Deer Creek Watershed

Deer Creek begins as a trickle in the Sierra Nevada foothills, high above Scotts Flat Reservoir at 4000′ elevation. A ribbon of nature, it winds its way through pine forests and alpine meadows, forging canyons and shaping the landscape on its journey downhill. As it rushes through downtown Nevada City, it hosts spawning rainbow and brown trout. Downstream, little known but beautiful, Deer Creek Falls hurries the water towards Lake Wildwood, where residents enjoy swimming and boating. Below the lake, pine forest gives way to willow and oak, and the creek teems with beaver, river otter, eagles, and great blue herons. At 600′ elevation and 34 miles from its source, Deer Creek joins the Yuba River, where it greets the native salmon spawn each fall.

Sierra Streams Institute coordinates a Citizen Science Water Quality Monitoring program on the Deer Creek Watershed. Each month monitors measure nitrate, orthophosphate, dissolved oxygen, turbidity, pH, conductivity, water temperature, ambient air temperature, and bacteria (total coliform and E. coli) on 18 sites along Deer Creek and its tributaries. Additionally in June and October, citizen scientists along with SSI scientists collect Benthic macroinvertebrates (BMI) samples at 16 of the 18 monitoring locations. These samples are then identified to family level by citizen scientists in our “macro lab”.

Monitoring Site Overview Map

This map displays the monitoring sites along the main stem of Deer Creek along with the associated California Stream Condition Index (CSCI) score. The CSCI is a statewide tool that translates complex data about benthic macroinvertebrates (BMIs) living in a stream into an overall measure of stream health. The scores range from 0 (most stressed) to 1 (similar to reference sites i.e. good ecological health).

Hover over the site of interest to see the Family Level CSCI score. The default information is set to average all data since 2005. To look at a specific year, use the water year toggle at the bottom of the map to chose the year of interest.

Analysis by Parameter

See below for box and whisker charts by parameter. Data dating from 2005 is included in this analysis. To download the complete dataset visit our public tableau page and choose the data you wish to download.


Conductivity objectives have not been defined in the Deer Creek Watershed by the California Regional Water Quality Control Board a conductivity threshold of 150 micromhos/cm (150 microsiemens) is a common threshold for comparison because salinity imbalances can make stream conditions unfavorable for a wide variety of species (CRWQCB 2016).


Average monthly pH at each monitoring site. 6.5-8.5 is the range recommended by the CRWQCB as optimal for the majority of aquatic organisms.

Dissolved Oxygen (DO)

The California Regional Water Quality Control Board (CRWQCB) water quality objective for dissolved oxygen is above 7.0 mg/L (CRWQCB 2010). Fish die-offs begin to occur at less than 7.0 mg/L.

Water Temperature

A 25 °C threshold can be lethal to juvenile Chinook salmon when present as the average daily maximum for 7 consecutive days and 18 °C is the ideal maximum for sustaining healthy salmon populations.

E. Coli

The US EPA has set a threshold that recreational waters should not exceed 320 MPN/100ml of E. coli in order to protect public health.


Turbidity objectives have not been defined in the Deer Creek Watershed by the California Regional Water Quality Control Board (CRWQCB 2016), a threshold of 10 NTU is a common threshold for comparison.


The US EPA has set a threshold value of 0.1 mg/L of total phosphorus in cold freshwater habitats for fish spawning.


The US EPA has set a threshold value of 10 ppm for acceptable levels of nitrogen for fish consumption.