North Coast

Future loss of Arctic sea-ice cover could drive a substantial decrease in California’s rainfall

Nature Portfolio (Springer Nature) | December 5th, 2017

From 2012 to 2016, California experienced one of the worst droughts since the start of observational records. As in previous dry periods, precipitation-inducing winter st

From 2012 to 2016, California experienced one of the worst droughts since the start of observational records. As in previous dry periods, precipitation-inducing winter storms were steered away from California by a persistent atmospheric ridging system in the North Pacific. Here we identify a new link between Arctic sea-ice loss and the North Pacific geopotential ridge development. In a two-step teleconnection, sea-ice changes lead to reorganization of tropical convection that in turn triggers an anticyclonic response over the North Pacific, resulting in significant drying over California. These findings suggest that the ability of climate models to accurately estimate future precipitation changes over California is also linked to the fidelity with which future sea-ice changes are simulated. We conclude that sea-ice loss of the magnitude expected in the next decades could substantially impact California’s precipitation, thus highlighting another mechanism by which human-caused climate change could exacerbate future California droughts.

Future precipitation increase from very high resolution ensemble downscaling of extreme atmospheric river storms in California

American Association for the Advancement of Science (AAAS) | July 15th, 2020

Precipitation extremes will likely intensify under climate change. However, much uncertainty surrounds intensification of high-magnitude events that are often i

Precipitation extremes will likely intensify under climate change. However, much uncertainty surrounds intensification of high-magnitude events that are often inadequately resolved by global climate models. In this analysis, we develop a framework involving targeted dynamical downscaling of historical and future extreme precipitation events produced by a large ensemble of a global climate model. This framework is applied to extreme “atmospheric river” storms in California. We find a substantial (10 to 40%) increase in total accumulated precipitation, with the largest relative increases in valleys and mountain lee-side areas. We also report even higher and more spatially uniform increases in hourly maximum precipitation intensity, which exceed Clausius- Clapeyron expectations. Up to 85% of this increase arises from thermodynamically driven increases in water vapor, with a smaller contribution by increased zonal wind strength. These findings imply substantial challenges for water and flood management in California, given future increases in intense atmospheric river-induced precipitation extremes.

Gage Gap

Nature Conservancy | October 31st, 2018

Following a difficult five-year drought, California just had one of the wettest winters on record. The state is famous for its highly engineered water system, whi

Following a difficult five-year drought, California just had one of the wettest winters on record. The state is famous for its highly engineered water system, which moves millions of gallons of water from north to south and east to west. Thirty-nine million people and our $47 billion agricultural industry rely on that water, not to mention wildlife from the Sierra to the sea. And yet we have surprisingly little data about how much water is moving through our streams at any given time. There are over 3,600 locations in California where stream gages have been active at some point, but only 54% have been active recently. And even fewer of those provide the kind of rich, real-time reporting needed to manage what is arguably our state’s most precious and contentious resource.

Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California

U.S. Geological Survey (USGS) | January 12th, 2006

This study of the geohydrology and water chemistry of the Alexander Valley, California, was done to provide an improved scientific basis for addressing emerging wate

This study of the geohydrology and water chemistry of the Alexander Valley, California, was done to provide an improved scientific basis for addressing emerging water-management issues, including potential increases in water demand and changes in flows in the Russian River. The study tasks included (1) evaluation of existing geohydrological, geophysi- cal, and geochemical data; (2) collection and analysis of new geohydrologic data, including subsurface lithologic data, ground-water levels, and streamflow records; and (3) collection and analysis of new water-chemistry data. The estimated total water use for the Alexander Valley for 1999 was approximately 15,800 acre-feet. About 13,500 acre-feet of this amount was for agricultural use, primarily vineyards, and about 2,300 acre-feet was for municipal/industrial use. Ground water is the main source of water supply for this area. The main sources of ground water in the Alexander Valley are the Quaternary alluvial deposits, the Glen Ellen Formation, and the Sonoma Volcanics. The alluvial units, where sufficiently thick and saturated, comprise the best aquifer in the study area. Average recharge to the Alexander Valley is estimated from a simple, basinwide water budget. On the basis of an estimated annual average of 298,000 acre-feet of precipitation, 160,000 acre-feet of runoff, and 113,000 to 133,000 acre-feet of evapotranspiration, about 5,000 to 25,000 acre-feet per year is available for ground-water recharge. Because this estimate is based on differences between large numbers, there is significant uncertainty in this recharge estimate. Long-term changes in ground-water levels are evident in parts of the study area, but because of the sparse network and lack of data on well construction and lithology, it is uncertain if any significant changes have occurred in the northern part of the study area since 1980. In the southern half of the study area, ground-water levels generally were lower at the end of the 2002 irrigation season than at the end of the 1980 season, which suggests that a greater amount of ground water is being pumped in the southern half of the study area in recent years compared with that pumped in the early 1980s. Water-chemistry data for samples collected from 11 wells during 2002–04 indicate that water quality in the study area generally is acceptable for potable use. Two wells, however, each contained one constituent (241 μg/L of manganese and 1,350 μg/L of boron) in excess of the recommended standards for drinking water (50 μg/L and 1,000 μg/L, respectively). The chemical composition of water from most of the wells sampled for major ions plot as a mixed cation-bicarbon- ate, magnesium-bicarbonate, or calcium-bicarbonate type water. The ionic composition of the historical and recent samples from wells in the Alexander Valley is similar to that of the historical surface-water samples collected from the Russian River near Healdsburg. This suggests a similar source of water, particularly for wells that are less than 200 feet total depth and perforated in Quaternary alluvial deposits. Water from deeper, non-alluvial wells may contain slightly higher concentrations of sodium as a result of cation exchange. Water samples collected from several wells over an approximately 30–year period suggest a progressive change in water chemistry over time. Samples from the southern part of the valley show a trend towards higher ionic concentrations and increasing concentrations of particular constituents such as sulfate.

Geology and Ground Water Features of the Butte Valley Region Siskiyou County California

U.S. Geological Survey (USGS) | January 14th, 1960

The Butte Valley region includes an area of about 600 square miles, between long 121°37' and 122°10' W. and lat 41°38' and 42° N., in northern Siskiyou County, Cali

The Butte Valley region includes an area of about 600 square miles, between long 121°37' and 122°10' W. and lat 41°38' and 42° N., in northern Siskiyou County, Calif. U.S. Highway 97, connecting Weed with Klamath Falls, traverses the region in a northeasterly direction, and the Southern Pacific railroad serves several small farming communities in Butte Valley. The region is near the west edge of the Modoc plateau. It includes along its western border a part of the Cascade Range, Butte and Red Rock Valleys, the Oklahoma district, and a prominent northwestward-trending fault block (the Mahogany Mountain ridge) which separates Butte Valley fro-n the Oklahoma district and the Lower Klamath Lake marshland. Geologic units have been divided into two groups: Volcanic rocks which range in age from Eocene to Recent; and sedimentary rocks which range in age from Pliocene to Recent. From oldest to youngest the volcanic rocks include: (a) Predominantly andesitic lavas and pyroclastic rocks comprising the volcanic rocks of the "Western Cascades"; (b) older volcanic rocks of the "High Cascades"; (c) basaltic flows and pyroclastic rocks east of the Cascade Rang; and (d) younger volcanic rocks of the "High Cascades." Volcanic rocks of the "Western Cascades" are the oldest rocks in the region. They range in age from late Eocene to late Miocene. These rocks are chiefly pyroxene andesite, and andesitic tuff-breccia, but include lesser amounts of basalt, rhyolite, and associated pyroclastic rocks. In most places they are badly decomposed and less permeable than the younger volcanic rocks. They are best exposed in the Klamath River canyon, where the prevailing dips are to the east and northeast. The angle of dip diminishes in these directions from about 15° near the base of the series to nearly zero where the rocks disappear beneath a younger series of volcanic rocks designated on plate 1 as the older volcanic rocks of the "High Cascades." The volcanic rocks of the "Western Cascades" are at least 12,000 feet thick. The older volcanic rocks of the "High Cascades," which UE conformably overlie the volcanic rocks of the "Western Cascades," are Pliocene and Pleistocene (?) in age. They consist chiefly of basalt and basaltic andesite that spread out in successive sheets from a chain of northward-trendinr shield volcanoes built along the crest of the Cascade Range. Here the topography is almost wholly constructional, and even the oldest cones retain much of their original shape. East of the Cascade Range several large dome-shaped lava cones and most of the northwestward-trending fault block called Mahogany. Mountain ridge are composed of volcanic rocks of similar lithology. In most places the older volcanic rocks of the "High Cascades" are highly fractured and moderately permeable; they serve as a large intake area and groundwater reservoir. East of the Cascade Range, basalt of Pleistocene and Recent age issued from vents and fissures and spread out over alluvial deposits and lava sediments in the southern parts of Butte and Red Rock Valleys and the Lover Klamath Lake marshland. One of these flows the Butte Valley basalt forms the most productive water-bearing formation in the region. In the southwestern part of Butte Valley, where it is overlain by about 20 to 60 feet; of alluvial materials and lake deposits, this basaltic flow is an excellent aquifer. Yields of more than 100 gpm (gallons per minute) for each foot of drawdown are common and yields of 1,000 gpm for each foot of drawdown have been recorded. Late Pleistocene and Recent lava flows and cinder cones in the Cascade Range and extensive basaltic extrusions near Sharp Mountain are important chiefly as recharge (intake) areas for ground water. Sedimentary deposits range in age from Pliocene to Recent. The oldest of these deposits is a massive fresh-water diatomite which underlies a large part of the Oklahoma district. The diatomite is impermeable, but wells penetrating interbedded sand or cindery lapilli lenses in the diatomite may yield moderate quantities of water. Glacial moraines and fluvioglacial outwash deposits of late Pleistocene age occur near the mouth of Butte Creek canyon. These deposits are unstratified or poorly sorted and commonly are only slightly permeable. Semi-consolidated lake deposits, ranging in age from Pleistocene to Recent, underlie most of the Butte Valley plain. West of U.S. Highway 97 these deposits are composed principally of impermeable layers of clay, diatomaceous clay, and volcanic ash. However, east of U.S. Highway 97, and especially near the eastern border of the valley, the lake deposits contain a larger percentage of sand, and permeabilities range from about 50 to 230 gpd per square foot as determined from tests made in 3 pumped wells. Alluvial-fan deposits on the west side of Butte Valley range from Pleistocene to Recent in age. They are composed of poorly sorted rock debris derived from the Cascade Range and are only slightly permeable. Areas mapped as alluvium include thin beds of gravel, sand, dry, and peat covering older lake deposits in Butte Valley and the area around Lower Klamath Lake. They include also small playa deposits, poorly sorted alluvium collected in broad, shallow basins and depressions, and alluvluir in present intermittent stream channels. In most places alluvium forms a thin cover resting on lava flows or lake deposits. In general the alluviuir is slightly permeable and of little hydrologic importance except in the southwestern part of Butte Valley, where it consists of sand and gravel, ranging in thickness from 20 to 60 feet and rests on the Butte Valley basalt. In this area the alluvium probably yields moderate quantities of water to wells. Elsewhere the alluvium is largely above the saturated zone and is important chiefly because of its ability to absorb precipitation and surface runoff which percolate through it into underlying rocks. Linear wedge-shaped talus strips, formed at the foot of precipitous fault scarps, are partly concealed beneath and probably interfinger with alluvium and lake deposits. The blocky talus debris is very permeable and, where saturated, yields water readily to wells. East of the Cascade Range, block faulting is the dominant structural feature. The faults are normal and displacement is almost wholly vertical. Vertical displacements range from a few feet along minor faults to perhaps several thousand feet along major faults; there are no appreciable horizontal displacements. Butte Valley is a complexly downfaulted basin nearly surrounded by well-preserved fault scarps of late Pleistocene and Recent age. Groundwater moves eastward and northeastward across the valley into the buried talus and volcanic rocks that compose the Mahogany Mountain ridge, and may flow through that ridge to supply recharge to the area to the east. Th« direction of water movement in Red Rock Valley and in the Oklahoma district was not determined. Records of water-level fluctuations in observation wells show that water levels recover each winter, and during the period 1951-54 there was little overall change in the height of yearly recovery. Ground-water recharge in the southern part of the region occurs mainly by seepage loss from perennial spring-fed streams and unlined canals along the western margin of Butte Valley, by seepage loss from small spring-fed streams that discharge onto alluvial fans, and along the north, west, and south sides of the valley by lateral movement from the volcanic rocks. In irrigated tracts throughout the area some recharge probably occurs by deep percolation of irrigation water. Ground water is discharged by natural means and by pumping. In Butte Valley about 21,000 acre-feet of ground water was used for irrigation in 1953. In Red Rock Valley pumping of ground water for irrigation purposes was negligible. In the Oklahoma district ground water for irrigation and domestic requirements is supplied by springs and flowing and pumped wells. The quality of most of the ground water in the region is satisfactory for most uses, but in the east-central part of Butte Valley some wells yield water containing high percentages of sodium, probably derived from buried playa deposits. The chemical quality of the surface water is such that it can be used for most purposes. However, analyses of water from Meiss Lake show high concentrations of dissolved solids, ranging from 473 to 1,380 ppm, and high percentages of sodium, ranging from 75 to 91. Here the salts have been concentrated by evaporation of the lake water.

Geology and Ground Water in Russian River Valley Areas and in Round, Laytonville and Little Lake Valleys, Sonoma and Mendocino Counties, California

U.S. Geological Survey (USGS) | December 31st, 1965

Geology and Ground-Water Features of Shasta Valley, Siskiyou County California

U.S. Geological Survey (USGS) | January 15th, 1959

Shasta Valley is in the central part of Siskiyou County, Calif., and about 12 miles south of the Oregon border. It lies between the Klamath Mountains on the west and th

Shasta Valley is in the central part of Siskiyou County, Calif., and about 12 miles south of the Oregon border. It lies between the Klamath Mountains on the west and the Cascade Range 011 the east. The valley has an area of about 250 square miles; the north-south length is about 30 miles and the maximum width is about 15 miles. The average precipitation from July 1 to June 30 at Yreka and Montague is about 17 and 12 inches, respectively, and the average annual temperature at Yreka is 51.5°F. The area has a population of about 12,000, most of whom are employed in farming, cattle raising, and lumbering. The farm income is derived chiefly from livestock, principally beef cattle, hogs, and sheep. Alfalfa, wheat, barley, oats, and rye are the main crops grown in the valley. The Klamath Mountains are underlain by metamorphic and sedimentary rocks of Paleozoic age and by intrusive rocks of Mesozoic age that form the basement complex. Near Yreka the Chico formation of Late Cretaceous age, which is composed of shale, sandstone, and some conglomerate, overlies the older rocks with profound unconformity. The Chico formation in turn is overlain disconformably by the Umpqua formation of Eocene age, which consists mainly of black shale. These rocks are covered by a thin veneer of older alluvium which floors much of the northern part of the valley. Volcanic rocks make up much of the valley floor from Montague southward to Edgewood. The southeastern, flatter part of the valley is occupied by the Plutos Cave basalt, which is a relatively large single flow erupted from the northeast flank of Mount Shasta within the last few thousand years. The western half of the valley floor is occupied largely by the older volcanic rocks of the western Cascades, which range in age from Eocene to Miocene and which have been eroded into hillocks that range in height from a few feet to as much as 300 feet. Between these hillocks lie many small ponds and marshes and the alluvial flats formed by slow, winding streams. The valley is drained principally by the Shasta River and Parks Creek, which rise in the Klamath Mountains, and the Little Shasta River, which rises in the high Cascades. The volcanic rocks of the high Cascades were built by eruptions that commenced at the close of the Miocene epoch and continued intermittently to Recent time. Mount Shasta was built mainly during the Pleistocene epoch. Morainal and fluvioglacial deposits, which are concentrated at the south end of the valley, were formed mainly during Pleistocene time by glaciers that descended the northwest flanks of Mount Shasta. Glaciers still remain on Mount Shasta and have supplied fluvioglacial debris to the valley during Recent time. The Plutos Cave basalt constitutes the principal aquifer in the valley, yielding abundant water for irrigation, stock, and domestic wells in the vicinity of Big Springs. Yields of irrigation wells in the basalt average about 1,300 gpm (gallons per minute). The andesitic lavas of the western Cascades supply sufficient water for domestic and stock uses. Yields of wells tapping the andesites vary greatly because of rapid changes in lateral and vertical permeability. Abundant water for irrigation is yielded from fractures in the volcanic rocks of the western Cascades in the Gazelle-Grenada area. The basement complex and the Chico and Umpqua formations are tapped by relatively few wells in the area, although locally these wells seem to yield sufficient water for domestic and stock uses. The basement complex yields water from joints, faults, shear zones, and openings along foliation planes. The morainal and fluvioglacial deposits generally yield sufficient water for domestic and stock uses. Several irrigation wells tapping glacial materials east of Edgewood yield 600 to 1,500 gpm. The younger and older alluviums of Recent and Pleistocene age yield water sufficient for domestic and stock uses. Along the west side of the valley the younger alluvium yields sufficient water for irrigation and supplies Yreka with abundant water for municipal uses. Ground water moves generally northward in the southern part of Shasta Valley and troughward from the east and west, converging toward the Shasta River along the valley axis. At the north end of the valley an eastward-trending divide separates the ground water that moves north to Willow Creek from ground water that moves south to the Shasta River. Recharge to ground water is effected by deep infiltration of precipitation that falls on the tributary drainage area, principally the western slopes of Mount Shasta, and by seepage from streams. The mean annual precipitation on the valley floor of 12-15 inches probably is not sufficient to contribute much recharge to ground water, but during years of above-average precipitation some deep penetration probably occurs. Recharge from irrigation water in 1953 was about 15,000 acre-feet from a total surface-water diversion of 58,000 acre-feet, and recharge from ground water pumped for irrigation was about 2,000 acre-feet. Ground-water discharge in Shasta Valley occurs principally by seepage into streams, which is estimated crudely to have been 70,000 acre-feet in 1953. Big Springs has an annual discharge of about 30,000 acre-feet. Evapotranspiration from subirrigated crops is estimated to have been 28,000 acre-feet in 1953. Pumpage for all uses in 1953 was approximately 6,000 acre-feet, and net draft was about 4,000 acre-feet. Ground-water discharge in 1953 by all these principal means was about 130,000 acre-feet. In addition, there was minor discharge from flowing wells, unestimated discharge from small springs on the valley floor, and evapotranspiration losses from relatively small areas of phreatophytes. Because of the relatively small pumpage in the valley, water levels in wells show declines of only 5-10 feet during the summer and autumn. So far as is known, the levels each winter and spring recover nearly completely, and as of 1953 there had been no indication of a long-term decline of water levels in the valley. Surface water and ground water are generally low in dissolved mineral content and with few exceptions meet minimum standards for irrigation and domestic use. A close correlation exists between the composition of the various rock types in the area and the mineralization of surface and ground waters in areas adjacent to each rock type.

Geology of Northern California Bulletin 190

California Division of Mines and Geology | December 1st, 1966

Glaciers in California’s Sierra Nevada are likely disappearing for the first time in the Holocene

American Association for the Advancement of Science (AAAS) | October 1st, 2025

Mountain glaciers are sensitive climate indicators. Glaciers in the western United States are projected to disappear by 2100 CE, but whether they were previously absent i

Mountain glaciers are sensitive climate indicators. Glaciers in the western United States are projected to disappear by 2100 CE, but whether they were previously absent in the current interglacial (past 11,700 years) remains debated. Here, we present evidence that two of the largest glaciers in California’s Sierra Nevada near Yosemite National Park persisted throughout the Holocene. Cosmogenic in situ carbon-14 and beryllium-10 exposure dating in newly exposed proglacial bedrock indicates continuous Holocene cover, likely by ice. At a nearby smaller glacier, bedrock exposure-burial ages suggest glacier expansion at ~7 thousand years ago, earlier than previously recognized. Moraine exposure ages at these sites and the Sierra Nevada’s largest glacier are distributed across the past several thousand years, suggesting that glaciers were near their preindustrial extent for much of the late Holocene. These findings imply that a glacier-free Sierra Nevada is unprecedented since before the Holocene. Future alpine glacial environments in California are thereby likely a no-analog scenario within the current interglacial.

Global climate mode resonance due to rapidly intensifying El Niño-Southern Oscillation

Publisher not available | October 16th, 2025

Increasing ENSO amplitude and teleconnection patterns imply that remote extratropical precipitation responses, such as in Southern California and the Iberian Peninsula (F

Increasing ENSO amplitude and teleconnection patterns imply that remote extratropical precipitation responses, such as in Southern California and the Iberian Peninsula (Fig. 5), will also become stronger between alternating El Niño and La Niña events. Even though the recurrence of these events may become more predictable due to the increased regularity/periodicity and amplitude (Fig. 1)44, future ENSO teleconnections might generate enhanced whiplash effects on hydroclimate, which requires additional planning and management strategies to minimize the costs of climate damage. While similar increases in ENSO regularity and amplitude can be found in some CMIP6 model projections (Fig. 2), future work needs to assess the detailed dynamics across these models and assess the likelihood of the ENSO regime changes seen in AWI-CM3.