DEVELOPMENT OF A PRELIMINARY GROUND-WATER FLOW MODEL FOR WATER-RESOURCES MANAGEMENT IN THE PINGTUNG PLAIN, TAIWAN

Pingtung Plain is formed by Quaternary alluvial fan material from the three main rivers: Kaoping, Tungkang and Linpien. Ground water is the major water supply source on the plain. This is principally extracted from two aquifers, The natural ground water source is derived mainly f rom direct rainfall percolation and infiltration from the three rivers , with their catchments lying partly outside the plain. Rainfall chara cteristics are therefore the main factors controlling water resources availability, Pingtung Plain is an important primary production area f or southern Taiwan, the comparatively warm climate allowing a long gro wing season, diversified cropping and the rearing of aquacultural prod uces, Approximately 75 percent of irrigation and domestic water suppli es are derived from ground water, A mater balance for the entire plain indicates that ground water resources, under optimized management, ar e sufficient to meet the existing multi-purpose uses, Development of a hydrogeological conceptual model is the first phase of a numerical gr ound water flow simulation, Preliminary results are encouraging, with the final simulations affording better insight to the hydraulic behavi or of the aquifer system, Data input requirements for model operation fall into three categories: hydrological stresses, hydrogeological par ameters and boundary conditions, After the model is built, the normal numerical modeling process requires significant calibration and sensit ivity analyses for the hydrogeological parameters and stresses which a re the most sensitive, but the least well defined, A well-calibrated s imulation model can lead to a reliable and realistic management model, With this in mind, the calibration processes detailed are presented, and these data are introduced as initial values in the calibration pro cess.