This paper describes the background and the development of a hydrologic network flow model. The model was development to simulate daily water demand and supply for selected stream reaches within a watershed, and used as a tool for evaluating, simulating, and planning a water resources system. The proposed network flow model considers daily runoff from subareas, various water demands, and diversion structures within each subarea. Daily streamflow at a reach is simulated after balancing the water demands from subareas. The lateral inflow from subareas is simulated using a modified tank model. Total water demands consist of the daily demands for agricultural, domestic, industrial, livestock, fishery, and environmental uses within a rural district. The return flow, diversions from sources and storage components such as reservoirs were also incorporated into the mode l . The developed model is a generalized version that may be applied to different combinations of river reaches for a given system. This may help potential users identify areas where water supply does not suffice the demands for different time horizons.

In order to obtain the basic information for the optimal settlement planning in the reclaimed area, various existing settlement conditions on reclaimed farming village were analysed through a case study of in-and-round farming villages in Deuk Ryang Reclaimed Area. By comparison study between in-and-around villages, the allocation policy of farming settlement in the samll and medium scale area was proposed. The results obtained in this study were as follows ; 1.The population structure of the inner village(Ansim village) had become worse than the around village during 1976~1981 period from the viewpoint of total and female emigration ratios. Especially, the originally unbalanced sex ratio of Ansim village had worsen to the unacceptable ratio of 1.5 : 1(male : female). Therefore, the structural stability of the population should be carefully improved in the newly reclaimed farming villages by the systematic long-term controlling machanism.2.The farming status of Ansim village was much lower than the around villages viewing of the cultivated acreage and agricultural machinery stock Therefore, the continuous and intensive governmental support different from the existing farming area should be required for the settling of reclaimed farming. 3. The regularity of the village site as a planned village, though pursed in the first phase of village construction, had been severely disturbed inflowing of squatters. Recently, there are increasing vaccant houses in the village, and the level of living amenities and personal mobility of Ansim village are much lower than the around village. So, now, the physical structure of the village should be improved to the level of village reconstruction or new village construction. 4. The cultivated area of Ansim village leans to the south side which would be unfavoured by the farmers of the around villages, while its distributing pattern should be concentric around the village site. This phenomenon disturbs the central fuction of the planned farming village. In this respect, role assignment, relationship and balance of competence in farming activities should be planned between in-and-around villages in the reclaimed area from the initial stage. 5. Putting together the above results in this study, the farming and living conditions of Ansim village threaten its existence as a planned new farming village in the reclaimed area. And, so, the full scale reconstruction of village structure, including moving to the new site, should be designed as soon as possible. Although further many studies should be carried out, it would be sure that the new village planning should be reconsidered in the small and-medium scale reclamation works.

The laboratory tests are performed on how the liquefaction potential of the sea dike structures on the saturated sand or silty sand seabed could be affected due to earthquake before and after construction results are given as follows ; 1. Earthquake damages to sea dike structures consist of lateral deformation, settlement, minor abnormality of the structures and differential settlement of embankments, etc. It is known that severe disasters due to this type of damages are not much documented. Because of its high relative cost of the preventive measures against this type of damages, the designing engineer has much freedom for the play of judgement and ingenuity in the selection of the construction methods, that is, by comparing the cost of the preventive design cost at a design stage to reconstruction cost after minor failure. 2. The factors controlling the liquefaction potential of the hydraulic fill structure are magnitude of earthquake(max. surface velocity), N-value(relative density), gradation, consistency(plastic limit), classification of soil(G & vs), ground water level, compaction method, volumetric shear stress and strain, effective confining stress, and primary consolidation. 3. The probability of liquefaction can be evaluated by the simple method based on SPT and CPT test results or the precise method based on laboratory test results. For sandy or silty sand seabed of the concerned area of this study, it is said that evaluation of liquefaction potential can be done by the one-dimensional analysis using some geotechnical parameters of soil such as Ip, Υt' gradation, N-value, OCR and classification of soils. 4. Based on above mentioned analysis, safety factor of liquefaction potential on the sea bed at the given site is Fs =0.84 when M = 5.23 or amax= 0.12g. With sea dike structures H = 42.5m and 35.5m on the same site Fs= 3.M~2.08 and Fs = 1.74~1.31 are obtained, respectively. local liquefaction can be expected at the toe of the sea dike constructed with hydraulic fill because of lack of constrained effective stress of the area.

A modified kinematic wave model of the overland flow in vegetated filter strips was developed. The model can predict both flow depth and hydraulic radius of the flow. Existing models can predict only mean flow depth. By using the hydraulic radius, erosion, deposition and flow's transport capacity can be more rationally computed. Spacing hydraulic radius was used to compute flow's hydraulic radius. Numerical solution of the model was accomplished by using both a second-order nonlinear scheme and a linear solution scheme. The nonlinear portion of the model ensures convergence and the linear portion of the model provides rapid computations. This second-order nonlinear scheme minimizes numerical computation errors that may be caused by linearization of a nonlinear model. This model can also be applied to golf courses, parks, no-till fields to route runoff and production and attenuation of many nonpoint source pollutants.

When a drought occurs in an area irrigated by multi-reservoirs, onerating a single reservoir separately to control the reservoir' storage is not a desirable solution. In order to reduce damages effectively for the areal drought, the storage of the reservoirs within the areal boundary should be managed as a group. Storage management procedures are as follows : 1. Collecting and checking the present storages of all reservoirs 2. Computing the drought frequency and depth; and finally, establishing a suitable storage saving strategy based on the estimated drought depth. For the purpose of this storage management, the RESTOMS(Reservoirs Storage Management System) was developed and the system was composed of the PRIME computer and the ORACLE as a distributed database management system, which was the host computer of Rural Development Corporation and would be on-lined with the regional offices throughout the country. Reservoirs operated by Farm Land Improvment Association were comprised in the DB system. Using the RESTOMS, the drought frequencies and drought depths were calculated with respect to the reservoir storage records(1967 to 1992). It was obvious that the results were closely corresponding to the real drought records.

A simplified physiologically-based dynamic model, SIMRIW was selected for predicting the growth and yield of rice. The applicability of the model to the rice cultivars and weather conditions in the Republic of Korea was evaluated. Parameters of the model were calibrated using actual rice yields in Suweon region and an optimization scheme, Constrained Rosenbrock Algorithm. The simulated results from the calibrated model were in good agreement with the field data. The model with parameters calibrated for Suweon was applied to other five regions for the evaluation of transferability, but the simulated results fell short of satisfaction. However, the model is found to be applied to real-time prediction of the growth and yield of rice crop, which is believed to be useful for timely rice crop management, agricultural policy making, and optimal irrigation water management.

This study was performed to evalute effects of fillers on the mixing characteristics and mechanical properties of polymer concrete. Two types of unsaturated polyester polymer and two types of epoxy resin were used as binder material, and the portland cement, a fly ash and heavy calcium carbonate were used as filler. Following conclusions were drawn from the research results. 1. Working life of polymer concrete was not affected by filler types, but affected significantly by polymer types and quantities of hardener and catalysts. 2. Without concerning polymer types, use of heavy calcuim carbonate as filler was the best in improving workability.3. The highest strength was achieved by heavy calcium carbonate in using unsaturated polyester resin and by fly ash in using epoxy resin type.4. Elastic modulus was in the range of 2.05X 10-5~2.6X 10-5gf/cm$^2$, which was approximatly 60% of that of cement concrete. Heavy calcium carbonate with unsaturated polyester resin and fly ash with epoxy resin showed relatively higher elastic modulus.

A sunday system with a horizontal bin-type composter was constructed and operated to evaluate its composting performance for four days for each test in October, 1992. A sundry system is one of popular systems for composting livestock manure, of which main benefit is to utilize unlimited, clean, and free solar radiation. A rectangular concrete bin(composter) with dimension of 300cm(length) X90cm(width) X60cm(height) was bedded alternatively with four lanes of aeration pipes and heating pipes, and was insulated at three walls with 50mm styrofoam. Each aeration pipe of a diameter of 25mm had 4mm perforated holes at every 15cm longitudinally, and supplied air of about 2m$^3$/min to the composter to maintain aerobic condition . A stirrer rotating at 1 rpm made one round trip every 20 minutes on the conveying chain along the the length of the composter. Five tests (Test 1~Test 5) were implemented to evaluate the composting effectiveness of a sundry system with a horizontal bin-type composter. Treatments of two levels of the mixture ratio of swine manure and paper sludge cakes(manure : paper sludge cakes= 1 : 4 and 1 : 2) and two levels of the water content(W/C ; 70% and 50%) were made to test the significance of the physicochemical properties for decomposition of the mixture materials. Temperature, C/N ratio, water content, microbial activity of the composting materials were taken measurements to evaluate its performance with the lapse of composting time for tests. A small-scale sundry system with a bin-type composter did not appear to be an appropriate system for composting livestock manure. Since heat generation by the composting materials could not overcome heat loss due to areation in a small-scale composter, a proper thermal enviroment could not be maintained to propagate massively thermopilic microorganism relatively in a short period of time. Different from the result of Chol et al.(1992) 6), a temperature variation of the composting materials did not show the peak clearly and C/N ratio didn't lower with time as expected. Mesophilic microoragnism seemed to play an important role for decomposition of the mixture materials. A sundry system with a bin-type composter may be good for a large-scale livestock farm household which may produce enough animal manure. Therefore a decision should be made very carefully to choose a system for composting livestock waste.

The objectives of this paper were to develop predictive equations for reservoir deposits and watershed sediment yields based on sediment survey data for irrigation reservoirs. Hundred reservoirs of various sizes, which have the surveyed data for sediment deposits, were chosen and fourteen watershed physiological and hydrological parameters were investigated. Correlationships between watershed parameters and sediment deposits were investigated and a best fit regression equation was derived, which may be applied for estimating reservoir sediment deposits. The sediment deposits were converted to the watershed sediment yields by applying the trap efficiencies and specific weights. The resulting sediment yields were related to watershed parameters and an empirical predictive equation was also proposed that may be used for rough estimations of watershed sediment yields.