Simulation of Groundwater and Surface-Water Resources of the Santa Rosa Plain Watershed, Sonoma County, California

U.S. Geological Survey (USGS) | April 25th, 2014

Water managers in the Santa Rosa Plain face the challenge of meeting increasing water demand with a combination of Russian River water, which has uncertainties in its fut

Water managers in the Santa Rosa Plain face the challenge of meeting increasing water demand with a combination of Russian River water, which has uncertainties in its future availability; local groundwater resources; and ongoing and expanding recycled water and water from other conservation programs. To address this challenge, the U.S. Geological Survey, in cooperation with the Sonoma County Water Agency, the cities of Cotati, Rohnert Park, Santa Rosa, and Sebastopol, the town of Windsor, the California American Water Company, and the County of Sonoma, undertook development of a fully coupled groundwater and surface-water model to better understand and to help manage the hydrologic resources in the Santa Rosa Plain watershed. The purpose of this report is to (1) describe the construction and calibration of the fully coupled groundwater and surface-water flow model for the Santa Rosa Plain watershed, referred to as the Santa Rosa Plain hydrologic model; (2) present results from simulation of the Santa Rosa Plain hydrologic model, including water budgets, recharge distributions, streamflow, and the effect of pumping on water-budget components; and (3) present the results from using the model to evaluate the potential hydrologic effects of climate change and variability without pumpage for water years 2011–99 and with projected pumpage for water years 2011–40.

Simulation of Water-Management Alternatives in the Mojave River Ground-Water Basin, California

U.S. Geological Survey (USGS) | July 1st, 2002

Small Tributaries Pollutants of Concern Reconnaissance Monitoring: Loads and Yields-based Prioritization Methodology Pilot Study

San Francisco Estuary Institute (SFEI) | October 1st, 2019

Watershed yields (mass exported per unit watershed area) can be used as an indicator variable to help identify watersheds or source areas of higher management interest i

Watershed yields (mass exported per unit watershed area) can be used as an indicator variable to help identify watersheds or source areas of higher management interest in relation to mass loads that impact the Bay. When prioritization includes an analysis of uncertainty, a recommendation can also be made for priority investigations necessary to reduce uncertainties. A method is presented for generating comparable yield estimates for small industrial watersheds where only a single storm has been sampled and for which a watershed boundary has been generated. The method generates standardized storm-based yields for each sampled site for a 0.5-year annual return frequency storm with 2-hour peak rainfall intensity. No attempt has been made to estimate annual average yields (the metric upon which the TMDL was based).

Socio-hydrological drought impacts on urban water affordability

Nature Portfolio (Springer Nature) | January 19th, 2023

In water-stressed regions, droughts pose a critical challenge to urban water security for low-income households. Droughts reduce water availability, forcing water provide

In water-stressed regions, droughts pose a critical challenge to urban water security for low-income households. Droughts reduce water availability, forcing water providers to invest in additional supplies or enact expensive, short-term emergency measures. These costs are frequently passed on to households through increased rates and surcharges, driving up water bills for low-income households and altering patterns of water consumption. Here we have developed a socio-hydrological modelling approach that integrates hydrology, water infrastructure, utility decision-making and household behaviour to understand the impacts of droughts on household water affordability. We present here an application based on Santa Cruz, California and show that many drought resilience strategies raise water bills for low-income households and lower them for high-income households. We also found that low-income households are most vulnerable to both changing drought characteristics and infrastructure lock-in.

Solar and wind energy enhances drought resilience and groundwater sustainability

Nature Portfolio (Springer Nature) | November 6th, 2019

Water scarcity brings tremendous challenges to achieving sustainable development of water resources, food, and energy security, as these sectors are often in co

Water scarcity brings tremendous challenges to achieving sustainable development of water resources, food, and energy security, as these sectors are often in competition, especially during drought. Overcoming these challenges requires balancing trade-offs between sectors and improving resilience to drought impacts. An under-appreciated factor in managing the water-food-energy (WFE) nexus is the increased value of solar and wind energy (SWE). Here we develop a trade-off frontier framework to quantify the water sustainability value of SWE through a case study in California. We identify development pathways that optimize the economic value of water in competition for energy and food production while ensuring sustainable use of groundwater. Our results indicate that in the long term, SWE penetration creates beneficial feedback for the WFE nexus: SWE enhances drought resilience and benefits groundwater sustainability, and in turn, maintaining groundwater at a sustainable level increases the added value of SWE to energy and food production.

Southwestern United States drought of the 21st century presages drier conditions into the future

Nature Portfolio (Springer Nature) | September 19th, 2022

Intense drought has occurred in the United States Southwest this century, causing unprecedented stress to water resources. Here we use paleoclimate and instrumental reco

Intense drought has occurred in the United States Southwest this century, causing unprecedented stress to water resources. Here we use paleoclimate and instrumental records to establish that the recent temperature rise is incompatible with random draws from past fluctuations, including the current period of warming. Consistent with and extending previous reconstructions, we find that the ongoing drought is the most intense at the 21-year scale back to 600 CE. Evaluation using standardized regression coefficients shows that recent warming damps the effect of moisture delivery on the Standardized Precipitation-Evaporation Index by approximately one-third. The probability of full recovery of the current moisture deficit is unlikely even by mid-century and about five percent in 10-15 years. Evaluation of future climate simulations indicates increasing regional temperature stress and soil moisture depletion, and coupled with long recovery periods for moisture delivery, very low chance for regional mega-reservoirs to regain full-capacity levels assuming current demand.

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. 

Strategy for In-Bay Fate Modeling to Support Contaminant and Sediment Management in San Francisco Bay

San Francisco Estuary Institute (SFEI) | August 15th, 2022

This report presents a strategy and multi-year workplan for modeling polychlorinated biphenyls (PCBs), contaminants of emerging concern (CECs), and sediment in San Franci

This report presents a strategy and multi-year workplan for modeling polychlorinated biphenyls (PCBs), contaminants of emerging concern (CECs), and sediment in San Francisco Bay (the Bay). Robust in-Bay fate modeling is needed to address priority management questions that have been identified for these constituents.