Guajome Lake

Located in the far eastern edge of Oceanside lies Guajome Lake, a County-managed waterbody that is part of the Guajome Regional Park. This 12-acre lake is in the larger San Luis Rey Watershed. Adjacent to the Lake is Guajome Marsh, which is separated from the Lake by a stream, called Guajome Creek, that drains approximately 1,293 acres into Guajome Lake.

The Lake has undergone many structural changes as a result of diking and dredging activities done prior to the 1970s. At one time, the marsh, creek and lake were all combined. However, sediments have filled in the area and contributed to loss of lake depth over the years. A study conducted by the County of San Diego in 1994 showed that the lake receives approximately 1,041 tons of sediments annually, though the quantity could vary year to year.

Guajome Lake is surrounded by one of the larger freshwater marsh habitats in San Diego County, with a stand of riparian woodland at the east end of the lake. The marsh habitat is dominated by bulrush and cattails. Riparian habitat in the area has primarily willow species, pickleweed and mulefat. There have been a few endangered bird species observed around Guajome Lake, including the California Least Tern and the Light Footed Clapper Rail.

The areas draining runoff into the lake include a mixture of residential, commercial, agricultural and open space. Due to a few of these land uses, Guajome Lake has been listed by the State Water Resources Control Board as being impacted by eutrophication, or having too many nutrients in the water which contribute to the overproduction of algae. Due to the eutrophication impairment, few fish reside in the lake.

The County of San Diego is concerned about the health of the Guajome Lake and strives to continually improve its water quality, which is why in January of 1994 the County initiated a study to identify the sources of the pollutants impacting its water quality. Today, the County of San Diego is looking at projects to assist in the reduction of these pollutants, such as aeration machines to increase the levels of oxygen in the water.