This study was conducted to seek the effective water management method of the irrigation reservoirs. Joongpyong reservoir was selected for the hydrologic monitoring, and investigated from May in 1999 to December in 2001. The water level and amount of outlet discharge were measured, the stage discharge equation as a rating curve was induced, and which were compared to the irrigation water requirements calculated by a daily simulation model. The water balance of Joongpyong reservoir was analyzed, mainly on the reservoir storage ratio during irrigation period. Comparing the observed storage and simulation data, the results of the simulation were well agreed with the measured data.

The PTDRT model as prediction techniques for desalinization in reclaimed tidelands was developed and verified whether it is applicable to reclaimed tidelands at the beginning stage. The changes of salt concentration during desalinization, the water requirements and period required for desalinization, were simulated according to soil properties and desalinization methods by repression analyses. The program was also designed to systematize input data and analysis data associated with desalinization, and to confirm the results by a graphic form. All input data and the results can be printed after the form of a typical report.

In order to plan the effective irrigation project in unripened reclaimed paddy fields, the estimation of criteria of irrigation water requirements for the normal growth of crops is very important. This study was carried out to determine the leaching requirements before cultivating crops, the consumptive use of water by the growth of crops, and preventive water requirements of resalinization during the growth period in unripened reclaimed paddy fields. The irrigation water requirements in good permeable soils were estimated as 2,530mm for culvert treatment(S1CW3) and 3,080mm for non-culvert treatment(S1NW4), which were 1.8 times and 2.4 times as high as the irrigation water requirements in common rice fields, respectively. And, in case of poor permeable soils, 3,360mm for culvert treatment(S2CW4) and 3.580mm for non-culvert treatment(S2NW4) were estimated, which were 2.5 times and 2.8 times higher than the normal irrigation water requirements, respectively.

Changes of chemical properties by times of the reclaimed tidal land soils and soil surface water, underground infiltration water with precipitation-runoff on natural meteological condition in the unripened tidal reclaimed paddy fields were investigated. This study was carried out to use environment-friendly farm land in the reclaimed tidal lands. The soils used in this study were saline-alkaline soils with the high Na+ and Mg++ content. As the results of investigation outflow loading of nutriments through outflow water in the unripened tidal reclaimed paddy fields by precipitation during the survey period, nutriments equivalent to T-N 1~2 kg 10a -1 and T-P 0.01~0.02 kg 10a-1 from in the unripened tidal lands were discharged. Besides, the results of comparison losses of cation through outflow water showed Na+> K+> Mg++ > Ca++, and the highest appeared water discharge of Na+. In case of saemangeum reclaimed tidal land soils water discharge of cations showed Ca++ 1.3 kg 10a-1, Mg++ 1.6 kg 10a-1, Na+ 17.7 kg 10a-1, and K+ 3.2 kg 10a-1 respectively. On the other hand, in case of koheung reclaimed tidal lands soils water discharge of cations showed Ca++ 18.1 kg 10a-1, Mg++ 31.2 kg 10a-1, Na+ 320.8 kg 10a-1 and K+ 51.2 kg 10a-1 respectively.

This study was carried out to provide the basic informations for the water quality management in Boryung fresh water reservoir watershed. Four agricultural reservoirs were selected and the water qualify of the reservoirs were investigated from November 1998 to December 2000, periodically. Including storage rate, temporal variation of water quality constituents such as water temperature, pH, EC, total nitrogen, total phosphorus were analysed. The result showed that pH ranged 6.7~10.4, EC 56.1~1079μS/cm, COD 0.75~8.0mg/L, respectively. And, total-N concentration affected by the livestock wastes and agricultural activity ranged from 0.21 to 4.66mg/L and which was almost over the agricultural water quality standard(1.0mg/L). Total-P ranged from 0.001 to 0.080mg/L as lower than the agricultural water quality standard(0.1mg/L).

This study was carried out to measure the amount of outlet discharge and analyse the water quality from an agricultural reservoir. Joongpyong reservoir was selected as the monitoring site. Daily discharge was determined by measured water level data of delivery canal and the stage-discharge relation curve. The measured water discharge through culvert outlet of Joongpyong reservoir was 593,200m3 which was equivalent to irrigation depth 1,186mm during irrigation period in 1999. And water samples were taken from the surface water of reservoir and delivery canal, periodically. Temporal variation of water quality constituents such as water temperature, pH, EC, total nitrogen, total phosphorus were investigated. The result showed that pH was ranged 6.9 7.8, total nitrogen 1.39 4.11mg/L, total phosphorus 0.007 0.036 mg/L, respectively.

The high salt concentration of reclaimed tidelands in the beginning of reclamation interferes with the growth of most crops. Although the crops are cultivated in the unripened tidal reclaimed paddy fields after desalinization to be arable, they we apt to be injured from salt by the resalinization through accumulated salts in the root zone during the growing period. In oder to make the reasonable irrigation plan in the unripened tidal reclaimed paddy fields, the preventive water requirements of resalinization as well as leaching requirements have to be included in irrigation water requirements. The critical salinity for the normal growth of crops should be determined to estimate the preventive water requirements of resalinization, and the changes of salinity in soil and water should be analyzed during the growing period, In this study, the growth tests of crops were conducted by soil textures and water management methods in the experimental field with lysimeters, using the samples of good drainage soils and poor drainage soils. And the changes of salinity in soil and water during the growing period, were analyzed to obtain the basic data for determining the critical salinity and making the estimation criteria of the preventive water requirements of resalinization. As the results obtained from analyzing the changes of salinity during the growing period in the unripened tidal reclaimed paddy fields, the exchanging interval of water for the prevention of resalinization was estimated to be within two weeks in good drainage soils and a week in poor drainage soils. And the total exchanging requirements of water for the prevention of resalinization during the growing period was estimated to be over 280mm in good drainage soils and 540mm in poor drainage soils.