A serious concern for managers of water resources, pathogens in the urban environment easily enter waters through a number of pathways, including discharge of inadequately treated sewage, stormwater runoff, combined sewer overflows and sanitary sewer overflows. Pathogens in US ambient water bodies are regulated under the Clean Water Act (CWA), while pathogens in drinking water supplies are regu...

High levels of fecal indicator bacteria (FIB) in surface waters is a common problem in urban areas that often leads to impairment of beneficial uses such as swimming. Once impaired, common management and regulatory solutions include development of total maximum daily loads (TMDLs) and other water quality management plans. A critical element of these plans is establishment of a "reference" level...

Transport of pesticides by surface runoff during rainfall events is a major process contributing to pesticide contamination in rivers. This study presents an empirical regression model that describes pesticide loading over time in the Sacramento and San Joaquin Rivers. The empirical model is physically based, but uses highly aggregated parameters, allowing the prediction of pesticide loading wi...

Watersheds using surface water for irrigation often return a portion of the water to a water body. This irrigation return flow often includes sediment and nutrients that reduce the quality of the receiving water body. Research in the 82,000-ha Upper Snake Rock (USR) watershed from 2005 to 2008 showed that, on average, water diverted from the Snake River annually supplied 547 kg ha of total susp...

the karkheh dam reservoir with a capacity of more than 5 billion cubic meter is the largest dam in iran with both agricultural and drinking usages. its hydrodynamics and water quality were modeled and simulated to analyze the total maximum daily load (tmdl) of total dissolved solids (tds). the simulation was supported with measurements of temperature and tds measurements during two years. a lat...

San Francisco Bay is facing a legacy of polychlorinated biphenyls (PCBs) spread widely across the land surface of the watershed, mixed deep into the sediment of the Bay, and contaminating the Bay food web to a degree that poses health risks to humans and wildlife. In response to this persistent problem, water quality managers are establishing a PCB total maximum daily load (TMDL) and implementa...

The BASINS (Better Assessment Science Integrating point and Non-point Sources, Release 2) system, created under the auspice of the U.S. Environmental Protection Agency (EPA), uses An'Vie\\, as a framework to integrate several hydrologic/hydraulic and water quality models. The BASINS system also includes a national stream characteristic database that contains reach-scale data on mean stream widt...