• Journal of Korea Water Resources Association
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• v.43 no.3
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• pp.295-308
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• 2010

As an attempt to explore the impact of droughts which may be worse by the climate change, the change in the water balance of the Han-river basin is analyzed. To accomplish it, we suggest a procedure consisting of three successive sub-procedures: daily rainfall generation for 70 years by the RegCM3 RCM ($27{\times}27\;km$) with the A2 scenario, daily discharge simulations by SLURP using the generated daily rainfall data, and monthly water balance analysis by K-WEAP (Korean Water Evaluation and Planning System) based on the SLURP simulation. Since significant uncertainty is involved in forecasting the future water consumption and water yields, we assumed three water consumption scenarios and fifty water yields scenarios. Three water consumption scenarios are, namely, "LOW", "MEDIUM", and "HIGH" according to the expected amount of water consumption. The fifty daily discharges are obtained from the SLURP simulations during the drought period. Finally, water balance analysis is performed by K-WEAP based on 150 combinations from three water consumption scenarios and the fifty daily discharges. Analysis of water scarcity in small basins of the Han River basin showed concentration of water scarcity in some small basins. It was also found that water scarcity would increase in all small basins of the Han River basin.

• Journal of Korea Water Resources Association
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• v.48 no.3
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• pp.233-243
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• 2015

The bimodal flocculation of cohesive sediments in water environments describes the aggregation and breakage process developing a bimodal floc size distribution with dense flocculi and floppy flocs. A two class population balance equation (TCPBE) was tested for simulating the bimodal flocculation by a model-data fitting analysis with two sets of experimental data (low and high turbulent flows) from 1-D flocculation-settling column tests. In contrast to the Single-Class PBE (SCPBE), the TCPBE could simulate interactions between flocculi and flocs and the flocculation mechanism by differential settling in a low turbulent flow. Also, the TCPBE could perform the same quality of simulation as the elaborate Multi-Class PBE (MCPBE), with a small number of floc size classes and differential equations. Thus, the TCPBE was proven to be the simplest model that is capable of simulating the bimodal flocculation of cohesive sediments in water environments and water, wastewater treatment systems.

• Journal of Environmental Science International
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• v.20 no.7
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• pp.919-927
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• 2011

A ecosystem model was applied for understanding of circulation process of state variables in marine ecosystem. A mass balance was conducted by calculating the physical process. The sensitivity analysis was conducted to know which coefficient is the most effective factor to the state variables in the model. The results of the mass balance indicate that the primary production was 58.6 ton C/day in the case of mass flux. DIN and DIP in nutrient ingestion of phytoplankton were each 7.9 ton N/day, 1.1 ton P/day. POC and DOC in mineralization of organic matter were each 10.8 ton C/day, 40.6 ton C/day. The results of sensitivity analysis showed that the maximum growth rate of phytoplankton was the most important factor for overall state variables. In the case of nutrients, Half saturation constant of DIN, and mineralization rate of DOM for COD were important factor.

• Journal of Korea Water Resources Association
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• v.57 no.1
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• pp.59-72
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• 2024

Agricultural reservoirs supply water for various purposes such as irrigation, maintenance, and living. Since agricultural reservoirs respond sensitively to seasonal and climate changes, it is essential to estimate supply and inflow for efficient operation, and water management should be done based on these data. However, in the case of agricultural reservoirs, the measurement of supply and inflow is relatively insufficient compared to multi-purpose dams, and inflow-supply analysis in agricultural reservoirs through water balance analysis is necessary for efficient water management. Therefore, rainfall-runoff analysis models such as ONE model and Tank model have been developed and used for reservoir water balance analysis, but the applicability analysis for ungauged watersheds is insufficient. The ONE model is designed for daily runoff calculation, and the model has one parameter, which is advantageous for calibration and ungauged watershed analysis. In this study, the water balance was analyzed through the ONE model and the Tank model for 15 watersheds upstream of dams, and R² and NSE were used to quantitatively compare the performance of the two models. The simulation results show that the ONE model is suitable for predicting the inflow of agricultural reservoirs with the ungauged watershed

• Journal of The Korean Society of Agricultural Engineers
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• v.62 no.6
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• pp.63-72
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• 2020

With the implementation of integrated water management policies, the need for information sharing with respect to agricultural water use has increased, necessitating the quantification of irrigation water supply using monitoring data. This study aims to estimate the irrigation water supply amount based on the relationship between the water level and irrigation canal discharge, and evaluate the reliability of monitoring data for irrigation water supply in terms of hydrology. We conducted a flow survey in a canal and reviewed the applicability of the rating curve based on the exponential and parabolic curves. We evaluated the reliability of the monitoring data using a reservoir water balance analysis and compared the calculated results of the supply quantity in terms of the reservoir water reduction rate. We secured 26 readings of measurement data by varying the water levels within 80% of the canal height through water level control. The exponential rating curve in the irrigation canal was found to be more suitable than the parabolic curve. The irrigation water supplied was less than 9.3-28% of the net irrigation water from 2017 to 2019. Analysis of the reservoir water balance by applying the irrigation water monitoring data revealed that the estimation of the irrigation water supply was reliable. The results of this study are expected to be used in establishing an evaluation process for quantifying the irrigation water supply by using measurement information from irrigation canals in agricultural reservoirs.

• Journal of The Korean Society of Agricultural Engineers
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• v.47 no.3
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• pp.59-68
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• 2005

The rainfall-runoff potential of Jangseong reservoir watershed was studied based on SCS (Soil Conservation Service, which is now the NRCS, Natural Resources Conservation Service, USDA) runoff curve number (CN) technique. Precipitation and reservoir operation data had been collected. The rainfall-runoff pairs from the watershed for ten years was estimated using reservoir water balance analysis using reservoir operation records. The maximum retention, S, for each storm event from rainfall-runoff pair was estimated for selected storm events. The estimated S values were arranged in descending order, then its probability distribution was determined as log-normal distribution, and associated CNs were found about probability levels of Pr=0.1, 0.5, and 0.9, respectively. A subwatershed that has the similar portions of land use categories to the whole watershed of Jangseong reservoir was selected and hydrologic monitoring was conducted. CNs for subwatershed were determined using observed data. CNs determined from observed rainfall-runoff data and reservoir water balance analysis were compared to the suggested CNs by the method of SCS-NEH4. The $CN_{II}$ measured and estimated from water balance analysis in this study were 78.0 and 78.1, respectively. However, the $CN_{II}$, which was determined based on hydrologic soil group, land use, was 67.2 indicating that actual runoff potential of Jangseong reservoir watershed is higher than that evaluated by SCS-NEH4 method. The results showed that watershed runoff potential for large scale agricultural reservoirs needs to be examined for efficient management of water resources and flood prevention.

• Journal of Korea Water Resources Association
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• v.53 no.8
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• pp.569-582
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• 2020

Recently, Korea has faced a change in the pattern of water use due to urbanization, which has caused difficulties in understanding the rainfall-runoff process and optimizing the allocation of available water resources. In this perspective, spatially downscaled analysis of the water balance is required for the efficient operation of water resources in the National Water Management Plan and the River Basin Water Resource Management Plan. However, the existing water balance analysis does not fully consider water circulation and availability in the basin, thus, the obtained results provide limited information in terms of decision making. This study aims at developing a novel water circulation analysis model that is designed to support a quasi-real-time assessment of water availability along the river. The water circulation model proposed in this study improved the problems that appear in the existing water balance analysis. More importantly, the results showed a significant improvement over the existing model, especially in the low flow simulation. The proposed modeling framework is expected to provide primary information for more realistic hydrological drought monitoring and drought countermeasures by providing streamflow information in quasi-real-time through a more accurate natural flow estimation approach with highly complex network.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2002.10a
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• pp.265-268
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• 2002

The ground water regime analysis method, numerical analysis method, water budget method, and baseflow analysis method have been used for estimating ground water recharged quantity. This study, adapting water budget concept of unsaturated zone, and saturated zone of the DAWAST model, proposed a new method to estimate ground water recharged quantity.

• Magazine of the Korean Society of Agricultural Engineers
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• v.32 no.3
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• pp.56-66
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• 1990

To investigate the status of irrigation water use and the degree of repeated use of irrigation water, observations for water balance analysis were made during the irrigation periods in 1986 and 1987 crop year. The total area of studied site is 1,441 ha. The site is a major portion of Jedaecheon basin which is located in Bubuk-myeon, Miryang-gun, Gyeongnam Province. The studied area was subdivided into six small blocks. The water balance analysis for these subdivided blocks were carried out considering characteristics of each block. Obtained results are as follow: 1.In mountainous sloppy paddy area(less than 7% slope), the surface inflow was 5A mm/day in average that is one third of the surface inflow into plain paddy area ; 16.7 mm/day. 2.The surface inflows at the vegetative stage and the ripening stage were 15.5 mm/day and 10.4 mm/day, respectively. Those figures were larger than the actual consumptive use at respective same stages ; 13.3 mm/day and 9.2 mm/day, respectively. Whereas, the surface inflow at generative stage was 12.5 mm/day which was less than 14.0 mm/day ; the actual consumptive use. 3.The range of the variation of water storage term was 1 mm/day. This means that there were no change in depth of ponded water on paddy fields. The relationship between the variation of water storage(AS) and the variation of ground water table(H) could be expressed as follow: : AS=0.14H+0.26 4.The ground water inflow: into the transition region ; paddy fields which are located continuously from the mountainous area to the plain area, was larger than the out flow from this region, in general. Rowever, in the plain region where the ground water utilization was predominant, the ground water outflow from this region was larger than inflow: to this region. The relationship between the ground water flow(G2- G1) and the consumptive use in large paddy area(D1-D2) could be expressed as follow: (G2-G1) =0.95(D1-D2) -3.79

• Journal of The Korean Society of Agricultural Engineers
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• v.63 no.5
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• pp.1-11
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• 2021

Soil moisture plays a critical role in hydrological processes, land-atmosphere interactions and climate variability. It can limit vegetation growth as well as infiltration of rainfall and therefore very important for agriculture sector and food protection. Recently, due to the increased damage from drought caused by climate change, there is a frequent occurrence of shortage of agricultural water, making it difficult to supply and manage stable agricultural water. Efficient water management is necessary to reduce drought damage, and soil moisture management is important in case of upland crops. In this study, soil moisture was calculated based on the water balance model, and the suitability of soil moisture data was verified through the application. The regional soil moisture was calculated based on the meteorological data collected by the meteorological station, and applied the Runs theory. We analyzed the spatiotemporal variability of soil moisture and drought impacts, and analyzed the correlation between actual drought impacts and drought damage through correlation analysis of Standardized Precipitation Index (SPI). The soil moisture steadily decreased and increased until the rainy season, while the drought size steadily increased and decreased until the rainy season. The regional magnitude of the drought was large in Gyeonggi-do and Gyeongsang-do, and in winter, severe drought occurred in areas of Gangwon-do. As a result of comparative analysis with actual drought events, it was confirmed that there is a high correlation with SPI by each time scale drought events with a correlation coefficient.