Pathogen Total Maximum Daily Loads Modeling in the Chino Basin

Science Center Objects

The Santa Ana River in Southern California is the primary water supply for approximately 2 million people. The main constituent of regulatory concern is pathogens that have impaired the use of waters for the beneficial uses of warm freshwater habitat and noncontact water recreation. Pathogen loadings from the tributary watershed flows into lakes and streams leading into the Santa Ana River. Baseflow in the river consists primarily of secondary treated wastewater. Periodic storm events during the rainy season (December through March) supply water to the river that consists primarily of urban runoff. In addition to urban runoff, there is considerable runoff from the Dairy Preserve located in Chino Basin, the home of more than 300,000 dairy cows. A Total Maximum Daily Load (TMDL) now is being established for pathogens in this section of the river. 

Bridge over Santa Ana River

Bridge over Santa Ana River

The objective of the study is the development of a rainfall/runoff/transport model representing hydrologic and surface-water transport processes in the Chino Basin to assess the relative impacts of various land use scenarios, the evaluation of the impact of the existing land uses (in terms of sources areas), and the development of a better understanding of watershed processes affecting water quality.

The proposed project relates closely to issues 1 and 2 in the strategic plan for the Water Resources Discipline: effects of urbanization and suburbanization on water resources and effects of land use and population increases on water resources in the coastal zone. The project builds on ongoing USGS hydrologic studies in the Santa Ana watershed, including the SANA NAWQA and the Santa Ana Stormwater runoff study. The study addresses statewide and national water management issues related to the development TMDLs for pathogens.

The project involves targeted sampling of fecal-indicator bacteria to characterize pathogen loading from different sources and development, calibration, and initial application of a watershed model of the Chino Basin using Hydrologic Simulation Program-FORTRAN.