San Benito County Water District San Benito County Water District

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eduction measures at the wells it operates, by blending, demineralization, or softening of the water before pumping it into the distribution system. Hollister Urban Area Urban Water Management Plan (UWMP). In June 2005, Sunnyslope County Water Agency, along with the City of Hollister and the District, began preparing a joint Urban Water Management Plan (UWMP). The UWMP is a central document to long term water supply planning for the region. The UWMP includes detailed information on the current and future water demand and supply as well as best management practices for water conservation. The UWMP was approved by the City of Hollister and Sunnyslope in spring 2008. The UWMP is slated to be approved by the District and the County in November 2008. RECOMMENDATION FOR 2009 ANNUAL REPORT Water year 2008 was marked by substantial progress on water management, particularly urban water and wastewater issues. Specifically, the Hollister Area Water and Wastewater Master Plan and the City of Hollister Long-Term Wastewater Management Program were approved in late 2008, Sunnyslope County Water District decided in 2008 to pursue its own wastewater management plan, and the UWMP was approved. These documents provide important direction for resolution of linked water and wastewater issues in the existing urban portion of the basin. In the meantime, the cutbacks in CVP allocations and prospects for continuing drought are likely to result in increased basin-wide groundwater pumping. This will occur over the near term, including the unknown duration of the drought and the time period needed to resolve Sacramento-San Joaquin Delta issues and to increase the certainty of CVP deliveries. Despite the recent economic downturn, the near term also is likely to reveal significant development in the basin (e.g., El Rancho San Benito) with as-yet undefined but important implications for the groundwater basin. Recognizing the pending increase in reliance on groundwater basin-wide, additional focus should be placed on enhanced management of groundwater storage (pumping and replenishment) to minimize high groundwater problems, help avoid adverse groundwater level drawdown while satisfying water demand and progressing toward improved groundwater quality. Some of the new projects and programs to meet these goals already have been defined and evaluated in previous studies and planning documents, but others likely remain to be identified. The Annual Reports have regularly provided brief summaries of specific District groundwater basin management activities, including the subbasin hydrogeologic assessments and drainage/high groundwater studies. However, these summaries have not been scoped to provide a comprehensive and integrated overview of existing groundwater basin management in light of pending changes. Given the immediacy of these changes, it is recommended that the 2009 Annual Report included an expanded discussion and evaluation of the overall state of the groundwater basin (using existing reports), planned development, and current and planned management activities. These will be examined within the context of the overarching water resource management planning documents—namely the groundwater management plan and integrated regional water management plan—with the intent of coordinating groundwater management planning and actions to address future issues. Annual Groundwater Report for Water Year 2008 December 2008 San Benito County Water District 11
REPLENISHMENT OF GROUNDWATER The District operates Hernandez and Paicines reservoirs in the San Benito River watershed to store runoff and release it during the dry season to replenish groundwater. In addition, the District has percolated imported CVP water as part of its management activities. Wastewater also is recharged to groundwater from municipal and industrial wastewater treatment plants. Figure 5 highlights the stream channels and sites that have been used for percolation of local surface water and CVP water, and also shows the locations of wastewater treatment plants. Appendix D provides information for water year 2008 on the operation of Hernandez and Paicines reservoirs, storage of CVP water in San Justo Reservoir, releases of CVP water for percolation along stream channels, and percolation of municipal wastewater. Recharge of Local Surface Water. Local surface water from Hernandez and Paicines reservoirs is percolated along the San Benito River and Tres Pinos Creek. Historically, releases have been managed to limit flows to the San Benito River channel above Lucy Brown Lane in San Juan Valley with the intent of maximizing percolation in the basin. Since 1998, releases of local surface water have been limited to percolation upstream of the Cienega Bridge near Hollister. In Water Year 2008, percolation was further reduced to a negligible volume. This minimizes or eliminates potential impacts on local high-groundwater conditions and avoids competition for storage capacity with percolation from City of Hollister wastewater percolation ponds. As shown in Table D-1 of Appendix D, 2008 inflows to Hernandez Reservoir were only 10,662 af, but contributed to an increase in storage relative to 2007. Over 45 percent of inflows occurred during the wet month of January. No reservoir spills occurred. However, 7,646 af were released for downstream percolation. Reservoir releases ranged from 423 af per month in January and February to 2,814 af in August. Releases generally are greatest in August and September as storage is reduced to ensure adequate capacity for flood control before the rainy season. Over water year 2008, Hernandez Reservoir storage increased from 590 af to 2,693. The reduced storage at the beginning of the water year reflects the intentional releases in water year 2007 for maintenance purposes. The District operates Paicines Reservoir to provide off-stream storage of San Benito River water diverted for percolation in the Tres Pinos Creek channel. Paicines storage began the water year at 625 af, increased to 1,652 af, and then decreased to 300 af at the end of the water year, with 495 af released to Tres Pinos Creek for percolation, approximately 40 percent of water year 2007’s releases. Figure 6 shows the annual releases of local surface water for percolation from Hernandez and Paicines reservoirs from 1996 through 2008. Releases from Hernandez have ranged between 3,500 af/yr and 26,300 af/yr, generally reflecting variations in inflow. The 2008 Hernandez release of 7,646 af amounted to 65 percent of the average over this period, reflecting dry conditions; precipitation was 70 percent of normal. Annual Groundwater Report for Water Year 2008 December 2008 San Benito County Water District 12
Page 1: San Benito County Water District An
Page 5 and 6: TABLE OF CONTENTS EXECUTIVE SUMMARY
Page 7 and 8: EXECUTIVE SUMMARY This Annual Groun
Page 9: Zone 6 and a groundwater charge of
Page 12 and 13: SANTA CRUZ SANTA CLARA Legend DWR G
Page 14 and 15: Pacheco Valley Llagas Pajaro River
Page 16 and 17: Hollister San Juan Bautista Legend
Page 19 and 20: WATER MANAGEMENT ACTIVITIES The Dis
Page 21: disposal alternatives against a set
Page 25 and 26: 30,000 25,000 Hernandez Paicines Re
Page 27 and 28: Recharge of CVP Water. As shown in
Page 29 and 30: WATER SUPPLY SOURCES AND USE WATER
Page 31 and 32: evaporation and seepage from San Ju
Page 33 and 34: 60,000 Groundwater CVP Water 50,000
Page 35 and 36: 50,000 CVP Water Annual Water Use (
Page 37 and 38: GROUNDWATER LEVELS AND TRENDS GROUN
Page 39 and 40: 120 140 220 240 100 160 260 280 180
Page 41 and 42: 80 80 40 20 0 Legend 20-foot depth
Page 43 and 44: Table 5. Change in Storage during W
Page 45 and 46: WATER BALANCE Annual reports prepar
Page 47 and 48: Agricultural groundwater pumping is
Page 49 and 50: Table 7. Water Balance for Water Ye
Page 51 and 52: 60,000 Water Balance Element Contri
Page 53 and 54: REVENUES AND CHARGES DISTRICT REVEN
Page 55 and 56: CONDITIONS EXPECTED FOR WATER YEAR
Page 57 and 58: RECOMMENDATIONS This annual report
Page 59: CONSIDERATIONS FOR FUTURE STUDIES M
Page 62 and 63: San Benito County Water District, P
Page 65 and 66: Appendix A Reporting Requirements a
Page 67 and 68: App. 70- 7.6 70- 7.6. Groundwater;
Page 69: Appendix B Local Climate Data Annua
Page 72 and 73:
Table B-1a. Monthly Precipitation a
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4E 5E 6E Surface Water Monitoring L
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140 140 220 120 200 220 80 240 160
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Table C-3. Groundwater Elevations O
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Appendix D Managed Percolation Data
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Table D-2. Releases of CVP Water fo
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Appendix E Water Balance Methodolog
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Table E-1. Estimated parameters for
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Reservoir Releases San Benito River
Page 94 and 95:
Each of the variables and how they
Page 96 and 97:
Reclaimed Water Percolation Several
Page 98 and 99:
Legend Zones Subbasin December 2008
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Table E-4. Crop Coefficients Used i
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Table E-7. Approximate Groundwater
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Table F-1. Historical and Current S
Page 107:
Table F-3. 2006/2007 Recommended Gr
Page 111:
LIST OF ACRONYMS af ...............
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San Benito County Water District San Benito County Water District

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