The Tao Yuan Irrigation Association service area covers the entire Tao Yuan county and parts of the Taipei and Hsin Chu counties with a total irrigation area of approximate 26,000 hectares. The water supplied from effective rainfall and delivered from Shin Men Dam via rivers and Tao Yuan canals are the sources of irrigation water in this area. The surface water was sufficient for irrigation needs in the past when the water demand was relative low. However, due to the shortage of water resources and the increases in water demand in the entire Taiwan island, the effective utilization of surface water and the use of groundwater as the major substitute for surface water in the dry seasons become the major directions in water resource management now and in the foreseeable future. In this research, the distribution of the potential groundwater resources in the Tao Yuan Irrigation Association service area is investigated. The local hydrogeological profiles for the subsurface area are first established so that the interrelationship between aquifers and aquitards, the variation of the groundwater table, and the direction of the groundwater flow are determined. Then the major groundwater recharge areas, the means for groundwater recharge, and the potential quantities of groundwater recharge are delineated and estimated. Based on the results from the investigation described above, the quantity of groundwater storage (deposit) and the safe yield are suggested. Additionally, the conservation guides for land utilization in the groundwater recharge zone are also suggested to achieve the protection of groundwater quality and the goal of sustainable utilization of groundwater resources.The detail tasks of this project are as follows;(1)Establishment of the hydrogeological profiles: a.Data collection from governmental agencies. b.Examination of the distribution of the stratigraphic profiles. c.Analyses of the distribution of the hydrogeological profiles. (2)Areal groundwater flow analyses: a.Data collection from observation records of groundwater levels. b.Establishment of the potential contours. c.Analysis of the direction of groundwater flows. d.Calculation of the velocities of groundwater flows. (3)Evaluation of the recharge zonesa.Site selection of the recharge zones. b.Analysis of the current land utilization. c.Recharge zone conservation. (4)Estimation of groundwater capacity. a.Estimation of potential quantities of groundwater capacity. b.Estimation of the safe yield of groundwater.c.Comparison of the surface water and groundwater resources. The annual infiltrations from paddy fields and ponds in the Tao Yuan Irrigation Association service area are 0.08 billion tons and 0.087 billion tons, respectively. The total annual infiltration is 0.167 billion tons. The effect groundwater recharge in this region than can be calculated as 0.139 billion tons per year based on the assumption of a ratio of 5:1 between vertical and lateral infiltrations. Besides, the total capacity of groundwater storage is approximately 2.9 billion tons.
