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North American diadromous fishes: Drivers of decline and potential for recovery in the Anthropocene

American Association for the Advancement of Science (AAAS) | January 28th, 2022

Summary

Diadromous fishes migrate between freshwater and marine habitats to complete their life cycle, a complexity that makes them vulnerable to the adverse effects of current

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North American drought: Reconstructions, causes, and consequences

Earth Science Reviews (Elsevier) | January 3rd, 2007

Summary

Severe drought is the greatest recurring natural disaster to strike North America. A remarkable network of centuries-long annual tree-ring chronologies has now allowed fo

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North American Droughts of the Last Millennium from a Gridded Network of Tree-Ring Data

American Meteorological Society (AMS) | April 1st, 2007

Summary

Drought is the most economically expensive recurring natural disaster to strike North America in modern times. Recently available gridded drought reconstructions

Drought is the most economically expensive recurring natural disaster to strike North America in modern times. Recently available gridded drought reconstructions have been developed for most of North America from a network of drought-sensitive tree-ring chronologies, many of which span the last 1000 yr. These reconstructions enable the authors to put the famous droughts of the instrumental record (i.e., the 1930s Dust Bowl and the 1950s Southwest droughts) into the context of 1000 yr of natural drought variability on the continent. We can now, with this remarkable new record, examine the severity, persistence, spatial signatures, and frequencies of drought variability over the past milllennium, and how these have changed with time. The gridded drought reconstructions reveal the existence of successive “megadroughts,” unprecedented in persistence (20–40 yr), yet similar in year-to-year severity and spatial distribution to the major droughts experienced in today’s North America. These megadroughts occurred during a 400-yr-long period in the early to middle second millennium A.D., with a climate varying as today’s, but around a drier mean. The implication is that the mechanism forcing persistent drought in the West and the Plains in the instrumental era is analagous to that underlying the megadroughts of the medieval period. The leading spatial mode of drought variability in the recontructions resembles the North American ENSO pattern: widespread drought across the United States, centered on the Southwest, with a hint of the opposite phase in the Pacific Northwest. Recently, climate models forced by the observed history of tropical Pacific SSTs have been able to successfully simulate all of the major North American droughts of the last 150 yr. In each case, cool “La Niña–like” conditions in the tropical Pacific are consistent with North American drought. With ENSO showing a pronounced signal in the gridded drought recontructions of the last millennium, both in terms of its link to the leading spatial mode, and the leading time scales of drought variability (revealed by multitaper spectral analysis and wavelet analysis), it is postulated that, as for the modern day, the medieval mega- droughts were forced by protracted La Niña–like tropical Pacific SSTs. Further evidence for this comes from the global hydroclimatic “footprint” of the medieval era revealed by existing paleoclimatic archives from the tropical Pacific and ENSO-sensitive tropical and extratropical land regions. In general, this global pattern matches that observed for modern-day persistent North American drought, whereby a La Niña–like tropical Pacific is accompanied by hemispheric, and in the midlatitudes, zonal, symmetry of hydroclimatic anomalies.

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North American droughts of the mid to late nineteenth century: a history, simulation and implication for Mediaeval drought

Holocene (Sage Journals) | February 1st, 2006

Summary

Unlike the major droughts of the twentieth century that are readily identified in the instrumental record, similar events in the nineteenth century have to be identified

Unlike the major droughts of the twentieth century that are readily identified in the instrumental record, similar events in the nineteenth century have to be identified using a combination of proxy data, historical accounts and a sparse collection of early instrumental records. In the USA, three distinct periods of widespread and persistent drought stand out in these records for the latter half of the nineteenth century: 1856-1865, 1870-1877 and 1890-1896. Each of these events is shown to coincide with the existence of an anomalously cool, La Nifia-like tropical Pacific. To examine the physical mechanisms behind these droughts two ensembles of simulations with an atmosphere general circulation model (AGCM) were generated: the first forces an AGCM with the observed history of Sea Surface Temperatures (SSTs) everywhere from 1856 to 2001 (the GOGA experiment), the second forces the AGCM only with tropical Pacific SSTs, being coupled to a two-layer entraining mixed layer (ML) ocean elsewhere (the POGA-ML experiment). Owing to a sparsity of instrumental precipitation data at this time, proxy evidence from tree rings is used as verification. A comparison of modelled soil moisture with tree-ring reconstructions of the Palmer Drought Severity Index (PDSI), a proxy for soil moisture, from the North American Drought Atlas is made. Both the POGA-ML and GOGA ensemble means capture the three multi-year droughts of the mid to late nineteenth century, indicating that the droughts were SST forced. The similarity of the POGA-ML and GOGA simulations implies that the component of each drought signal that is forced by the SST is driven ultimately by the La Nifia-like tropical Pacific. The global atmosphere-ocean context of each of the mid to late-nineteenth century droughts reveals a zonally and hemispherically symmetric pattern consistent with forcing from the tropics. In addition, Rossby wave propagation from the cooler equatorial Pacific amplifies dry conditions over the USA. Finally, using published coral data for the last millennium to reconstruct a NINO 3.4 history, the modern-day relationship between NINO 3.4 and North American drought is applied to recreate two of the severest Mediaeval ‘drought epochs’ in the western USA. The large-scale spatial similarity to the Drought Atlas data demonstrates the potential link between a colder eastern equatorial Pacific and the persistent North American droughts of the Mediaeval period.

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North American Subbasin Groundwater Sustainability Plan

Sacramento Groundwater Authority | December 15th, 2021

Summary

In 2014, the Sustainable Groundwater Management Act (SGMA) was signed by the Governor of the state of California, setting the framework for local agencies to sustainably

In 2014, the Sustainable Groundwater Management Act (SGMA) was signed by the Governor of the state of California, setting the framework for local agencies to sustainably manage California’s groundwater basins. To avoid potential State intervention, SGMA requires groundwater basins/subbasins designated by the California Department of Water Resources (DWR) as medium- or high-priority to follow four basic steps: 1) form a Groundwater Sustainability Agency (GSA); 2) develop and adopt a Groundwater Sustainability Plan (GSP or Plan); 3) implement the Plan to achieve a sustainability goal and avoid undesirable results within 20 years; and 4) report the implementation activities to the DWR to document whether the sustainability goal and the avoidance of undesirable results is being achieved. Ultimately, five GSAs were formed to manage groundwater in the North American Subbasin (NASb or Subbasin), completing Step 1. This GSP and adoption by each GSA will complete Step 2. This GSP will be assessed every 5 years, with amendments as needed to ensure the Plan is meeting its sustainability goal. This GSP is a framework to provide for the sustainability of the NASb of the Sacramento Valley Groundwater Basin for the next 20 years. The NASb, designated as subbasin No. 5-021.64 by the DWR, is bounded on the north by the Bear River, on the south by the American River, to the west by the Feather and Sacramento rivers, and on the east by the Sierra Nevada foothills. The NASb was designated by DWR as a high priority subbasin and therefore the formation of GSAs and the completion of a GSP is required to avoid potential State Water Resources Control Board (SWRCB) intervention. Surrounding subbasins were also designated as medium- or high-priority and are required to comply with SGMA. Groundwater is a critical resource to the Subbasin’s community, economy, and environment by providing an average of 280,000 acre-feet per year (AFY) for public and agricultural supply or just under 50 percent of total water supply. Agencies in the NASb have been actively managing groundwater for decades and have achieved positive groundwater management results. Groundwater levels within the Subbasin have been relatively stable for decades and have shown the ability to recover after periods of prolonged pumping and droughts. The passage of SGMA created an opportunity for a cooperative endeavor to develop a single GSP for the entire NASb. Beginning in January 2017, representatives of local agencies began coordination meetings that ultimately led to agreement to form five GSAs to cover the entirety of the Subbasin, while ensuring broad representation of the various stakeholder interests throughout the parts of the three counties comprising the NASb. Due to size, this file has been divided. Part 1, Part 2, Part 3, Part 4, Part 5, Part 6, Part 7, Part 8, Part 9

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North Bay Mercury Biosentinel Project 2016 - 2017

San Francisco Estuary Institute (SFEI) | March 1st, 2018

Summary

Concentrations of methylmercury throughout San Francisco Bay are high enough to warrant concern for the health of humans and wildlife. Large-scale tidal wetland restorat

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North Bay Selenium Monitoring Design

San Francisco Estuary Institute (SFEI) | December 3rd, 2018

Summary

The San Francisco Bay Regional Water Quality Control Board developed a Total Maximum Daily Load (TMDL) and implementation plan for selenium in North San Francisco Bay (N

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North Coast Hydrologic Region Groundwater Update

California Department of Water Resources (DWR) | April 1st, 2015

Summary

The primary goal of the North Coast Hydrologic Region (North Coast region) groundwater update is to expand information about region-specific groundwater conditions for Ca

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North Coast Regional Water Quality Control Board Fact Sheet

California State Water Resources Control Board (SWRCB) | March 1st, 2010

Summary

The North Coast Region receives more precipitation than any other part of California. Abundant in surface water and groundwater resources, the North Coast Regio

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North Coastal Area Action Program: A Study of the Smith River Basin and Plain

California Department of Water Resources (DWR) | December 17th, 1970

Summary

The 770-square-mile Smith River Basin and Plain in the northwestern corner of California has adequate water supplies overall, but a problem exists in distributing the w

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Page : 311

North American diadromous fishes: Drivers of decline and potential for recovery in the Anthropocene

North American drought: Reconstructions, causes, and consequences

North American Droughts of the Last Millennium from a Gridded Network of Tree-Ring Data

North American droughts of the mid to late nineteenth century: a history, simulation and implication for Mediaeval drought

North American Subbasin Groundwater Sustainability Plan

North Bay Mercury Biosentinel Project 2016 - 2017

North Bay Selenium Monitoring Design

North Coast Hydrologic Region Groundwater Update

North Coast Regional Water Quality Control Board Fact Sheet

North Coastal Area Action Program: A Study of the Smith River Basin and Plain

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