Trends and environmental impacts of virtual water trade

Nature Portfolio (Springer Nature) | November 5th, 2024

Trends in atmospheric patterns conducive to seasonal precipitation and temperature extremes in California seasonal precipitation and temperature extremes

American Association for the Advancement of Science (AAAS) | April 1st, 2016

Recent evidence suggests that changes in atmospheric circulation have altered the probability of extreme climate events in the Northern Hemisphere. We investigate northe

Recent evidence suggests that changes in atmospheric circulation have altered the probability of extreme climate events in the Northern Hemisphere. We investigate northeastern Pacific atmospheric circulation patterns that have historically (1949–2015) been associated with cool-season (October-May) precipitation and temperature extremes in California. We identify changes in occurrence of atmospheric circulation patterns by measuring the similarity of the cool-season atmospheric configuration that occurred in each year of the 1949–2015 period with the configuration that occurred during each of the five driest, wettest, warmest, and coolest years. Our analysis detects statistically significant changes in the occurrence of atmospheric patterns associated with seasonal precipitation and temperature extremes. We also find a robust increase in the magnitude and subseasonal persistence of the cool-season West Coast ridge, resulting in an amplification of the background state. Changes in both seasonal mean and extreme event configurations appear to be caused by a combination of spatially non-uniform thermal expansion of the atmosphere and reinforcing trends in the pattern of sea level pressure. In particular, both thermal expansion and sea level pressure trends contribute to a notable increase in anomalous northeastern Pacific ridging patterns similar to that observed during the 2012–2015 California drought. Collectively, our empirical findings suggest that the frequency of atmospheric conditions like those during California’s most severely dry and hot years has increased in recent decades, but not necessarily at the expense of patterns associated with extremely wet years.

Trends in Fish and Invertebrate Populations of Suisun Marsh January 2017 - December 2017

University of California, Davis (UC Davis) | January 31st, 2019

Suisun Marsh, at the geographic center of the northern San Francisco Estuary, is important habitat for native and non-native fishes. The University of California, Davis,

Suisun Marsh, at the geographic center of the northern San Francisco Estuary, is important habitat for native and non-native fishes. The University of California, Davis, Suisun Marsh Fish Study, in partnership with the California Department of Water Resources (DWR), has systematically monitored the marsh's fish populations since January 1980. The study’s main purpose has been to determine environmental and anthropogenic factors affecting fish distribution and abundance. 

Trends in nitrogen, phosphorus, and sediment concentrations and loads in streams draining to Lake Tahoe, California, Nevada, USA

Science of the Total Environment (Elsevier) | August 19th, 2020

Lake Tahoe, a large freshwater lake of the eastern Sierra Nevada in California and Nevada, has 63 tributaries that are sources of nutrients and sediment to the lake. The

Lake Tahoe, a large freshwater lake of the eastern Sierra Nevada in California and Nevada, has 63 tributaries that are sources of nutrients and sediment to the lake. The Tahoe watershed is relatively small, and the surface area of the lake occupies about 38% of the watershed area (1313 km2). Only about 6% of the watershed is urbanized or residential land, and as part of a plan to maintain water clarity, wastewater is exported out of the basin. The lake's clarity has been diminishing due to algae and fine sediment, prompting development of management plans. Much of the annual discharge and nutrient load to the lake results from snowmelt in the spring and summer months. To understand the relative importance of land use, climate, forest management, and other factors affecting trends in nutrient stream concentrations and loads, a Weighted Regression on Time Discharge and Season (WRTDS) model simulated these trends over a time frame of >25 years (mid-1970s to 2017). All studied locations generally show nitrate concentration and load trending down. Ammonium concentration and load initially trended down then increased continuously after 2005. Some locations show initially decreasing orthophosphate trends, followed by small significant increases in concentration and loads starting around 2000 to 2005. Total Kjeldahl nitrogen, total phosphorus and suspended sediment mostly trended downward. Overall, the trends in various forms of nitrogen were observed at most sites irrespective of the degree of development and indicate a change in ecological conditions is affecting the nitrogen cycle throughout the watershed, most likely attributable to forest aggradation and fire suppression. Ratios of bioavailable nitrogen in the form of nitrate and ammonium to orthophosphate have also trended downward during the period of record suggesting a shift of these streams from phosphorus limited to nitrogen limited.

Trends in Snowfall versus Rainfall in the Western United States

American Meteorological Society (AMS) | September 15th, 2006

The water resources of the western United States depend heavily on snowpack to store part of the wintertime precipitation into the drier summer months. A well-documented

The water resources of the western United States depend heavily on snowpack to store part of the wintertime precipitation into the drier summer months. A well-documented shift toward earlier runoff in recent decades has been attributed to 1) more precipitation falling as rain instead of snow and 2) earlier snowmelt. The present study addresses the former, documenting a regional trend toward smaller ratios of winter-total snowfall water equivalent (SFE) to winter-total precipitation (P) during the period 1949–2004. The trends toward reduced SFE are a response to warming across the region, with the most significant reductions occurring where winter wet-day minimum temperatures, averaged over the study period, were warmer than 5°C. Most SFE reductions were associated with winter wet-day temperature increases between 0° and 3°C over the study period. Warmings larger than this occurred mainly at sites where the mean temperatures were cool enough that the precipitation form was less susceptible to warming trends. The trends toward reduced SFE/P ratios were most pronounced in March regionwide and in January near the West Coast, corresponding to widespread warming in these months. While mean temperatures in March were sufficiently high to allow the warming trend to produce SFE/P declines across the study region, mean January temperatures were cooler, with the result that January SFE/P impacts were restricted to the lower elevations near the West Coast. Extending the analysis back to 1920 shows that although the trends presented here may be partially attributable to interdecadal climate variability associated with the Pacific decadal oscillation, they also appear to result from still longer-term climate shifts.

Trends in tree cover change over three decades related to interannual climate variability and wildfire in California

Institute of Physics (IOP) | January 19th, 2025

The U.S. State of California has experienced frequent drought events, hotter temperatures and other disruptions to the climate system whose effects on ecosystems have bee

The U.S. State of California has experienced frequent drought events, hotter temperatures and other disruptions to the climate system whose effects on ecosystems have been widely reported in recent decades. Studies primarily confined to specific vegetation communities or species, individual drought incidents, or analysis over a relatively short intervals, has limited our understanding of the broad-scale effects on tree cover and the spatiotemporal variability of effects across broader regions. We focused analysis on multi-annual land cover and land surface change to assess patterns and trends in tree cover loss in tree-dominated Californian ecoregions from 1986 to 2019. The top three years of total tree cover loss for the state were 2018 (1901 km2), 2015 (1556 km2), and 2008 (1549 km2). Overall, annual tree cover loss had upward trends. Tree cover loss rapidly surged later in the study period and was apparently driven by climate stress and wildfires. Underlying geographic variability was apparent in both non-fire and fire-related tree cover loss that sharply increased during hotter multi-year droughts. The increasingly hotter and drier climate conditions were associated with significant increases in fire-induced mortality. Our findings indicate that a possible effect of future hotter and drier climate would lead to further tree cover loss, thereby endangering California's ecosystem goods and services. Geographic variability in tree cover trends indicates that ecoregion-specific mitigation and adaptation strategies would be useful to conserve the region's forest resources. Such strategies may benefit from consideration of historical disturbances, ecoregion's sensitivity to disturbance types, as well as potential ecoregion-specific climate-vegetation-fire feedbacks.

Tri-County Water Authority Groundwater Sustainability Plan

Tri-County Water Authority | December 18th, 2019

Tribal Collaboration in IRWM: Challenges, Solutions and Recommendations

University of California, Davis (UC Davis) | May 5th, 2017

The Integrated Regional Water Management (IRWM) Tribal Collaborative Effectiveness Study evaluates Tribal participation in the Department of Water Resources’ (DWR) Inte

The Integrated Regional Water Management (IRWM) Tribal Collaborative Effectiveness Study evaluates Tribal participation in the Department of Water Resources’ (DWR) Integrated Regional Water Management (IRWM) grant program.  The Department administers the overall IRWM program, and individual regions form Regional Water Management Groups (RWMG) develop IRWM plans and submit specific water management projects for funding consideration by DWR. Following indigenous collaborative research protocols, we conducted surveys, interviews and focus-group meetings with Tribal representatives throughout the state. While we collected data from Tribes statewide, our efforts were focused in five specific IRWM regions. The aim of our research is to identify strengths, weaknesses, and opportunities for Tribal participation in the IRWM program.

Tribal Communication Plan

California Department of Water Resources (DWR) | June 1st, 2008

Tribal environmental and natural resource assistance handbook

U.S. Environmental Protection Agency (EPA) | March 11th, 1999

This handbook was developed by the Domestic Policy Council Working Group on American Indians and Alaska Natives (Working Group). The first draft of this document was poss

This handbook was developed by the Domestic Policy Council Working Group on American Indians and Alaska Natives (Working Group). The first draft of this document was possible thanks to the significant contributions of the Native American Fish & Wildlife Society. Previous drafts of the handbook were reviewed by each federal contributor and also went through the interagency review process at the Office of Management and Budget. The result is a compilation of the federal sources of financial and/or technical assistance programs available for Tribal environmental management. The handbook is intended to provide a central location for federal sources of both technical and financial assistance available to Tribes for environmental management. Many Tribes have limited environmental staffs that are faced with the challenge of addressing a broad range of environmental issues. Unlike State environmental programs that have received annual federal funding for many years, Tribal environmental programs generally must compete annually for their funds. With 554 federally recognized Tribes, there simply is not enough money to go around. Therefore, Tribal environmental staffs spend a large part of their time applying for grants and searching for sources of federal assistance. This document is an effort to assist Tribal staff in their search and hopefully save them valuable time. The handbook can also assist federal, regional, State and Local government employees in becoming better informed about the sources of environmental assistance available in order to improve customer service to the Tribes. The Working Group recognizes that this document does not contain every federal resource available to Tribes. This is an evolving document and will be updated periodically. Future versions of this document will be available on the Internet (see Comments section).