A water balance analysis was performed for a paddy field neighboring the Dongchang stream, downstream of the Unmun reservoir, which is constructed for the urban water supply. Daily rainfall data were collected and irrigation water flow rate, drainage flow rate, evaportranspiration, infiltration, and piezometeric head were measured in the field. The flow rates were continuously observed by water level logger during the growing season. The evaportranspiration and the infiltration were measured by N-type depletion meter and cylindrical infiltrometer, respectively. PVC pipes with 12mm diameter were used for piezometric head measurement. Total Irrigation and drainage flows were 3,608mm and 1,170mm in 1999, and 3,971mm and 1,548mm in 2000, respectively. The mean and range of the daily infiltration rate were 4.4mm/d and 3.4mm/d to 5.5mm/d in 1999 and 5.1mm/d and 4.1mm/d to 6.5mm/d in 2000, respectively. The net ground water flow including the change of soil water storage was 2,855mm in 1999 and 2,540mm in 2000. The evapotranspiration was 458.3mm in 1999 and 553.5mm in 2000. The range of daily evapotranspiration rate was from 1.6 to 8.7mm/d. The return flow ratio was about 32% in 1999 and 39% in 2000 and three year average was 35% including previous study in 1997. The amount of irrigation water was much higher than design standards or references in this study, This was caused by the inadequate water management practice in the area where water was oversupplied on farmers’ request rather than following sound water management principles.

An artificial neural network model was developed to analyze and forecast daily steamflow flow a small watershed. Error Back propagation neural networks (EBPN) of daily rainfall and runoff data were found to have a high performance in simulating stremflow. The model adopts a gradient descent method where the momentum and adaptive learning rate concepts were employed to minimize local minima value problems and speed up the convergence of EBP method. The number of hidden nodes was optimized using Bayesian information criterion. The resulting optimal EBPN model for forecasting daily streamflow consists of three rainfall and four runoff data (Model34), and the best number of the hidden nodes were found to be 13. The proposed model simulates the daily streamflow satisfactorily by comparison compared to the observed data at the HS#3 watershed of the Baran watershed project, which is 391.8 ha and has relatively steep topography and complex land use.

The daily streamflow in the Yaluhe watershed located in the north-eastern part of China was simulated by DAWAST model and the water balance parameters of the model were calibrated by simplex method. Model verification tests were carried out. The range of root mean square error was 0.34∼1.50mm, that of percent error in volume was -16.9∼-62.0% and that of correlation coefficient was 0.727∼0.920. DAWAST model was revised to consider the phreatic evaporation from the ground water in the frozen soil by adjusting soil moisture content in the unsaturated layer at the end of the melting season. The results of estimation of the daily streamflow by the revised model were statistically improved, that is, the range of root mean square error was 0.31∼1.49mm, that of percent error in volume was -11.7∼-12.1%, and that of correlation coefficient was 0.810∼0.932. The accuracy of DAWAST model was improved and the applicability of DAWAST model was expanded to the frozen region.

The basic concept of the model is to minimize the error range between forecasted flood inflow and actual flood inflow, and forecast accurately the flood discharge some hours in advance depending on the concentration time(Tc) and soil moisture retention storage(Sa). Simplex method that is a multi-level optimization technique was used to search for the determination of the best parameters of RETFLO (REal-Time FLOod forecasting) model. The flood forecasting model developed was applied to several strom event of Yedang reservoir during past 10 years. Model perfomance was very good with relative errors of 10% for comparison of total runoff volume and with one hour delayed peak time.

A pilot study was performed at the experimental field of Konkuk University in Seoul, to examine the feasibility of the constructed wetland system for sewage and the effect of treated sewage irrigation on the paddy rice culture and its soil characteristics. The constructed wetland performed well, in that effluent concentrations of pollutants were significantly lower than concentrations of the influent. Median removal efficiencies of BOD$_{5}$ was about 78% and slightly lower during winter. Removal efficiencies form TN and TP were approximately 48 and 21%, respectively, and relatively less effective than that of BOD$_{5}$. Irrigation of treated sewage to paddy rice culture did not affect adversely in both growth and yield of rice. Instead, plots of treated sewage irrigation showed up to 50% more yield in average than the control plot. It implies that treated sewage irrigation might be beneficial to rice culture rather than detrimental as long as it is treated adequately and used properly. Soil was sampled and analyzed before transplanting and after harvesting. pH was slightly increased due to irrigation water, but it may not be concerned as long as the treated sewage is within the normal range. EC was increased in first year but decreased in second year, therefore salts accumulation in the soil could be less concerned. OM and CES was slightly increased, which might be beneficial on growing plants. TN did not show apparent pattern. Available phosphorus was decreased after rice culture, but the quantity of phosphorus(TP-available phosphorus) was rather increased which implies that excessive phosphorus supply may result in phosphorus accumulation in the soil. Overall, the constructed wetland was thought to be an effective sewage treatment alternative, and treated sewage could be reused as a supplemental source of irrigation water for paddy rice culture without causing adverse effect as long as it is treated adequately and used properly. For full-scale application, further investigation should be followed on environmental risk assessment, tolerable water quality, and fraction of supplemental irrigation.ion.

This study is performed to develop an agricultural hydraulic structure for collecting and draining pipe using polymer concrete. The water permeability of collecting and draining pipe shows an 5.917$\ell$/$\textrm{cm}^2$/h, it is more 190 times as large as in the world maximum rainfall. The external pressure on the collecting and draining pipe is in the range of 1.85~5.25tf/m under 2-edge test, 2.6~6.2tf/m under sand mat and the vertical displacement is in the range of 0.48~1.06mm, 1.01~1.89mm, respectively. Also, an increasing rate of external pressure on the developed pipe is higher than that of PVC pipe to the variation of t/D. Accordingly, the pipe developed in this study will be used widely in agricultural hydraulic structures such as collecting and draining structure.

In this study, a spatial location-allocation model of center villages (SLAMCV) was developed for selecting spatial center villages and allocating their rear villages. In SLAMCV, rural space was considered as a network with villages for nodes and roads for connecting lines. For quantification of residents’ accessibilities in the network, a disutility index (DUI) was developed and used, which is dependent upon travelling distance between the center and its hinter villages, design vehicle speed in connecting road and population of hinter villages. SLAMCV was verified to Christaller’s hexagonal hierachical settlement system to test the theoretical reasonability and computing algorithm of the model.

When mixed with lime, sand-bentonite mixture is characterized by considerable hydraulic properties similar to natural pozzolans and may therefore be increased in the strength of sand-bentonite mixture. The present study reports that results obtained in a series of laboratory tests carried out using particular mixing ratio of lime-sand-bentonite with the aim of investigating physical characteristics, permeability and strength. The results were compared and analyzed according to hydration time and lime content. Test results showed that increasing of strength and decreasing of permeability by proper lime content. Curing for longer periods increased unconfined compressive strength of mixture. Based on results of the falling head permeability test, mixtures of lime content 3%, 6% and 9% were satisfied in using as liner after 8-day curing periods.

This study deals with coal-mine waste (CMW) for use in concrete as a replacement of normal aggregates. The CMW was collected from Sabuk region. Ganwon-do. Fine and coarse aggregates from CMW were prepared by using a crusher and separating debris with #4 sieve. CMW aggregates showed good physical and mechanical properties with having specific gravity over 2.65, absorption less than 1%, and abrasion ratio below 20%. However, particle shape of CMW was poor because of non-isotropic nature of matrix which cause particles to be long or flat. Since irregular particles caused a poor workability, to make workability better, a 1/4 of coarse aggregate was replaced with normal aggregate together with a superplasticizer. Compressive strength and other mechanical properties of CMW concrete were very good. Color of the concrete was darker than normal concrete due to black color of CMW. In conclusion, characteristics of CMW concrete was acceptable for use as a structural concrete material.