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SAN JOAQUIN RIVER BASIN HYDROLOGY sources collectively contributed 26%of total flow and 63%of estimated TDS loading in the San
<br /> Joaquin River at Vemalis. The largest non-tributary TDS loadings were made by groundwater
<br /> San Joaquin River Basin hydrology is predominantly influenced by tributary inflows,agricultural (191,000 tons)and surface water return flows(150,000 tons). Municipal and industrial sources
<br /> diversions and return flows,and tidal flows. For the purpose of this antidegradafion analysis,the contributed minor discharge volumes(1%)and TDS loads(2-3%),similar in magnitude to
<br /> Lower San Joaquin River can be divided into two main sections based on the presence or contributions from subsurface return flows(Quinn and Tulloch,2002).
<br /> absence of tidal flows. The Lower San Joaquin River from Mendota Pool to Vernalis receives
<br /> inflow from a variety of sources including east-side tributaries,dominated by reservoir releases; Table 6: Sources and Percent Contributions of Flow and TDS in the San Joaquin River at Vernalis
<br /> west-side tributaries,dominated by agricultural return flows;groundwater recharge;and (1985-1994)
<br /> discharges from wetlands and publicly owned wastewater treatment facilities. Diversions can Discharge(') Percent TDS Loadi2) Percent
<br /> remove a significant amount of San Joaquin River flow,especially during periods of below Source (acre-feet x 1000) Contribution (tons x 1000) Contribution
<br /> normal rainfall. The Lower San Joaquin River is not typically affected by tidal flows,being
<br /> sufficiently upstream of the Pacific Ocean's tidal influence. East-side tributaries 1,323 70 148 16
<br /> Groundwater 90 5 191 20
<br /> The second main section of the Lower San Joaquin River is the tidally influenced reach from West-side tributaries 68 4 201 21
<br /> Vernalis to its confluence with the Sacramento River near Collinsville. Major tributary inputs to
<br /> this section are provided by the Cosumnes and Mokelumne rivers where their commingled flows Grassland wetlands 60 3 74 8
<br /> enter the central Delta near Webb Tract. Significant non-tributary inflows are provided from Groundwater inflow 11 1 77 8
<br /> irrigation return flows that are pumped from adjacent agricultural lands into the San Joaquin West-side surface returns 70 4 57 6
<br /> River. The major diversion of San Joaquin River water occurs at the junction of Old River, Subsurface return flows 11 1 25 3
<br /> where,depending on Delta hydraulics,up to 50%of San Joaquin flows may be diverted to the (main stem SJR)
<br /> south Delta(Quinn and Tulloch,2002). Surface return flows 250 13 150 16
<br /> An understanding of the hydrology and hydrochemistry of the San Joaquin River can be gained (main stem SJR)
<br /> through a review of the relative flow contributions made by east-side tributaries,west-side Municipal and Industrial 15 1 14 2
<br /> tributaries,and other inflows. As shown in Figure 1,the major east-side tributaries are the Total 1,899 100% 938 100%
<br /> Merced,Tuolumne,and Stanislaus rivers which join the Lower San Joaquin River upstream of Source:Quinn and Tulloch,2002.
<br /> Vernalis. There are also three minor east-side tributaries in the Basin,including Bear Creek,the (1)10-year mean annual flow calculated from 1985—1994.
<br /> (2)10-year mean annual load calculated from 1985—1994.
<br /> east-side Bypass,and the Mariposa Bypass. There are nine significant streams and conveyances
<br /> that drain the west-side of the San Joaquin Basin and are tributary to the San Joaquin River.
<br /> These tributaries include Panoche-Silver Creek,San Luis Drain,Salt Slough,Mud Slough, LAND USE
<br /> Spanish Grant Drain,Orestimba Creek,Hospital Creek,Ingram Creek,and Del Puerto Creek. Land use in the Delta is dominated by agriculture(about 538,000 acres). Open water covers
<br /> Many of these streams are ephemeral,conveying rainfall runoff during the winter season and approximately 60,000 acres,while urban and commercial property account for about 64,000
<br /> agricultural return flows during the summer months. The San Luis Drain is a concrete-lined acres of developed land(DWR,2005). The remainder of the region currently consists of
<br /> conveyance that once formed part of a Valley Master Drain system providing drainage for the undeveloped public lands and open space. Of the portions of six counties that encompass the
<br /> entire west-side of the Basin. The Drain presently serves five agricultural water districts and legal Delta,San Joaquin County comprises the majority of land included within the legal Delta
<br /> conveys subsurface drainage water into Mud Slough,six miles upstream of the confluence with boundary. Within San Joaquin County,approximately 77%of the total county acreage is used
<br /> the San Joaquin River. Due to the Drain's importance to the hydrology of the San Joaquin River, for agriculture and grazing,followed by medium-density residential(7%),low-density
<br /> it is considered a west-side tributary(Quinn and Tulloch,2002). residential(4%),and industrial land uses(3%)(U.S.Fish and Wildlife Service et al.,2006).
<br /> A comparison of flow and TDS(salts)inputs into the San Joaquin River by a variety of sources The valley portion of the San Joaquin River Basin shows a similar land use pattern as the Delta,
<br /> is provided in Table 6. During the period 1985-1994,annual average flows from all east-side with the area predominantly comprised of farmland. Growing urban centers exist in Stockton,
<br /> tributaries collectively accounted for 70%of the flow measured in the San Joaquin River at Tracy,Modesto,Manteca,Lathrop,and Merced. Agriculture is the major economic and land use
<br /> Vernalis. In contrast,west-side tributaries contributed 4%of the flow measured at Vernalis. activity in the San Joaquin River Basin. The San Joaquin Valley is recognized as one of the
<br /> While east-side tributaries contributed approximately 17.5 times the flow of west-side tributaries, most important agricultural regions in California,with approximately 2 million acres of irrigated
<br /> the estimated TDS loading of the east-side tributaries was about three quarters of that provided cropland and an annual agricultural output valued at more than$4.9 billion in the year 2000.
<br /> by west-side tributaries. This difference in TDS loading can be attributed to the fact that snow- Non-agricultural commerce in the region is generated by a variety of industries including food
<br /> melt comprises a large proportion of east-side flow volume,while return flows from agriculture processing,chemical production,lumber and wood products,glass,textiles,paper,machinery,
<br /> and wetlands dominate west-side hydrology. Tributary contributions not withstanding,all other fabricated metal products,and various other commodities(DWR,2005).
<br /> City of Manteca Antidegradation Analysis 17 June 2007 City of Manteca Antidegradation Analysis 18 June 2007
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