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Wetland Research and Findings

Research has been conducted by the US Bureau of Reclamation, the National Biologic Service, the US Geologic Survey – Biological Resources Division and Water Resources Division, the University of California – Riverside and Davis, the University of Colorado, Boulder, and California State Polytechnic University – Pomona. Research topics at the wetlands include:

  • Water/soil quality and chemistry
  • Modeling and hydrodynamics
  • Mosquitoes, flies, and vector control
  • Vegetation and vegetation management
  • Birds and wildlife
  • Weather monitoring

Major Findings

Bird and Wildlife Studies demonstrate the success and value of recycled water for use in habitat development and environmental enhancement; contribute to public acceptance of recycled water; and promote the use of recycled water over potable water for “green” uses. Nearly 120 species of birds have visited and utilized the H/SJ wetlands.

Tricolored Blackbirds 

In 1994, the world population of tricolored blackbirds totaled 370,000 and by 1997 it had been reduced to 240,000, primarily due to loss of habitat. These birds inhabit marshes from southern Oregon to northwest Baja California. While conducting a census for US Fish & Wildlife, for the purpose of possibly listing the tricolored blackbird, it was discovered that approximately one tenth of the entire world population of these birds was at the H/SJ Multipurpose Constructed Wetlands and that these wetlands were ideal habitat for this species. As a result, listing was not recommended and the H/SJ wetlands is serving as a model of habitat creation for the tricolored blackbird.

Diptera Populations (Flies, Midges, and Mosquitoes) 

The vegetation management practices were not detrimental to any of the taxa examined; chironomid midges benefited from the addition of hummocks, the secondary effluent supports a diverse dipteran community; the shoe fly community (28 species) is comparable to the species richness of natural marshes; and the design of wetlands supporting more ecotonal areas (i.e., mud flats and other semi-aquatic areas) will promote further production of insects important to ecosystem establishment and function.

Use of Native Fish for Mosquito Control 

Using fish for mosquito control is effective, however, alternative strategies such as larvicidal agents should be planned in event proactive control measures are required during unusual outbreaks. Gambusia (mosquito fish) were hardier and more successful than the stickleback (native fish species.) Screens to prevent fish from entering the distribution system may need to be installed.

Effectiveness of Mosquito Abatement Measures 

Use of bacterial larvicides against mosquitoes at the wetlands, as well as review of other studies, suggest that some degree of mosquito control was provided. However, future control programs must incorporate application strategies that reduce the likelihood of evolved resistance to the mosquitocidal toxins.

Influence of Three Vegetation Management Practices on Mosquito Populations in Constructed Treatment Wetlands 

The hummocks showed considerable promise as a method for slowing proliferation of bulrush growth and significantly reducing mosquito production during the two years after vegetation management practices were carried out. Mosquito production increased concomitantly with vegetation growth during year two. By year two, populations of potential predators of larval mosquitoes were most abundant in the open water, particularly the deep ponds. Even though larval abundance and adult production per square meter of vegetated water surface did not differ significantly among the treatments during 1999, the hummock cells maintained comparatively more open water than did the other treatments and produced fewer mosquitoes. Larvivorous fish were not added to the cells in this study, but would be expected to reduce mosquito populations in the comparatively open hummock cells to an extent greater than was observed in the fishless wetlands during 1999.

Modeling Wetland Nutrient Dynamics 

The resulting program simulates the water quality in surface flow wetlands. The input can be created in files and read by the program and some of the input can be changed or entered by the user during the run. The main output of the program included concentrations of algae, organic nitrogen, ammonia nitrogen, nitrate nitrogen, organic phosphorus, dissolved phosphorus, carbonaceous biochemical oxygen demand, and oxygen. In addition to water quality, water evaporation and evapotranspiration are calculated.

Effects of vegetation management strategies on vegetation establishment and water quality in the Hemet research cells 

A habitat-driven approach to constructed wastewater treatment wetlands design is the basis for this study to determine whether habitat values can be maximized concurrently while meeting specific treatment criteria. By the end of the 1998 growing season, there were marked differences in the vegetation regrowth and the wildlife use within the vegetated portions of the cells. During the same time, ammonia-nitrogen removal was more than 60% across the cells. The following year as the vegetation became increasingly more dense, the removal efficiencies declined and the mosquito populations increased. The cells that restricted vegetation coverage to 58% of the shallow areas (those with hummocks) consistently maintained higher removal efficiencies than the controls (with 95% vegetation coverage of shallow areas) and the mechanically thinned cells (with 93% vegetation coverage of shallow areas). These data confirmed the hypothesis that many of the same design features that enhance habitat quality also improve water treatment functions.

Fate and Transport of Indicator Microorganisms in a Constructed Wetland 

One objective of the study was to determine the removal efficiency of coliphage within a constructed wetland. MS2 coliphage removal from wetland inlets to outlets averaged 97.1%.

Nitrogen Removal 

Analysis by EMWD showed total inorganic nitrogen removal in the three-phase cells averaged 51% compared to only 7% removal in the single-phase cells.

Investigation of nitrogen transformations in a southern California constructed wastewater treatment wetland 

During May 1996, the relatively low external loading, the 36% open water surface area, and only a moderate coverage of vegetation biomass allowed for a wide range of potential nitrogen transformations. The potential transformations included: 1) nitrification and the possibility of subsequent denitrification; 2) biomass assimilation into both algae and the emergent vegetation; 3) sedimentation of vegetation and algal biomass releasing organic nitrogen; and 4) ammonification of the organic nitrogen and anoxic areas. During September 1997, the combination of heavy external loading of the un-nitrified, anoxic RWRF effluent, plus the abundant mature plant material, resulted in a limitation of nitrogen transformations. The abundant vegetation created less open water areas and a build-up of senescent material causing internal organic matter loading and subsequent release of ammonia. This loading combination limited the potential nitrogen transformations to include only:

  • rapid denitrification of any incoming NO2-N and NO3-N;
  • biomass assimilation of NH4-N; and
  • ammonification of organic nitrogen released from decaying biomass.

Algal biomass assimilation and sedimentation were probably the main mechanisms for nitrogen removal.

Transformation of Dissolved Organic Matter (DOM) 

The purpose of the study was to develop a better understanding of the nature and transformation dynamics of DOM in treatment wetlands. Many factors, including operating conditions and climate, play a role in transformation. In the climates such as that found in the Hemet/San Jacinto area, evapotranspiration and water loss result in an increase of DOM. Further research is necessary to understand the relation between DOM transformation in treatment wetlands and wetland operational conditions. Data does not give an indication whether wetlands reduce THM precursors.

Demo Wetlands Toxicity Characterization 

Tests showed toxicity at the wetlands inlets to all species tested; no toxicity to any organism exposed in the outlets.

Amoxicillin in Waste Water 

Man and animals contribute antibiotics into the water stream leading to eco-system disruption and development of antibiotic-resistant bacteria. This study attempted to trace amoxicillin in wastewater. Concentration levels were found to be in parts per billion or less; concentration methods need to be devised.