Hydrologic Modeling of the Santa Clara River Watershed with the U.S. EPA Hydrologic Simulation Program - FORTRAN (HSPF)

Ventura County Watershed Protection District | January 24th, 2009

The purpose of the Santa Clara River (SCR) Watershed Feasibility Study as described in the PMP (October, 2003) is to determine the impact of the upstream urbanization, s

The purpose of the Santa Clara River (SCR) Watershed Feasibility Study as described in the PMP (October, 2003) is to determine the impact of the upstream urbanization, specifically in Los Angeles County, to the present natural state of the river in Ventura County and communities adjacent to the River that expect to develop close to the river banks. It is the goal of the watershed study to develop the necessary baseline data and analytical tools. In order to evaluate these impacts the feasibility study will include: • A comprehensive update of hydrologic, hydraulic, and sediment (yield and transport) models for a range of flow rates for existing conditions and future conditions within the Santa Clara River. The hydrologic model provides the flow data needed as input to the hydraulic and sediment transport models. • The hydrologic model will also be used to evaluate baseline and changes to water quality and pollutant loadings as a result of development or any proposed regional solutions to flooding or water quality problems. • Generate computer models that can simulate the impacts of land use changes under existing, natural and future conditions, and provide data to forecast the resulting changes to streamflow in the Santa Clara River. • Existing conditions include recently installed flood control and water supply/storage facilities. For future conditions, the modeling will include proposed land use changes, any additional flood control or sediment control facilities, and the effects of changes in sediment flow to the downstream areas as a result of proposed alternatives to mitigate flooding or water quality problems. The Natural Condition will be modeled by assuming the watershed has not been developed or subjected to extensive ranching or agricultural activities (pre-European). This document is the Final Report for the watershed hydrology model of the Santa Clara River Watershed using the U.S. EPA Hydrologic Simulation Program FORTRAN (HSPF). This effort was funded directly and wholly by contract with the Ventura County Watershed Protection District (VCWPD). This report identifies and describes the watershed characteristics and types of data required/available for the model, the segmentation of the watershed for modeling purposes, model calibration and validation efforts, and the results for the Baseline and Natural Conditions Scenario model runs. This effort has been designed to produce a comprehensive watershed model that meets the needs of the hydrologic model component of the SCR Watershed Feasibility Study as described above. This model was designed to: a. Represent hydrologic conditions throughout the SCR watershed for a wide range of flow conditions continuously for both high flows, low flows and individual storm events b. Provide continuous flow boundary conditions for the hydraulic and sediment transport models, at the appropriate spatial scales and boundary locations identified by the Feasibility Study participants c. Provide a modeling framework for subsequent sediment yield and water quality modeling requirements of the Feasibility Study d. Include a long-term database of 40 or more years of model input (e.g. precipitation, evaporation, diversions, POTWs) to allow long-term model simulations needed to develop the required flood (and low flow) frequency information at selected points throughout the SCR Watershed e. Provide long-term model simulations for both Baseline (current) and Natural Condition alternatives as a basis for assessing and comparing with planned Future Condition alternatives.

Hydrological processes, groundwater recharge and surface-water/groundwater interactions in arid and semi-arid areas

Cambridge University Press (CUP) | December 1st, 2010

The traditional development of water resources in arid areas has relied heavily on the use of groundwater. Groundwater uses natural storage, is spatially distributed and,

The traditional development of water resources in arid areas has relied heavily on the use of groundwater. Groundwater uses natural storage, is spatially distributed and, in climates where potential evaporation rates can be of the order of metres per year, provides protection from the high evaporation losses experienced by surface-water systems. Traditional methods for the exploitation of groundwater have been varied, including the use of very shallow groundwater in seasonally replenished riverbed aquifers (as in the sand rivers of Botswana), the channelling of unconfined alluvial groundwater in afalaj (or qanats) in Oman and Iran, and the use of hand-dug wells. Historically, abstraction rates were limited by the available technology, and rates of development were low, so that exploitation was generally sustainable. However, in recent decades, pump capacities have dramatically increased and hence agricultural use of water has grown rapidly, while the increasing concentration of populations in urban areas has meant that large-scale well fields have been developed for urban water supply. A common picture in arid areas is that groundwater levels are in rapid decline; in many instances this is accompanied by decreasing water quality, particularly in coastal aquifers where saline intrusion is a threat. Associated with population growth, economic development and increased agricultural intensification, pollution has also become an increasing problem. The integrated assessment and management of groundwater resources is essential so that aquifer systems can be protected from pollution and over-exploitation.

Hydrology and Water Quality Analysis Report for the Amendments to the Cemex Eliot Quarry SMP-23 Reclamation Plan

Alameda County Community Development Agency | December 6th, 2016

The proposed Reclamation Plan Amendment at the CEMEX Eliot Quarry facility in Pleasanton, California has been evaluated from the perspective of the criteria in Appendix G

The proposed Reclamation Plan Amendment at the CEMEX Eliot Quarry facility in Pleasanton, California has been evaluated from the perspective of the criteria in Appendix G of the California Environmental Quality Act (CEQA) and the requirements of Section 3706 of the Surface Mining and Reclamation Act (SMARA), for potential impacts on hydrology and water quality.  Click here for the California CEQA Eliot Quarry page

Hyper-Salinity Toxicity Thresholds for Nine California Ocean Plan Toxicity Test Protocols

California State Water Resources Control Board (SWRCB) | July 1st, 2012

A growing number of coastal cities in California are exploring the potential for ocean desalination as a means to augment freshwater supplies. There are currently a numbe

A growing number of coastal cities in California are exploring the potential for ocean desalination as a means to augment freshwater supplies. There are currently a number of desalination facilities proposed or operating in California. The process of desalination most commonly utilizes reverse osmosis (RO) to remove salts from groundwater, reclaimed water, and seawater. This process results in production of hypersaline reject brine. This reject brine may be discharged into the marine environment, sometimes in combination with discharge from a sewage treatment plant or power plant effluent. Typical RO reject brine produced using 100% seawater can have approximately twice the original salt content of seawater. In order to ensure that brine discharges do not pose risk to coastal receiving waters, it is anticipated that desalination plants will be required to monitor effluent toxicity. Monitoring requirements will likely include testing for effluent toxicity using some combination of the short-term chronic toxicity test protocols listed in the 2009 California Ocean Plan (SWRCB, 2009). While the tests listed in the Ocean Plan have been the subject of ongoing research, no comprehensive studies of the effects of hyper-salinity have been conducted with all seven toxicity test organisms (nine protocols when including sand dollar and urchin fertilization endpoints). The results from these tests will allow determination of the toxicity of hypersaline brine in the absence of any additional toxic constituents that may be produced during the desalination process. These results provide resource managers with background information to facilitate interpretation of toxicity test results from desalination plant effluent testing and permitting of desalination facilities. The results will also be used in the development of an amendment to the California Ocean Plan that addresses impacts to marine life from intakes and discharges from desalination facilities.

Hyperspectral characterization of wastewater in the Tijuana River Estuary using laboratory, field, and EMIT satellite spectroscopy

Elsevier | May 8th, 2025

Hundreds of millions of liters of untreated wastewater are discharged into the Tijuana River annually, impacting communities on both sides of the US-Mexico border. Curren

Hundreds of millions of liters of untreated wastewater are discharged into the Tijuana River annually, impacting communities on both sides of the US-Mexico border. Current monitoring methods are resource-intensive and limited in coverage. Optical satellite imaging may enable broader spatiotemporal monitoring, yet retrievals of bacterial concentrations and other key water quality indicators remain challenging. Here we investigate the utility of spectroscopic sensors to monitor the presence of wastewater in this estuarine-coastal system, as a proxy for bacterial concentrations and other water quality parameters. We prepared dilutions of untreated wastewater and uncontaminated seawater, measuring visible through shortwave infrared (VSWIR; 350–2500 nm) reflectance spectra of each sample. At high wastewater concentrations, a distinct spectral feature centered near 620 nm strongly correlated with paired water quality measurements (R2 ≥ 0.97, p-value < 0.01). This feature is additionally observed in multispectral resolution, in field observations, and in hyperspectral satellite imagery. An example application of plume mapping with this feature is presented, representing one of the earliest adoptions of EMIT hyperspectral satellite imagery for water quality monitoring. These results are promising for the use of spectroscopic sensors to map and monitor wastewater pollution in the Tijuana River Estuary and potentially, similarly polluted coastal and estuarine systems.

Identification of Bacteria in Groundwater Used for Domestic Supply in the Southeast San Joaquin Valley, California, 2014

U.S. Geological Survey (USGS) | June 22nd, 2021

Groundwater is an important source of drinking water in California. Water-borne diseases caused by microbial contamination are a growing concern. The MI test, a membrane

Groundwater is an important source of drinking water in California. Water-borne diseases caused by microbial contamination are a growing concern. The MI test, a membrane filtration method for the chromogenic-/-fluorogenic detection of total coliforms and Escherichia coli, was used for samples collected January to April 2014 from 42 domestic wells in the southeastern San Joaquin Valley. The wells were sampled as part of the Groundwater Ambient Monitoring and Assessment Program Priority Basin Project (GAMA-PBP), a cooperative study between the U.S. Geological Survey and the California State Water Resources Control Board. Polymerase chain reaction analysis and sequencing of deoxyribonucleic acid (DNA) were used for 34 target and nontarget colonies that grew on the MI media from samples collected from 13 of the domestic wells to identify what genera of bacteria could exist in groundwater used by domestic wells. Gene sequences obtained using the Sanger method were entered into the basic local alignment search tool (BLAST) database, and 17 genera of bacteria were identified. Of these, 13 genera contain species that are human pathogens or opportunistic human pathogens. All the genera that include human pathogens are naturally present in soil, plants, or water; one of the pathogens also can be found in fecal matter. Six of the human pathogens were from non-target colony growth on the MI media. Target and non-target microbial growth on MI media are indicators of the possible presence of pathogenic bacteria even if the bacteria naturally are from soil rather than from a fecal source.

Identification of Bacteria in Groundwater Used for Domestic Supply in the Southeast San Joaquin Valley, California, 2014

U.S. Geological Survey (USGS) | June 22nd, 2021

Groundwater is an important source of drinking water in California. Water-borne diseases caused by microbial contamination are a growing concern. The MI test, a membrane

Groundwater is an important source of drinking water in California. Water-borne diseases caused by microbial contamination are a growing concern. The MI test, a membrane filtration method for the chromogenic / fluorogenic detection of total coliforms and Escherichia coli, was used for samples collected January to April 2014 from 42 domestic wells in the southeastern San Joaquin Valley. The wells were sampled as part of the Groundwater Ambient Monitoring and Assessment Program Priority Basin Project (GAMA-PBP), a cooperative study between the U.S. Geological Survey and the California State Water Resources Control Board. Polymerase chain reaction analysis and sequencing of deoxyribonucleic acid (DNA) were used for 34 target and nontarget colonies that grew on the MI media from samples collected from 13 of the domestic wells to identify what genera of bacteria could exist in groundwater used by domestic wells. Gene sequences obtained using the Sanger method were entered into the basic local alignment search tool (BLAST) database, and 17 genera of bacteria were identified. Of these, 13 genera contain species that are human pathogens or opportunistic human pathogens. All the genera that include human pathogens are naturally present in soil, plants, or water; one of the pathogens also can be found in fecal matter. Six of the human pathogens were from non-target colony growth on the MI media. Target and non-target microbial growth on MI media are indicators of the possible presence of pathogenic bacteria even if the bacteria naturally are from soil rather than from a fecal source.

Identification of fresh submarine groundwater off the coast of San Diego, USA, using electromagnetic methods

Hydrogeology Journal (Springer) | March 1st, 2022

Climate change has a pronounced effect on water resources in many semiarid climates, causing populated areas such as San Diego County (USA), to become more vulnerable to

Climate change has a pronounced effect on water resources in many semiarid climates, causing populated areas such as San Diego County (USA), to become more vulnerable to water shortages in the coming decades. To prepare for decreased water supply, San Diego County is adopting policies to decrease water use and to develop additional local sources of water. One new local source of freshwater is produced by a desalination facility that purifies brackish groundwater from the coastal San Diego Formation. This formation has been studied extensively onshore, but little is known about the geology or groundwater quality offshore in the adjacent continental shelf. Because most groundwater systems are interconnected and complex, further analysis is needed to identify offshore geology, possible sequestration of freshwater in the shelf, and potential pathways for saltwater intrusion. This comprehensive understanding is important because seawater intrusion may limit use of the San Diego Formation and longevity of desalination facilities. Controlled-source electromagnetic methods are uniquely suited to detecting offshore groundwater as they are sensitive to changes in pore fluids such as the transition from fresh to brackish groundwater. This paper describes results from surface-towed electromagnetic surveys that mapped the pore-fluid salinity and possible fluid pathways in the continental shelf off the coast of San Diego. The results indicate a considerable volume of fresh-to-brackish groundwater sequestered in the shelf, both in continuous lenses and isolated pockets, that appear influenced by fault systems and shallow stratigraphy.

Identifying and Addressing Contaminant Sources Impacting an Urban Estuary

San Francisco Estuary Institute (SFEI) | July 1st, 2016

Identifying organic contaminants at trespass cannabis grows on federal land in California, USA

Elsevier | September 25th, 2025

Despite the legalization of recreational cannabis in California, USA, illegal cannabis cultivation remains pervasive, partly through the establishment of illegal cult

Despite the legalization of recreational cannabis in California, USA, illegal cannabis cultivation remains pervasive, partly through the establishment of illegal cultivation on public lands (trespass grows). These operations often illegally divert water for irrigation and perform unauthorized applications of chemical fertilizers and pesticides. This work investigates a broad suite of these chemicals, focusing on their persistence in topsoil and presence in water and bed sediment in adjacent streams. Quantitative analyses of pesticides were conducted (183 compounds in water; 176 in topsoil/bed sediment), supplemented by qualitative nontargeted screening at three trespass grows that had no active cultivation for 8 months to 2 years. Targeted multi-residue analysis of topsoil detected the insecticides bifenthrin, cyfluthrin, malathion and imidacloprid (with concentrations up to 38 ng/g dry weight, d.w.), and the fungicides fluopyram, myclobutanil, and triadimefon (concentrations up to 8.1 ng/g d.w.). No pesticides were detected in the companion water or streambed sediment samples from adjacent streams. In addition, no water samples were found to have measurable estrogenic activity. Nontargeted screening uncovered additional pesticides (i.e., spiromesifen, trinexapac) in the topsoil and cannabis-related compounds (i.e., cannabidol, delta9-tetrahydrocannabinol) in both topsoil and streambed sediment suggesting the likelihood of offsite transport of cannabis related compounds. Phthalate plasticizers, rubber-related compounds, pharmaceuticals and personal care product chemicals were detected in topsoil, water, and streambed sediment and may be related to extensive irrigation infrastructure installed at these trespass grows. This work begins to establish a contaminant profile associated with illegal cannabis growing activities, providing a foundation for future research focused on their potential ecological impacts.