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Drought and landslide are two common hazards that occurred in mountainous regions of Taiwan. This study is intended to develop a new concept of hazard prevention and management for solving both hazards simultaneously, in which the complex hazard has increased over the years in intensity and frequency due to climate variability and change. The proposed concept is a win–win solution that contains the feature of efficiency to mitigate two hazards together. When pumping groundwater as daily water demand at landslide-prone sites, the pore-water pressure decreases and the thickness of the unsaturated zone increases, which can result in stabilizing landslide-prone slopes and increasing flood storage capacity as an underground detention basin, respectively. Consequently, this approach can reduce the risk induced by the two hazards. To reinforce the effectiveness and instantaneity of hazard management, the technologies of smart sensing, smart transmission, and smart computing are then incorporated into a novel framework to develop an intelligent hazard prevention and management system. Thus, the groundwater supply-slope stability management system was installed and tested in the remote Kaoshi tribe, which is situated in Kaoshi Village of Mudan Township, Pingtung County, southern Taiwan. Hydrogeological issues for subsurface complexity, field investigations, and numerical modelling for preliminary evaluation and system design are also highlighted in this study. The developed system, which can offer valuable support for decision-making processes of hazard prevention, is capable of monitoring dynamic signals from various in-situ sensors, helping water resource allocations, and stabilizing hill slopes by means of drainage.

On the assessment of groundwater potentiality in aquifers, a better understanding of the recharge patterns and flow pathways at the deeper depth is required but remains difficult. By studying the long-term temperature-depth variation data derived from using fiber-Bragg-grating (FBG) sensors, the objective of the present research is to discuss and demonstrate how this technique can provide information on the groundwater flow dynamics in a multilayered fractured formation. A series of borehole geophysical tests were first conducted to enable the characterization of the geological features and the presence of fracture flow. An array of 12 FBG sensors is deployed at multiple predetermined screening depths after well construction has completed, and the temperature-depth (T-z) trend line was established by fitting a polynomial curve to all the data points. The obtained temperature gradients in the upper depth of 5–80 m were found to be convex upward from January to April, uniform from May to July, and concave upward from August to December, which reveals a trend that the subsurface flow pattern actually varied throughout the year. In other words, groundwater recharge is not always a continuous steady‐state process, a significant time delay between rainfall and its substantial contribution to the aquifer as a form of deep groundwater recharge may take place and needs to be systematically investigated.

This paper presents an improved borehole prospecting methodology based on a combination of techniques in the hydrogeological characterization of fractured rock aquifers. The approach is demonstrated by on-site tests carried out in the Hoshe Experimental Forest site and the Tailuge National Park, Taiwan. Borehole televiewer logs are used to obtain fracture location and distribution along boreholes. The heat-pulse flow meter log is used to measure vertical velocity flow profiles which can be analyzed to estimate fracture transmissivity and to indicate hydraulic connectivity between fractures. Double-packer hydraulic tests are performed to determine the rock mass transmissivity. The computer program FLASH is used to analyze the data from the flowmeter logs. The FLASH program is confirmed as a useful tool which quantitatively predicts the fracture transmissivity in comparison to the hydraulic properties obtained from packer tests. The location of conductive fractures and their transmissivity is identified, after which the preferential flow paths through the fracture network are precisely delineated from a cross-borehole test. The results provide robust confirmation of the use of combined flowmeter and packer methods in the characterization of fractured-rock aquifers, particularly in reference to the investigation of groundwater resource and contaminant transport dynamics.

Drawing from the lessons learnt from the Fukushima nuclear disaster in Japan, the assessment of subsurface environmental hazard around nuclear power plants has emerged as a critical task. Consequently, aiming to better understand the possible environmental impact of radiation leaks into the groundwater, a prescreening programme was initiated in 2011 by the Taiwanese government. As part of this programme, this study conducted various borehole prospecting techniques to identify in situ hydrogeological characteristics at Chin-Shan Nuclear Power Plant. Borehole electrical log, sonic log and temperature/conductivity log were conducted to explain the regional lithologic conditions and permeability of the formation. In conjunction with this, the interwell tracer and pumping test was carried out to simultaneously determine the hydraulic parameters. In our opinion, the implementation of such in situ end-to-end investigations is essential in interpreting in situ fluid and solute transport dynamics prior to programming any numerical scheme for early warning, vulnerability assessment and regular monitoring of a nuclear power plant site.

Groundwater and river-water have a different composition and interact in and below the riverbed. The riverbed-aquifer flux interactions have received growing interest because of their role in the exchange and transformation of nutrients and pollutants between rivers and the aquifer. In this research our main purpose is to identify the physical processes and characteristics needed for a numerical transport model, which includes the unsaturated recharge zone, the aquifer and the riverbed. In order to investigate such lateral groundwater inflow process, a laboratory J-shaped column experiment was designed. This study determined the transport parameters of the J-shaped column by fitting an analytical solution of the convective-dispersion equation for every flux on individual segments to the observed breakthrough curves of the resident concentration, and by inverse modelling for every flux simultaneously over the entire flow domain. The obtained transport-parameter relation was tested by numerical simulation using HYDRUS 2-D/3-D. Four steady-state flux conditions (i.e. 0.5 cm hr−1, 1 cm hr−1, 1.5 cm hr−1 and 2 cm hr−1) were applied, transport parameters including pore water velocity and dispersivity were determined for both unsaturated and saturated sections along the column. Results showed that under saturated conditions the dispersivity was fairly constant and independent of the flux. In contrast, dispersivity under unsaturated conditions was flux dependent and increased at lower flux. For our porous medium the dispersion coefficient related best to the quotient of the pore water velocity divided by the water content. A simulation model of riverbed-aquifer flux interaction should take this into account.

Land subsidence basically is the deprivation of water and earth resources, further inducing social and economical undesirable impact. The principal direction of land subsidence prevention is properly management of groundwater. However groundwater management should be developed on the basis of combined technical, economical, social and institutional approaches to management that reflect local conditions and can be adapted and evolved. Therefore, the aim of this paper is to make land subsidence prevention strategies for government to refer. Before year 1969, agriculture was the main land utilization business in Pingtung Plain. Due to intensive development of fish breeding after 1970’s, the aquaculture area along the estuary region of Pingtung Plain have been dramatically increased. Groundwater thus became the main fresh water resource for aquacultural water diluting and flushing because of the insufficiency in surface water supply. The uncontrolled development of groundwater resources has led to undesirable effects, especially in the south where aquaculture is concentrated. These effects are land subsidence, saline water intrusion, lowering of water tables and reductions in well yields. Government stressed on the improvement of breeding technology in the past, which mainly focused on the water quality control in order to raise the culture density, however, it neglected the impact to the environment and quantity control. This paper promotes a reasonable aquacultural water consumption policy aims at finding out the most suitable breeding species considering water consumption and its reasonable breeding area under the premise that it will not depress the original profit of aquatic products trading.