Watershed Modeling for the Santa Clara River in Southern California

Ventura County Public Works Agency (VCPWA) | July 24th, 2019

A calibrated watershed hydrologic model of the Santa Clara River (SCR) Watershed was developed for use as a tool for watershed planning, resource assessment, and ultima

A calibrated watershed hydrologic model of the Santa Clara River (SCR) Watershed was developed for use as a tool for watershed planning, resource assessment, and ultimately, water quality management purposes. The study was a joint effort of the Ventura County Watershed Protection District (VCWPD), Los Angeles County Department of Public Works (LACDPW), and U.S. Army Corp of Engineers Los Angeles District. The modeling package used for the study was the U.S. EPA Hydrologic Simulation Program – FORTRAN (HSPF). The SCR main stem flows east-to-west from the San Gabriel Mountains of central Los Angeles County to its mouth at the Pacific Ocean near the cities of Ventura and Oxnard. The 4,263 square kilometer watershed includes rapidly urbanizing valleys and extensive agriculture, and is subject to severe flooding and erosion. There are four large reservoirs within the watershed. Although the Santa Clara River watershed remains primarily in a natural physical state, the flow regime within the watershed is highly engineered to optimize water deliveries and aquifer recharge. The SCR Watershed was segmented into 209 subwatersheds and 192 stream reaches, based on precipitation patterns, drainage boundaries, hydrography, stream gage locations, and impaired water segments. Each land segment was further subdivided into individual model segments based on land use/cover categories. A long-term data base of 46 years of model input data (precipitation, evaporation, diversions, POTWs, etc.) was developed. The model was calibrated and validated to observed flow at multiple locations, using both graphical and statistical model-data comparisons. Long-term simulations were run to assess the impacts of alternative conditions (baseline, natural) on flow and flood frequencies. The model was also used to generate design storm event hydrographs for selected return intervals with synthetic input rainfall hyetographs for the corresponding rainfall return period developed from available rain gage data. The design storm results were submitted to FEMA for the Flood Insurance Study currently underway.

West Valley Watershed Assessment 2018: Baseline Ecological Condition Assessment of Southwest San Francisco Bay Creeks in Santa Clara County; Calabazas, San Tomas Aquino, Saratoga, Sunnyvale East and West

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

This report describes baseline information about the amount and distribution of aquatic resources, and evaluates the overall ecological conditions of streams using the Ca

This report describes baseline information about the amount and distribution of aquatic resources, and evaluates the overall ecological conditions of streams using the California Rapid Assessment Method (CRAM), for the West Valley watershed in Santa Clara County; consisting of Sunnyvale East and West Channels, Calabazas Creek, San Tomas Aquino and Saratoga creeks (subsequently referred to in this document as San Tomas-Saratoga), and many smaller tributaries. 

West-Wide Climate Risk Assessments: Irrigation Demand and Reservoir Evaporation Projections

U.S. Bureau of Reclamation (USBR) | February 5th, 2015

Section 9503 of the SECURE Water Act, Subtitle F of Title IX of P.L. 111-11 (2009) (SECURE Water Act), authorizes the Bureau of Reclamation (Reclamation) to evaluate the

Section 9503 of the SECURE Water Act, Subtitle F of Title IX of P.L. 111-11 (2009) (SECURE Water Act), authorizes the Bureau of Reclamation (Reclamation) to evaluate the risks and impacts of climate change in each of the eight major Reclamation river basins identified in the Act, and to work with stakeholders to identify climate adaptation strategies. Reclamation implements Section 9503 of the SWA through the Department of Interior’s WaterSMART Program1, which is working to achieve a sustainable water strategy to meet the Nation’s water needs now and for the future. Through Basin Studies, part of WaterSMART, Reclamation works with State and local partners to evaluate the ability to meet future water demands within a river basin and to identify adaptation and mitigation strategies of the potential impacts of climate change. Through another activity, West-Wide Climate Risk Assessments (WWCRA), Reclamation is working to provide projections of future changes in water supplies, water demands, and river system operations that could result from changes in climate. As part of WWCRA, Reclamation has conducted an analysis of the potential changes in crop irrigation demand in eight major river basins in the West and projections of evaporation for 12 reservoirs within those river basins when considering observed and projected impacts of climate change. This report contains the results of that analysis. The findings presented in this report are intended to be used for future basin-specific WWCRA impact assessments and Basin Studies conducted under WaterSMART if the teams conducting those studies elect to do so. This technical assessment report provides: (1) an analysis of changes in irrigation demand, and (2) an analysis of changes in evaporation for selected reservoirs across the major Reclamation river basins with respect to presently observed and projected future impacts of global climate change. The analysis involved developing irrigation demand and reservoir evaporation projections associated with World Climate Research Programme Coupled Model Intercomparison Project3 (WCRP CMIP3) climate projections that have been bias-corrected and spatially downscaled (BCSD) and served at the following Web site: http://gdo-dcp.ucllnl.org/downscaled_cmip_projections/dcpInterface.html. For the purposes of this study, CMIP3 climate projections were used because they represented the best available collection of climate projections at the onset of this effort (summer 2011 which was begun prior to the release of CMIP5). Although the CMIP3 and CMIP5 projections are considered equally likely potential climate futures at this time, there is significant variability in the two sets of projections. This is especially true with regard to precipitation projections, and it is significant to note the potential impact of this variability on future irrigation demand and net evaporation estimates. Changes to irrigation demand (model, described below) were analyzed for five climate change scenarios (warm-dry, warm-wet, hot-dry, hot-wet, and central tendency – ensemble median) that were informed by 112 BCSD-CMIP3 projections at three future periods: 2020s (years 2010-2039), 2050s (years 2040–2069), and 2080s (2070-2099) with 1950–1999 as the baseline period. The reservoir evaporation modeling (described below) was performed as transient simulations using the individual 112 BCSD-CMIP3 projections. Both the irrigation demands modeling and the reservoir evaporation modeling used observed data from weather stations representative of irrigated land areas and reservoir sites in a secondary bias correction step to account for local scale climate conditions in the climate change scenarios. Although it would be ideal to calculate future irrigation demands for all 112 projections using the transient method as was done for the future reservoir evaporation estimates, such calculations were not feasible given the multiple crops and numerous locations modeled.

Westside Sacramento Integrated Regional Water Management Plan Update

Westside Sacramento Regional Water Management Group | January 3rd, 2019

This Integrated Regional Water Management Plan (IRWM Plan) defines a clear vision for the management of water resources in the Westside Sacramento Region (Region) and

This Integrated Regional Water Management Plan (IRWM Plan) defines a clear vision for the management of water resources in the Westside Sacramento Region (Region) and highlights important actions needed to help accomplish that vision through the year 2040. This IRWM Plan Update complies with the 2016 Integrated Regional Water Management Grant Program Guidelines applicable to Proposition 1 IRWM grant funding published by the California Department of Water Resources (DWR) in July 2016. This IRWM Plan defines a clear vision for the management of water resources in the Region and highlights important actions needed to help accomplish that vision through the year 2040. The 2018 IRWM Plan complies with the Integrated Regional Water Management Guidelines for Proposition 1 published by DWR in November 2016.

Westside Subbasin Groundwater Sustainability Plan

Westlands Water District | January 23rd, 2020

Westside Subbasin Groundwater Sustainability Plan (Clarified and Amended GSP)

Westlands Water District | July 18th, 2022

Due to size, this file has been divided into 11 parts. Part 1, Part 2, Part 3, Part 4, Part 5, Part 6, Part 7, Part 8, Part 9, Part 10, Part 11

Due to size, this file has been divided into 11 parts. Part 1, Part 2, Part 3, Part 4, Part 5, Part 6, Part 7, Part 8, Part 9, Part 10, Part 11

What Can We Learn From How the State Responded to the Last Major Drought?

Legislative Analyst's Office (LAO) | May 13th, 2021

For the second consecutive year, the state is experiencing extremely low rates of precipitation. As we prepare for what could be an extended period of dry conditions, it

For the second consecutive year, the state is experiencing extremely low rates of precipitation. As we prepare for what could be an extended period of dry conditions, it is helpful to review how the state responded to the last major drought. Such information can inform—and thereby potentially improve—the state’s current and ongoing response to developing conditions. In this report, we summarize the major activities, spending, and policy actions undertaken by the state to respond to the severe drought that occurred from 2012 through 2016. We also describe current conditions, and highlight some key lessons the Legislature can learn from previous efforts to help guide its response to the emerging drought.

What If California’s Drought Continues?

Public Policy Institute of California (PPIC) | August 20th, 2015

California is in the fourth year of a severe, hot drought—the kind that is increasingly likely as the climate warms. Although no sector has been untouched, impacts so

California is in the fourth year of a severe, hot drought—the kind that is increasingly likely as the climate warms. Although no sector has been untouched, impacts so far have varied greatly, reflecting different levels of drought preparedness. Urban areas are in the best shape, thanks to sustained investments in diversified water portfolios and conservation. Farmers are more vulnerable, but they are also adapting. The greatest vulnerabilities are in some low-income rural communities where wells are running dry and in California’s wetlands, rivers, and forests, where the state’s iconic biodiversity is under extreme threat. Two to three more years of drought will increase challenges in all areas and require continued—and likely increasingly difficult—adaptations. Emergency programs will need to be significantly expanded to get drinking water to rural residents and to prevent major losses of waterbirds and extinctions of numerous native fish species, including most salmon runs. California also needs to start a longer-term effort to build drought resilience in the most vulnerable areas.

What will it take to stabilize the Colorado River?

American Association for the Advancement of Science (AAAS) | July 21st, 2022

The Colorado River supplies water to more than 40 million inhabitants in the southwestern United States and northwestern Mexico. A basin-wide water supply crisis is occur

The Colorado River supplies water to more than 40 million inhabitants in the southwestern United States and northwestern Mexico. A basin-wide water supply crisis is occurring because of decreased watershed runoff caused by a warming climate and legal and water management policies that allow systematic overuse. By the end of 2022, combined storage in Lake Powell and Lake Mead, the two largest reservoirs in the United States, will have declined from 95% full in 2000 to approximately 25% full. If this “Millennium Drought” persists, then stabilizing reservoir levels to avoid severe outcomes will require reducing water use to match diminished runoff. With a process underway to renegotiate interstate and international agreements on consumptive uses of the river, we describe a promising new management approach based on combined storage of both reservoirs, rather than just Lake Mead as currently used, to trigger consumptive use reductions to the Lower Basin and Mexico.

When the water runs dry: supporting adaptive governance in transboundary river basins

Water International | February 21st, 2021

Impacts of global climate change will primarily be felt through the water cycle. Adaptation to changing conditions in transboundary basins is an important precondition to

Impacts of global climate change will primarily be felt through the water cycle. Adaptation to changing conditions in transboundary basins is an important precondition to ensure regional sustainable development and political stability. However, adaptation measures in one basin country can affect water resources and adaptation options elsewhere, therefore often requiring coordinated or joint responses by riparian countries. The paper examines the potential of climate policy instruments in strengthening adaptation to changes in transboundary river basins in North America’s Colorado River Basin and Southern Africa’s Orange-Senqu River Basin. It finds that climate policy instruments are yet rarely employed to jointly manage adaptation in shared rivers but nonetheless harbour great potential.