Home


      
 About CRRF


      
 Accomplishments


      
Current Projects


      
Membership Info


      
Conservation Partners


      
Contact Us 



 The Stanislaus River Restoration Plan Information Site

CHAPTER 3

EXISTING CONDITIONS OF THE LOWER STANISLAUS RIVER

3.1 OVERVIEW:

The lower Stanislaus River has been extensively developed to provide water, hydroelectric power, gravel, and conversion of floodplain habitat for agricultural and residential uses. Developments in the lower San Joaquin River and Delta that may affect anadromous fish as they migrate between the Stanislaus River and the ocean are also discussed.

3.2 WATER AND HYDROELECTRIC PROJECTS:

The 32 dams within the Stanislaus basin large enough to be regulated by the Division of Safety of Dams have a total capacity of 2,846,500 acre-feet or 237% of the average unimpaired runoff. New Melones dam, which was completed in 1979 and approved for filling in 1981, has a storage capacity of 2,400,000 acre-feet and was designed to control floods up to the 100-year-flood (Kondolf and others 2001).

The operating criteria for New Melones Reservoir are governed by water rights, instream fish and wildlife flow requirements (including AFRP objectives), Bay-Delta flow requirements, dissolved oxygen requirements, Vernalis water quality, CVP contracts, and flood control considerations. Water released from New Melones Dam and Powerplant is re-regulated at Tulloch Reservoir, and is either diverted at Goodwin Dam or released from Goodwin Dam to the lower Stanislaus River.

Flows in the lower Stanislaus River serve multiple purposes. These include provision of water for riparian water rights, instream fishery flow objectives, and instream dissolved oxygen (DO). In addition, water from the Stanislaus River enters the San Joaquin River, where it contributes to flow and helps improve water quality conditions at Vernalis. State Water Resources Control Board Decision (D)-1422, issued in 1973, provided the primary operational criteria for New Melones Reservoir and permitted USBOR to appropriate water from the Stanislaus River for irrigation and M&I uses. D-1422 requires that the operation of New Melones Reservoir include releases for existing water rights, fish and wildlife enhancement, and the maintenance of water quality conditions on the Stanislaus and San Joaquin rivers.

3.2.1 New Melones Interim Plan of Operation:

Proposed CVP operations on the Stanislaus River are derived from the New Melones Interim Plan of Operation (NMIPO). The NMIPO was developed as a joint effort between USBOR and USFWS, in conjunction with the Stanislaus River Basin Stakeholders (SRBS). The process of developing the plan began in 1995 with a goal to develop a long-term management plan with clear operating criteria. In 1996, the focus shifted to development of interim operations plans for 1997 and 1998. At an SRBS meeting on January 29, 1997, a final interim plan of operation was agreed to in concept. The NMIPO was transmitted to the SRBS on May 1, 1997. Although meant to be a short-term plan, it continues in effect. In summary, the NMIPO defines categories of water supply based on storage and projected inflow. It then allocates annual water release for fishery, water quality, Bay-Delta, and use by CVP contractors (Tables 3.2.1-1 and 3.2.1-2).

 

Table 3.2.1-1 Inflow characterization for the New Melones Interim Plan of Operation:

 

3.2.2 Water Rights Obligations:

When USBOR began operations of New Melones Reservoir in 1980, the obligations for releases to meet downstream water rights were defined in a 1972 Agreement and Stipulation among USBOR, OID, and SSJID. The 1972 Agreement and Stipulation required that USBOR release annual inflows to New Melones Reservoir of up to 654,000 acre-feet per year for diversion at Goodwin Dam by OID and SSJID, in recognition of their water rights. Actual historical diversions prior to 1972 varied considerably depending upon hydrologic conditions. In addition to releases for diversion by OID and SSJID, water is released from New Melones Reservoir to satisfy riparian water rights for agricultural irrigation totaling approximately 48,000 acre-feet annually downstream of Goodwin Dam.

In 1988, following a year of low inflow to New Melones Reservoir, the Agreement and Stipulation among USBOR, OID, and SSJID was superseded by an agreement that provided for conservation storage by OID and SSJID. The new agreement required USBOR to release New Melones Reservoir inflows of up to 600,000 acre-feet each year for diversion at Goodwin Dam by OID and SSJID. In years when annual inflows to New Melones Reservoir are less than 600,000 acre-feet, USBOR provides all inflows plus one-third the difference between the inflow for that year and 600,000 acre-feet per year. The 1988 Agreement and Stipulation created a conservation account in which the difference between the entitled quantity and the actual quantity diverted by OID and SSJID in a year may be stored in New Melones Reservoir for use in subsequent years.

Tri-Dam Project and Stockton East Water District Reservoirs

The Tri-Dam project is a partnership between the Oakdale Irrigation District (OID) and the South San Joaquin Irrigation District (SSJID) that was formed in 1948. Tri-Dam was formed to develop, operate and maintain the Beardsley/Donnells project on the middle fork of the Stanislaus River and the Tulloch project downstream of New Melones Reservoir for water storage and power generation. The Beardsley/Donnells project can store about 160,000 acre-feet of water and the Tulloch Project can store about 67,000 acre-feet of water. OID, SSJID, and the Stockton East Water District (SEWD) also own Goodwin Dam, which is just downstream of Tulloch. Goodwin, which can store up to 500 acre-feet of water, is the point of diversion for water for all three districts. It has no hydropower generating facilities. OID and SSJID also obtain water by recapturing drainage water and pumping from deep wells. The water is currently used to irrigate about 144,000 acres of land within the Districts. The irrigated land supports almonds, peaches, apples, walnuts and other crops.

The Beardsley/Donnells and Tulloch projects combined produce about 533,000,000 kwh of power annually. The Tulloch Powerhouse is operated primarily as a run-of-river operation and the Tulloch Reservoir also serves as an afterbay for the New Melones Powerhouse. OID and SSJID also own and operate the Sand Bar Project, which is purely a hydroelectric project located downstream of the Beardsley Afterbay Dam; it generates about 73,000,000 kwh annually. The power is sold to PG&E with the revenues used to: 1) pay off the bonds used to finance the projects; 2) maintain the power project facilities; 3) maintain and improve the water delivery system; and 4) offset the increasing cost of water for their customers.

3.2.3 Instream Flow Requirements:

Under D-1422, USBOR is required to release up to 98,000 acre-feet of water per year from New Melones Reservoir to the Stanislaus River on a distribution pattern to be specified each year by CDFG for fish and wildlife purposes. In 1987, an agreement between USBOR and CDFG provided for increased releases from New Melones to enhance fishery resources for an interim period, during which habitat requirements were to be better defined and a study of Chinook salmon fisheries on the Stanislaus River would be completed. During the study period, releases for instream flows would range from 98,300 to 302,100 acre-feet per year. The exact quantity to be released each year was to be determined based on storage, projected inflows, projected water supply and water quality demands, and target carryover storage. Because of dry hydrologic conditions in the 1987 to 1992 drought period, the ability to provide increased releases was limited. USFWS published the results of a 1993 study, which recommended a minimum instream flow on the Stanislaus River of 155,700 acre-feet per year for spawning and rearing (Aceituno 1993).

3.2.4 Anadromous Fish Restoration Plan Flows:

AFRP flow volumes on the Stanislaus River, as part of the NMIPO, are based on the New Melones end-of-February storage plus forecasted March to September inflow as shown in the NMIPO (Tables 3.2.1-1 and 3.2.1-2). The AFRP volume is then initially distributed based on modeled AFRP distributions and patterns used in the NMIPO. Actual flows below Goodwin Dam will be determined in accordance with Attachment 2 of the Department of the Interior Decision on Implementation of Section 3406 (b)(2) of the Central Valley Project Improvement Act October 5, 1999.

3.2.5 Bay-Delta Vernalis Flow Requirements:

D-1641 sets San Joaquin River at Vernalis flow requirements from February to June. These flows are commonly known as San Joaquin River base flows. USBOR has committed to provide these flows during the interim period of the Bay-Delta Accord. The NMIPO describes the commitment USBOR has made regarding the operation of New Melones Reservoir. If the NMIPO does not commit resources to this objective and the objective is at risk of non-compliance, USBOR will pursue other strategies (for example, water purchases) to meet the base flow commitment.

3.2.6 Dissolved Oxygen Requirements:

D-1422 requires that water be released from New Melones Reservoir to maintain DO standards in the Stanislaus River. The 1995 revision to the Water Quality Control Plan (WQCP) established a minimum DO concentration of 7milligrams per liter (mg/l), as measured on the Stanislaus River near Ripon.

3.2.7 Vernalis Water Quality Requirement:

D-1422 also specifies that New Melones Reservoir be operated to maintain an average monthly level of conductivity, commonly measured as total dissolved solids (TDS), on the San Joaquin River at Vernalis as it enters the Delta. D-1422 specifies an average monthly concentration of 500 parts per million (ppm) TDS for all months. Historically, releases have been made from New Melones Reservoir for this standard, but due to shortfalls in water supply, USBOR has not always been successful in meeting this objective. In the past, when sufficient supplies were not available to meet the water quality standards for the entire year, the emphasis for use of the available water was during the irrigation season, generally from April through September. D-1641 modified the water quality objectives at Vernalis to include the irrigation and non-irrigation season objectives contained in the 1995 Bay-Delta WQCP. The revised standard is an average monthly conductivity 0.7 microSiemens per centimeter (approximately 455 ppm TDS) during the months of April through August, and 1 mS/cm (approximately 650 ppm TDS) during the months of September through March.

3.2.8 Hydropower Operations:

New Melones Powerplant operations began in 1979. The powerhouse is rated at 300 MW. Power generation occurs when reservoir storage is above the minimum power pool of 300,000 acre-feet. When possible, reservoir levels are maintained to provide maximum energy generation.

3.2.9 Flood Control:

New Melones Reservoir flood control operation is coordinated with the operation of Tulloch Reservoir. The flood control objective is to maintain flood flows at the Orange Blossom Bridge at less than 8,000 cfs. When possible, however, releases from Tulloch Dam are maintained at levels that would not result in downstream flows in excess of 1,250 cfs to 1,500 cfs because of potential damage to permanent crops in the floodplain that may occur at flows above this level. Up to 450,000 acre-feet of the 2.4 million acre-foot storage volume in New Melones Reservoir is dedicated for flood control and 10,000 acre-feet of Tulloch Reservoir storage is set aside for flood control. Based upon the flood control diagrams prepared by USACE, part or all of the dedicated flood control storage may be used for conservation storage, depending on the time of year and the current flood hazard.

3.2.10 CVP Contracts:

USBOR has entered into water service contracts for the delivery of water from New Melones Reservoir, based on a 1980 hydrologic evaluation of the long-term availability of water in the Stanislaus River Basin. Based on this study, USBOR entered into a long-term water service contract for up to 49,000 acre-feet per year of water annually (based on a firm water supply), and two long-term water service contracts totaling 106,000 acre-feet per year (based on an interim water supply). Because diversion facilities were not yet fully operational and water supplies were not available during the 1987 to 1992 drought, no water was made available from the Stanislaus River for delivery to CVP contractors prior to 1992.

3.2.11 San Joaquin River Agreement:

Adopted by the SWRCB in Water Rights Decision 1641, the San Joaquin River Agreement (SJRA) includes a 12-year experimental program providing for flows and exports in the lower San Joaquin River during a 31-day pulse flow period during April-May. It also provides for the collection of experimental data during that time to further the understanding of the effects of flows, exports, and the barrier at the head of Old River on salmon survival. This experimental program is commonly referred to as the Vernalis Adaptive Management Program (VAMP).

An Environmental Impact Statement/Environmental Impact Report (EIS/EIR) is prepared annually for the water acquisition (flow) portion of the SJRA. Within the SJRA, the NMIPO has been assumed to form part of the basis for which flows will be provided on the San Joaquin River to meet the target flows for the 31-day pulse during April-May. Additional flows to meet the targets will be provided from other sources in the San Joaquin River under the control of the parties to the SJRA.

The operations forecasts include Vernalis flows that meet the appropriate pulse flow targets for the assumed hydrologic conditions. The flows in the San Joaquin River upstream of the Stanislaus River are forecasted for the assumed hydrologic conditions. These flows are then adjusted so that when combined with the forecasted Stanislaus River flow based on the NMIPO, they provide the appropriate Vernalis flows consistent with the pulse flow target identified in the SJRA. An analysis of how the flows are produced upstream of the Stanislaus River is included in the SJRA EIS/EIR.

3.2.12 Release Temperatures From New Melones Dam:

The presence of Old Melones Dam within New Melones Reservoir causes the release of warm surface water from New Melones Reservoir whenever storage levels fall below about one million acre-feet, a problem that occurred in 1991 and 1992 (Loudermilk 1996). In addition, Tulloch Reservoir can be warmer than 56 oF through the end of October although cold water releases are made from New Melones (CDFG 1998?). A new water temperature model is currently being developed to address this problem.

3.3 GEOMORPHIC PROCESSES AND GRAVEL MINING:

3.3.1 Historical Flows:

The USGS gage (# 11302500) records at Oakdale between 1895 and 1899 provide the best available representation of flows prior to the construction of reservoirs in the watershed (Kondolf 2001). During 1896, 1897, and 1899, the hydrograph can be characterized by (1) flashy winter storms that increased flows up to 14,000 cfs in January and February; (2) snowmelt that provided consistently high flows between 2,000 and 13,000 cfs from March to June, (3) small runoff events between late-September and December, and (4) minimum base flows of 50 to 180 cfs from mid-July through October (Appendix 1). During 1898, which was the driest year between 1895 and 1899, snowmelt flows ranged between 500 to 4,000 cfs flows and the minimum base flow was 27 cfs (Appendix 1).

During the pre-reservoir period, the prolonged period of high flows from snowmelt between March and June corresponds exactly with the time when adult spring-run Chinook salmon and adult stream-maturing (summer-run) steelhead migrated upstream to holding habitat in the upper watershed. Adult ocean-maturing (winter-run) steelhead would have migrated upstream to spawn in the mid- to lower basin during the flashy fall and winter storms. Adult fall-run Chinook salmon probably began their upstream migration in response to small storm events that produced runoff of 50 to 760 cfs between 1895 and 1899 in late-September and October. The runoff from these small storms probably was an important cue for the adult salmon because it provides the scent of their natal stream, which they rely on for navigation once they enter the Delta (Mesick 2001c). Most of the juvenile salmon probably migrated downstream during the high flows during either the winter storms as fry or during the spring snowmelt period as smolts. Most juvenile steelhead would have reared in the Stanislaus River for two years before migrating downstream as 200-mm long smolts during the spring snowmelt period.

3.3.2 Bed Mobility Flow Estimates:

Kondolf and others (2001) conducted a crude bed mobility flow evaluation at five Knights Ferry Gravel Replenishment sites between Goodwin Dam and Oakdale where gravel had been added in late summer 1999. They estimated that flows around 5,000 to 8,000 cfs are necessary to mobilize the median size of the gravel (D50) placed at these sites. They also concluded that higher flows would be needed to mobilize bars to prevent further encroachment of riparian vegetation in the active channel. Before construction of New Melones Dam, a bed mobilizing flow of 5,000 to 8,000 cfs was equivalent to a 1.5 to 1.8 year return interval flow. After the construction of New Melones Dam, 5,000 cfs is approximately a 5-year flow and 8,000 cfs exceeds all flows within the twenty-one year study period.

3.3.3 Sediment Budget:

Kondolf and others (2001) roughly estimate that a minimum of 1,031,800 cubic-yards of gravel were extracted from the active channel and an additional 5,292,500 cubic-yards of gravel were extracted from the floodplain between Goodwin Dam and Oakdale from 1939 to 1999 based on a reconnaissance-level assessment. The total amount of gravel extracted is estimated to be 600% of the amount naturally supplied from the watershed, which is about 1,033,900 cubic-yards. The amount of sand and gravel produced in the unregulated tributaries below Goodwin Dam was estimated to almost two orders of magnitude smaller than the volume extracted. Furthermore, the tributaries below Goodwin dam probably produce a small amount of gravel-sized sediment (Kondolf and others 2001). Kondolf and others (2001) estimated that if mining were to cease today and the natural annual sediment supply was restored, it would take 300 to 400 years to make up for the losses from extraction over the last 50 years.

3.3.4 Geomorphic Changes Due to New Melones Dam:

A study of aerial photographs and field observation by Kondolf et al (2001) indicate that the Stanislaus River has changed from a dynamic river system, characterized by depositional and scour features, to a relatively static and entrenched system. Changes since the construction of New Melones Dam include: (1) large scale vegetation encroachment in the active channel, primarily by willow and blackberry; (2) reduced reproduction of cottonwoods; and (3) substantial encroachment by urban and agricultural development, particularly orchards, in floodplain areas, thereby altering the natural river channel-floodplain connection. Kondolf and others (2001) also speculate that the dam reduced channel diversity through loss of alternating bar sequences and that the active channel has become incised. A comparison of field measurements between 1996 and 1999 suggest that the channel widened from 2.3 to 13.4 feet at five different riffles between Two-Mile Bar and Oakdale during prolonged releases in 1997 and 1998 (Schneider 1999, Kondolf and others 2001). However, CMC (2002) speculates that the loss of alternating bar sequences and channel incision was primarily a result of gravel mining in the active channel (see Section 3.3.5). CMC agrees with Kondolf and others (2001) that encroachment of the riparian vegetation and reduced gravel recruitment has led to the coarsening of the bed material, particularly within spawning habitat in the unmined reaches between Goodwin Dam and Honolulu Bar.

3.3.5 In-River Gravel Mining:

Drag lines were used to dredge the gravel and the spawning habitat from several reaches of the active riverbed primarily during the 1940s until about 1980 (P. Frymire, personal communication, see "Notes"). The dredged channels are now either large instream pits or long, uniform ditches that provide almost no habitat for salmonids. CDFG maps of the spawning riffles in 1972 show the locations of dredger tailings and "old drag lines" adjacent to the mined reaches (CMC 2002c). The following table presents the estimated amount of habitat that was mined in different reaches of the lower Stanislaus River based on an evaluation of the 1972 CDFG riffle maps and spawning surveys in 1994 and 1995 by CMC (2002c).


Small instream mine pits that occur in the primary salmonid spawning areas include one just upstream of Two-Mile Bar at rivermile 56.9, two adjacent pits near rivermile 53.5, Willm's Pond at rivermile 51.8, and the Button Bush Pond at rivermile 48.2. There is a large, approximately one-mile long pit at rivermile 39.4 that is called the Oakdale Recreation Pond. Captured mine pits trap bedload sediment, store large volumes of sand and silt, and pass sediment-starved water downstream where it typically erodes the channel bed and banks to regain its sediment load (Kondolf and others 2001). At the upstream and downstream ends of the pit, the over-steepened bed is an unstable knickpoint, which causes bed erosion such that the pit elongates in both an upstream and downstream direction. On the Stanislaus River, incision has been limited due to the reduction in channel forming flows since the construction of New Melones Dam.

Dredged channels and pits also reduce flow turbulance and thereby potentially reduce dissolved oxygen concentrations and provide habitat for fish that prey on juvenile salmonids. Reduced dissolved oxygen may contribute to mortality of juvenile and adult salmonids when water temperatures are unsuitably warm in late spring and early fall.

Concentrations of predator species in slow, flowing ditches that lack cover may also result in high rates of juvenile mortality.

3.4 FLOODPLAIN CONVERSION FOR AGRICULTURAL USES:

Typical riparian vegetation along the lower Stanislaus River consists of black cottonwood (Populus trichocarpa), California sycamore (Platanus racemosa), several species of willow (Salix spp.), alder (Alanus spp.) and oak (Quercus spp.), with an understory of California wild grape (Vitis californica), blackberry (Rubus vitifolius), elderberry (Sambucus glauca), and a variety of grasses (CDFG 1972). No analyses have been conducted to assess the amount of riparian habitat along the lower Stanislaus River that has been converted for agricultural use or commercial gravel mining. The Department of Fish and Game conducted analyses of aerial photographs taken in 1958 and 1965 that indicated that there were approximately 3,300 acres of riparian habitat between the Knights Ferry Bridge and the San Joaquin River in 1958, but only 2,550 acres in 1965 as a result of conversion for agricultural uses and commercial gravel mining (CDFG 1972). The amount of riparian habitat appears to have stabilized since 1965 based on a third analysis conducted by the U.S. Fish and Wildlife Service with 1994 aerial photos (USFWS 1995). The USFWS analysis indicates that there were approximately 2,590 acres of riparian and wetland habitat in this reach (see table below). They also estimated that there were approximately 4,155 acres of agricultural land, 725 acres of land disturbed primarily for commercial gravel mining, and 823 acres of land converted for urban use within a 1,500 foot wide corridor of riparian and upland habitats in this reach (USFWS 1995). Moreover, the presence of riparian habitat does not imply that connectivity exists between the floodplain and the active channel under the current flow regime; instead, groundwater may sustain some species of riparian vegetation without flooding. Although the USFWS study did not distinguish between riparian/floodplain habitat and upland habitat and so the amount of riparian habitat converted for agricultural and mining use cannot be estimated with this data, the USFWS habitat maps clearly indicate that much of the riparian habitat of the lower Stanislaus River has been converted into other uses (USFWS 1995).

Habitat Type

Foothill Reach (acres)

Valley Reach (acres)
Riparian

326.17

2,255.56
Wetland

6.35

1.08
Riverine

77.36

538.43
Gray Pine-Oak Woodland

55.85

1.40
Grassland

282.46

473.38
Rockland

31.31

0.00
Agriculture

230.80

3,924.19
Disturbed

225.24

500.46
Urban

126.44

696.19
Total

1,361.98

8,390.69

The Foothill Reach began at the covered bridge in Knights Ferry and ended at the Orange Blossom Bridge. The Valley Reach began at the Orange Blossom Bridge and ended at the confluence with the San Joaquin River.

3.5 DOWNSTREAM CONDITIONS:

Although beyond the scope of this restoration plan, the survival of anadromous fish of the Stanislaus River is highly dependent on conditions in the mainstem San Joaquin River, San Joaquin Delta, San Francisco Bay estuary, and ocean.

3.5.1 Delta Reclamation and the Deep-Water Ship Channel:

Prior to 1850, the Sacramento-San Joaquin Delta, an area of nearly 750,000 acres, was mostly a tidal marsh that consisted of a network of sloughs and channels during low flows and a large inland lake during flooding. The development of the Delta into farmland began in 1850 when the Swamp Land Act conveyed ownership of all swamp and marshes from the federal government to the State. Initial reclamation consisted of the construction of levees with peat soils on Rough and Ready Island and Roberts Island. These initial levees failed and in the 1870s steam-powered dredges were used to excavate alluvial soils to construct much larger levees. By the 1930s, reclamation was considered complete and the number of operating dredges declined greatly. However, due to continued subsidence of the peat soils, the Army Corps of Engineers continually adds material to maintain the levees, many of which range between 15 and 25 feet high.

The Port of Stockton and the deepwater ship channel in the San Joaquin Delta were completed in 1933. Activity at the Port of Stockton increased greatly in 1942 with the construction of military ships, mine sweepers, and landing craft. Shortly thereafter, large passenger cruise ships began navigating through the Delta. Currently the river is dredged to a depth of 35 feet to allow passage of deep draft ships; whereas upstream of the ship channel, depths range between 8 and 12 feet.

The Port of Stockton has recently contracted with the U.S. Army Corps of Engineers (ACOE) to study the feasibility of deepening the deep-water ship channel between the port and Pittsburg (The Sacramento Bee, July 18, 2002). The first phase of the study will analyze the effects on water quality and the economics of deepening the 25-mile channel.

3.5.2 Water Quality in the Deep-Water Ship Channel:

Dissolved oxygen (D.O.) concentrations are low in the deep-water ship channel during summer and early fall months partly (if not primarily) as a result of the decomposition of algal biomass that is produced in the comparatively shallow, nutrient-rich water upstream of Mossdale and subsequently transported into the much deeper waters of the ship channel (McCarty 1969; Van Nieuwenhuyse, personal communication). The algae, mostly diatoms, are not adapted to deep-water conditions and quickly settle out and decompose on the streambed. Simulations performed using the City of Stockton's D.O. model (Schanz and Chen 1993) indicate that increasing flow at Vernalis with the head of Old River barrier closed generally improves D.O. conditions at Stockton during most months. But in October, warm temperatures and the D.O. demand exerted by ammonia from the Stockton wastewater plant, the rotting algal biomass, and other organic matter usually keep D.O. levels well below the 6 mg/l standard.

The chlorophyll levels at Vernalis are literally among the highest ever recorded for streams worldwide and much of this production may be fueled by feedlot operations in the catchment. On the other hand, it is possible that the nutrient loading responsible for the high algal production stems from much more diffuse processes, such as tile drainage from row crops or orchards. An EPA-style TMDL (total maximum daily load) analysis for nutrients (especially phosphorus) for the San Joaquin catchment would be the first step toward resolving these issues (Lee and Jones-Lee 2001).

The Stockton D.O. model does not yet explicitly include algae, however, so its predictions about the effects of increased flow should be viewed with healthy skepticism. It is conceivable that under some circumstances sending more Vernalis water to the ship channel could make matters worse by increasing its organic matter loading rate. Ideally, the continuous monitoring stations upstream of the ship channel would be equipped with fluorometers calibrated to measure chlorophyll concentration (an indirect measure of algal biomass). Such a system would alert managers when algal biomass levels at Vernalis or further upstream are extremely high and give them time to take appropriate action.

Under most circumstances, the loading of algal biomass produced naturally in the San Joaquin river upstream is probably a much more serious problem for D.O. in the ship channel than organic matter loading from the Stockton wastewater treatment ponds. The loading of dissociated ammonium from the wastewater facility, however, may pose a potential toxicity problem. When algae are abundant and D.O. upstream becomes supersaturated (due to photosynthesis), pH levels also increase. High pH and high ammonium concentration lead to higher levels of undissociated ammonia, which is toxic to fish and aquatic invertebrates. It is possible that the salmon are responding to this toxicity rather than to low D.O.




      
View The Entire Stanislaus River Restoration Plan On Your Web Browser







      
Introduction


      
Public Outreach


      
 Existing River Conditions


      
Conceptual Models Of Potentially Limiting Factors





      
 Prioritized Restoration Actions and Research


      
Literature Cited


      
Download Using MS Word


      
Download Using Adobe Acrobat




To Send Comments Contact Dr. Mesick


Home ~ About CRRF ~ Accomplishments ~ Current Projects ~ Membership Info ~ Conservation Partners ~ Contact Us
 The Stanislaus River Restoration Plan Information Site.

( Note: All Information contained on this site is the property of the California Rivers Restoration Fund Copy Right California Rivers restoration Fund.)