• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.253-257
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• 2007

Channel-aquifer interaction is one of the key hydrological processes that determine water flows in the stream/river channel. Field measurements of channel-aquifer interaction, however, is very difficult and costly, particularly when one intends to understand its variations across a catchment for a long period. Hydrological simulations using a catchment model are a relatively easier and cheaper alternative provided the model structure is appropriate for describing channel-aquifer interaction. In this study, a catchment model called CAMEL (Chemicals from Agricultural Management and Erosion Losses) is used for estimating channel-aquifer interaction over time and space. CAMEL is a distributed catchment model to simulate transformation and transport processes of sediment and pollutants as well as water flows at the catchment scale. In the model, a catchment is represented using a network of square columns each of which is comprised of various storages of water. CAMEL explicitly simulates both surface and subsurface processes including channel-aquifer interaction. This paper presents an application study results of CAMEL for the Tarland Burn Catchment, a small (catchment area $52\;km^2$) rural catchment in Scotland, UK, demonstrating some of the channel-aquifer interaction dynamics across the catchment during a 2-year period.

• Journal of Soil and Groundwater Environment
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• v.21 no.1
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• pp.61-71
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• 2016

Visual MODFLOW was used for quantifying stream-aquifer interactions caused by seasonal groundwater pumping. A hypothetical conceptual model was assumed to represent a stream-aquifer system commonly found in Korea. The model considered a two-layered aquifer with the upper alluvium and the lower bedrock and a stream showing seasonal water level fluctuations. Our results show that seasonal variation of the stream depletion rate (SDR) as well as the groundwater depletion depends on the stream depletion factor (SDF), which is determined by aquifer parameters and the distance from the pumping well to the stream. For pumping wells with large SDF, groundwater was considerably depleted for a long time of years and the streamflow decreased throughout the whole year. The impacts of return flow were also examined by recalculating SDR with an assumed ratio of immediate irrigation return flow to the stream. Return flow over 50% of pumping rate could increase the streamflow during the period of seasonal pumping. The model also showed that SDR was affected by both the conductance between the aquifer and the stream bed and screen depths of the pumping well. Our results can be used for preliminary assessment of water budget analysis aimed to plan an integrated management of water resources in riparian areas threatened by heavy pumping.

• Journal of Soil and Groundwater Environment
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• v.18 no.5
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• pp.65-76
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• 2013

The water-table fluctuation (WTF) method has been often used for estimating groundwater recharge by analysis of waterlevel measurements in observation wells. An important assumption inherent in the method is that the water level rise is solely caused by precipitation recharge. For the observation wells located near a stream, however, the water-level can be highly affected by the stream level fluctuations as well as precipitation recharge. Therefore, in applying the WTF method, there should be consideration regarding the effect of stream-aquifer interactions. Analysis of water-level hydrographs from the National Groundwater Monitoring Wells of Korea showed that they could be classified into three different types depending on their responses to either precipitation recharge or stream level fluctuations. A simple groundwater flow model was used to analyze the errors of the WTF method, which were associated with stream-aquifer interactions. Not surprisingly, the model showed that the WTF method could greatly overestimate recharge, when it was used for the observation wells of which the water-level was affected by streams. Therefore, in Korea, where most groundwater hydrographs are acquired from wells nearby a stream, more caution is demanded in applying the WTF method.

• Journal of Korea Water Resources Association
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• v.31 no.2
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• pp.177-187
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• 1998

The spatially integrated model (SIM) which can evaluate temporal variation of groundwater quality is proposed in the stream-aquifer setting entered by nonpoint source contaminants. And the developed SIM included unsaturated soil zone and was tested against the spatially distributed model (SDM) of the coupled advection-dispersion and Richards equations for the various hydrologic and aquifer simulating conditions. The result of the comparison showed that the average concentration responses of saturated aquifer and groundwater outflow between the SIM and the SDM was in good agreement, except for the case of the large dispersivity ratio and thick aquifer system. And it is shown that for the cases of the large dispersivity ratio and thick aquifer system the performance of the nonlinear SIM is better than that of the linear SIM for evaluating the average concentration of groundwater outflow response.

• Journal of Korea Water Resources Association
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• v.43 no.10
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• pp.893-909
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• 2010

The purpose of this study is to consider the interaction between surface water and groundwater in basin scale by developing TANK_GS model. The soil moisture structure of tank model with 3 tanks is improved to simulate the appropriate stream-aquifer interactions. Maximum likelihood method is applied to calibrate parameters with variance functions to deal with heteroscedasticity of residuals. The parameters of improved TANK_GS model and variance function are simultaneously estimated by Simulated Annealing method, a global optimization technique. The results of TANK-GE are compared to those of the SWMM-GE model which had been developed to consider the stream-aquifer interactions. The new TANK_GS model and SWMM-GE model are applied to Gapcheon basin, which belongs to Geum River basin. TANK_GS model showed better model performance compared to the original TANK model and characterized the relationship of stream-aquifer interactions as satisfactorily as the SWMM-GE model. The sustainable groundwater yield can be estimated for the regional water resources planning using the TANK_GS model

• Journal of Soil and Groundwater Environment
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• v.9 no.4
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• pp.32-41
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• 2004

Analysis of water-level fluctuation due to goundwater-surface water interaction in coastal aquifers is carried out by numerical modeling. The conceptual model used in this study has a stream boundary and a tidal boundary that forms a right angle and the stream partially penetrates the aquifer. We analyzed the effect of each boundary and the simultaneous effect of the two boundary conditions. The area of influence caused by the stream boundary increased during the simulation, while the influence zone of the coastal boundary was relatively constant. The groundwater level near the zone where two boundaries meet may rise by the action of combined effect of the two boundaries or may not change by cancelling the effect of each boundary. Thereafter, care must be taken when hydraulic parameters are estimated using sinusoidal oscillations of hydraulic head in coastal aquifers. Sensitivity analysis is employed to develop insight into the controls on groundwater level fluctuations. In this study our analyses focused on the effect of conductance and the stream width to the aquifer nearby.

• Journal of Korea Water Resources Association
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• v.45 no.10
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• pp.1051-1067
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• 2012

Increased use of water curtain facilities to keep green house warm during winter cultivation has been known to cause excessive groundwater ion which might lead to decline of groundwater level, resulting in streamflow depletion. Therefore it is required to quantitatively assess the effects of groundwater ion on the streamflow depletion such as magnitude and extent. The objective of this study is to assess the change of stream-aquifer interaction according to groundwater ion near stream. To this end, a green house cultivation land in Sooha-ri, Sindun-myun, Icheon-si, Gyonggi-do was selected as a field experimental site, and monitoring wells were established near and within stream to observe the water level and temperature changes over a long period of time. From the observed water level and temperature data, it was found that the river reach of interest changed to a losing stream pattern during the winter cultivation season due to groundwater level decline around pumping wells near the stream. The continuous exchange rates between stream and aquifer were estimated by plugging the observed water level data series into the experimental relation between head difference and exchange rate, showing the streamflow depletion by 16% of the groundwater pumping rate in Feb, 2011.

• Journal of Korea Water Resources Association
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• v.41 no.9
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• pp.919-927
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• 2008

Flow exchanges between stream and groundwater are assessed on urban streams in Daegu, Korea. Two rivers and 25 streams with the total length of 240 km run through the study area. The interaction between surface water and groundwater was estimated using Darcy's method. The study was conducted by dividing the basin into 16 smaller watersheds, and for comparison purposes. Groundwater level, surface water level, hydraulic conductivity, thickness of aquifer, and the distance between the well and the nearest stream were used for quantifying the interaction. To investigations the groundwater interaction in the watersheds, the amount of effluent seepage from groundwater to the stream, the amount of influent seepage from the stream to groundwater, and the amount of annual interaction between surface water and groundwater were computed. The total amount of effluent seepage from the groundwater to stream in the basin was approximately $72{\times}10^6m^3/year$. The total amount of influent seepage from the stream to groundwater was approximately $35{\times}10^6m^3/year$. It appeared that the total amount of annual interaction between surface water and groundwater was approximately $108{\times}10^6m^3/year$ and the total groundwater flow balance was approximately $37{\times}10^6m^3/year$. The annual amount of interaction between the surface water and groundwater was the largest in the Goryung Bridge Basin($29{\times}10^6m^3/year$) and the least in the Dalchang Dam Basin($0.2{\times}10^6m^3/year$). The results show that flow exchanges between stream and groundwater are very active and that there are significant difference among the smaller watersheds. Finally, the results indicate that it is necessary to further investigate to more precisely understand the interaction characteristics between surface water and groundwater in urban areas.

• Journal of Environmental Science International
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• v.18 no.9
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• pp.1017-1026
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• 2009

In Jeju island, the surface runoff characteristics are quite different from those of inland. Most of streams show dried characteristics by means of large portion of recharge which goes to the deep aquifer. For this reason, the accurate estimation of hydrologic components by using watershed model like SWAT is very difficult. On the other hand, the integrated SWAT-MODFLOW model is able to simulate the complex runoff structure including stream-aquifer interaction, spatial-temporal groundwater recharge and so on. The comprehensive results of Pyoseon region in Jeju island show that the amount of groundwater discharge to stream is very small, but it might be added to the discharge into the sea. Statistical analysis shows that SWAT-MODFLOW's results represent better than SWAT's. Also, SWAT-MODFLOW produces a reasonable water budget which shows a quite similar pattern of observed one. This result proves that the integrated SWAT-MODFLOW can be used as a proper tool for hydrologic analysis of entire Jeju island.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5B
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• pp.481-488
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• 2006

This paper suggests a novel approach of integrating the quasi-distributed watershed model SWAT with the fully-distributed groundwater model MODFLOW. Since the SWAT model has semi distributed features, its groundwater components hardly considers distributed parameters such as hydraulic conductivity and storage coefficient. Generating a detailed representation of groundwater recharge, head distribution and pumping rate is equally difficult. To solve these problems, the method of exchanging the characteristics of the hydrologic response units (HRUs) in SWAT with cells in MODFLOW by fully combined manner is proposed. The linkage is completed by considering the interaction between the stream network and the aquifer to reflect boundary flow. This approach is provisionally applied to Gyungancheon basin in Korea. The application demonstrates a combined model which enables an interaction between saturated zones and channel reaches. This interaction plays an essential role in the runoff generation in the Gyungancheon basin. The comprehensive results show a wide applicability of the model which represents the temporal-spatial groundwater head distribution and recharge.