Groundwater in the Lost Valley Basin

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Groundwater Analysis of Lost Valley Basin Introduction The purpose of this study is to evaluate the present groundwater of the Lost Valley Basin in Southern California. The aquifer conditions such as recharge and discharge are examined to figure out the correlation between groundwater and surface water. If the relationship can be properly understood, the necessary work can be done to extend the life of the aquifer(s) present. Methods 5 wells (TH1, TH2…TH5) are place along side the stream running NW to SE, which correlated lithologies, constructed a cross section, measured depth to the water table and helped determine the location of the aquifer(s). The cross section helped to better understand the thickness, flow direction and distribution of the aquifer(s) within the mapping area. 3 river stream gages are placed in the stream in order to better understand the relationship between groundwater and surface water by giving quantities of discharge/recharge in cubic feet per second (cfs). Understanding the relationship between the groundwater and surface water gives aid for producing the potentiometric surface map which includes the gaining (effluent) and losing (influent) parts of the stream. Results Two aquifers were located, a confined and unconfined aquifer. The unconfined aquifer, or the upper aquifer, (see cross and contour map) consists of a predominately sand rich and partial gravel unit and is approximately 50 feet thick. The upper aquifer pinches out between wells TH4 and TH3 and lies within the proximity of gage 3. The confined or lower aquifer is a fine sand and fine gravel unit confined by clays that extends the entire length of the stream. Below is the measured recharge and discharge values. Discussion The recharge of the lower aquifer is predominately from the NW where the land elevation is higher and steeper (see map). At the area of

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