• KCID journal
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• v.18 no.1
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• pp.68-80
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• 2011

To provide a operation rule curve for reservoir with low ratio of watershed area to paddy field area, Duckyong reservoir with watershed area of $15.8km^2$ and paddy field area of 1,071ha was selected, in which 4 meters are being heightened and full water levels will be increased from EL.26.0m to EL.30.0m, total water storages from 365.6M $m^3$ to 708.0M $m^3$. There was no operation rule curve that satisfied over 90% reliability of water supply in reservoir with watershed area of 1.48 times of paddy field area. The differences between observed and simulated reservoir daily water storages were minimized to determine parameters for simulating reservoir inflow in case of paddy field area of 550ha from 1991 to 2010. A operation rule curve was drawn to have a maximum storage with total water storage, which was in paddy field area of 700ha with ratio of 2.3 between watershed area and paddy field area. This case showed that annual irrigation water supply was 668M $m^3$ and instream flow of 57M $m^3$, water supply reliability of 55.6% in normal operation, and annual irrigation water supply was 605M $m^3$ and instream flow of 38M $m^3$, water supply reliability of 95.6% in withdrawal limited operation. Water supply reliabilities showed 35.6% without flood regulation and 17.8% with flood regulation in existing reservoir before heightening.

• Magazine of the Korean Society of Agricultural Engineers
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• v.10 no.2
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• pp.1443-1453
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• 1968

The reservoir is one of the important partsof facilities for development of irrigation water in Korea. Accordingly, construction of the reservoir will be stressed in the field of future development of agricultural water resources. In the meantime, storage capacity is actually is limited to some extent with various conditions. Acreage of benefited area shall be determined according to such conditions as catchment area, precipitation and unit water requirment within benefited area. According to results of the past construction of the reservoir, the ratio of catchment area to benefited area would be 4:1 to 2.5:1 or catchment area is approximately 2.5 times larger and over than benefited area. In order words, it is the ordinary practice in the construction of reservoir that benefited area should be less than 1/2.5 times as large as catchment area. Moreover, limitation of catchment area would prevent largely the vast drought-stricken area from being benefited by irrigation facilites. This has been, in fact, caused by the fact that a good deal of water stored in the reservoir overflows wastefully through spillway of the reservoir at th time of flood season, and that only very little of the overflowed water is available for irrigation. However, if the more wasted water is stored during the flood season, the larger area of farmland can irrigated. That is, catchment area can reduced to less than 2.5 times as large as benefited area. On the other hand, it is afraid that such reduction should bring about the increase of unit storage capacity. And storage capacity being maximized, costs for construction of the reservoir will be raised too highly, thus making the economics feasibility unfavorable. The purpose of this study is to decide the ratio of catchment area to benefited area toward the minimum level as possible in consideration of the hydrological and economic aspects. Kopung Project which is located in Sosan-kun, Chungnam Province is taken as an example for the review and analysis in this study, and as an example for crop, rice is taken. After consideration of this project, we can find out that annual average inflow is 726mm and annual average water requirements is 811mm. And the ratio of catchment area to benefited area is 1.2:1. This means that catchment area can be reduced even to 1.2 times as large as benefited area. In conclusion, this study reveals that the construction of reservoir is feasible in view of economic and technical points provided that catchment area is more than 1.5 times as large as benefited area.

• Journal of Ginseng Research
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• v.12 no.1
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• pp.68-75
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• 1988

Yields of ginseng seedlings and cultivation methods were investigated in 29 Ban-Yang-Jik (semimodified soil) nurseries to obtain some information about the production of ginseng seedling. The average number of available seedlings (useful for transplanting in the main field) per Kan ($180{\times}90$ cm) was 362. The percentage of available seedlings to the total seedlings harvested (rate of available seedlings) was 45 %. Although there were severe variations in the numbers and rates of available seedlings among the nurseries surveyed, the number of available seedlings were reduced due to both the short weighted and poor shaped (obese shape with poor root development) seedlings. The number of poor shaped seedlings was negatively correlated with height of seed-bed and frequencies of irrigation. Quadratic relations were noticed between rate of available seedling and heights of front post and rear post of shade. On the other hand, negative correlation was recognized between rate of available seedling and breadth of shade, but positive correlation was noted between rate of available seedling and frequencies of irrigation.

• Korean Journal of Food Science and Technology
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• v.32 no.5
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• pp.1122-1127
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• 2000

Cultivation methods for clean soybean sprouts were investigated using irrigating solutions with grapefruit seed extract, chitosan and phosphate buffer. Chitosan and phosphate buffer did not inhibit the growth of soybean sprouts and increased the yield. Especially phosphate buffer was effective in yield increase and rot inhibition. As the times of irrigation with phosphate buffer increased, the yield of soybean sprouts increased up to 12.3% compared to that of the control. The high increase of yield and rot inhibition of soybean sprouts were detected even in $4{\sim}8$ times irrigation with phosphate buffer.

• KCID journal
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• v.18 no.1
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• pp.33-43
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• 2011

Jundae reservoir has basin area of 234ha, average depth of 3.77m and total storage of $619{\times}10^3m^3$, and is located in Dangin-gun, Chungcheongnam-do. The water quality of Jundae reservoir exceeded the IV grade of water quality standard as available for irrigation water in COD, TN, TP, Chl-a. COD and Chl-a were higher in spring season, because the algal bloom by phytoplankton increased. And the algal blooms in October by inflow non-point pollution during summer rainy season. The most dominant zooplankton was rotifers during study period at all stations. Dominant species were Keratella cochlearis, Polyarthra spp., and Trichocerca spp. We successfully established 2 isolated clone cultures as predator. One is Rotifer, Euchlanis sp. and another is cladocerans, Bosmina sp. To test the removal rate of 2 cultures against Microcystis aeruginosa, we inoculated Euchlanis sp. and Bosmina sp. separately when the abundance reached at $1.0{\times}10^6$cells/ml. Euchlanis sp. removed M. aeruginosa around 98.9% and Bosmina sp. removed it around 98.4%. They are useful grazers for controling algae blooms, Euchlanis sp. and Bosmina sp. feeding on M. aeruginosa highly.

• Journal of Bio-Environment Control
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• v.24 no.3
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• pp.153-160
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• 2015

The objectives of this study were to determine optimal length of off-time between irrigation cycles to improve irrigation efficiency using a frequency domain reflectometry (FDR) sensor-automated irrigation (FAI) system for tomato (Solanum lycopersicum L.) cultivation aimed at minimizing effluent from coir substrate hydroponics. For treatments, the 5-minute off-time length between 3-minute run-times (defined as 3R5F), 10-minute off-time length between 3-minute run-times (defined as 3R10F), or 15-minute off-time length between 5-minute run-times (defined as 5R15F) were set. During the 3-minute or 5-minute run-time, a 60mL or 80mL of nutrient solution was irrigated to each plant, respectively. Until 62 days after transplant (DAT) during the autumn to winter cultivation, daily irrigation volume was in the order of 3R5F (858mL) > 5R15F (409mL) > 3R10F (306mL) treatment, and daily drainage ratio was in the order of 3R5F (44%) > 5R15F (23%) > 3R10F (14%). Between 63 and 102 DAT, daily irrigated volume was in the order of 5R15F (888mL) > 3R5F (695mL) > 3R10F (524mL) with the highest drainage ratio, 19% (${\pm}2.6$), at the 5R15F treatment. During the spring to summer cultivation, daily irrigation volume and drainage ratio per plant was higher in the 3R5F treatment than that of the 3R10F treatment. For both cultivations, a higher water use efficiency (WUE) was observed under the 3R10F treatment. Integrated all the data suggest that the optimal off-time length is 10 minutes.

• Journal of The Korean Society of Agricultural Engineers
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• v.62 no.4
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• pp.1-12
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• 2020

The extreme 2017 spring drought affected a large portion of South Korea in the Southern Gyeonggi-do and Chungcheongnam-do districts. This drought event was one of the climatologically driest spring seasons over the 1961-2016 period of record. It was characterized by exceptionally low reservoir water levels, with the average water level being 36% lower over most of western South Korea. In this study, we consider drought response methods to alleviate the shortage of agricultural water in times of drought. It could be to store water from a stream into a reservoir. There is a cyclical method for reusing water supplied from a reservoir into streams through drainage. We intended to present a decision-making plan for water supply based on the calculation of the quantity of water supply and leakage. We compared the rainfall-runoff equation with the TANK model, which is a long-term run-off model. Estimations of reservoir inflow during non-irrigation seasons applied to the Madun, Daesa, and Pungjeon reservoirs. We applied the run-off flow to the last 30 years of rainfall data to estimate reservoir storage. We calculated the available water in the river during the non-irrigation season. The daily average inflow from 2003 to 2018 was calculated from October to April. Simulation results show that an average of 67,000 tons of water is obtained during the non-irrigation season. The report shows that about 53,000 tons of water are available except during the winter season from December to February. The Madun Reservoir began in early October with a 10 percent storage rate. In the starting ratio, a simulated rate of 4 K, 6 K, and 8 K tons is predicted to be 44%, 50%, and 60%. We can estimate the amount of water needed and the timing of water pump operations during the non-irrigation season that focuses on fresh water reservoirs and improve decision making for efficient water supplies.

• Journal of Bio-Environment Control
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• v.12 no.1
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• pp.7-11
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• 2003

Cellular glass foam (CGF), the reprocessed glass, has a possibility to be used as a medium component in plug culture of horticultural crops due to the its excellent air and water permeability as comparable to perlite. An experiment was conducted to investigate growth of plug seedlings of Lycopersicum esculentum 'Segye' as influenced by irrigation frequency in various medium combinations of CGF (2.0-4.0 mm particle size) and peatmoss. Seeds were sown in 200-cell plug trays, filled with mixtures of CGF and peatmoss either at 33：67 or 25：75 (％. v/v) and were germinated on a fogged propagation bed. The irrigation frequencies used were one, two or three times per every two days. A commercial plug medium (Tosilee medium) was used as the control, and the irrigation frequency in the control was one time per day. Growth of seedlings, and medium pH and EC were measured at 33 days after sowing. The medium composition had little influence on overall growth of seedlings. Irrigation frequency very significant affected number of leaves, leaf area, chlorophyll concentration, fresh and dry weights of shoots and roots, and dry matter. Growth of seedlings was the greatest with the highest irrigation frequency in the 25% CGF＋75% peatmoss mixture.

• Journal of agriculture & life science
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• v.45 no.6
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• pp.237-249
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• 2011

The purpose of this study was to monitor the streamflow of rural streams for investigating the status of stream depletion located downstream of irrigation reservoir. Bonghyun and Hi reservoirs area, located in Gyeongnam, Gosung-gun, Hi-myeon, were selected for study watersheds and streams. Streamflow monitoring were conducted 6 times during the paddy growing season of 2010 from May to October. Streamflow was measured for 18 stations downstream from two reservoirs with the interval of 300m to 500m, The amount of streamflow were highly dependent on the antecedent precipitation and irrigation amount. In most observation stations, streamflow was depleted when precipitation and irrigation were not provided. Pumping from stream for irrigation and water supply for factory and irrigation return flow were also factors on streamflow. Continuous monitoring for rural streams located in downstream of reservoirs are required to quantify the status of streamflow depletion and determine the amount of environmental flows.

• Journal of Korean Society of Forest Science
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• v.111 no.3
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• pp.394-404
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• 2022

This study was conducted to optimize the amount of drip irrigation for Prunus×yedoensis Matsum., one of the major medium-sized landscaping trees used mainly for streetscapes and as ornamentals. The experiment was conducted in a container nursery, where we assessed the growth and physiological characteristics of 4- and 8-year-old seedlings watered at different rates (x) by a drip irrigation system. The relative growth rates (based on height and root collar diameter (RCD) measurements) were highest at 288 and 416 L/year/tree for the 4- and 8-year-old containerized seedlings, respectively. These age and treatment combinations also produced significantly different dry weight and seedling quality index values, indicating good growth. The two age groups had significantly different total root lengths, root diameters, and root volumes under these respective irrigation treatments. In addition, the 4-year-old containerized seedlings irrigated at 288 L/year/tree and the 8-year-old containerized seedlings irrigated at 416 L/year/tree had the highest activations in their chlorophyll contents. Overall, the results (differences in irrigation amounts affect the seedlings morphological relative growth, biomass growth, seedling quality, and physiological reaction) indicate that the optimal irrigation amounts for container-grown Prunus×yedoensis are 288 L/year/tree for 4-year-old (RCD class, 3cm) and 416 L/year/tree for 8-year-old (RCD class, 7 cm) containerized seedlings.