HEC-HMS Models for the Sacramento and San Joaquin River Basins Comprehensive Study

U.S. Army Corps of Engineers (USACE) | August 1st, 2001

Due to several large and damaging flood events on the Sacramento and San Joaquin Rivers (California) during the 1980s and 1990s, the U.S. House of Representatives

Due to several large and damaging flood events on the Sacramento and San Joaquin Rivers (California) during the 1980s and 1990s, the U.S. House of Representatives directed the Sacramento District to develop comprehensive plans for flood control for the two rivers and to develop hydrologic and hydraulic models of the river systems. The models will be used to provide better forecasts and evaluations of flood damage reduction alternatives. Additionally, the model results will be used as input for reservoir simulation models. The Sacramento River Basin and the San Joaquin River/Tulare Lake Bed Basins comprise nearly 60,000 square miles, drain California’s Central Valley floor and receive much of their runoff from the Sierra Nevada mountain range. Developing hydrologic models for the tributary basins (which included extremely variable terrain) within a ten month time period was a formidable task. The District contacted the Hydrologic Engineering Center (HEC) to assist with the development of these models. HEC used the Hydrologic Modeling System program, HEC-HMS, and introduced the HEC-GeoHMS grid-based technology to perform the hydrologic study. GeoHMS is an ArcView® extension that provides automated subbasin delineation methods and calculates many physical characteristics used for estimation of hydrologic parameters. HEC developed and calibrated 33 individual HEC-HMS models for the major tributaries and portions of the valley floors of the Sacramento River Basin and the San Joaquin River / Tulare Lake Bed Basins. GeoHMS was used to delineate the individual river basins, perform initial subbasin delineation and develop the physical characteristics for the subbasins. Tools within GeoHMS allowed the modelers to iteratively redelineate their subbasins, as appropriate, to meet project needs. Keeping the modeling effort consistent was critical to the success of the study. To ensure this consistency of procedures and results, HEC developed modeling guidelines that each of the 11 modeling teams followed. Once the grid-based HEC-HMS models were developed, HEC contracted with the Corps’ Cold Regions Research and Engineering Laboratory (CRREL) to perform a snowmelt study for the watersheds. HEC provided a gridded precipitation file (4 km2) to CRREL. Through the use of their Distributed Snow Process Model (DSPM), CRREL then provided a gridded snowmelt/ precipitation file to HEC. DSPM computes snowmelt and rainfall depths at the soil surface on a grid-cell basis. This data is used directly by HEC-HMS as precipitation on the watershed. The ModClark rainfall to runoff transformation was used to compute the subbasin hydrographs. HEC-HMS parameter optimization models were developed at hourly flow gages for the unregulated headwater streams. The runoff parameter optimization models allowed the modelers to develop the runoff parameters necessary for the regression analysis. A number of physical characteristics were evaluated for correlation with variations in Clark’s time of concentration, TC, for the optimization models. The results of the regression analysis allowed the modelers to populate the ungaged subbasins with appropriate unit hydrograph parameters. Approximately 200 hourly flow gages and 83 reservoirs were considered in calibrating the models. The 33 individual basin models were then given to the Sacramento District.

Height-related changes in forest composition explain increasing tree mortality with height during an extreme drought

Nature Portfolio (Springer Nature) | July 7th, 2020

Recently, Stovall et al. showed that during an extreme drought, remotely sensed mortality of tall trees was more than double that of short trees. They interpreted this t

Recently, Stovall et al. showed that during an extreme drought, remotely sensed mortality of tall trees was more than double that of short trees. They interpreted this to be a consequence of inherently greater hydraulic vulnerability of tall trees, and suggested that tall-tree vulnerability should generalize more broadly. Here we reassess their conclusions using contemporaneous, ground-based data from near their study sites. We find that 90% of trees belong to taxonomic groups showing declining, not increasing, mortality with height, and that the overall increase in mortality with height is instead a consequence of height-related changes in forest composition, not intrinsically greater vulnerability of tall trees. Similar mechanisms likely explain mortality patterns at Stovall et al.’s sites, and, regardless, we show that their conclusions should not be accepted in the absence of robust tests of alternative mechanisms.

Helium isotope studies in the Mojave Desert, California: implications for groundwater chronology and regional seismicity

Chemical Geology (Elsevier) | November 7th, 2003

Hemet San Jacinto Stipulated Judgment

Superior Court of California, County of Riverside | April 18th, 2013

Background from "An Evaluation of California’s Adjudicated Groundwater Basins," Langridge et al, 2016 (UC Davis) Groundwater problems in the San Jacinto Basin were f

Background from "An Evaluation of California’s Adjudicated Groundwater Basins," Langridge et al, 2016 (UC Davis) Groundwater problems in the San Jacinto Basin were first addressed by the court in a 1954 judgment that allocated pumping rights for the Fruitvale Mutual Water Company in the upper San Jacinto Basin. Declining groundwater levels persisted into the 1970s, and local water purveyors attempted to develop a groundwater management plan to address the declines. Eastern Municipal Water District (EMWD), which had acquired the Fruitvale Company in 1972, worked with the water purveyors in the 1990s to implement an AB 3030 groundwater management plan for the West San Jacinto Groundwater Management Area. In 2001, a Memorandum of Understanding between the Department of Water Resources (DWR) and local agencies required a water management plan for the Hemet/San Jacinto Groundwater Management Area, the eastern portion of the San Jacinto Basin, and a plan was released in 2007. At the same time, the Soboba Band of Luiseño Indians, negotiating with the local agencies to specify their groundwater rights from the Hemet/San Jacinto Groundwater Management Area, also pushed for a management plan. These negotiations culminated in the 2008 Soboba Settlement Agreement Act that established their water rights. A 2013 stipulated judgment allocated pumping rights for public water agencies, provided for water rights outlined in the Soboba Settlement Agreement, incorporated the Water Management Plan, and mandated a Watermaster."

Henry Miller Water District Revised Groundwater Sustainability Plan, Kern County Subbasin

Henry Miller Water District | July 21st, 2022

This Groundwater Sustainability Plan (GSP) for the Henry Miller Water District (HMWD) Groundwater Sustainability Agency (GSA) has been prepared pursuant to Water Code §1

This Groundwater Sustainability Plan (GSP) for the Henry Miller Water District (HMWD) Groundwater Sustainability Agency (GSA) has been prepared pursuant to Water Code §10727. HMWD is located in the Kern County Subbasin (Basin 5-22.14) as defined by the Department of Water Resources’ (DWR) Bulletin 118. The Kern Subbasin is considered to be in a condition of critical overdraft and has been designated as a high priority basin. This GSP is one of the five GSPs being prepared in the Subbasin, which collectively has and will coordinate to avoid, to the best of their abilities, any and all Undesirable Results as a result of unsustainable groundwater management practices. HMWD formed its own GSA on March 15, 2017; it is the only Water District located within the GSA. HMWD GSA is one of five GSAs that are preparing a GSP within the Subbasin. This GSP, in coordination with the four other GSPs within the Subbasin, will provide a path to sustainability and the preservation of groundwater resources for all beneficial users of groundwater. Because the Subbasin has multiple GSPs, the GSPs are prepared under a coordination agreement. This Coordination Agreement exemplifies the ways that the various GSPs were able to work together to achieve a common goal: groundwater sustainability for the Subbasin. For example, the entire Subbasin has utilized Todd Groundwater’s services to analyze historic, current, and future groundwater conditions with a C2VSIM model. This Plan includes a description of the historic groundwater conditions in the Subbasin, a Subbasin water budget, sustainable management criteria for future monitoring, and projects and/or management actions that may be implemented to ensure groundwater sustainability is achieved by 2040 and maintained through 2070. Due to size, the file has been divided. Part 1, Part 2, Part 3, Part 4, Part 5

Heresy in ENSO teleconnections: Atmospheric rivers as disruptors of canonical seasonal precipitation anomalies in the Southwestern US

Springer Nature | February 7th, 2025

In spite of forecasts for anomalous dryness based on the canonical La Niña signal, Water Years 2011, 2017, and 2023 brought copious precipitation to California and the S

In spite of forecasts for anomalous dryness based on the canonical La Niña signal, Water Years 2011, 2017, and 2023 brought copious precipitation to California and the Southwestern United States (SWUS). Although El Niño–Southern Oscillation (ENSO) is the main source of seasonal precipitation predictability for the region, outstanding Atmospheric River (AR) activity produced the unexpected regional wetness in each of these heretical water years (WYs). We define heretical WYs as those that result in precipitation anomalies that oppose those expected based on ENSO canon. We assess the contribution of ARs and other storms to these WYs, finding that heretical La Niña/El Niño WYs were characterized by anomalously robust/deficient AR activity. In California, precipitation accumulation during the heretical La Niña WYs was comparable to or even exceeded that observed during the exceedingly wet WY1998—the textbook canonical El Niño year. Our findings indicate a weaker/stronger relationship between ENSO and AR/non-AR precipitation, primarily driven by storm frequency. Although ARs can disrupt the ENSO-precipitation signal, ENSO still influences the frequency of AR precipitation in the southwestern U.S. desert, the region influenced by ARs that make landfall in Baja California, Mexico. These results highlight the complexity of ENSO's impact on precipitation in the Western US and underscore the need for a nuanced understanding of ENSO’s influence on ARs to improve seasonal precipitation prediction.

Hetch Hetchy Restoration Study

California Department of Water Resources (DWR) | July 17th, 2006

The restoration of Hetch Hetchy Valley on the upper Tuolumne River has once again captured the public’s imagination. In order to provide for an informed dialogue about

The restoration of Hetch Hetchy Valley on the upper Tuolumne River has once again captured the public’s imagination. In order to provide for an informed dialogue about this issue, the Resources Agency has objectively evaluated the many Hetch Hetchy Valley restoration studies produced during the past two decades. In so doing, the state also recognized the great value and benefit of providing a central clearinghouse of all Hetch Hetchy restoration work. Moreover, in conducting the study, the state provided a neutral, public forum to discuss issues related to Hetch Hetchy restoration, such as water supply and water quality, flood management, cultural resources, environmental impacts, energy generation, and recreation. In all, several hundred people participated in a July 2005 workshop in Sacramento and at other stakeholder meetings throughout the state. In addition, many interested Californians provided written comments for our consideration. This final report is a comprehensive analysis of Hetch Hetchy Valley restoration studies. But even as a comprehensive analysis, we find, first and foremost, that much study remains to be done because there are major gaps in vital information. For example, objectives for replacing the water supply for the Bay Area, dam removal methods and impacts, and considerations of the public use and benefit of a restored Valley remain largely undefined. Another critical, missing element is a formal public involvement process to engage agencies, Native American tribes, stakeholders and other interested parties in this issue. While we offer no formal recommendation about next steps, it is clear that further investigations into Hetch Hetchy Valley restoration cannot be led by the State of California alone. Federal participation will be important to help shape future studies and to work with the San Francisco Public Utilities Commission, tribes, and the public on any next steps in this process. Moving forward, the Resources Agency’s role in studies and planning for Hetch Hetchy will be consistent with the state’s approach to other significant natural resources such as the Sacramento-San Joaquin Delta or the Salton Sea — to protect the public trust by ensuring that these natural places are protected and utilized for the benefit of all Californians.

Hexavalent Chromium Maximum Contaminant Level (MCL) Standardized Regulatory Impact Assessment (SRIA)

California State Water Resources Control Board (SWRCB) | May 4th, 2023

The Division of Drinking Water (DDW) of the State Water Resources Control Board (State Water Board) is responsible for adopting drinking water standards. Primary drinking

The Division of Drinking Water (DDW) of the State Water Resources Control Board (State Water Board) is responsible for adopting drinking water standards. Primary drinking water standards, as defined in section 116275 of the California Safe Drinking Water Act (Health & Safety Code (HSC), div. 104, pt. 12, ch. 4, section 116270 et seq.), must be set in accordance with the requirements of HSC 116365. The purpose of the proposed regulation addressed in this Standardized Regulatory Impact Assessment (SRIA) is to adopt a primary drinking water standard for hexavalent chromium in drinking water consisting of a maximum contaminant level (MCL) and pertinent monitoring and reporting requirements. Consistent with title 1 of the California Code of Regulations (CCR), section 2003(a), the economic impact method used for the assessment was the Regional Input-Output Modeling System (RIMS II) developed by the U.S. Bureau of Economic Analysis (BEA).

Hidden Oasis: Water Conservation and Efficiency in Las Vegas

Pacific Institute | November 20th, 2007

Two of the West’s preeminent water organizations report Las Vegas Valley is sitting on an oasis of water and money savings. In their new report, the Pacific Institute a

Two of the West’s preeminent water organizations report Las Vegas Valley is sitting on an oasis of water and money savings. In their new report, the Pacific Institute and Western Resource Advocates find up to 40% of water could be saved in some sectors through improvements to indoor and outdoor water efficiency. They also found that through improving indoor water efficiency in particular, Las Vegas residents and businesses can cut water-related energy use and greenhouse gases. These findings are contained in Hidden Oasis: Water Conservation and Efficiency in Las Vegas available for download below. “Ninety percent of Las Vegas’ water efficiency money is spent on one program—turf removal. This program is important, but participation has waned and it is far from the only tool at their disposal,” said Heather Cooley, report co-author and Pacific Institute Senior Associate. “Las Vegas should capitalize on strategies that other Western cities have proven to be effective.” Hidden Oasis reveals that the Southern Nevada Water Authority, which provides water to Las Vegas and surrounding communities, can tap a number of tested, cost-effective efficiency measures to cut current water waste by up to 86,000 acre-feet. Single-family homes in Las Vegas use 100 gallons of water outside, per person, per day—almost entirely for landscaping. This use is substantially higher than in Los Angeles, Tucson, or Albuquerque. Reducing Las Vegas’ outdoor water use to more reasonable levels could cut Nevada’s total Colorado River withdrawals by 10 percent. Researchers found that by improving and expanding existing programs, and adding programs proven elsewhere in the West, the SNWA can cut Las Vegas homeowners’ indoor water waste by 40% and hotel and casino water waste by 30%. These indoor efficiency gains come from upgrading fixtures and appliances, not changing behavior. Improving total water efficiency not only saves significant water and energy expenses, it also better insulates the region from drought. “Improving indoor and outdoor water efficiency makes Las Vegas less vulnerable to current and future droughts,” said Taryn Hutchins-Cabibi, report coauthor and Water Policy Analyst at WRA. “Given the scarcity of fresh water, rising energy prices, and the looming threat of climate change, Las Vegas’ water customers need the SNWA’s help to curb unnecessary water waste and save money.”

High organofluorine concentrations in municipal wastewater affect downstream drinking water supplies for millions of Americans

National Academy of Sciences (NAS) | January 6th, 2025