Big Bear Lake TMDL Task Force

The Big Bear Lake nutrient TMDL Task Force addresses water quality in Big Bear Lake and its surrounding watershed. This Task Force effort was initiated by SAWPA in September 2007 in response to the Santa Ana Regional Water Quality Control Board formally adopting nutrient TMDLs for Big Bear Lake through Resolution No.R8-2006-0023. The TMDL task force works together with stakeholders and the Regional Board to implement a number of actions required in the Basin Plan Amendment.

Big Bear Lake Nutrient TMDL Task Force

Big Bear Lake Nutrient TMDL Task Force

In the TMDL, the Regional Board set forth five specific objectives for the watershed-wide monitoring plan:

  1. To review and update the Big Bear Lake Nutrient TMDL
  2. To determine specific sources of nutrients
  3. To develop TMDLs for other hydrologic conditions (wet & moderate years)
  4. To determine compliance with phosphorus targets in the TMDL, the load and wasteload allocations under dry weather conditions
  5. To determine compliance with the water quality objective for total inorganic nitrogen in the Basin Plan

Over the last few years, with considerable support from state and federal grant funds, local stakeholders developed comprehensive monitoring programs for the watershed and the lake itself. A large database of water quality information was created as part of these prior studies. The watershed-wide monitoring plan is intended to continue and enhance previous efforts to characterize water quality in the runoff draining to Big Bear Lake.

In the TMDL, the Regional Board specified seven mandatory sampling stations on the major tributaries to Big Bear Lake; one each on Bear Creek, Grout Creek, Summit Creek, Knickerbocker Creek and Boulder Creek and two on Rathbun Creek.

Big Bear Lake

Big Bear Lake

Big Bear Lake, located in the San Bernardino Mountains, was created by the construction of the Bear Valley Dam in 1884. The lake supports many different beneficial uses. Among the most important are irrigated agriculture, water contact recreation and freshwater habitat for both cold and warm-water species.

The Lake has a surface area of approximately 3,000 acres, a storage capacity of 73,320 acre-ft and an average depth of 24 feet. The lake reaches its deepest point of 72 feet at the dam. The Big Bear Lake drainage basin encompasses 37 square miles and includes more than 10 streams.

Local stream runoff and precipitation on the Lake are the sole source of water supple to the Lake. The major inflows to the lake are creeks, including Rathbone Creek, Summit Creek and Grout Creek. Outflow from the Lake is the Bear Creek, which is a tributary to the Santa Ana River at about the 4,000-foot elevation level. Water from Big Bear Lake flows thru the dam, down Bear Creek and into the Santa Ana River above Seven Oaks Dam. Along the way, it is used to generate hydroelectric power, recharge groundwater basins and, ultimately, to supplement municipal drinking water supplies in the Inland Empire.

Big Bear Lake Nutrient TMDL

Big Bear Lake Nutrient TMDL

In 1990, the Santa Ana Regional Water Quality Control Board (“Regional Board”) added Big Bear Lake to California’s list of impaired water bodies due to elevated nitrogen and phosphorus concentrations. These pollutants act as fertilizers and cause encourage growth of noxious aquatic plants such as Coontail and Eurasion Milfoil that interfere with human recreation and despoil the native freshwater habitat. In addition, high nutrient loads cause excess algae growth which, in turn, reduces dissolved oxygen levels in the water and leads to fish kills. After several years of intensive study, the Regional Board adopted a Total Maximum Daily Load (“TMDL”) to protect the designated beneficial uses by regulating the level of certain nutrients in Big Bear Lake. U.S. EPA approved the proposed TMDL in 2007. The TMDL establishes numeric targets for phosphorus concentrations in the lake. It also sets targets for minimum dissolved oxygen and maximum algae levels. The TMDL requires invasive weeds to be significantly reduced and restricts the overall density of aquatic plants in Big Bear Lake. The TMDL targets must be attained during dry weather conditions no later than the year 2015. And, the targets must be attained during all other weather conditions no later than 2020. Click here to access the U.S. Environmental Protection Agency’s TMDL web site to see the impaired water bodies in the State of California. Other California TMDL information can be found at the California State Water Resources Control Board (SWRCB) TMDL site.

SAWPA staff, working with stakeholders of the Big Bear Lake TMDL Task Force is working to implement a number of Tasks prescribed in the 2006 Basin plan Amendment to Incorporate a Nutrient Total Maximum Daily Load (TMDL) for Dry Hydrological Conditions for Big Bear Lake. These include

  • Implementing a watershed-wide nutrient compliance monitoring program
  • Developing a In-Lake sediment nutrient reduction plan for Big Bear Lake
  • Working with the Regional Board to investigate possible mercury (Hg) TMDL for Big Bear Lake

In September 2007 upon the request of stakeholders, the SAWPA Commission authorized SAWPA staff support for the development of a Big Bear Lake Total Maximum Daily Load (TMDL) Task Force Agreement and its administrative role for the new task force. Similar to other TMDL task force efforts, this task force serves an important role in assisting local stakeholders address the Regional Water Quality Control Board TMDL implementation tasks to be undertaken by specific stakeholders as described in the Big Bear Lake TMDL Task force Agreement. The purpose of the TMDL is to insure attainment of water quality standards in Big Bear Lake that are due to nutrients.

Task Force Documents




TMDL Deliverables

Task 4 – Big Bear Lake – Annual Water Quality Reports

Appendix B

Appendix C

Appendix D (contact SAWPA)

Appendix E

Appendix F (contact SAWPA)