Artificial recharge is a practical tool available for increasing the groundwater storage capacity. The efficiency of artificial recharge is related to various hydrogeological factors of the target area. In this study, a variable saturated groundwater flow model, FEM-WATER, was used to evaluate the arrival times of recharged water that infiltrates from an artificial recharge pond to the groundwater table under various hydrogeological conditions. Forty-five arrival times were generated by FEMWATER. The relationships between the arrival times and hydrogeological factors used in the simulation of FEMWATER were analyzed by the grey correlation method. The results show the order of importance of the factors as they influence the arrival time. In order from high to low importance, they are a, D g , h e , D p , K S and b. D g and D p are interpreted as the potential for movement of the recharge water; h e is the water storage capacity of soil, and K S represents the ability of soil to transport water. a and b describe the characteristic curve of the unsaturated soil. The method was applied to evaluate a suitable site for artificial recharge in the Yun-Lin area. Grey correlation analysis was performed to obtain the grey correlation grade using the minimum arrival time as a reference sequence. An index is proposed herein to determine the recharge efficiency of 20 sampling sites. A contour mapping of index values at the 20 sampling sites identified three areas for artificial aquifer recharge in Yun-Lin. Area A in the upper plain is considered more appropriate for groundwater recharge than areas B and C in the coast.
Effectively managing groundwater relies heavily on estimating the amount of precipitation that may infiltrate the subsurface and supply groundwater. In this study, we present a novel estimation method based on a stochastic approach to evaluate the quantity of precipitation that may recharge groundwater. The precipitation recharge coefficient is also investigated based on an unconfined aquifer with an unbound, infinitely extended boundary condition. Moreover, a spectrum's relationship to the precipitation and groundwater level variation is also derived. The precipitation recharge coefficient can be obtained from the solution of the spectrum equation. Furthermore, sensitivity analysis is performed in order to determine the key variable on the precipitation recharge coefficient. Analysis results indicate that the location of an observation well affects the estimated precipitation recharge coefficient. If the precipitation recharge area is large enough, the precipitation recharge coefficient becomes insensitive to the location of the observation well. The spectrum's relationship between the precipitation recharge and groundwater level variation is also applied when estimating the precipitation recharge coefficient upstream of the Cho‐Shui River alluvial fan. According to those results, the precipitation recharge coefficient is 0·03 and the amount of groundwater recharge from precipitation is 35 million tons of water annually upstream of the Cho‐Shui River alluvial fan. Copyright © 2000 John Wiley & Sons, Ltd.
Abstract:The largest and most disastrous earthquake in Taiwan (Mw: 7Ð3) in the 20th century, the Chi-Chi earthquake, hit central Taiwan at 01 : 47 local time on September 21, 1999. The groundwater level changes were rapid at that time. Studies have found that the rapid change in groundwater levels was a co-seismic phenomenon. This work analyzes the possibility that the abnormal change in groundwater levels may have occurred before the earthquake. Three well stations with a total of five wells are considered. They are all near the Che-Lung-Pu fault, which caused the Chi-Chi earthquake. The time series decomposition method was applied to decompose the seasonal groundwater level, the trend in groundwater levels, and the period of the change in the groundwater level. Residual groundwater levels were found by subtracting the determined seasonal, trend and period data from corresponding data for the original groundwater level. The computed residual water levels in July, August and September of 1999, were transformed into a frequency spectrum by a Fourier method. Additionally, the effects of barometric pressures on the groundwater level changes were also evaluated. Analytical results show that the spectral density functions of the irregular groundwater level in the confined aquifer at the Chu-Shan well in September behaved differently from those in July and August. We posit that a pre-seismic hydrogeological anomaly may have existed before the Chi-Chi earthquake, and can be considered in future studies of anomalies associated with earthquakes.
Analyses of environmental xenobiotic pollutants, such as polycyclic aromatic hydrocarbons (PAHs), were an important worldwide issue because of their detrimental effects on aquatic biota. In this study, we had investigated the distribution, origin and toxicity of PAHs in the Donggang watershed sediments in southwestern Taiwan. The study results showed that the sixteen representative PAHs were detected in all collected samples with concentrations ranging from 23 to 2534 ngg(-1) dw. The highest concentration was detected in the downstream end at near the estuarine portion of the river. The mean ± standard deviation and median of ΣPAH concentrations were 528.5 ± 72.3 and 156 ngg(-1) of dry matrix in collected samples. The highest and lowest concentrations of Σ16 PAHs samples differed significantly (p < 0.05) and naphthalene, phenanthrene, fluoranthene and pyrene were detected in all sediment samples. The random variations between sampling sites were consistent with watershed land use. The present study showed that the ratios of phenanthrene/anthracene (Phe/Ant) and fluoranthane/pyrene (FLu/Pyr) in samples suggested that PAHs sources exhibited mixed pattern of petrogenic and pyrolytic inputs. The PAHs with high molecular weight (5-6 ring) accounted for 95.5% of total-BaPeq while the low molecular weight PAHs (2-3 ring) only appeared 0.20%. There was a high correlation (R(2)= 0.967) between mean concentrations and the BaPeq of the PAHs within the sediments. In summary, the adverse biological effect was low according to the effects-range-low (ERL) values of the Sediment Quality Guidelines (SQGs) in sediments from Donggang river and its tributaries in Taiwan.
This work presents a novel mathematical model to evaluate the effect of pumped well bore mixing volume on formation decontamination. The model equation is solved by the Laplace transform finite difference method. The developed model is applied to assess the effect of well bore mixing volume on contaminant remediation. The simulated results indicated that the well bore volume effect is pronounced for initial plumes with a small maximum contaminated radius, and in media such as bedrock formation where aquifer porosity and longitudinal dispersivity are small. In such systems, the pumped well bore mixing effect reduces the early contaminant concentrations, shifts the peak breakthrough curves to the right and spreading the breakthrough curve, and thus increases the decontamination time. If such a system does not account for pumped well mixing bore effect, estimates of decontamination time required to the regulatory level will be inaccurate.
In this study, we use canonical correlation analysis to interpret the relationship between water quality parameters (T, Alk, Cl, EC, TN, TP, UV-254, pH, HPC, DO) and primary productivity parameters (algae and chlorophyll-a). In these two sets of constructed canonical variables, the water quality parameters can account for 39.25% of the total variance of primary productivity. The majority of the explanatory power is from the first set of canonical variables, which has a correlation coefficient of 0.84. The main factors that control chlorophyll-a are HPC, Alk, T, TN, and pH.
This paper investigated whether differences exist in the surface water quality when the wetland was under the management of different organizations through factor analysis. Factor scores suggest that overall there is a regular reduction of nutrient sources BOD, COD, TKN, TN, NH3-N, NO2-N and fecal pollution in this wetland. The nutrient content is the highest at the water inlet and gradually decreases over densely planted zone I, the open water zone, densely planted zone II and the discharge orifice, reaching the minimum level at the outlet. The influence factors of suspended solids TB and SS exhibit irregular variation in the different water bodies. Cluster analysis is conducted based on water quality using data collected between 2008 and 2012. Results reveal that regardless of wet or dry seasons, similar water quality is observed in the open water zone and densely planted zone II. Water quality at the inlet resembles that in densely planted zone I.
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