• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2005.10a
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• pp.74-79
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• 2005

Many reservoirs have been constructed for sustainable utilization of water resources in Korea. Effective management of water resources in Korea becomes very important in resent years. Especially, the dredging in reservoirs is important for effective water resources management and one in easy water resources security methods. According to "The reservoir dredging mid-long term planning investigation report", it was investigated that 1221 reservoirs need to dredge among 3,288 reservoirs managed by KARICO. And, KARICO made a survey of reservoirs for the sediment and storage change in $2002{\sim}2004$. In results, it was investigated total storage $1,406{\pm}10^6m^3$, effective storage $1,344{\pm}10^6m^3$ in mid-small 2,748 reservoirs and the storage ratio decreased total storage ratio 15.7%, effective storage ratio 4.4%.

• Journal of The Korean Society of Agricultural Engineers
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• v.50 no.3
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• pp.51-58
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• 2008

Ninety five percent of the agricultural reservoirs were constructed by earth or rock. There are 18,000 agricultural dams and reservoirs in Korea. Therefore, it is easy to evaluate or identify their problems. Reservoirs should be repaired before too late. It is required to guarantee the proper functions of the existing agricultural dams and reservoirs in time to minimize the damage. In this study, in order to evaluate degradation of agricultural reservoir, grasps the safety of reservoir choosing for agriculture of 25 reservoirs which are distributed in Chungbuk region rural and analyzed using possibility as reservoir of agricultural usage. The degradation was evaluated by a compilation of the result where embankment and structure were separately handled, measured and then multiplied scores for each categories. By activating this research, current status of agricultural reservoir and degradation status will be easily measured. In addition, the research could be also used as a tool for an effective control or maintenance.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.516-516
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• 2022

Agricultural reservoirs are critical water resources structures to ensure continuous water supplies for rice cultivation in Korea. Climate change has increased the risk of reservoir failure by exacerbating discrepancies in upstream runoff generation, downstream irrigation water demands, and evaporation losses. In this study, the variations in water balance components of 400 major reservoirs during 1973-2017 were examined to identify the reservoirs with reliable storage capacities and resilience. A conceptual lumped hydrological model was used to transform the incident rainfall into the inflows entering the reservoirs and the paddy water balance model was used to estimate the irrigation water demand. Historical climate data analysis showed a sharp warming gradient during the last 45 years that was particularly evident in the central and southern regions of the country, which were also the main agricultural areas with high reservoir density. We noted a country-wide progressive increase in average annual cumulative rainfall, but the forcing mechanism of the rainfall increment and its spatial-temporal trends were not fully understood. Climate warming resulted in a significant increase in irrigation water demand, while heavy rains increased runoff generation in the reservoir watersheds. Most reservoirs had reliable storage capacities to meet the demands of a 10-year return frequency drought but the resilience of reservoirs gradually declined over time. This suggests that the recovery time of reservoirs from the failure state had increased which also signifies that the duration of the dry season has been prolonged while the wet season has become shorter and/or more intense. The watershed-irrigated area ratio (W-I_ratio) was critical and the results showed that a slight disruption in reservoir water balance under the influence of future climate change would seriously compromise the performance of reservoirs with W-I_ratio< 5.

• Korean Journal of Ecology and Environment
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• v.47 no.3
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• pp.146-159
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• 2014

In this study, we evaluated the temporal changes of water quality in the 90 reservoirs in Korea and the relationships between water quality and their environmental factors in the reservoirs for effective management of reservoirs. The majority of study reservoirs were categorized as the eutrophic state based on Carlson's trophic index. Among 90 reservoirs, more than 55.0% were nutrient-rich based on $TSI_{TP}$ in each month, where more than 50.0% were nutrient-rich based on $TSI_{Chl-a}$ from June to November. Seasonal Mann-Kendall test was used to analyze temporal variation of water quality in the selected 60 reservoirs using monthly data from 2004 to 2008. The results showed that 27 (45.0%) reservoirs showed the improvement of water quality based on TP and Chl-a concentrations, while 14 (23.3%) and 11 (18.3%) reservoirs displayed the degradation of water quality based on TP and Chl-a concentrations, respectively. Meanwhile, a self-organizing map classified the study reservoirs into five groups based on differences of hydrogeomorphology (altitude, catchment area, bank height, lake age, etc.). Physicochemical factors and land use/cover types showed clear differences among groups. Finally, hydrogeomorphology of reservoirs were related to water quality, indicating that the hydrogeomorphological characters strongly affect water quality of reservoirs.

• Journal of Korean Society of Rural Planning
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• v.26 no.1
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• pp.69-75
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• 2020

In this study, the value of reservoir landscape improvement among agricultural infrastructures was analyzed using the CVM(contingent valuation method). The results can be summarized as follows. First, in the decision to pay for all types of large, medium and small scales, the probability of acceptance decreased as the price range increased, and the probability of acceptance increased as the interest in landscape increased. Second, the WTP(willingness to pay) to improve landscape derived from logistic estimation was 29,284 won per year for large reservoirs, 20,736 won per year for medium reservoirs, and 16,682 won per year for small reservoirs. Third, conservative estimates using the economically active population to estimate the overall value of the reservoir landscape improvement show that large reservoirs were 955 billion won per year, medium reservoirs were 600 billion won per year, and small reservoirs were 468 billion won per year.

• Journal of Korea Water Resources Association
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• v.30 no.6
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• pp.629-639
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• 1997

Many reservoirs have been constructed and operated for utilizing and controlling water in main rivers of Korea since 1960's. New reservoirs are planned to satisfy increasing water demands according to the National Long-Term Water Resources Development Plan, that will make the entire water resources system more complex. That means reasonable approach is necessary to review many alternatives for future policy decision making of water resources management. As an attempting to simplify the water problem of the large-scale reservoirs system with more than 10 reservoirs, two stages approach such as simulation approach(HEC-5) is first applied to medium and small reservoirs and the results are used as inputs to final optimization approach (IDP) including large reservoirs is used in the water budget analysis of Han river water resources. In addition, existing multi-purpose reservoirs and planned reservoirs in Han river are formulated into one system and DPSA is applied to solve the basin-wide water resources assessment problem.

• Journal of Korean Society of Rural Planning
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• v.22 no.2
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• pp.165-173
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• 2016

Water management information system used by KRC(Korea Rural Community Corporation) operates widely including RIMS, RAWRIS and etc. Other systems are operated by each government department, for example, K-water(Korea Water Resources Corporation)'s WAMIS. Even though small scale reservoirs managed by city/country is just about 12% of total water resource, the reservoirs are important for controlling and securing water resource as the reservoirs, including about 14,700 reservoirs nationwide, are located at main subwater shed. So, it is necessary for KRC to execute integrated informatization. In this research, system analysis was performed to comprise the integrated water management information system including the reservoirs controlled by city and country at first. And then, improvement plan for informatization of the reservoirs controlled by city and country was proposed. This study proposed the improvement plan for informatization of the reservoirs managed by the city and country, which was systematically proposed through systemic analysis including from reservoir site to the integrated water management information system. The objects includes 1. Reservoir (basin, facilities, water depth-area curve, benefiter area), 2. Field supervision organization for the reservoir 3. Local government administrative organization, 4. Center organization 5. Network for information transfer, 6. integrated water management information system. As the reservoirs controlled by city and country are important considering managing water and facilities, operated by local government with minimum budget due to budget problem, securing sufficient budget is necessary to form an specialized organization controlling facilities and the water management system in terms of drought and flood control.

• Korean Journal of Ecology and Environment
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• v.46 no.3
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• pp.343-359
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• 2013

In order to understand shoreline environment characteristics of Korean reservoirs, the interrelationships between environmental factors of geomorphology, hydrology, water quality and shoreline soil were analyzed, and the reservoir types were classified according to their environmental characteristics in the 35 reservoirs selected by considering the purpose of dam operations and annual water-level fluctuations. Geomorphological and hydrological characteristics of reservoirs were correlated with the altitude and the size scale of reservoirs. The annual range of water level fluctuation showed a wide variation from 1 m to 27 m in the various reservoirs in Korea. The levels of eutrophication of most reservoirs were mesotrophic or eutrophic. From the result of the soil texture analysis, sand contents were high in reservoir shorelines. Range, frequency and duration of water-level fluctuation were distinctive from the primary function of reservoirs. Flood control reservoirs had a wide range with low frequency and waterpower generation reservoirs had a narrow range with high frequency in the water-level fluctuation. According to the result of CART (classification and regression tree) analysis, the water quality of reservoirs was classified by water depth, range of water-level fluctuation and altitude. The result of PCA (principal component analysis) showed that the type of reservoirs was classified by reservoir size, water-level fluctuation, water quality, soil texture and soil organic matter. In conclusion, reservoir size, the water-level fluctuation, water quality and soil characteristics might be major factors in the environment of reservoir shorelines in Korea.

• Journal of The Korean Society of Agricultural Engineers
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• v.55 no.6
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• pp.77-85
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• 2013

The efficient operation and management strategies of reservoirs in irrigation periods of drought events are an essential element for drought planning and countermeasure. Korea Rural Community Corporation has developed the real-time water level observation system of agricultural reservoirs to efficiently operate reservoirs, however, it is not possible to predict drought conditions, and only provides information of current situation. Hence, it is necessary to evaluate accurate irrigation vulnerability and efficiently reservoir operation rules using current water level. In this paper, the improvement methods of reservoir operation planning were developed with water supply vulnerability characteristic curves comparing to automatic water gauge at agricultural reservoirs. The 11 reservoirs were simulated applying the reservoir operation rules which was determined by irrigation vulnerability characteristic curves criteria and real time water level, and evaluated water supply situation in 2012 year. The analysis of results can be identified probabilistic possibility of water supply failures compared with the existing reservoir operation criteria. These results of efficient reservoir operation rules can be achieved enable irrigation planners to optimally manage available water resources for decision making, and contributed to maintain the water supply according to demand strategy for agricultural reservoirs management.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.515-515
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• 2022

Climate change is strongly threatening the performance of agricultural reservoirs, which are instrumental in ensuring uninterrupted water supplies for rice cultivation in Korea. In this study, various performance indices were derived and overall sustainability of the 400 agricultural reservoirs was evaluated in the context of climate change trends during 1973-2017. Rice crop evapotranspiration, irrigation water requirements, runoff generation in the upstream watershed, and volumetric evaporation losses were plugged into a water balance model to simulate the reservoir operation during the study period. Resilience, reliability, and vulnerability are the three main indicators of reservoir performance, and these were combined into a single sustainability metric to define the overall system credibility. Historical climate data analysis confirmed that the country is facing a gradual warming shift, particularly in the central and southern agricultural regions. Although annual cumulative rainfall increased over the last 45 years, uneven monthly rainfall distribution during the dry and wet seasons also exacerbated the severity and frequency of droughts/floods. For approximately 85% of the selected reservoirs, the sustainability ranged between 0.35 to 0.77, and this range narrowed sharply with time, particularly for the reservoirs located in the western and southern coast regions. The study outcomes could help in developing the acceptable ranges of the performance indices and implementing appropriate policy and technical interventions for improving the sustainability of reservoirs with unacceptable ranges of the performance indices.