CACHE CREEK WATERSHED

• Watershed Overview– Physical Description– Land Uses Present– Flow Characteristics– Beneficial Uses

• Point and Non-Point Source Pollutants– Pollutants Present in Watershed– Pollution Management Measures

Physical Description

• Entire watershed approx. 1,200 mi2 in area

• Divided into three sections based on watershed topography and shape– Upper Section

• Encompasses 80% of total watershed• Three branches (main fork, North Fork, Bear Creek)• Two large water bodies are present (Clear Lake,

Indian Valley Reservoir)• Several small communities border Clear Lake

Physical Description (cont.)

– Middle Section (Capay Valley)• 16% of total watershed

• No significant tributaries

• Capay Dam (water diversion)

• Sparsely populated

– Lower Section (Sacramento Valley)• Includes City of Woodland

• Entirely length controlled by levees

• Discharges to Yolo Bypass and Sacramento River

Cache Creek Watershed

Land Use Distribution

– Over 70% undeveloped (forest, woodland)– Approximately 23% agricultural

• Limited to lower Cache Creek and Clear Lake area

• Orchards (most commonly almond)

• Croplands (alfalfa, corn, rice)

– Low density rangeland throughout watershed– Minor urban/suburban land uses (Woodland,

Clear Lake communities)

Flow Characteristics

– Highly variable flow rates (0 to 41,400 cfs)

– Wide seasonal variations reflect lack of flow controls

– Flow patterns vary widely within watershed 0

200400600800

1000120014001600

Nor

th F

ork

at Y

olo

Dry Flow(cfs)

WetFlow(cfs)Annual(cfs)

Watershed Shape and Flooding

– Watershed shape has significant impact on flood potential

– High flood frequency in Capay Valley

– Urban areas along Clear Lake encroach on flood plain

– Frequent flooding increases pollutants load from runoff

Beneficial Uses

• Primary Beneficial Uses– Agricultural supply

(canal diversions)

– Groundwater recharge

– Contact/non-contact recreation (rafting, fishing, etc…)

– Fresh water habitat

– Wildlife Habitat

• Secondary Beneficial Uses– Industrial service

supply (gravel mining)

– Biological habitats of special significance

– Migration of aquatic organisms

– Spawning/ Reproduction

Point Source Pollutants

• Primary Point Sources (pollutants)– Precious metal mining (Hg)– Gravel mining (sediment, physical disturbance)– Industrial discharges (petroleum HC, synthetic

organics, metals)– Landfill discharges (just about anything)– Wastewater treatment discharges

(biostimulants)

Point Source Pollutants

Non Point Source Pollutants

• Primary Non-Point Sources (pollutants)– Human-induced erosion (sediment, physical

disturbance)– Agricultural runoff (nitrates, phosphates, synthetic

organics)– Animals wastes (biostimulants, fecal coliform)– Urban runoff (petroleum HC, metals, etc…)– Septic wastes (biostimulants, fecal coliform)– Improper waste disposal (just about anything)

Non Point Source Pollutants

Pollution Management Problems– Some pollutants may also be

introduced by natural means• Sediment discharge up to 3

million tons annually

• Significant area is underlain by bedrock containing Hg

– Point and non-point source pollutants may interact

• gravel mining increases erosion potential

• erosion may transport mercury to waterways in sediment

Prioritizing Pollutant Impacts

– Pollutant with greatest potential impact is Hg • detrimental to fish and wildlife

• reduces recreational uses

• limits domestic supply/stock watering uses

• potential groundwater problems

– Sedimentation is a close second• physical damage to wildlife/fish habitat

• reduced recreational uses (except whitewater)

• increased transport of mine wastes

Management Strategies

– Integrate point source and non-point source management strategies (e.g. Hg mining/runoff)

– Focus on pollutants or sources that can be effectively managed (e.g. It is unreasonable to apply sedimentation BMPs throughout watershed)

– Educate the public on the risks of non-point source pollutants and their role in its management

Potential Management Measures• Point Source

– Mine abandonment

– Tailings stabilization

– Gravel mining restrictions

– Habitat restoration

– Industrial discharge permit enforcement

• Non-point Source– Educational programs

– Permit limits for septic systems in sensitive areas

– Construction BMPs in areas with Hg-bedrock

– Flood plain zoning restrictions

– Land set asides for critical groundwater recharge areas