Are Groundwater Monitoring Networks Economical? Cost-Benefit Analysis on the Long-Term Groundwater Supply Project of South Korea

Analyses of the relative economic efficiencies of surface-water and groundwater are important for policy-makers in many water-stressed countries. Groundwater is becoming an increasingly attractive and viable option as a supplementary water source, but its economic background must be understood before implementation. Employing the basic frameworks of the British and US Geological Surveys, we examined the economic viability of groundwater monitoring networks in South Korea, based on an analytic hierarchy process (AHP), pairwise comparison, and cost–benefit analysis. The total cost including installation, maintenance and servicing over the next 50 years is estimated to be US$0.79 billion, while the benefits are valued at US$ 2.31 billion. The monitoring network should provide benefits worth 292% of the costs, with the monitoring project thus clearly being economically viable. A sensitivity analysis indicates that the monitoring project is still economical, even if the network installation schedule is delayed slightly. As this study combines both economic and scientific perspectives, it might provide a concrete economic background for implementing groundwater utilization projects elsewhere

Effects of Hybrid-Type Artificial Groundwater Recharge and Underground Barrier in a Small Basin

Climate change is exacerbating water shortages in upstream basins in the Korean peninsula that lack agricultural water supply systems. The basin investigated in this study requires an extra 208 m3·d−1 of agricultural water during May (the busiest month for agriculture). The purpose of this study was to assess a hybrid-artificial recharge and circulation system, which was composed of a hybrid-recharge source and re-infiltration of pumped water in the field, and to estimate yield capacity by a field injection test and a numerical model. Injecting pretreated stream water for 42 d increased groundwater levels in the recharge basin. Water budget analysis in MODFLOW simulations revealed that injecting water increased groundwater levels as well as stream discharge due to the terrain’s gentle slope. To prevent downstream discharge and maintain groundwater levels after injection, we assumed the installation of an underground barrier at the basin outlet in the model, following which changes in groundwater levels and water balance were simulated. Water level was persistently maintained after a ~31-cm water level rise, and 590 m3·d−1 of water could be supplied from the collector well, which can ease water shortages. Therefore, it is necessary to develop structures to prevent recharged water escape when artificially recharging groundwater in small upstream basins. In upstream areas where reservoirs or water supply conduits are unfeasible, artificial recharge systems could solve water shortages

Evaluation of Seasonal Groundwater Quality Changes Associated with Groundwater Pumping and Level Fluctuations in an Agricultural Area, Korea

This study was conducted to evaluate seasonal groundwater quality due to groundwater pumping and hydrochemical characteristics with groundwater level fluctuations in an agricultural area in Korea. Groundwater levels were observed for about one year using automatic monitoring sensors, and groundwater uses were estimated based on the monitoring data. Groundwater use in the area is closely related to irrigation for rice farming, and rising groundwater levels occur during the pumping, which may be caused by the irrigation water of rice paddies. Hydrochemical analysis results for two separate times (17 July and 1 October 2019) show that the dissolved components in groundwater decreased overall due to dilution, especially at wells in the alluvial aquifer and shallow depth. More than 50% of the samples were classified as CaHCO3 water type, and changes in water type occurred depending on the well location. Water quality changes were small at most wells, but changes at some wells were evident. In addition, the groundwater quality was confirmed to have the effect of saltwater supplied during the 2018 drought by comparison with seawater. According to principal component analysis (PCA), the water quality from July to October was confirmed to have changed due to dilution, and the effect was strong at shallow wells. In the study areas where rice paddy farming is active in summer, irrigation water may be one of the important factors changing the groundwater quality. These results provide a qualitative and quantitative basis for groundwater quality change in agricultural areas, particularly rice paddies areas, along with groundwater level and usage