Santa Paula Basin
2000 Annual Report
Santa Paula Basin
2000 Annual Report
Prepared for the Santa Paula Basin
Technical Advisory Committee
Prepared by
Groundwater Resources Department
August 2001
In March 1996, the Superior Court of the State of California for the County of Ventura filed a stipulated Judgment for Santa Paula Basin. The Judgment recognized that all of the parties have an interest in the Santa Paula Basin, and in the proper management and protection of both the quantity and quality of this important groundwater supply. The Basin is a significant water resource in the County of Ventura. Members of the Santa Paula Basin Pumpers Association and the City of San Buenaventura exercise rights to pump water from the basin for reasonable and beneficial uses. The United Water Conservation District does not produce water from the basin, but the basin is located within its boundaries and the District is authorized to engage in groundwater management and replenishment activities and to commence actions to protect the water supplies which are of common benefit to the lands within the District or its inhabitants.
The stipulated Judgment provides for the creation of a Technical Advisory Committee. The committee is charged with establishing a program to monitor conditions in the basin, including, but not necessarily limited to, verification of future pumping amounts, measurements of groundwater levels, estimates of inflow to and outflow from the basin, increases and decreases in groundwater storage, and analyses of groundwater quality.
The Court Judgment requires an annual report of the results of the monitoring program. The stipulated Judgment requires that “United Water Conservation District shall have the primary responsibility for collecting, collating, and verifying the data required under the monitoring program, and shall present the results thereof in annual reports to the Technical Advisory Committee.” In addition, the Judgment stipulates that “UWCD will then analyze the information and prepare a Santa Paula Basin Annual Report.”
The Judgment also allows for the development of a management plan for the operation of the basin, empowering the committee to determine the safe yield of the basin.
This annual report provides and analyzes geohydrologic data for the Technical Advisory Committee for their consideration in developing a management plan for the operation of the basin and includes an annual basin status statement.
Precipitation for the water year 2000 was 14.76 inches. (A water year begins on October 1st and ends on September 30th.) Precipitation for the calendar year 2000 was 14.15 inches. This was 2.67 inches below average precipitation for the water year. Groundwater pumpage for the calendar year 2000 was 26,790 acre-feet. This was 822 acre-feet above the long-term average pumpage from 1980 to 2000. The Santa Paula Basin groundwater level index for the water year 2000, a below average rainfall year, was down 4.7 feet from the groundwater level index for the water year 1999, which was also a below average rainfall year. Significant hydrologic parameters for the Santa Paula Basin are listed in Table 1 and Table 2 below.
Table 1 summarizes 1999 and 2000 precipitation, diversions at UWCD’s Freeman Diversion, pumpage as compared to the Santa Paula Basin base pumping allocation, and Santa Paula Creek flow.
The groundwater level index (Table 2) tracks regional changes in groundwater levels in the Santa Paula Basin from the years 1983 to present. The index represents the high groundwater level from February through April of each year for each of 10 wells, averaged among the 10 wells. The groundwater level index for the entire basin for the 1990’s shows that groundwater levels are down relative to 1983. In 1995 the basin had nearly recovered from the drought except for a few wells which are located in the far west portion of the basin.
Table 1. Significant Hydrologic Indicators
Table 2. Basin Index Wells (Average Change in Groundwater Elevations)
This report presents and analyzes data on the Santa Paula groundwater basin for calendar year 2000. The data provided will be used to determine the response of the basin to year 2000 pumpage. This information will also be used in the future to assist in determining the safe yield for the basin.
United Water Conservation District (UWCD) has prepared this 2000 Annual Report to meet its requirements as stipulated in the March, 1996 Court Judgment (UWCD vs. City of San Buenaventura, 1996; Case No. 115611). This report is prepared for the Santa Paula Basin Technical Advisory Committee (TAC) which consists of the United Water Conservation District, the City of Ventura, and the Santa Paula Basin Pumpers Association.
The data and information provided include:
1) summary tables of pumpage and other key hydrologic indicators;
2) precipitation and stream flow;
3) groundwater pumpage;
4) new wells and status of non-pumping wells;
5) groundwater surface level monitoring;
6) groundwater level index;
7) surface water quality monitoring;
8) groundwater quality monitoring; and,
9) long-term trends and 2000 data analysis.
This report was prepared by the staff at UWCD under the management of Steve Bachman, Ph.D. and Pete Dal Pozzo, Hydrogeologist.
This is the fifth Annual Report of the Santa Paula Basin. The background information on the Santa Paula Basin pumping allocations and water systems are included in the Santa Paula Basin Judgement (United Water Conservation District vs. City of San Buenaventura, March 7, 1996).
The status of the basin is the same for 2000 as it was for 1999. Our understanding of the basin is improving as we gather more information. Over the past few years the Santa Paula Basin Technical Advisory Committee has developed an effective working relationship.
There has been significant progress on work efforts to determine operational yield of the basin. As we progress through a work plan to determine operational yield, we expect to find ways to more effectively manage the basin. This will ensure that water quality and quantity are manageable.
Information and data in this report have been collected from hundreds of sources, all of which are checked for accuracy or reasonableness. Corrections or any additional information will be published in the subsequent year’s report within this section.
The change in groundwater level index for the period from 1983 to 1995 has been corrected from -3.3 feet, to -4.4 feet.
Basin Location and Dimensions
The Santa Paula Basin is located along the Santa Clara River, between the town of Saticoy and Santa Paula Creek. The basin is bounded by the Sulphur Mountain foothills on the north and South Mountain on the south. The basin is elongated in a northeast-southwest direction, about 10 miles long and as much as 3.5 miles wide. The surface area of the basin is approximately 13,000 acres, and ranges in elevation from 130 feet above sea level near Saticoy to 270 feet above sea level near the City of Santa Paula. Ongoing uplift along the Oak Ridge and other faults has created a deep basin, with Plio-Pleistocene deposits exceeding 10,000 feet in thickness.
Hydrogeology
The principal fresh water-bearing strata of the Santa Paula Basin are the Pleistocene San Pedro Formation, overlying Pleistocene river deposits of the ancient Santa Clara River, alluvial fan deposits shed from the uplifted mountain blocks, and recent river and stream sediments deposited locally along the Santa Clara River and its tributaries. These water-bearing sediments are underlain by relatively impermeable Pliocene and older units.
The sediments of the basin have been warped into a syncline that is oriented in a northeast-southwest direction along the center of the basin. To the east, the Santa Paula Basin is considered to be in hydraulic connection with the Fillmore Basin. To the south, the Oak Ridge fault forms a partial barrier to groundwater movement. On the north, the portion of the aquifer represented by the San Pedro Formation is exposed in outcrop along the foothills. The Santa Paula Basin borders the Montalvo and Mound basins on the west. The western boundary of the Santa Paula Basin is more complex, with local uplift, artesian conditions, and faults mapped by some investigators. Although there is general agreement that there is some hydraulic connection between Santa Paula Basin and the Mound Basin, the degree of connection is uncertain.
Hydrogen and oxygen isotope data indicate that the Santa Paula Basin receives recharge from the Santa Clara River, by rainfall percolation through the San Pedro Formation outcrops that are exposed along the foothills to the north, and by percolation of streams crossing these sediments. Other sources of recharge are by percolation into the recent alluvium of Santa Paula Creek and other tributaries, and underflow from the Fillmore Basin. Recharge from the Santa Clara River is limited to reaches north of the Oak Ridge fault. The Santa Clara River flows north of the fault in an approximately two-mile stretch just south of the City of Santa Paula. The benefit of this recharge is seen in groundwater level hydrographs. This is especially true for wells in the eastern half of the basin which show full recovery of groundwater levels since the drought. Where the river flows south of the Oakridge fault, it overlies impermeable Santa Barbara Formation. This may restrict the amount of recharge the basin can receive from the river in any one year.
Groundwater levels in the majority of wells throughout the basin show significant seasonal variability. During high rainfall years, monitor wells in the western portion of the basin just northwest of the Freeman Diversion located on the Edwards Ranch near the Santa Clara River, may have artesian flow.
The apparently steep groundwater
gradient, in conjunction with the complex subsurface geology in the western
portion of the basin, complicates the interpretation of groundwater flow in
western Santa Paula Basin. Additional geophysical, water chemistry, and groundwater
level data may be necessary to adequately define the subsurface flow between
Santa Paula Basin and the adjacent Mound and Montalvo basins.
Historical water year precipitation data from UWCD’s rainfall gauging station in Santa Paula are shown on the graph in Figure 1a. Data from October 1, 1890 through September 30, 2000 can be found in Appendix B. The precipitation graph includes: 1) total annual precipitation by water year; 2) total average precipitation over the period of record; and, 3) annual cumulative departure from the total average precipitation. During the 2000 water year (October 1, 1999 to September 30, 2000) the recorded precipitation was 14.76 inches, which is 2.67 inches below normal. Calendar year precipitation was slightly lower (14.15 inches). Year 2000 was the fourth year out of the last five years in which the Santa Paula Basin had approximately average or below average precipitation. Note Figure 1b which shows monthly precipitation amounts for both water year and calendar year 2000.
Figure
1a. Historical Precipitation for Santa Paula Basin (Santa Paula Precipitation
Gauge)
Figure 2a shows historical Santa Paula Creek flow at the Steckel Park gauge, just north of the City of Santa Paula, for the water years 1928 through 2000. The flows have been highly variable through time, as would be expected through California’s drought and wet years. Streamflow for water year 2000 at 8,610 acre-feet was 47 % below historical average streamflow and 3 % above historical median streamflow.
The effectiveness of the precipitation and streamflow in recharging the basin is controlled by factors such as the pre-existing conditions of the soil, the intensity and duration of the precipitation, and the duration and volume of the stream flow. Note Figure 2b which shows monthly Santa Paula Creek flow. The monthly Santa Paula Basin precipitation graph (Figure 1b) should be compared with the monthly Santa Paula Creek flow graph.
Figure
2b. Monthly Santa Paula Creek Flow for Water Year 2000 (U.S. Geological Survey)
During calendar year 2000, 26,790 acre-feet of groundwater were pumped from the Santa Paula Basin. This pumpage is reported on the semiannual groundwater production statements filed with UWCD’s Finance Department by individual pumpers. These production statements constitute all known pumping from the Santa Paula Basin (see Appendix C). A breakdown of the 26,790 acre-feet of pumpage is as follows:
a) City of Ventura pumped 1,621 acre-feet
b) Parties and Non-Parties listed in the Judgment excluding the City of Ventura pumped 24,073 acre-feet
c) Non-Parties not listed in the Judgment pumped 1,096 acre-feet
Approximately 12,000 acres of mostly lemons and avocados are irrigated by groundwater. The 2000 pumpage is a 900 acre-feet decrease from 1999 pumpage. The 2000 pumpage is 3,710 acre-feet under the allocation of 30,500 acre-feet established in the Santa Paula Basin Judgment. The average annual pumpage from 1980 to 2000 is 25,968 acre-feet. The pumpage varies from a high of 33,453 acre-feet in 1990 during the peak of the last drought, to a low of 16,710 acre-feet during the very wet year of 1983.
The historical reported pumpage for the Santa Paula Basin is shown in Table 3 and Figure 3. The graph shows the combined City of Ventura and Santa Paula Basin Pumpers Association base settlement allocation of 30,500 acre-feet per year. The Santa Paula Basin Pumpers Association is entitled to 27,500 acre-feet of this allocation. The City of Ventura is entitled to 3,000 acre-feet of this allocation.
A map of 2000 reported pumpage by well is shown in Figure 4. The amount pumped from a particular well is reflected by the size of the dot at the well location.
Table
3. Santa Paula Basin Groundwater Pumpage (as reported to United Water from 1980-2000)
Figure 3. Santa Paula Basin Reported Groundwater Pumpage From 1980-1999
New Wells and Status of Non-Pumping Wells
According to the Ventura County Water Resources Division, there was one new production well permitted and drilled in 2000 within the Santa Paula Basin. Table 4 lists wells that: 1) have had zero pumpage reported to UWCD in 2000; 2) have not been reported to UWCD in 2000; 3) have been destroyed in 2000; or, 4) have been permitted to be drilled in 2000.
Table 4. Production Well Status Summary
Wells monitored for groundwater levels in the Santa Paula Basin are shown on the map in Figure 5. There are currently 76 wells being monitored. Groundwater level monitoring is conducted by United Water Conservation District, the City of Santa Paula, Farmer’s Irrigation Company, Ventura County Water Resources, Alta Mutual Water Company, the City of Ventura and Ventura County Water Works District.
Groundwater levels are normally measured in wells that are not pumping and are accordingly called static water levels. For the purposes of evaluating the trends in long-term water levels, static groundwater levels are preferred. Static groundwater levels represent the potentiometric level of the groundwater in the absence of pumping. However, the groundwater level in a non-pumping well may be depressed due to residual drawdown in the well being monitored and/or pumping interference from a nearby well. Although it is not possible to completely eliminate all effects of pumping when measuring groundwater levels in a developed groundwater basin, monitoring conducted by UWCD is only conducted when the measured well is shut off and no nearby wells are pumping. When water level measurements are taken during the low-irrigation season during the winter and early spring, potential pumping effects in the basin are minimized.
Figures 6 through 9 show groundwater level hydrographs for wells in the Santa Paula Basin. Additional hydrographs are shown in Appendix D. These include UWCD’s SP-1 and SP-2 nested monitor well hydrographs. All of the wells for which hydrographs are shown in the report, except for the SP-1 and SP-2 nested monitor wells, make up the groundwater level index wells (see section on groundwater level index). These wells were chosen for the index because: 1) they are distributed across the basin somewhat uniformly; 2) they represent a variety of hydrogeologic conditions in the basin; and, 3) they have been monitored over a period of 18 years. Recording groundwater level fluctuations through time within the Santa Paula Basin will contribute toward the determination of the safe yield for the basin and a better understanding of the physical operation of the basin.
A groundwater level contour map for Spring 2000 is shown in Figure 10. This map reflects the shallowest groundwater level for 2000. The contours that are shown on this map represent lines of equal groundwater surface elevation. Most of the groundwater levels being contoured are from wells perforated at depths greater than 100 feet. The exceptions include the shallow monitor wells located in the southern Santa Paula Basin near the Freeman Diversion. The perforation interval being contoured at UWCD’s clustered monitor well sites SP-1 and SP-2 are 260 feet to 280 feet, and 150 feet to 170 feet, respectively.
Figure 6. Historical Groundwater Surface Elevations at Well 3N/21W-12E4
Figure 7. Historical Groundwater Surface Elevations at Well 3N/21W-16K1
A groundwater level index was established for the set of ten wells shown on the location map in Figure 11. Ten wells were chosen to minimize the influence of any single well. These ten wells were chosen because: 1) they are distributed somewhat uniformly across the basin (Figure 11); 2) they represent a variety of hydrogeologic conditions in the basin; and, 3) they have been monitored over the period of 18 years from 1983 to 2000. The shallowest measured groundwater level in each well during the period of February through April was used in computing the groundwater level index. These ten maximum levels were averaged each year to derive the groundwater level index. The results of this average can be seen in Figure 12. The year 1983 was chosen for the first year of the index because all 10 index wells have data as far back as 1983. In addition, the cumulative departure from the average precipitation curve shows that this was the last year of the wet cycle before the dry cycle commenced.
The groundwater level index declined from the wet cycle in 1983 to the drought year of 1991 by 23.4 feet. By 1998 the groundwater level index recovered 20.4 feet of that decline, but remained 3.0 feet below the 1983 level. In 1999 and 2000, the index declined an additional 4.2 feet and 4.7 feet respectively, for a total of 11.9 feet below the 1983 level. It is important to note that the groundwater level index is for the entire basin. Individual hydrographs show that by 1995 the basin had nearly recovered from the drought except for a small area located in the far west basin. Individual hydrographs are shown in Figures 6 through 9, and Figures D-1 through D-6 in Appendix D.
UWCD has implemented a more intensive groundwater level monitoring program for Santa Paula Basin. In 1998 UWCD began measuring index well groundwater levels on a monthly basis. This monitoring is combined with UWCD’s bimonthly and semi-annual groundwater level monitoring.
Figure 12. Groundwater Level Index for Santa Paula Basin
(high groundwater level during February through April of each year for each of 10 wells, averaged among the 10 wells)
Surface Water Quality Monitoring
UWCD conducts quarterly general mineral sampling at Santa Clara River at Willard Road; April and October at Harvard Boulevard; April and October general mineral sampling, and January and June abbreviated general mineral sampling at Todd Barranca near the Freeman Diversion; and quarterly general mineral sampling and bimonthly abbreviated general mineral sampling on the Santa Clara River at the Freeman Diversion. Table 5 compares volume weighted average concentrations of the Santa Clara River at the Freeman Diversion with Regional Water Quality Control Board (RWQCB) groundwater basin objectives and California Department of Health Services (DHS) primary and secondary drinking water standards.
For the water year 2000, the volume weighted average sulfate, chloride, nitrate and TDS concentrations associated with the Santa Clara River are close to the long-term average. The UWCD report, “Water Quality of the Santa Clara River and the Montalvo and Oxnard Plain Groundwater Basins, October, 1996”, identified a strong correlation between low flows in the Santa Clara River and increased concentrations of sulfate, chloride and TDS. The 2000 concentrations of TDS, sulfate, chloride and nitrate are less than the RWQCB’s objectives for the basin.
Table
5. Santa Paula Basin Surface Water Quality
Groundwater Quality Monitoring
Groundwater quality data from wells 2N/22W-2K7, 3N/21W-19G4, 3N/21W-11F3 and 3N/21W-16K1 were selected for groundwater quality time-series. The locations of these wells are shown in Figure 13. The wells were selected based on geographic location, a long history of record, and current monitoring. Groundwater quality time-series are shown for sulfate, chloride, nitrate, and total dissolved solids (TDS) in Figures 14 through 17.
Groundwater quality for sulfate, chloride, nitrate and TDS are plotted for the calendar year 2000 in Figures 18 through 21. The concentrations shown are the maximum and minimum values available in the UWCD water quality database for this year.
Well 3N/21W-11F3 within the City of Santa Paula has a maximum nitrate concentration above 45 mg/L in 2000. The nitrate concentrations in this well have been quite variable. Nitrate concentrations have exceeded the 45 mg/L drinking water standard in well 3N/21W-11F3 frequently since 1964. The high nitrate concentration seen in this well is not believed to be typical of the basin.
Figure 14. Historical Sulfate
Concentrations in Santa Paula Basin Groundwater
Figure 15. Historical Chloride Concentrations in
Santa Paula Basin Groundwater
Figure 16. Historical Nitrate Concentrations in
Santa Paula Basin Groundwater
Figure 17. Historical TDS Concentrations in Santa
Paula Basin Groundwater
LONG TERM GROUNDWATER TRENDS, AND 1999 DATA ANALYSIS
The groundwater level index plotted wit the cumulative departure from average precipitation is shown in Figure 22. There is a correlation between the groundwater level index curve and the cumulative departure from average precipitation curve. The cumulative departure from average precipitation curve shows that from 1983 to 1995 there is a zero departure from the average. This tells us that the Santa Paula Basin has been through one complete dry-wet cycle during this period. The groundwater level index shows that groundwater levels did not fully recover in 1995 to the groundwater levels seen in 1983. The groundwater level index, however, is for the entire Santa Paula Basin. Individual hydrographs show that groundwater levels for the basin nearly recovered in 1995 except for a few wells in the far west basin. The groundwater level recovery that we see can be attributed to the 145% of normal rainfall the Santa Paula Basin has experienced from 1991 to 1998. The Santa Paula Basin groundwater level index for the water year 2000, a below average rainfall year, was down 4.7 feet from the groundwater level index for the water year 1999, which was also a below average rainfall year.
United Water Conservation District vs. City of San Buenaventura, March 7, 1996, Judgment, Superior Court of the State of California, Case No. 115611.
United Water Conservation District, October 1996, Water Quality of the Santa Clara River and the Montalvo and Oxnard Plain Groundwater Basins. 22 pp. 1 appendix.
This table lists precipitation data from UWCD's precipitation station in Santa Paula.
APPENDIX C. GROUNDWATER ALLOCATIONS AND PUMPAGE
Table 1. Party or Nonparty listed in Judgment
Table 2. Pumpers not listed in
Judgment
Appendix D. Groundwater Elevation hydrographs
Figure D-1. Historical Groundwater Surface Elevations at Well 3N/21W-15C4
Figure D-2. Historical Groundwater Surface Elevations at Well 3N/21W-17Q1
Figure D-3. Historical
Groundwater Surface Elevations at Well 3N/21W-30F1
Figure D-4. Historical Groundwater Surface Elevations at Well 2N/22W-2C1
Figure D-5. Historical Groundwater Surface Elevations at Well 3N/22W-34R2
Figure D-6. Historical Groundwater Surface Elevations at Well 2N/22W-3M2
Figure D-7. Historical Groundwater Surface Elevations at Wells 3N/21W-15G1 through 15G5
Figure D-8. Historical Groundwater Surface Elevations at Wells 3N/21W-16H5 through
16H8
These are review comments on the 2000 draft report
from the City of Ventura and consultants for Santa Paula Basin Pumpers Association,
exactly as they were received by UWCD. Also included are UWCD's responses to
these comments.
Santa Paula Basin 1999 Annual Report.
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