View File - Development Services - City of Oxnard

WATER RESOURCES TECHNICAL REPORTThe simulated hydrologic budgets for these recharge and discharge components underpredevelopment conditions are shown in Figure 2-12. Total recharge and discharge for theSanta Clara-Calleguas Basin were 59,900 AFY. Most recharge occurred from stream flowinfiltration (67 percent), followed by mountain front and bedrock recharge (25 percent), andvalley floor recharge (8 percent). Most discharge occurred as stream base flow (44 percent),followed by coastal outflow to the ocean (31 percent), and evapotranspiration (25 percent).Groundwater DevelopmentDevelopment has led to pumpage of groundwater from thousands of water supply wellsacross the Santa Clara-Calleguas Basin, which is now the largest source of outflow from theaquifer system. This pumpage has severally lowered groundwater levels; diminishedcoastal outflow to the ocean; and, for some periods of time, reversed coastal outflow tolandward flow, which has resulted in seawater intrusion.Hydrographs are provided for select wells in the UAS and LAS across the Oxnard Plain andPleasant Valley areas to illustrate groundwater level changes during historical development.The well locations for these hydrographs are shown in Figure 2-13, and the hydrographs areprovided in Figure 2-14. The wells are grouped into two hydrographs as follows: one forwells in the Forebay and northern Oxnard Plain areas and the second for wells in thesouthern Oxnard Plain and Pleasant Valley areas.• Oxnard Plain Forebay and Northern Oxnard Plain Area−−12R01, 22M04, and 05G02: UAS wells that illustrate water levels in the northern areafrom northeast (inland) to southwest (coastal), respectively23B07 and 23B05: UAS/LAS wells used to monitor groundwater at the El Riospreading groundwater• Southern Oxnard Plain and Pleasant Valley Area−−−34D02 and 32Q04: LAS wells that illustrate water levels in the inland and coastalareas, respectively07H01 and 32Q06: UAS wells that illustrate water level in the inland and coastalareas, respectively32Q06 and 32Q4: Co-located UAS/LAS wells used to monitor groundwater in thePt. Mugu area that is degraded with chlorides from overdraft conditionsThe cumulative departure from the 114-year average precipitation is also provided inFigure 2-14 to illustrate the relationship between groundwater levels and climatic patterns,which are discussed above. In general, groundwater levels (1) increase with wetter climaticperiods representing increased recharge and reduced pumping and (2) decrease with drierclimatic periods representing decreased recharge and increased pumping. For generalinformation, hydrographs prepared by the USGS for the groundwater modeling study arealso provided in Figures 2-15, 2-16, and 2-17. These figures provide hydrographs for wellscompleted in the UAS, wells completed in the LAS, and wells completed at specific depthswithin the UAS and LAS, respectively. The correlation between groundwater levels andW112003002SCO LW1458.DOC/ 033390002 19