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10 , <br /> An analysis of drainage patterns and landforms using a combination of topographic maps, <br /> geologic maps,and site visits will be made to identify and map suspected fracture traces. Aerial <br /> photographs,perhaps in combination with satellite imagery,will be analyzed for photo <br /> lineaments that may indicate large-scale(regional)fracture systems. Any photo lineaments not <br /> related to cultural features will be included on the fracture-trace map. Possible correlations <br /> between well yields,the distribution of well yields,and fracture traces or lineaments will be <br /> evaluated by mapping wells and interpreted fractures,and evaluating the spatial relation between <br /> these features. <br /> 2. Estimate the total amount of ground water available: <br /> Available ground water consists of two components,drainable storage and recharge. By <br /> measuring the depth to the water table at sampling wells and accounting for aquifer <br /> characteristics such as rock type,porosity,and specific yield,it is possible to estimate the total <br /> amount of ground water in storage and the quantity available horn storage. <br /> Long-team availability of ground water also depends on the rate of recharge to the aquifer, <br /> which is determined by the type of rock forming the aquifer,amount of rainfall,soil type,land <br /> use and vegetation,land surface slope,and depth to the water table. The USGS pilot study <br /> (completed for the County in 1996)provides the recharge rates and areas for the major watershed <br /> areas of Orange County. This information will be integrated into analysis of long-term <br /> availability. <br /> Using data on ground-water storage and recharge in the County,the safe yield—the amount of <br /> water that can be withdrawn without causing long-term water-table decline--will be estimated for <br /> major aquifers/hydrogeologic units. The evaluation is to contain sufficient detail that it will <br /> enable the County to establish a base line for evaluating the effects of long-term seasonal <br /> climatic patterns,changes in land use and impervious surface on ground-water levels and aquifer <br /> storage,ground-water withdrawals,and other factors. For example,the program will be designed <br /> to mount for variations in hydrogeologic units,topography,and soil characteristics. <br /> 3. Estimate ground-water use and possible effects of increased demand: <br /> In order to ascertain the County's future water supply needs and to assess the long-term <br /> ability of ground water to mace these needs,it is necessary to evaluate the projected growth in <br /> demand for ground-water resources given various land use plans and the associated effects of <br /> population distribution. This evaluation process is to be accomplished by using water supply <br /> demand projections which are based on population projections from various sources for various <br /> land use patterns in conjunction with past water demand data and estimates of per capita <br /> consumption rates. The Orange County Planning staff will provide the necessary population <br /> projections,including Orange County,adjacent county,and State figures. The project staff will <br /> acquire and analyze available community water supply records,census-tract records,and will <br /> also employ the USGS statewide water use report to develop rural water consumption rate <br /> estimates. The County's future water supply needs and the availability of ground water will be <br /> analyzed and graphed. Different growth scenarios will be evaluated by means of a planning <br /> 6 <br />