Case Study

Creative ideas preserve body contact recreation in multipurpose reservoir

Both body contact recreation and grazing pose the biggest threat to the quality of water in a reservoir used for treated water purposes in urban areas. It takes some creative thinking to come up with solutions that present a win-win for everyone.

By Perri Standish-Lee, Director of Integrated Watershed Planning, Black & Veatch; Grant Kreinberg, Water Resources Consultants and Jay Hesby, Vice President, Black & Veatch

Population growth and the increasing demand for recreation opportunities have put public and political pressure on making every body of water available for multipurpose use—including recreation.


Direct body contact recreation, including swimming and
wading, can adversely affect source water quality.

Body contact recreation introduces more viruses
At the same time, there is increasing evidence that direct body contact recreation—including swimming, wading, water skiing and jet skiing—may add significantly more microorganisms such as viruses, Giardia and Cryptosporidium to a water body than does non-body contact recreation.

Woodward Reservoir, located in Stanislaus County in northern California, is owned and operated by the South San Joaquin Irrigation District. The district can impound up to 36,000 acre-ft of Stanislaus River water in the reservoir.

The water has been used for agricultural irrigation within the district's boundaries since the early 1900s. The reservoir is also used for recreational activities including body contact recreation, boating and fishing.

District now proposes to use reservoir as source of treated water for nearby towns
The district is proposing to use its surface water supply as a source of treated water to supplement groundwater supplies being used by the cities of Manteca, Escalon, Tracy and Lathrop to meet growing urban demands. These cities currently use groundwater from an overdrafted basin; the supplemental supply of surface water is expected to reduce the overdraft.

Irrigation demands, which consume the lion's share of the water, control upstream releases into the reservoir from Goodwin Dam on the Stanislaus River. Water releases typically occur between March and October.

The reservoir level is lowered in the fall for flood control. Agricultural use—mostly farmland and non-irrigated—accounts for most of the land within the tributary sub-watershed along the canal conveying water into Woodward Reservoir. There is a small dairy, grazing and some almond orchards.


The South San Joaquin Irrigation District is working with
famers to minimize the water quality impacts of grazing.

Recreation and grazing hold biggest threat
Recreational use is limited to the area immediately surrounding the reservoir. Recreation and grazing activities have the most potential to affect source water quality.

Steps given to minimize impacts of grazing
To minimize the impacts of grazing, the district is working with the farmers to:

  • Provide watering troughs for animals away from the canal.
  • Fence and berm the canal.
  • Move salt licks away from the canal to discourage animals from approaching the canal.
  • Establish a buffer zone around the reservoir perimeter protected by earthen berms and a fence barrier.

Regs prohibit body contact recreation
To address the impacts of body contact recreation and California Department of Health Services regulations prohibiting body contact recreation at reservoirs used for a potable water supply, the district is considering the following approaches:

  • Eliminate body contact recreation on the reservoir. (This would be a potentially unpopular action in the local communities.)
  • Obtain a legislative waiver from DOHS regulations such that the prohibition on body contact activities does not apply to Woodward Reservoir. (This may be only a short-term solution.)
  • Demonstrate that the source control measures at the recreation area together with proposed water treatment processes (including ozone disinfection) would provide full compliance with water quality and public health protection standards.
  • Add a second raw-water intake at Woodward Reservoir upstream and separated from the area of the reservoir used for body contact recreation. The second intake would be used until reservoir levels drop to a level that requires use of the downstream main intake located at the dam. This approach would allow body contact recreation during the heavy-use summer season when irrigation flows keep the reservoir levels high. Body contact recreation would be prohibited in the fall and winter months when the main intake is used.

At present, construction and operation of a second intake seems to be the alternative preferred and supported by Stanislaus County, which operates the recreation program at the reservoir.

The county would share the cost of the second intake with the district and develop a revised recreation program. This approach also received preliminary endorsement from DOHS.

The district has applied for state revolving-fund money set aside for source water protection by DOHS and is at the top of the priority list.

For more information, contact Standish-Lee at 916-652-0627 or 916-316-0197; Hesby at 925-246-8000; Kreinberg at 916-874-8734; or Black & Veatch.