Watershed Assessment and Planning Project

This three year $1.2 million project was funded by Authority member contributions and $950,000 in grants under the CALFED Watershed Program. The project was undertaken to advance the understanding of watershed water quality and related environmental issues and to develop tools which will facilitate the long-term evaluation and management of Upper Mokelumne River watershed water and natural resources. The project was completed in 2008.

The assessment and planning effort was guided by the Project Advisory Committee (PAC). When the PAC was initially formed an outreach plan and a calendar of community workshops were developed to guide the stakeholder-driven effort.The PAC represents a wide range of watershed interests such as hydropower, forestry, environmental, resource management, drinking water, and recreation. PAC member organizations include Alpine Watershed Group, Amador County Recreation Agency, Amador Water Agency, Central Sierra Resource Conservation and Development District, East Bay Municipal Utility District, Foothill Conservancy, Jackson Valley Irrigation District, Sierra Pacific Industries, USDA Forest Service, and the Upper Mokelumne River Watershed Council. The Regional Water Quality Control Board was an active participant and supporter.

Key products developed under this project include the following.

Baseline Watershed Water Quality Characterization– The Upper Mokelumne River watershed is largely a pristine watershed with minimal urban development. This water quality characterization establishes baseline water quality (i.e. measures of existing water quality conditions) which provides a reference point for assessing water quality impacts associated with future changes in the watershed.

WARMF (Watershed Analysis and Risk Management Framework) Model– This watershed hydrologic simulation model was developed and used to analyze the entire watershed’s existing hydrologic and water quality characteristics.It also modeled how water quality conditions could change based on changes to land uses and activities.The model engendered a better understanding of watershed processes, particularly in areas of the watershed with limited data.This enabled the PAC to explore potential responses to changing watershed conditions and will inform future decision-making in the watershed.

Additional information regarding the model can be accessed by clicking the WARMF Model link on the Upper Mokelumne River Watershed page on this website.

Wildfire Models– Fire behavior was modeled throughout the watershed to gain a better understanding of high risk areas and potential impacts from wildfire.FlamMapwas used to determine the relative hazard and flammability of selected watershed areas. This model allows prediction of fire behavior on a spatial basis by modeling flame length, heat release, rate of spread and type of fire (e.g. surface fire, crown fire). TheFARSITEmodel predicts fire behavior simulates where and how fast fire would spread from pre-selected burn ignition sites. The fire behavior prediction outputs of the model were translated into three burn severity categories; low, moderate and high. The spatial distribution of the burn severity categories for the selected ignition sites was used as an input into the WARMF model to simulate potential effects on water resources.

Water Quality Vulnerability Zones– Areas within the watershed considered to have very high to moderate vulnerability to water quality contamination were identified and mapped into ‘zones’. These zones were defined based on key physical characteristics of the watershed including slope, soils, vegetation and proximity to water.

Watershed Assessment– The water quality in the Upper Mokelumne River watershed was assessed in a three-step process. Guided by the stakeholder PAC, water quality benchmarks were established, specific water quality parameters of concern were identified, and selected parameters exhibiting historical concentrations of concern were analyzed to determine source locations and characteristics.

Upper Mokelumne River Watershed Management Plan– The management plan addresses the findings of the watershed assessment by coupling scientifically valid data and technically-based recommendations to maintain and improve source water quality with stakeholder understanding and support. The PAC guided plan contains a series of recommended management actions designed to reduce sources of contaminants, manage contaminated flows and sediments, and encourage regulatory and institutional controls. The most urgent plan recommendation was to comprehensively address failed and failing septic systems.A Septic System Management Program was developed to focus specifically on septic system related issues in the region (discussed further below).

Septic System Management Program – Due to widespread concerns regarding microbial contamination from aging septic systems to the water quality ofUpper Mokelumne River watershed streams (as documented in the Watershed Assessment) a separate Septic System Management Program Technical Memorandum was prepared. With the majority of watershed residents living in homes with septic systems (see Figure 1 below), and with many of these homes either built before permits were required and/or in need of repair or replacement, a plan to address failing and poorly maintained septic systems was identified as an urgent need. The Septic System Management Program provides a detailed series of actions that are designed to correct deficiencies in suspected failed and failing septic systems and to protect watershed waters from contamination from new septic systems by accomplishing the following.

  • conclusively demonstrate the sources and causes of elevated pathogen levels found in the watershed
  • determine the feasibility of extending existing sewage collection facilities to serve more of the communities of West Point, Wilseyville and Mokelumne Hill
  • create maps showing the locations of permitted and unpermitted septic systems proximate to waterways within the watershed
  • assess the condition and functionality of existing septic systems proximate to waterways within the watershed
  • educate owners of property served by septic systems with respect to onsite wastewater system design, use, maintenance, consequences of system failure, and other pertinent information

Figure 1 - Potential Septic Systems in the Upper Mokelumne River Watershed

A copy of the Technical Memorandum which describes the essential elements of a Septic System Management Program can be accessed by clicking the Septic System Management Program link on the Upper Mokelumne River Watershed page on this website.