Modeling Functional Flows in California’s Rivers

Frontiers in Environmental Science (Frontiers) | March 11th, 2022

Modeling guides groundwater management in a basin with river–aquifer interactions

California Agriculture (UCANR) | March 13th, 2018

The Sustainable Groundwater Management Act (SGMA) of 2014 seeks to maintain groundwater discharge to streams to support environmental goals. In Scott Valley, in Siskiyou

The Sustainable Groundwater Management Act (SGMA) of 2014 seeks to maintain groundwater discharge to streams to support environmental goals. In Scott Valley, in Siskiyou County, the Scott River and its tributaries are an important salmonid spawning habitat, and about 10% of average annual Scott River stream flow comes from groundwater. The local groundwater advisory committee is developing groundwater management alternatives that would increase summer and early fall stream flows. We developed a model to provide a framework to evaluate those alternatives. We first created a water budget for the Scott Valley groundwater basin and integrated the detailed, spatiotemporally distributed water budget results into a computer model of the basin that simultaneously accounted for groundwater flow, stream flow and landscape water fluxes. Different conceptual representations (using the MODFLOW RIV package and MODFLOW SFR package) of the stream–aquifer boundary provided significantly different results in the seasonal dynamics of groundwater–surface water fluxes. As groundwater sustainability agencies draw up plans to meet SGMA requirements, they must choose and test simulation tools carefully.

Multi-century reconstructions of temperature, precipitation, and runoff efficiency for the Upper Colorado River Basin

U.S. Geological Survey (USGS) | January 27th, 2017

With increasing concerns about the impact of warming temperatures on water resources, more attention is being paid the relationship between runoff and preci

With increasing concerns about the impact of warming temperatures on water resources, more attention is being paid the relationship between runoff and precipitation, or runoff efficiency. Temperature is a key influence on Colorado River runoff efficiency, and warming temperatures are projected to reduce runoff efficiency. Here, we investigate the nature of runoff efficiency in the upper Colorado River (UCRB) basin over the past 400 years, with a specific focus on major droughts and pluvials, and to contextualize the instrumental period. We first verify the feasibility of reconstructing runoff efficiency from tree-ring data. The reconstruction is then used to evaluate variability in runoff efficiency over periods of high and low flow, and its correspondence to a reconstruction of late runoff season UCRB temperature variability. Results indicate that runoff efficiency has played a consistent role in modulating the relationship between precipitation and streamflow over past centuries, and that temperature has likely been the key control. While negative runoff efficiency is most common during dry periods, and positive runoff efficiency during wet years, there are some instances of positive runoff efficiency moderating the impact of precipitation deficits on streamflow. Compared to past centuries, the 20th century has experienced twice as many high flow years with negative runoff efficiency, likely due to warm temperatures. These results suggest warming temperatures will continue to impact runoff efficiency in wet or dry years, and that future flows will be less than anticipated from precipitation due to warming temperatures.

Notice of Entry of Order for Implementation of Preliminary Injunction – Case No. Bcv-22-103220-Gap, Bring Back the Kern et al v. City of Bakersfield et al

Superior Court of California, County of Kern | November 14th, 2023

Old and Middle River Flow Review: USGS Gauge Readings versus Index Calculations for 2011 through 2017

California Department of Water Resources (DWR) | November 17th, 2017

This report will demonstrate the strong flow correlation between the United States Geological Survey gages at the Old and Middle Rivers (USGS OMR), and the OMR Index calc

This report will demonstrate the strong flow correlation between the United States Geological Survey gages at the Old and Middle Rivers (USGS OMR), and the OMR Index calculations, which have been used by the State Water Project and the Central Valley Project (the Projects) to operate to, and comply with, Old and Middle River (OMR) flow requirements. The results of the two different methodologies for determining OMR will be compared with daily, 5-day average, and 14-day average values, and will demonstrate a close correlation and tracking between the two methodologies. The time-span will be from December to June of the Water Years 2011 to 2017 and gives a background view and general effectiveness of using the OMR Index. The difference between the methodologies is that the USGS OMR values are based on tidally filtered hourly flow values of Old and Middle Rivers near Bacon Island, whereas the Index methodology uses an empirical equation based on net flows into and out of the Southern Delta. The USGS OMR flow values have been difficult for the Projects to operate to, in large part because the tidally filtering calculation is lagged by three days. What’s more, atmospheric conditions exert an unpredictable influence on OMR values and missing data introduces errors. By contrast, the OMR Index is much easier to work with because the San Joaquin River at Vernalis (VNS) gage used in the OMR Index equation is located upstream of the Delta and is therefore not affected significantly by tidal effects or atmospheric conditions and has only a one-day delay in the OMR Index equation. Using prior day flows from the VNS gage allows the Projects’ operations to be more predictable since current day exports can be closely controlled. Through regression analysis and empirical graphs, this report will show that the OMR Index method produces results that are closely correlated with values from the USGS OMR. And since the Index method can be used to closely approximate the USGS OMR flow values over an averaging period, the Index method is a satisfactory alternative to using the lagged USGS OMR flow data for real-time operations.

Outmigration survival of wild Chinook salmon smolts through the Sacramento River during historic drought and high water conditions

Environmental Biology of Fishes (Springer) | January 27th, 2020

Patterns and magnitude of flow alteration in California, USA

Freshwater Biology (Wiley) | December 27th, 2017

The importance of the natural flow regime to stream and river health has received growing attention over the last two decades. Quantifying natural river flows has become

The importance of the natural flow regime to stream and river health has received growing attention over the last two decades. Quantifying natural river flows has become an essential component of water resource planning, including assessments of water supplies (Vicuna,Maurer, Joyce, Dracup, & Purkey, 2007; Wurbs, 2005), reservoir operations (Hejazi, Cai, & Ruddell, 2008) and drought risk (Meko,Therrell, Baisan, & Hughes, 2001). Understanding the natural flow regime is also crucial for managing stream ecosystems.

Petition For Rulemaking to Set Minimum Flows on the Shasta River

Mount Shasta Bioregional Ecology Center | January 20th, 2024

Decades of scientific inquiry make clear that adequate quality and quantity of flows are needed to prevent remaining fish populations from further decline. Yet this scien

Decades of scientific inquiry make clear that adequate quality and quantity of flows are needed to prevent remaining fish populations from further decline. Yet this science is not self-executing; effective government intervention is necessary to prevent the extirpation of salmonids in the Shasta. This type of government action is at the core of the Public Trust Doctrine, which requires the government to act as a trustee over public trust resources, and to the extent feasible, step in to protect these resources from over-allocation and over-use.

Policy for Maintaining Instream Flows in Northern California Streams

California State Water Resources Control Board (SWRCB) | September 28th, 2010

The State Water Resources Control Board (State Water Board or Board) adopted this state policy for water quality control on May 4, 2010. This policy is also known as the

The State Water Resources Control Board (State Water Board or Board) adopted this state policy for water quality control on May 4, 2010. This policy is also known as the North Coast Instream Flow Policy. It applies to applications to appropriate water, small domestic use and livestock stockpond registrations, and water right petitions. Water Code section 1259.4, which was added by Assembly Bill 2121 (Stats. 2004, ch. 943, § 3), requires the State Water Board to adopt principles and guidelines for maintaining instream flows in northern California coastal streams as part of state policy for water quality control, for the purposes of water right administration. This policy implements Water Code section 1259.4. The geographic scope of this policy, referred to as the policy area, extends to five counties—Marin, Sonoma, and portions of Napa, Mendocino, and Humboldt counties— and encompasses (1) coastal streams from the Mattole River (originating in Humboldt County) to San Francisco, and (2) coastal streams entering northern San Pablo Bay. This policy focuses on measures that protect native fish populations, with a particular focus on anadromous salmonids (e.g., steelhead trout, coho salmon, and chinook salmon) and their habitat. Beginning in 1996, the National Marine Fisheries Services (NMFS) and the California Department of Fish and Game (DFG) listed steelhead trout, coho salmon, and chinook salmon as “threatened” under the federal Endangered Species Act (ESA) and the California Endangered Species Act (CESA), respectively. In 2005, the coho salmon’s status was upgraded from threatened to “endangered” on both the ESA and the CESA lists. This policy establishes principles and guidelines for maintaining instream flows for the protection of fishery resources. It does not specify the terms and conditions that will be incorporated into water right permits, licenses, and registrations. It prescribes protective measures regarding the season of diversion, minimum bypass flow, and maximum cumulative diversion. Applicants may choose to implement the policy principles through the regionally protective criteria or site-specific studies. Site-specific studies may be conducted to develop alternative site-specific protective criteria. The policy also limits construction of new onstream dams and contains measures to ensure that approval of new onstream dams does not adversely affect instream flows needed for fishery resources. The policy provides for a watershed-based approach to evaluate the effects of multiple diversions on instream flows within a watershed as an alternative to evaluating water diversion projects on an individual basis. Enforcement requirements contained in this policy include a framework for compliance assurance, prioritization of enforcement cases, and descriptions of enforcement actions. The policy contains guidelines for evaluating whether a proposed water diversion, in combination with existing diversions in a watershed, may affect instream flows needed for the protection of fishery resources.

Recent advances in understanding flow dynamics and transport of water-quality constituents in the Sacramento–San Joaquin River Delta

University of California, Davis (UC Davis) | December 1st, 2016

This chapter describes advances during the past decade in understanding flow dynamics and how water-quality constituents, such as salinity, heat, oxygen, nutrients, conta

This chapter describes advances during the past decade in understanding flow dynamics and how water-quality constituents, such as salinity, heat, oxygen, nutrients, contaminants, and more, move within California’s Sacramento-San Joaquin River Delta. Water-quality constituents are affected by water diversions and other human manipulations of flow and they greatly affect the quantity and quality of habitats in the Delta. Along with human intervention, the Pacific Ocean, the Central Valley watershed, and the atmosphere, are a few drivers of flow and transport in the Delta. These drivers provide a conceptual framework for presenting recent findings. The tremendous expansion of acoustic and optical instruments utilized in the Delta over the past decade has greatly improved our understanding of how tidal variability affects flow and transport. Sediment is increasingly viewed as a diminishing resource needed to sustain habitat and tidal marsh, especially as sea level rises. Connections between the watershed, Delta, and San Francisco Bay that have been studied recently highlight that a landscape view of this system is needed rather than consideration of each region individually. Interactions of multiple drivers and information gaps are discussed.