Colorado River

Final Environmental Impact Report for Adoption of a Regulation for the Hexavalent Chromium Maximum Contaminant Level

California State Water Resources Control Board (SWRCB) | April 17th, 2024

As the lead agency in accordance with sections 15089 and 15132 of the California Environmental Quality Act (CEQA) Guidelines (Cal. Code Regs., tit. 14, § 15000 et seq.),

As the lead agency in accordance with sections 15089 and 15132 of the California Environmental Quality Act (CEQA) Guidelines (Cal. Code Regs., tit. 14, § 15000 et seq.), this document is the Final Environmental Impact Report (Final EIR) for the adoption of statewide regulations setting the maximum contaminant level (MCL) for hexavalent chromium (Proposed Regulations). The Proposed Regulations include a maximum contaminant level (MCL) of 10 μg/L for hexavalent chromium. (Cal. Code Regs. tit. 22, § 64431 Table 64431-A.) The Proposed Regulations also include a compliance schedule based on public water system size, by adding subdivision (p) and Table 64432-B to section 64432 of title 22 of the California Code of Regulations, identifies a detection limit for purposes of reporting, sets monitoring and reporting requirements and public notice requirements for violations of the MCL, and establishes the Best Available Technologies (BAT) for treating hexavalent chromium in drinking water. California State Water Resources Control Board (SWRCB) Chrom VI MCL rulemaking chronology.

Final Mojave Region Integrated Regional Water Management Plan

Mojave Water Agency (MWA) | June 1st, 2014

Finishing the All-American Canal

Scientific American | September 1st, 2020

Work on the All-American Canal is going forward so rapidly that the great 80-mile ditch and its appurtenant features will be ready to de­liver irrigation water to the Im

Work on the All-American Canal is going forward so rapidly that the great 80-mile ditch and its appurtenant features will be ready to de­liver irrigation water to the Imperial Valley in southeastern California some time during the first half of 1938. The waterway is being dug across a normally desert region that once formed the wa­ter bed of the prehistoric northern ex­tension of the Gulf of California, as we know it today. Paradoxically, that far­ flung section of the Gulf was transform­ ed into a generally barren and arid region by the very river that is to be tapped to assure the continued agricul­tural productivity · of soil that can be made amazingly fruitful by irrigation.

Fire influence on land–water interactions in aridland catchments

Oxford University Press (OUP) | January 9th, 2025

Wildfires have increased in size, frequency, and intensity in arid regions of the western United States because of human activity, changing land use, and rising temperatu

Wildfires have increased in size, frequency, and intensity in arid regions of the western United States because of human activity, changing land use, and rising temperature. Fire can degrade water quality, reshape aquatic habitat, and increase the risk of high discharge and erosion. Drawing from patterns in montane dry forest, chaparral, and desert ecosystems, we developed a conceptual framework describing how interactions and feedbacks among material accumulation, combustion of fuels, and hydrologic transport influence the effects of fire on streams. Accumulation and flammability of fuels shift in opposition along gradients of aridity, influencing the materials available for transport. Hydrologic transport of combustion products and materials accumulated after fire can propagate the effects of fire to unburned stream–riparian corridors, and episodic precipitation characteristic of arid lands can cause lags, spatial heterogeneity, and feedbacks in response. Resolving uncertainty in fire effects on arid catchments will require monitoring across hydroclimatic gradients and episodic precipitation.

First annual report of the Mojave Basin Area Watermaster 1993-1994

Mojave Basin Area Watermaster | February 28th, 1995

Fixing the Flawed Colorado River Compact

American Geophysical Union (AGU) | June 16th, 2023

Flood Size Increases Nonlinearly Across the Western United States in Response to Lower Snow-Precipitation Ratios

American Geophysical Union (AGU) | December 20th, 2019

Many mountainous and high-latitude regions have experienced more precipitation as rain rather than snow due to warmer winter temperatures. Further decreases in the annual

Many mountainous and high-latitude regions have experienced more precipitation as rain rather than snow due to warmer winter temperatures. Further decreases in the annual snow fraction are projected under continued global warming, with potential impacts on flood risk. Here, we quantify the size of streamflow peaks in response to both seasonal and event-specific rain-fraction using stream gage observations from watersheds across the western United States. Across the study watersheds, the largest rainfall-driven streamflow peaks are >2.5 times the size of the largest snowmelt-driven peaks. Using a panel regression analysis of individual precipitation and snowmelt events, we show that the empirical streamflow response grows approximately exponentially as the liquid precipitation input increases, with rain-dominated runoff leading to proportionately larger streamflow increases than snowmelt or mixed rain-and-snow runoff. We find that the response to changes in rain percentage is largest in the wettest watersheds, where wet antecedent conditions are important for increasing runoff efficiency. Similarly, the effect of rain percentage is larger across watersheds in the Northwest and West regions compared to watersheds in the Northern Rockies and Southwest regions. Overall, as a higher percentage of precipitation falls as rain, increases in the size of rainfall-driven and “rain-on-snow”-driven floods have the potential to more than offset decreases in the size of snowmelt-driven floods.

Flood-MAR Research and Data Development Plan

California Department of Water Resources (DWR) | October 31st, 2019

The Research Advisory Committee (RAC) is pleased to make this plan available to the growing network of farmers, researchers, planners, and water and land managers who wan

The Research Advisory Committee (RAC) is pleased to make this plan available to the growing network of farmers, researchers, planners, and water and land managers who want to expand our collective knowledge about using floodwaters for managed aquifer recharge (Flood-MAR). This plan outlines the priority information needed by those making management decisions about the where, when, and how of capturing available flood water to replenish California’s depleted aquifers.

Floods in California

Public Policy Institute of California (PPIC) | February 29th, 2024

Formation of California's Salton Sea in 1905-07 was not "accidental"

2020 Desert Symposium Field Guide and Proceedings | April 26th, 2020

It is widely thought that the Salton Sea was created accidentally in 1905-07 because of engineering negligence in the diversion of Colorado River water for agricultural u

It is widely thought that the Salton Sea was created accidentally in 1905-07 because of engineering negligence in the diversion of Colorado River water for agricultural use in California’s Imperial Valley. This is a misconception. Scientific data and historical records establish that formation of the Salton Sea was not accidental. The lake formed during 1905-07 in the same manner that numerous other large Salton Basin lakes did for at least tens of thousands of years from the Late Pleistocene through the late 19th century: as a result of the lower Colorado River’s natural hydrodynamic regime, floodplain morphodynamics, and established avulsion style in combination with changes in streamflow attributable to regional hydroclimate. A large body of scientific and historical evidence indicates the 1905-07 Colorado River flooding into the Salton Basin and the creation of a large lake there would have occurred regardless of man-made modifications to the river’s natural levee and distributary channels. In fact, the flooding would likely have been even worse in the absence of human intervention.