bernardo Creek	1200 acre ft/year, Little or no flow in dry season	15, 24, 30
San Luisito Creek	Little or no flow in dry season	15, 24, 30
Third Branch	Feeds into reservoir; minimal sediment load	28
Unnamed Creek 1		2
Unnamed reservoir	0.25-0.5 acre ft	7
Walters Creek	480 acres	3
West Branch	Feeds into reservoir; largest sediment load	28

Alterations	Comments	Contribution / Removal Amount	Date	Source
Wetland Alterations
Dams				6, 9, 10, 13, 20, 25, 31
Dams		90 acre ft/year	1965	28
Dams	Check Dam 1 - East Branch; prevents sediment flow into reservoir			28
Dams	Check Dam 2 - West Branch; prevents sediment flow into reservoir			28
Dams	Chorro Dam; Built 1941			15, 28
Dikes/Levees, Fill				7
Dikes/Levees, Fill	Levees for agriculture			11
Dikes/Levees, Fill	Levees on irrigated farmland			17
Dredged Channel/Inlet	Channels on irrigated farmland			17
Dredged Channel/Inlet	Dredged Chorro Creek channel		00/00/1940	32
Dredged Channel/Inlet	Small connector channel between North Chorro Creek and South Chorro Creek			17
Flow Diversions				1, 13
Flow Obstructions	Bridge			11
Flow Obstructions				22
Flow Obstructions	Bridge			16, 19, 24
Flow Obstructions	Bridge		1948	26
Flow Obstructions	Chorro Reservoir			25
Flow Obstructions	Culvert on East Branch, 5 ft in diameter			28
Flow Obstructions	Highway 1 Bridge			23
Flow Obstructions	List of obstructions for Chorro Watershed			6
Flow Obstructions	Twin Bridges		1930	17
Groundwater Extraction				9, 10
Groundwater Extraction	San Bernardo Creek			15
Groundwater Extraction	Well map			13
Non-point Source	Urban from golf course			9
Non-point Source				19
Non-point Source	2,000-20,000 acre ft/year		1980	15
Non-point Source	Agriculture			7, 24, 25, 31
Non-point Source	Agriculture and Urban Runoff			23
Non-point Source	Urban Runoff			11, 16, 26
Point Source Discharge				24
Point Source Discharge	California Men's Colony Wastewater Treatment Plant			6, 7, 9, 10, 15, 19, 23, 31
Point Source Discharge	California Men's Colony Wastewater Treatment Plant	1 ft/sec		14
Point Source Discharge	California Men's Colony WastewaterTreatment Plant; maximum load	1 cfs		17
Pumping Stations				31
Reservoir Spillway				28
Septic Tank Seepage				6

WATER QUALITY

Program Name	Parameters	Comments	Website	Source
Monitoring Programs
Central Coast Ambient Monitoring Program	Coastal Confluence Monitoring	At South Bay Boulevard	http://www.ccamp.org/ca/3/Sites/310 twb/310TWB.htm	35
Snapshot Day	Numerous	At Upper Chorro Flats; 2002-2004	http://www.coastal.ca.gov/publiced/ snapshot/snapshot1.html	36
MBNEP Volunteer Monitoring Program	Numerous	4 sites: At Twin Bridges; Near Highway 1 crossing; On Chorro Creek Ecological Reserve; At Canet Road	http://www.mbnep.org/volunt.htm	37

Parameter	Duration	Comments	Source
Water Quality Data
% Organic material			33
% Riparian Cover	April 29, 1993		24
Benthic Invertebrates	April 29, 1993		24
Chlorine	October 1975-January 1976		6
Chromium	1993		34
Depth	February 19, February 22, March 11, 1992	At Camp SLO, Cuesta, & SouthBay/Morro Bay SP	31
Dissolved Oxygen	1994		23
Dissolved Oxygen	April 29, 1993		24
Dissolved Oxygen	February 19, February 22, March 11, 1992	At Camp SLO, Cuesta, & SouthBay/Morro Bay SP	31
Exchangable cations			33
Flow	October 1975-January 1976		6
Macro Invertebrates	October 1975-January 1976		6
Nickel	1993		34
Nutrients			13
Nutrients		Phosphorus, Micronutrients	33
Nutrients	1994	Nitrate, Phosphate	23
Nutrients	February 19, February 22, March 11, 1992	At Camp SLO, Cuesta, & South Bay/Morro Bay SP	31
Nutrients	February 1956, March 1993		9
Salinity			16
Soil pH			33
Soil texture			33
Stream Flow	1982-1988		19
Stream Flow	Fall 1988, Fall 1989	Canet Road, Wells 8 and 11a	14
Stream Substrate	October 1975-January 1976		6
Stream Velocity	April 29, 1993		24
Temperature	1994		23
Temperature	April 29, 1993		24
Temperature	February 19, February 22, March 11, 1992	At Camp SLO, Cuesta, & SouthBay/Morro Bay SP	31
Turbidity	1994		23
Turbidity	February 19, February 22, March 11, 1992	At Camp SLO, Cuesta, & SouthBay/Morro Bay SP	31
pH	1993		34
pH	1994		23
pH	February 19, February 22, March 11, 1992	At Camp SLO, Cuesta, & SouthBay/Morro Bay SP	31
pH	February 1956, March 1993		9

SOILS

Comments	Source
Flat slopes, absence of ridges, and poorly drained soils in Flats area	2
Loamy sands, sandy loam, clays, clay loam, silty clay loam at Twin Bridges	17
Mostly silt/clay, some gravel	13
Quaternary alluvium & alluvial deposits; Pleistocene marine terrace deposits	12
Serpentine & sandstone formations at reservoir	28

VEGETATION

Common Name	Scientific Name	Source
Non Native Plants The Non-native plant list is not intended to be a representative list of all plants found in the wetland. To learn more about all plants found in the wetland, including natives, please refer to the lists documented in the Vegetation Comments section.
Annual grasses	None	2, 7, 10
Black mustard	Brassica nigra	2
Brome	Bromus spp.	5
Castor bean	Ricinus communis	7, 17
Eucalyptus (Blue gum)	Eucalyptus globulus	7, 17, 20
Hoary cress	Cardaria draba	16, 17
Iceplant	Carpobrotus edulis	7
Monterey Cypress	Cupressus macrocarpa	7, 17, 21
Oats	Avena spp.	2, 10
Poison hemlock	Conium maculatum	2, 17
Sow thistle	Sonchus sp.	2
Wild fennel	Foeniculum vulgare	7

Comments	Source
Vegetation Comments
Dominant plants	5
Native plant list	6, 9
Plant list	7
Vegetation map	38

ANIMALS

Common Name	Scientific Name	Federal	State	Source
Special Status Animals
American peregrine falcon	Falco peregrinus anatum	Species of Concern	Endangered	8
California black rail	Laterallus jamaicensis coturniculus	Species of Concern	Threatened	12
California red-legged frog	Rana aurora draytonii	Threatened	None	9, 25
Morro Bay blue butterfly	Icaricia icarioides morroensis	None	None	12
Morro shoulderband (=banded dune) snail	Helminthoglypta walkeriana	Endangered	None	12
Southwestern pond turtle	Clemmys marmorata pallida	None	None	12, 25
Steelhead - south/central California coast esu	Oncorhynchus mykiss irideus	Threatened	None	1, 14, 15, 17, 25
Tidewater goby	Eucyclogobius newberryi	Endangered	None	12, 25

Common Name	Scientific Name	Source
Non Native Animals
Bullfrog	Rana catesbeiana	25
European starling	Sturnus vulgaris	8
Sacramento squawfish	Ptychocheilus grandis	5, 6, 15, 25

Comments	Source
Animal Comments
Indigenous species list	5

Amphibian Sources

Bird Sources

10, 8, 9

Fish Sources

5, 6

Insect Sources

Mammal Sources

21, 9

Reptile Sources

WETLAND IMPACTING ACTIVITIES

Activity	Source
In the Wetland
Active/Severe riparian erosion	5, 15, 18, 28, 33
Agriculture	5, 7, 8, 10, 19, 21, 24
Camping	20
Excavation	11, 12, 13, 18
Fertilizer application	1, 9
Fishing	5
Flood control	11, 12, 13, 17, 25
Grazing	1, 5, 7, 10, 19, 21, 24
Hiking	9, 18, 20
Hydroelectric power	24
Impoundment	25, 28, 38
Land clearing	7, 10
Non-native fish	5
Non-native plant invasion	2, 10, 16, 17, 26
Pesticide Application/Mosquito Control	1, 21
Recreation (other)	20, 24
Resource extraction	25
Road construction	1, 7, 11, 12, 15, 16, 17, 19, 22, 23, 24, 26, 31
Surface/subsurface drainage	14, 17, 18
Wastewater treatment	7, 10, 17, 18, 22, 23, 24, 31

Activity	Source
Adjacent to the Wetland
Active/Severe riparian erosion	18, 33
Agriculture	5, 7, 8, 9, 10, 13, 15, 17, 18, 19, 20, 21, 22, 23, 24, 25, 31
Camping	5, 12
Earth moving equipment operation	24
Excavation	18
Fertilizer application	1, 9, 31
Flood control	12, 15, 17
Grazing	1, 5, 7, 9, 10, 13, 17, 18, 19, 20, 21, 24, 25, 31
Hiking	5, 18, 19
Impoundment	31, 38
Land clearing	7, 18
Mining	18, 28
Non-native plant invasion	10, 16, 17, 26
Pesticide Application/Mosquito Control	1, 9, 21
Recreation (other)	11, 16, 18
Resource extraction	22, 28
Road construction	1, 7, 11, 15, 16, 17, 18, 19, 22, 23, 24, 26, 38
Surface/subsurface drainage	18, 19
Tailing pipes	18
Wastewater treatment	9, 10, 13, 14, 15, 19, 25, 38

SOURCES

Source	Author(s)	Year Published	Document Name
1	Trust for Public Land, Calif.	2001	Morro Bay Watershed: Hollister Peak, Morro Bay Dunes.
2	Wolfington, Tara	2000	Habitat assessment of Chorro Flats and Osos Flaco Lake avian monitoring stations.
3	Pak, Margaret	2001	How effective are best management practices on the Morro Bay watershed.
4	Morro Bay National Estuary Program	2004	Personal Communication
5	Crawford, David	1994	A seasonal comparison of diversity of fish species in Chorro Creek.
6	Gray, Gerard A.	1976	Stream survey of Chorro Creek, San Luis Obispo, California.
7	Markle, Larry T.	1998	Vegetation survey of Chorro Creek Ranch: an initial database of flora found on the ranch.
8	Giles, Jeff	2002	The effects of a vineyard on avian diversity at Chorro Creek Ranch, San Luis Obispo, California.
9	Envicom Corp. for San Luis Obispo County Dept. of Planning and Building	1994	Final environmental impact report: El Chorro Regional Park golf course.
10	Palkovic, Amy	1998	The birds of Chorro Creek Ranch
11	Schram, Steven	1994	Realignment and improvement of South Bay boulevard at Twin Bridges.
12	Westec Services, Inc.	1988	Twin Bridges replacement project: draft environmental impact statement/report and 4(f) evaluation.
13	Cleath, Timothy S.	1988	Water resources study, Chorro Valley Ranch.
14	Calif. Dept. of Fish and Game	1991	Memorandum - from Dept. of Fish & Game to Ed Anton, Div. Of Water Rights
15	Morro Group and Tenera Environmental	1990	Freshwater Influences on Morro Bay
16	Rienecker, Erich	1991	Control plan for Hoary Cress(Cardaria draba L.) in the Chorro Creek Delta, Morro Bay State Park, Calif.
17	Rivera, Floriza V.	1994	Hydraulic and environmental assessment of the twin bridges at Chorro Creek.
18	Conover, Robert C.	1985	Inventory and assessment of abandoned and inactive mine sites in Chorro Creek Watershed.
19	Gamette, Sean A.	1991	Morro Bay watershed: a study of the input of all waters entering Morro Bay.
20	San Luis Obispo Co. Planning Dept.	1973	El Chorro regional county park: development plan.
21	Cordova, Daniel A.	1997	Mammals of the Chorro Creek Ranch: a presence-absence survey.
22	Stechman, John V.	1988	Agricultural map, California Polytechnic State University
23	Kabaker, Russell A.	1994	A chemical analysis of Chorro Creek during the dry season.
24	Bell, Jason	1993	A water quality analysis of Chorro Creek using benthic invertebrates as indicators.
25	Worcester, Karen	None	Aquatic Inhabitants of Chorro and Los Osos Creeks: Their Habitat Needs and Status
26	Morro Group, Inc.	1996	Wetlands Mitigation Plan for the Twin Bridges Replacement Project, on South Bay Boulevard, City of Morro Bay
27	Calif. Polytechnic State Univ., San Luis Obispo	1975	Chorro Creek Ranch.
28	Scott, Warren C.	1969	Determination of rate and source of Chorro Reservoir sediment.
29	Moore, Rodney R.	1962	A hydrological study of the Pennington Creek watershed.
30	Lopez, David A.	1999	Creek water analysis of San Luisito and San Bernardo Creeks.
31	Brecheisen, Vicki	1992	Survey of Osos and Chorro Creeks with empasis on nitrate and phosphate concentration and their effect on Morro Bay and groundwater quality.
32	Josselyn, M. et al.	1991	Chorro Delta Study - Hydrology, Sedimentation, and Hoary Cress Biology
33	Provencher, James	1995	Nutrient analysis of recent erosion deposits along Chorro Creek.
34	Mace, James E.	1993	Study of possible chromium contamination in the Morro Bay Estuary through Chorro Creek alluvium.
35	Central Coast Regional Water Quality Control Board	None	Central Coast Ambient Monitoring Program
36	Snapshot Day	None	None
37	Morro Bay National Estuary Program	2004	Morro Bay National Estuary Program Volunteer Monitoring Program
38	Brown, Michael D.	1982	Water resources of the upper Chorro Creek watershed.

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