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GROUND WATER IN THE CENTRAL VALLEY,C:ALIFORNiA A37
<br /> classification of ground water into hydrochemical facies Magnesium and calcium are the predominant cations in
<br /> or chemical water types is based on the relative concen- most of the southeastern part of the Sacramento Valley,
<br /> tration, in chemical equivalents, of cations and anions in and in particular, that area underlying the drainages of
<br /> the water.The cation and anion thatrepresent at least 50 the American and Cosumnes Rivers. Smaller areas of
<br /> percent of the total ions are used to designate the sodium, sodium calcium, and sodium magnesium bicar-
<br /> chemical water type, such as magnesium bicarbonate. If bonate water types are also present in the southeastern
<br /> no one cation or anion amounts to 50 percent, the water Sacramento Valley.
<br /> is designated by the two ions thatmake up the largest The most notable exception to the predominance of
<br /> percentages, such as calcium magnesium bicarbonate. bicarbonate as the major anion is the area in the southern
<br /> The distribution of chemical water types in the Central part of Sutter basin just south of the Sutter Buttes. In
<br /> Valley aquifer system is shown in figure 25. This map this area, calcium, magnesium, and sodium, as well as
<br /> shows only the general distribution pattern of water chloride, bicarbonate, and sulfate may be found in any
<br /> types. Because the map does not show vertical varia- combination. Sutter Buttes may be the source of the high
<br /> tions, these variations are discussed herein, where ap- i sodium and chloride concentrations(Fogelman, 1983), or
<br /> propriate.Areas where data are insufficient to define the the source may be a shallow layer of saline water
<br /> water type were left blank. surrounding the base of the Sutter Buttes(Berkstresser,
<br /> 1.973).
<br /> SAC,RAMEN10 VALLL1
<br /> 5AN.IOAQi IN VALLEY
<br /> Throughout the Sacramento Valley,with the exception The distribution of water types or hydrochemical facies
<br /> of part of the Sutter basin, bicarbonate is the predomi- in the San Joaquin Valley is more complex than in the
<br /> nant anion in the ground water. Ground water in the Sacramento Valley.The most important difference is the
<br /> northern and eastern parts of the Sacramento Valley has presence of chloride and sulfate as well as bicarbonate as
<br /> fairly homogeneous chemical character, with calcium and the dominant anions.Generally,chloride predominates in
<br /> magnesium being the predominant cations. Two areas, the northwest, sulfate predominates in the southwest,
<br /> one along Stony Creek and one along the Feather River, and bicarbonate predominates in the east. The major
<br /> stand out as being exclusively calcium or magnesium exceptions to this are the Hanford-Visalia area, where
<br /> bicarbonate,respectively,reflecting the recharge waters chloride and bicarbonate predominate, and the extreme
<br /> from the streams that drain into the valley at these southeastern part of the valley, where bicarbonate,
<br /> locations (Fogelman, 1983). sulfate, and chloride are all present in varying concen-
<br /> South of the Sutter Buttes, water types are more trations.
<br /> complex and sodium is the predominant cation. Sodium On the basis of water types, three areas of the San
<br /> bicarbonate type water is predominant along Salt Creek Joaquin Valley can be delineated:the east side, predom-
<br /> and downstream from the confluence of Salt Creek and inantly bicarbonate; the axial trough, variable anion
<br /> the Sacramento River. The sodium ion in this area is composition; and the west side, predominantly sulfate
<br /> probably derived from saline water in the Cretaceous and chloride.
<br /> formations that are drained by Salt Creek (Fogelman, Water types of the east San Joaquin Valley are fairly
<br /> 1983). Downgradieut on the west side of the valley, and uniform, most commonly resembling the chemical types
<br /> extending in a belt acmoss the valley, is an area where the of the local surface water that recharges the ground
<br /> chemical type of ground water is predominantly magne- water (Dale and others, 1966; Croft and Gordon, 1968;
<br /> sium sodium or sodium magnesium bicarbonate. The Page and LeBlanc, 1969;Mitten and others, 1970;Soren-
<br /> most notable exceptions to these water types are the son, 1981). Calcium bicarbonate, calcium sodium bicar-
<br /> areas adjacent to Cache and Putah Creeks and a small bonate, sodium calcium bicarbonate, and calcium
<br /> area around Dunnigan.The chemical water types in these magnesium bicarbonate are the predominant water types
<br /> areas are magnesium,calcium magnesium,or magnesium of ground water of the east side.
<br /> calcium bicarbonate. The water chemistry in the Dunni-- Because the axial trough has been the discharge area in
<br /> gan area is influenced largely by the Pliocene Tehama the past for the San Joaquin Valley,ground water in this
<br /> Formation, of which the Dunnigan Hills are largely area is a combination of water from the east aide and the
<br /> composed (Fogelman, 1983). Recharge from Cache and west side(Croft anti Gordon, 1968; Bertoldi, 1971). Local
<br /> Putah Creeps is the likely source of water in these areas. recharge from streams and surface water imported via
<br /> South of Putah Creek, sodium is again the predominant canals that infiltrates from irrigated fields to the water
<br /> cation, although small pockets of calcium sodium and table (Hotchkiss and Balding, 1971) also affects the
<br /> magnesium sodium ground water are also present. ground-water chemistry of the axial trough.
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