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:::Hydrogeological Investigation Study, Groundwater Observation Net
A. Analyze Geological Information, Recommend The Structure of Groundwater Observation Wells for The Various Stations
B. Analyze The Sedimentary Environments of The Various Groundwater Regions
A. Analyze Geological Information, Recommend The Structure of Groundwater Observation Wells for The Various Stations
(1) Investigating Groundwater Recharge Areas on Pingtung Plain
Major groundwater recharge areas for the Pingtung Plain groundwater system are situated at the apexes of the alluvial fans of Laonunghsi, Ailiaohsi, Linpianhsi, and Lilihsi. Rivers A groundwater recharge area is the ground surface area at the margin of a groundwater region where surface runoffs in the forms of rainwater, river water, and irrigation water percolate down the ground and travel downward through the unsaturated zone to reach the groundwater table, and recharge the groundwater. Through researches on hydrogeological framework, groundwater flow net, distribution of sand layers on the ground surface, thickness of subsurface clay layers, depth of the groundwater table, distribution to dissolved solid particle values, and characteristics of nitrogen nitrite it was pointed out that the apexes ofo alluvial fans of the Laonunghsi, Ailiaohsi, and the Linpianhsi Rivers, as well as the Linkou Hills are the major areas of recharge for the groundwater system of the Pingtung Plain.
Under the goal of sustained management of groundwater resources, land use in areas of groundwater recharge should be placed under appropriate administration and planning, thus effectively assure that the groundwater will not be polluted.
(2) Evaluation on Parameters for Twin-Well Pumping Test on Pingtung Plain
The Pingtung Plain groundwater is recharged by rainwater, irrigation water, and river water percolation and lateral recharge by subsurface water situated at the margin of the groundwater system. Major recharge areas are situated at apexes of alluvial fans of Laonunghsi, Ailiaohsi, Lilihsi, and Linpianhsi Rivers. Observation data indicated that the groundwater showed signs of reaction, and gradually rise or fall within several days after a sufficient rainfall, the strongest reaction sign occurred at apexes of these alluvial fans. This indirectly manifested that recharging of the groundwater is strongest at the apexes of the alluvial fans. Estimating the quantity of groundwater recharge is a challenge. Analysis through the groundwater time/history curve is more direct, simple and accurate than analysis through water budgeting method. Using the groundwater table time/history curve to calculate and analyze the groundwater recharge of an area should first obtain the water yield ratio Sy of a non-pressurized groundwater layer and the coefficient water storage S of a pressurized aquifer.
In Pingtung Plain, the value of water yield ratio Sy of a non-pressurized water layer ranges from 0.71 to 0.239, with the mean around 0.17. The coefficient of water storage S for a pressurized aquifer ranges from 3.79X10-5 to 1.64X10-3 with the mean 5.14X10-4. These parameters will be used to conduct analysis on groundwater recharge using groundwater table time/history curves.

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