Statement of Findings regarding the Periodic Review and Approval of the Livermore Valley Basin Alternative Groundwater Sustainability Plan

California Department of Water Resources (DWR) | June 27th, 2024

Statement of Findings Regarding the Periodic Review and Approval of the Santa Clara Valley – Santa Clara Subbasin Alternative Groundwater Sustainability Plan

California Department of Water Resources (DWR) | June 27th, 2024

Statement of Findings regarding the Periodic Review and Approval of the Tahoe Valley - Tahoe South Subbasin Alternative Groundwater Sustainability Plan

California Department of Water Resources (DWR) | June 27th, 2024

Statement of Findings Regarding the Periodic Review of Alternative Groundwater Sustainability Plan Coachella Valley – Mission Creek Subbasin (No. 7-021.02)

California Department of Water Resources (DWR) | June 27th, 2024

Statements of Water Diversions and Use: Providing a Better Picture of Water Use in the Delta

California State Water Resources Control Board (SWRCB) | April 5th, 2011

The purpose of this report is to outline the history of the Statements Program and explain recent statutory changes that will enable the program to more comprehensively f

The purpose of this report is to outline the history of the Statements Program and explain recent statutory changes that will enable the program to more comprehensively fulfill its original intent of providing meaningful information regarding water diversion and use, particularly in the Delta. The report also underscores a serious funding problem that threatens the integrity of the Statements Program and explores issues related to the new requirement for diverters to provide monthly records of water diversion based on the use of best available technologies.

Statewide Effects of Ending Long-Term Groundwater Overdraft in California

American Society of Civil Engineers (ASCE) | September 19th, 2019

Groundwater overdraft is a major problem globally and has been a growing problem for California for decades. This overdraft is predominantly driven by the economic value

Groundwater overdraft is a major problem globally and has been a growing problem for California for decades. This overdraft is predominantly driven by the economic value of water for agricultural production and cities. Spurred by the recent drought, California passed legislation requiring the elimination of groundwater overdraft by 2040. This paper employs a statewide hydroeconomic optimization model to explore potential water supply effects of ending long-term groundwater overdraft in California’s Central Valley for several general water policies with historical and warmer–drier climates. The model minimizes agricultural, urban scarcity, and operating costs over 82 years of historical hydrologic variability, given today’s infrastructure and environmental flow constraints. The model results assess effects of overdraft and Delta policies for different climates on water deliveries, economic costs, environmental flows, water market operations, and the economic value of expanding infrastructure capacities. Prohibiting long-term overdraft leads to reduced agricultural water use and reoperations, and reduced outflows to the sea from the Sacramento-San Joaquin Delta, where water availability policies become important. In combination with a warmer–drier climate, ending overdraft further exacerbates water scarcities, increases environmental and economic costs, and increases the marginal economic value of water exports from the Delta, which are likely to worsen water conflicts and illustrate connections of California’s groundwater and surface water problems. Economically useful adaptation actions include more water transfers involving the Delta, water markets, and trades; conjunctive use of surface water and groundwater; and recycled wastewater supplies for coastal urban users.

Statewide Perspective on Chemicals of Concern and Connections Between Stream Water Quality and Land Use

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

The California Surface Waters Ambient Monitoring Program (SWAMP) is tasked with assessing water quality in all of California’s surface waters. The program

The California Surface Waters Ambient Monitoring Program (SWAMP) is tasked with assessing water quality in all of California’s surface waters. The program conducts monitoring directly and through collaborative partnerships, and provides numerous information products designed to support water resource management in California. The Stream Pollution Trends (SPoT) program is a statewide monitoring effort focused on the SWAMP priority of assessing the levels to which aquatic life beneficial uses are supported in California streams (SWAMP 2010). The program has three primary goals: Determine long-term trends in stream contaminant concentrations and effects statewide. Relate water quality indicators to land-use characteristics and management effort. Establish a network of sites throughout the state to serve as a backbone for collaboration with local, regional, and federal monitoring. The SPoT program is specifically designed to fill critical information needs for state, regional and local resource management programs, including Clean Water Act (CWA) §303d impaired waters listing, CWA §305b condition assessment, total maximum daily load (TMDL) assessment and allocation, non-point source program water quality assessment, stormwater and agricultural runoff management, pesticide registration and labeling, and local land use planning. SPoT is a long-term trends monitoring program that will help managers understand how water quality conditions are changing over time in relation to land use change and resource management practice implementation. This report covers the rst annual survey, so trends assessment will not begin until the second and third year surveys are included in the next SPoT report (due in 2012). The focus of this report is on identifying chemicals of concern and the watershed land uses associated with their presence in California streams. The data collected can be used in a space-for-time-swap approach to estimate the effect that further land use change (such as increasing urbanization) would have on stream water quality in California. The results indicate that, on a statewide basis, levels of most measured pollutants in stream sediment increased as urban land cover in their watersheds increased. Industrial compounds, some metals, and many pesticides were found at higher concentrations in urban watersheds than in agricultural or other watersheds statewide. Pyrethroid pesticides were detected in stream sediments from more than half of the SPoT watersheds, and were measured at concentrations associated with toxicity in more than a quarter of the total samples. DDTs and PCBs, both banned for more than three decades, are still commonly detected in California streams, with DDTs frequently exceeding sediment quality guidelines. PBDEs and PAHs were common in urban areas, and mercury was above guideline values in a small number of samples from urban watersheds and watersheds where it is geologically abundant. The data presented here describe the baseline condition for the SPoT long-term trends assessment. They also demonstrate a significant relationship between land use and stream pollution, and provide data directly relevant to a number of agency water quality protection programs.

Statistical Clustering of Major Solutes: Use as a Tracer for Evaluating Interbasin Groundwater Flow into Indian Wells Valley, California

Geological Society of America (GSA) | February 9th, 2006

Many previous studies have demonstrated use of specific solutes or isotopes as tracers of groundwater flow. We present a technique that uses standard hydrochemical inform

Many previous studies have demonstrated use of specific solutes or isotopes as tracers of groundwater flow. We present a technique that uses standard hydrochemical information to create statistically based hydrochemical facies, which are then used as tracers of groundwater flow. This approach reduces potential subjective bias during interpretation of single tracer data in complex systems with multiple sources or conflicting multiple tracer data. Standard hydrochemical data from 1,368 water samples that spanned more than 80 years were analyzed using cluster analysis to decipher groundwater flow paths in Indian Wells Valley (IWV), California. The statistically derived hydrochemical facies form distinct spatial patterns in which all major-ion concentrations increase progressively from Sierra Nevada (recharge) to China Lake playa (discharge), consistent with the topographically driven flow of groundwater (the typical case for basin and range flow systems). However, once individual samples could be placed in the context of the normal hydrochemical evolution, anomalies are readily identifiable. The distribution of water chemistry in the southeastern part of the IWV does not conform to the regional trend. Groundwater from that part of the IWV is statistically more similar to waters from the Kern Plateau area (in the high Sierra Nevada outside the local watershed) than to waters from the local watershed. The groundwater is interpreted to originate from the fracture-directed interbasin flow from the Kern Plateau area that is directly recharging the alluvial aquifer in the subsurface. Inclusion of this flow could substantially alter current water budgets and water resources management approaches.

Statistical Downscaling Using Localized Constructed Analogs (LOCA)*

American Meteorological Society (AMS) | December 2nd, 2014

A new technique for statistically downscaling climate model simulations of daily temperature and precipitation is introduced and demonstrated over the western United Sta

A new technique for statistically downscaling climate model simulations of daily temperature and precipitation is introduced and demonstrated over the western United States. The localized constructed analogs (LOCA)method produces downscaled estimates suitable for hydrological simulations using amultiscale spatial matching scheme to pick appropriate analog days fromobservations. First, a pool of candidate observed analog days is chosen by matching the model field to be downscaled to observed days over the region that is positively correlated with the point being downscaled, which leads to a natural independence of the downscaling results to the extent of the domain being downscaled. Then, the one candidate analog day that best matches in the local area around the grid cell being downscaled is the single analog day used there. Most grid cells are downscaled using only the single locally selected analog day, but locations whose neighboring cells identify a different analog day use a weighted combination of the center and adjacent analog days to reduce edge discontinuities. By contrast, existing constructed analog methods typically use a weighted average of the same 30 analog days for the entire domain. By greatly reducing this averaging, LOCA produces better estimates of extreme days, constructs a more realistic depiction of the spatial coherence of the downscaled field, and reduces the problem of producing too many light-precipitation days. The LOCA method is more computationally expensive than existing constructed analog techniques, but it is still practical for downscaling numerous climate model simulations with limited computational resources.

Statistical Methods Development and Sampling Design Optimization to Support Trends Analysis for Loads of Polychlorinated Biphenyls from the Guadalupe River in San Jose, California, USA

San Francisco Estuary Institute (SFEI) | September 3rd, 2018

The Regional Monitoring Program for Water Quality in San Francisco Bay (RMP), with guidance from its Small Tributaries Loading Strategy (STLS) Team, has been conducting s

The Regional Monitoring Program for Water Quality in San Francisco Bay (RMP), with guidance from its Small Tributaries Loading Strategy (STLS) Team, has been conducting small tributary loading studies at several sites in the Bay Area since 2003. A current priority for the STLS is developing a strategy for measuring trends in pollutant loadings from small tributaries to the Bay.  This technical report presents the work to develop a statistical model for trends in loads of polychlorinated biphenyls (PCBs), and estimate the power for proposed monitoring designs as a basis for detecting trends for the Guadalupe River watershed (San Jose, California). The statistical approach builds upon the turbidity surrogate methodology that has been employed in the STLS since 2003. A novel, two-stage statistical modeling approach was used to incorporate the significant turbidity-PCB relationships that exist, and evaluate climatic, seasonal, and inter-annual factors as additional potential drivers of PCB loads. The longest-running time series of tributary monitoring by the STLS on the Guadalupe River was selected as the case study for developing and testing the statistical approach. As a result of this effort, a multiple linear regression model for detecting trends in PCB loads in the Guadalupe River was developed.