Lower Colorado River Basin Plan letter to the U.S. Bureau of Reclamation, 5/22/23

U.S. Bureau of Reclamation (USBR) | May 22nd, 2023

Lower Colorado River Mainstream Evaporation and Riparian Evapotranspiration Losses Report

U.S. Department of the Interior (DOI) | February 8th, 2024

On August 16, 2022, the Bureau of Reclamation (Reclamation) and Department of the Interior announced several administrative actions for consideration to improve and prote

On August 16, 2022, the Bureau of Reclamation (Reclamation) and Department of the Interior announced several administrative actions for consideration to improve and protect the long-term sustainability of the Colorado River System. The System is currently experiencing prolonged drought and low runoff conditions accelerated by climate change that have led to historically low water levels in Lakes Powell and Mead (Reclamation, 2021). One of the actions included reviewing and prioritizing additional administrative initiatives to address system losses in the lower Colorado River mainstream. As part of that action, this report provides an overview of historical mainstream evaporation and riparian evapotranspiration (ET) losses along the lower Colorado River and presents methodologies used to develop those datasets. This report does not make recommendations on how to account for system losses in the lower Colorado River mainstream. Supplemental documents: Appendix 1 – Reaches Identified in the Lower Colorado River Mainstream Evaporation and Riparian Evapotranspiration Losses Report Appendix 2 – LCRAS Open Water Monthly Evaporative Losses Appendix 3 – Lake Mead, Lake Mohave, and Lake Havasu Evaporation from Reclamation’s Hydrologic Database (HDB) Appendix 4 – LCRAS Riparian Monthly Evapotranspiration Losses by Vegetation Appendix 5 – Evaporation and Riparian Evapotranspiration (ET) Coefficients Appendix 6 – Evaporation and Riparian Evapotranspiration (ET) Rates

Management of the Colorado River: Water Allocations, Drought, and the Federal Role

Congressional Research Service (CRS) | August 4th, 2022

Management of the Colorado River: Water Allocations, Drought, and the Federal Role

Congressional Research Service (CRS) | September 7th, 2022

Management of the Colorado River: Water Allocations, Drought, and the Federal Role

Congressional Research Service (CRS) | April 4th, 2024

From its headwaters in Colorado and Wyoming to its terminus in the Gulf of California, the Colorado River Basin covers more than 246,000 square miles. The basin spans sev

From its headwaters in Colorado and Wyoming to its terminus in the Gulf of California, the Colorado River Basin covers more than 246,000 square miles. The basin spans seven U.S. states (Wyoming, Colorado, Utah, New Mexico, Arizona, Nevada, and California) and two countries (the United States and Mexico). Pursuant to federal law, the Bureau of Reclamation (Reclamation), a component of the Department of the Interior (DOI), plays a prominent role in the management of the basin’s waters. In the Lower Basin (i.e., Arizona, Nevada, and California), Reclamation also serves as water master on behalf of the Secretary of the Interior, a role that elevates the status of the federal government in basin water management. The federal role in managing Colorado River water is magnified by the multiple federally owned and operated water storage and conveyance facilities in the basin, which provide low-cost water and hydropower supplies.

Memorandum of Understanding by and among Colorado River Basin Municipal and Public Water Providers

Southern Nevada Water Authority (SNWA) | November 15th, 2022

Microplastics in Lake Mead National Recreation Area

U.S. Geological Survey (USGS) | October 9th, 2019

  This dataset describes the quantity and morphology of microplastics in water, surficial sediment, sediment core, fish, and shellfish samples from Lake Mead Nation

  This dataset describes the quantity and morphology of microplastics in water, surficial sediment, sediment core, fish, and shellfish samples from Lake Mead National Recreation Area (Nevada/Arizona). Water and surficial sediment samples were collected once at 9 locations. A sediment core (33 cm long) was extracted from Las Vegas Bay to assess changes in microplastic deposition over time. Striped bass (Morone saxatilis), common carp (Cyprinus carpio), quagga mussels (Dreissena bugensis), and Asian clams (Corbicula fluminea) were sampled at a subset of locations to assess biological uptake of microplastics. Sampling and analysis methods are described in the Processing Steps section of the metadata. All samples were collected in March 2017 except the sediment core, which was collected in March 2018.  

Microplastics in Lake Mead National Recreation Area, USA: Occurrence and biological uptake

PLOS | May 4th, 2020

Microplastics are an environmental contaminant of growing concern, but there is a lack of information about microplastic distribution, persistence, availability, and bio

Microplastics are an environmental contaminant of growing concern, but there is a lack of information about microplastic distribution, persistence, availability, and biological uptake in freshwater systems. This is especially true for large river systems like the Colorado River that spans multiple states through mostly rural and agricultural land use. This study characterized the quantity and morphology of microplastics in different environmental compartments in two large reservoirs along the Colorado River: Lakes Mead and Mohave, within Lake Mead National Recreation Area. To assess microplastic occurrence, surface water and surficial sediment were sampled at a total of nine locations. Sampling locations targeted different sub-basins with varying levels of anthropogenic impact. Las Vegas Wash, a tributary which delivers treated wastewater to Lake Mead, was also sampled. A sediment core (33 cm long, representing approximately 19 years) was extracted from Las Vegas Bay to assess changes in microplastic deposition over time. Striped bass (Morone saxatilis), common carp (Cyprinus carpio), quagga mussels (Dreissena bugensis), and Asian clams (Corbicula fluminea) were sampled at a subset of locations to assess biological uptake of microplastics. Microplastic concentrations were 0.44–9.7 particles/cubic meter at the water surface and 87.5–1,010 particles/kilogram dry weight (kg dw) at the sediment surface. Sediment core concentrations were 220–2,040 particles/kg dw, with no clear increasing or decreasing trend over time. Shellfish microplastic concentrations ranged from 2.7–105 particles/organism, and fish concentrations ranged from 0–19 particles/organism. Fibers were the most abundant particle type found in all sample types. Although sample numbers are small, microplastic concentrations appear to be higher in areas of greater anthropogenic impact. Results from this study improve our understanding of the occurrence and biological uptake of microplastics in Lake Mead National Recreation Area, and help fill existing knowledge gaps on microplastics in freshwater environments in the southwestern U.S.

Missing Water: The Uses and Flows of Water in the Colorado River Delta Region

Pacific Institute | September 1st, 2001

The Pacific Institute for Studies in Development, Environment, and Security is pleased to announce the release of Missing Water: The Uses and Flows of Water in the Color

The Pacific Institute for Studies in Development, Environment, and Security is pleased to announce the release of Missing Water: The Uses and Flows of Water in the Colorado River Delta Region. This new study describes the fate of the millions of acre-feet of water diverted from the Colorado River at and below Imperial Dam, and the total inflows to and outflows from the Colorado River delta region more generally. This study uses the classic hydrologic boundaries of the delta region described by Godfrey Sykes in 1937, encompassing some 3,325 square miles (8,611 square kilometers) in the states of Arizona, Baja California, California, and Sonora, including the Imperial, Mexicali, and San Luis valleys, Yuma Project lands, and the lower Coachella Valley. The study period examines the flows and uses of water in the years 1991-1998, divided into Flood and Non-Flood years to reflect the tremendous variability of mainstem Colorado River flows. Missing Water compiles flow data along the mainstem and along diversions within the delta region, the first time such data has been compiled for the region as a whole. The study also report consumptive uses of water in the agricultural and urban sectors, and estimates such use by the environment. Agricultural use is also reported for the major crops in the region, both by acreage and by water use.

Moving Forward Effort: Phase 1 Report

U.S. Bureau of Reclamation (USBR) | May 1st, 2015

In 2012, the Bureau of Reclamation (Reclamation), in partnership with the seven Colorado River Basin States (Basin States) and in collaboration with a wide spectrum of

In 2012, the Bureau of Reclamation (Reclamation), in partnership with the seven Colorado River Basin States (Basin States) and in collaboration with a wide spectrum of Colorado River Basin (Basin) stakeholders, published the most comprehensive study of future Basin supply and demand ever undertaken. The Colorado River Basin Water Supply and Demand Study (Basin Study) confirmed that, in the absence of timely action, there are likely to be significant shortfalls between projected water supplies and demands in coming decades. The Basin Study also confirmed that a wide range of solutions are needed to mitigate and adapt to such shortfalls, which are likely to affect each sector (agricultural, municipal, energy, and environmental, for example) dependent on the Colorado River and its tributaries. In response to the findings of the Basin Study, in May 2013, Reclamation and the Basin States, in collaboration with the Ten Tribes Partnership and conservation organizations, initiated the Moving Forward effort to build on future considerations and next steps identified in the Basin Study. The Moving Forward effort builds upon and enhances the broad, inclusive stakeholder process demonstrated in the Basin Study with an ultimate goal of identifying actionable steps to address projected water supply and demand imbalances that have broad-based support and provide a wide-range of benefits. The Moving Forward effort is being conducted in a phased approach. Phase 1, which was funded by Reclamation and the Basin States, began with the formation of a Coordination Team and three multi-stakeholder workgroups that focus on water conservation, reuse, and environmental and recreational flows. The Phase 1 Report documents the activities and outcomes of the workgroups during this phase. Commenting on the information provided in the Phase 1 Report is encouraged. Written comments should be submitted within 90 days following the release of this report. The comments will be summarized and posted to the Moving Forward website and will be considered in future Moving Forward phases. Instructions for submitting comments are provided at [this link].