Sacramento River

A Review of the Hydrologic Response Mechanisms During Mountain Rain-on-Snow

Frontiers in Earth Science (Frontiers) | April 26th, 2022

Mountain rain-on-snow (ROS) generates large flooding events worldwide. Climate warming will enhance the frequency, magnitude, and widespread nature of these events. Past

Mountain rain-on-snow (ROS) generates large flooding events worldwide. Climate warming will enhance the frequency, magnitude, and widespread nature of these events. Past studies indicate rainfall, not snowmelt, typically drives much of the runoff response during ROS. However, there is substantial event-to-event variability—resulting from shifting atmospheric drivers and nuanced physical mechanisms governing water flow through a snowpack. Historically, turbulent fluxes were assumed to dominate the energy balance for snowmelt during ROS. Recent research nonetheless suggests that other components of the energy balance might be larger drivers depending on: 1) the time of year; 2) the elevation; and 3) the aspect of the slope. This mini review summarizes the literature on the physical processes governing ROS and proposes that moving forward we utilize the terms “active” and “passive” to describe a snowpack’s contribution (via snowmelt) to terrestrial water input (TWI) during ROS. Active snowpacks readily contribute meltwater to TWI via the energy balance, bolstering rainfall-runoff totals. Passive snowpacks do not melt, but simply convey rainwater through the snow matrix. In both snowpack cases, preferential flow paths enhance transmissivity. This proposed classification scheme will help researchers and water managers better communicate and interpret past findings, and aid in forecasting discussions of future events.

A Review of the Use of Science and Adaptive Management in California’s Draft Bay Delta Conservation Plan

National Academy of Sciences (NAS) | May 5th, 2011

California’s draft Bay Delta Conservation Plan—a draft plan to conserve habitat for endangered and threatened species, while continuing to divert water to agriculture

California’s draft Bay Delta Conservation Plan—a draft plan to conserve habitat for endangered and threatened species, while continuing to divert water to agriculture and domestic water users in central and southern California—is incomplete and contains critical scientific gaps. The Bay Delta is a large, complex ecosystem that supplies water from the state’s wetter northern regions to the drier southern regions, and also serves as habitat for many species. The Bay Delta Conservation Plan describes a proposal to construct a tunnel or canal to divert water from the northern Delta to the south, thus reducing the need to convey water through the Delta. This report reviews the use of science and adaptive management in the draft Bay Delta Conservation Plan and identifies opportunities to develop a more successful plan.

A simmering revolt against groundwater cutbacks in California

Stanford University | December 14th, 2022

In 2014, California legislators, focused on groundwater’s accelerating decline during a prolonged drought, passed the Sustainable Groundwater Management Act. Its impera

In 2014, California legislators, focused on groundwater’s accelerating decline during a prolonged drought, passed the Sustainable Groundwater Management Act. Its imperatives: keeping groundwater levels sustainable by 2040 and keeping control of groundwater in local hands. Both goals are now in limbo. As the state endures yet another prolonged drought and state water managers have balked at approving plans covering the basins at greatest risk – the vast majority in the San Joaquin Valley – more growers in a few of the new local groundwater agencies are in revolt at the new rules that will curtail access to the water they once took for granted.

A State Role in Supporting Groundwater Trading with Safeguards for Vulnerable Users: Findings and Next Steps

California Department of Water Resources (DWR) | May 18th, 2022

In those parts of California where groundwater pumping has long exceeded replenishment, people are striving to bring groundwater basins into sustainable conditions within

In those parts of California where groundwater pumping has long exceeded replenishment, people are striving to bring groundwater basins into sustainable conditions within 20 years, between 2040 and 2042, as the Sustainable Groundwater Management Act (SGMA) requires. In some areas, groundwater sustainability agencies (GSAs) – the local agencies tasked with sustainable groundwater management – are beginning to work with other entities and stakeholders to discuss and experiment with the idea of giving groundwater pumpers allocations – allowances to remove a certain amount of water from a groundwater basin – and allowing them to either use their allocation individually or trade allocations between specified parties. Ideally, groundwater trading could ease the economic disruption of cutting back the overall amount of water pumped from a groundwater basin; growers who have less need for pumping could sell their allocation to others willing to pay for it, helping buyers keep their operations functional while compensating sellers. But the concept of groundwater trading raises many questions: How would wetlands, streams, and other ecosystems fed by aquifers be treated in a groundwater trading program? Would operators of farms who lack the resources of larger neighbors be able to benefit from trading? How might trading affect people who depend upon a household well or communities that need reliable groundwater supplies for homes and businesses? How can GSAs work with local stakeholders to develop, implement, and oversee trading programs that help with sustainable groundwater management? There is a State interest behind all of these questions – and a clear need for a focused discussion about groundwater trading.

A Study of Economic and Financial Policies for State Water Projects

State of California | August 5th, 1959

A western United States snow reanalysis dataset over the Landsat era from water years 1985 to 2021

Nature Portfolio (Springer Nature) | November 7th, 2022

Water stored in mountain snowpacks (i.e., snow water equivalent, SWE) represents an important but poorly characterized component of the terrestrial water cycle. The Weste

Water stored in mountain snowpacks (i.e., snow water equivalent, SWE) represents an important but poorly characterized component of the terrestrial water cycle. The Western United States snow reanalysis (WUS–SR) dataset is novel in its combination of spatial resolution (~500 m), spatial extent (31°–49° N; 102°–125° W), and temporal continuity (daily over 1985–2021). WUS–SR is generated using a Bayesian framework with model-based snow estimates updated through the assimilation of cloud-free Landsat fractional snow-covered area observations. Over the WUS, the peak SWE verification with independent in situ measurements show correlation coefficient, mean difference (MD), and root mean squared difference (RMSD) of 0.77, −0.15 m, and 0.28 m, respectively. The effects of forest cover and Landsat image availability on peak SWE are assessed. WUS–SR peak SWE is well correlated (ranging from 0.75 to 0.91) against independent lidar-derived SWE taken near April 1st, with MD

Accounting for Water "Wasted to the Sea"

University of California, Davis (UC Davis) | April 19th, 2018

Freshwater outflow from the Sacramento–San Joaquin Delta is a contentious management issue. Once mixed with salt water of San Francisco Bay, outflow is often characteri

Freshwater outflow from the Sacramento–San Joaquin Delta is a contentious management issue. Once mixed with salt water of San Francisco Bay, outflow is often characterized as having no value for urban and agricultural water supply, and thus “wasted to the sea.” In the July issue of San Francisco Estuary and Watershed Science, Cloern et al. (2017) showed how outflow from the Delta provides multiple and diverse benefits to the San Francisco estuary. Rather than being “wasted,” this outflow improves ecosystem conditions and water quality, and reduces wastewater treatment costs. The Cloern et al. (2017) essay highlights the importance of considering the multiple benefits of water as it moves within and out of the Delta. To do this, however, California needs a better water accounting system. In this report, we present an alternative approach. For the period 1980–2016, we assign inflow to the Delta to four categories: 1. Water used for diversions, 2. Outflow needed to meet salinity standards for diversions, 3. Outflow to meet ecosystem regulations, and 4. Water that results in outflow because of a lack of capacity for diversion. This approach highlights that much of the outflow from the Delta — particularly during dry periods — achieves multiple economic and environmental benefits and is hardly “wasted to the sea.”

Achievements in Conservation, Recycling, and Groundwater Recharge Covering Fiscal Year July 2018-June 2019

Metropolitan Water District of Southern California (MWD) | March 1st, 2020

Achieving State Goals for the Sacramento-San Joaquin Delta

Legislative Analyst's Office (LAO) | January 15th, 2015

The Sacramento-San Joaquin Delta (Delta) is a biodiverse ecosystem that covers about 1,150 square miles and supports over 700 species of fish and wildlife. The Delta is a

The Sacramento-San Joaquin Delta (Delta) is a biodiverse ecosystem that covers about 1,150 square miles and supports over 700 species of fish and wildlife. The Delta is an important source of water for the state and is used to convey water from Northern California to Southern California. The Delta faces several significant problems, including: (1) a decline in key native fish species, (2) reductions in the amount of Delta water available for use elsewhere, (3) water pollutants that cause harm to species and increase treatment costs, and (4) levees at significant risk of failure. The state has engaged in numerous efforts to address these problems and achieve its "coequal goals" for the Delta: water supply reliability and ecosystem restoration. There are many opportunities for the Legislature to improve the success of these efforts. We identified several issues for its consideration, including (1) demands for Delta water, (2) uncertain funding sources and slow implementation of some key activities, (3) limits on the effectiveness of governance in the Delta, and (4) challenges to restoring the Delta ecosystem. By addressing some of these issues, the Legislature can improve the likelihood that its goals and objectives for the Delta will be realized.

Achieving the Human Right to Water in California: An Assessment of the State's Community Water Systems

Office of Environmental Health Hazard Assessment (OEHHA) | January 15th, 2021

The Human Right to Water Framework and Data Tool (CalHRTW 1.0) provides a consolidated, stand-alone, quantitative assessment of baseline conditions in the quality, acces

The Human Right to Water Framework and Data Tool (CalHRTW 1.0) provides a consolidated, stand-alone, quantitative assessment of baseline conditions in the quality, accessibility and affordability of California’s drinking water. This assessment can help screen for drinking water challenges and analyze changes over time and complements existing cumulative impacts analyses (e.g., CalEnviroScreen (OEHHA, 2021b)) by providing information at a greater level of detail regarding drinking water.