• Journal of Advanced Marine Engineering and Technology
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• v.32 no.8
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• pp.1221-1230
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• 2008

Inflatable rubber dams are used for controlling flood, impounding water for recreations, preventing beach erosions, diverting water for irrigations, and generating hydropower. They are long, flexible, inflated with air, cylindrical structures on a rigid horizontal foundation such as concrete. The dam is modeled as an elastic shell inflated with air. The mechanical behaviors of the inflated dam model were investigated by using the finite element method. The analysis process such as One Way Coupling Fluid-Structure Interaction consists of two steps. First, the influences of the fluid side were investigated, viz, the shape changes of the inflated rubber dam due to the fluid motions was captured when the height of the dam was 30cm with air pressure 0.01MPa, at which the pressure distributions over the surface of the dam were calculated. And next, the structural deformations were calculated using the pressure distributions. The initial inlet velocity for flow field was set to 0.1m/s. The structural deformation behaviors were investigated. The final research goal is to develop a Korean Inflatable Rubber Dam to be used for generating small hydropower.

• Korean Journal of Agricultural Science
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• v.31 no.2
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• pp.135-148
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• 2004

Rice is not only main food but also key farm income source of Korean farmers. In spite of the above facts, rice productivity was decreased on account of drought in every 2 or 3 years interval owing to the vulnerability of irrigation facilities throughout Korea in the past decades. As an context of the first five year economic development plan, all weather farming programme including 4 big river basin comprehensive development projects and large and medium sized irrigation water development projects were carried out successfully. Therefore the area of irrigated paddy were increased from 58% in 1970 to 76.2% in 1999. In the past decades, the Government had invested heavy financial funds to develop irrigation water but as an factor share analysis, the contribution rates of irrigation water and investment for farmland base development project have not been identified yet in national agricultural economic level. It is very scarce to find out the papers concerned to macro-economic factor share analysis or contribution rates of water and investment cost to rice production value in Korea considering the production function of the quantity of irrigation water and investment cost as independent variables. Accordingly this paper covered and aimed at identifying (1) derivation of rice production function with the time serial data from 1965 to 1999 and the contribution rates of irrigation water and total investment cost for farmland base development project. The analytical model of the contribution rates was adapted the famous Cobb-Douglass production function. According to the model analysis, the contribution rate of irrigation water to rice production in Korea was shown 37.8% which was equivalent to 0.28 of the production elasticity of water. The contribution rate of farmland base development project cost was revealed 22% and direct production cost of rice was contributed 60% in the growth of rice production and farm mechanization costs contributed to 18% of it respectively. The two contribution rates comparing with the direct production cost were small but without irrigation water and farmland base development, application of high-pay off inputs and farm mechanization might be impossible. Considering the food security and to cope with the frequent drought, rice farming and investment for the irrigation water development should be continued even in WTO system.

• Environmental Engineering Research
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• v.24 no.1
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• pp.127-136
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• 2019

Land application of treated palm oil mill effluent (TPOME) could be used as an alternative tertiary wastewater treatment process. However, phenolic compounds in TPOME might be leached to the environment. This study investigated the ability of grasses on reducing phenolic compounds in the leachate after TPOME application. Several pasture grasses in soil pots were compared after irrigating with TPOME from stabilization ponds, which contained 360-630 mg/L phenolic compounds. The number of soil bacteria in planted pots increased over time with the average of $10^8CFU/g$ for mature grasses, while only $10^4-10^6CFU/g$ were found in the unplanted control pots. The leachates from TPOME irrigated grass pots contained lower amounts of phenolic compounds and had lower phytotoxicity than that of control pots. The phenol removal efficiency of grass pots was ranged 67-93% and depended on grass cultivars, initial concentration of phenolic compounds and frequency of irrigations. When compared to water irrigation, TPOME led to an increased phenolic compounds accumulation in grass tissues and decreased biomass of Brachiaria hybrid and Brachiaria humidicola but not Panicum maximum. Consequently, the application of TPOME could be conducted on grassland and the grass species should be selected based on the utilization of grass biomass afterward.

• Journal of Bio-Environment Control
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• v.20 no.2
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• pp.93-100
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• 2011

Maintenance of adequate soil water potential during the period of crop growth is necessary to support optimum plant growth and yields. A better understanding of soil water movement within and below the rooting zone can facilitate optimal irrigation scheduling aimed at minimizing the adverse effects of water stress on crop growth and development and the leaching of water below the root zone which can have adverse environmental effects. The objective of this study was to evaluate the feasibility of using a portable irrigation controller with an Watermark sensor for the cultivation of drip-irrigated vegetable crops in a greenhouse. The control capability of the irrigation controller for a soil water potential of -20 kPa was evaluated under summer conditions by cultivating 45-day-old tomato plants grown in three differently textured soils (sandy loam, loam, and loamy sands). Water contents through each soil profile were continuously monitored using three Sentek probes, each consisting of three capacitance sensors at 10, 20, and 30 cm depths. Even though a repeatable cycling of soil water potential occurred for the potential treatment, the lower limit of the Watermark (about 0 kPa) obtained in this study presented a limitation of using the Watermark sensor for optimal irrigation of tomato plants where -20 kPa was used as a point for triggering irrigations. This problem might be related to the slow response time and inadequate soil-sensor interface of the Watermark sensor as compared to a porous and ceramic cup-based tensiometer with a sensitive pressure transducer. In addition, the irrigation time of 50 to 60 min at each of the irrigation operation gave a rapid drop of the potential to zero, resulting in over irrigation of tomatoes. There were differences in water content among the three different soil types under the variable rate irrigation, showing a range of water contents of 16 to 24%, 17 to 28%, and 24 to 32% for loamy sand, sandy loam, and loam soils, respectively. The greatest rate increase in water content was observed in the top of 10 cm depth of sandy loam soil within almost 60 min from the start of irrigation.

• Journal of Bio-Environment Control
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• v.6 no.4
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• pp.250-257
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• 1997

Stem diameter and shoot fresh weight of tomato grown in greenhouse were measured non-destructively at 10 minutes interval from 1 to 16 July, 1996 with displacement detector using strain gauges and with suspension-type load cell, respectively, and simultaneously were measured soil water potential, transpiration and solar radiation. Ample water was irrigated before experiment, and thereafter, irrigations were made on the next morning when visual symptoms of wilting appeared. Shoot fresh weight and stem diameter showed very similar patterns in diurnal changes which are characterized by predawn maximum and afternoon minimum and in long- term evolutions, suggesting that stem diameter shrinkage and expansion are closely related to plant water content and growth, respectively, Shoot weight and stem diameter reached minimum values a little later than the time on which transpiration showed maximum. The daily net gains of fresh weight(DG) and stem diameter(DI) showed significantly Positive correlations with solar radiation in those days on which plants were not water-stressed. However, Dl and DG on those days of water stress showed much lower values than expected from the relationships between solar radiation and them. Transpiration was much lower than the expected potential transpiration on 10 July, implying that plants were water-stressed. In this case water stress was not detected from visual symptom of wilting and/or soil water potential, but was able to be identified by the lower DI and DG than the expected. The maximum contraction of stem diameter(MC) and the maximum loss of fresh weight(ML) during daytime showed significantly positive correlations with solar radiation in those days on which plants were not water-stressed and were observed greater than expected from the relationships on severely water-stressed days. But mild water stress could not be discernable by ML and MC. It would be concluded that the daily net gains of fresh weight and/or stem diameter could be used as criteria for diagnosing the water status of tomato and for triggoring the onset of irrigation in automatic system.

• Journal of Bio-Environment Control
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• v.23 no.2
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• pp.158-166
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• 2014

This experiment has investigated suitable methods to improve precision water content monitoring of coconut coir substrates to control irrigation by frequency domain reflectometry(FDR) sensors. Specifically, water content changes and variations were observed at different sensing distances and positions from the irrigation dripper location, and different spaces between the FDR sensors with or without noise filters. Commercial coconut coir substrates containing different ratios of dust and chips(10:0, 7:3, 5:5, 3:7) were used. On the upper side and the side of the substrates, a FDR sensor was used at 5, 10, 20, 30cm distances respectively from the irrigation dripper point, and water content was measured by time after the irrigation. In the glass beads, sensors were installed with or without noise filtering. Closer sensing distance had a higher water content increasing rate, regardless of different coir substrate ratios. There were no differencies of water content increasing rates in 10:0 and 3:7 substrates between the upper side and the side. Whereas, 7:3 and 5:5 substrates showed higher increasing rates on the upper side measurements. Substrates with higher ratios of chip(3:7) had lower increasing rates than others. And, with noise filters, the exatitude of measurement was improved because the variation and deviation were reduced. Therefore, in coconut coir with FDR sensors, an efficient water content measurment to control irrigations can be achieved by installing sensors closer to an irrigation point and upper side of substrates with noise filters.

• Magazine of the Korean Society of Agricultural Engineers
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• v.14 no.3
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• pp.2703-2715
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• 1972

1. Title of Research Research on the Loss of Irrigation Water Flowing in Earth Channel. 2. Purpose and Importance of Research The purpose of this research is to obtain the accurate loss rated of irrigation water flowing in earth channels so as to give a criterion of designing rational and effective suplpy project of irrigations water. It is the present status that the loss rates of 10 to 20% are obscurely applied without any scientific proof. Therefore, the importance of this research lies in securing loss rates, which are experimentally proves to be suitable for specific local conditions. 3. Content and Scope of Research The selected test reach of the main channel is 1,000m long. Discharges were measured at up and downstream enps by using current meter. The test reach of the lateral channel is 500m long, and parshall flumes were set at both ends to measure inflow and outflow. Finally, for the supply ditch, the test section is 200m long, and sharp-edged rectangular weirs were provided at both ends to measure inflow and outflow. In addition, various factors influence on the loss of irrigation water in channel wer examined. 4. Results of Research and Proposition Results: 1. In the main channel, which is 1,000 M long, and has a slope of 1/3,000 and was constructed by cutting earth, its loss rate is 9.64%. 2. In the lateral, which has a slope of 1/1,500, and is 500m long, and was constructed by cutting, its loss rate is 15.55%. Its average seepage rate is 2.08cm/day. 3. In the supply ditch, which has a slope of 1/300, and is 200m long, and was constructed by filling earth, its loss rate is 12.34%, its average seepage rate being 3.37cm/day. Proposition: As could be seen in the results above-mentioned, it is contradictory to apply a loss rate of 20% for every main channels and 15% for every laterals without variation, as done so for in planning irrigation project. The fact, however, is that loss rates must be different according to localities and characteristics. Due to the fact that this experiment is small in its scope and is nothing but a preliminary one, it is hardly possible to draw decisive conclusions with the results obtained in this research. Loss rates, that are secured through more extensive research, should be used, in order to establish precise irrigation project. Moreover, such researches should be carried out for a number of loclities throughout the nation.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.3
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• pp.390-399
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• 2010

Non-photochemical quenching (NPQ) values for utilizing them to detect osmotic tolerance in plants were examined with two different soybean cultivars, an osmotic tolerant soybean (Shinpaldalkong 2) and a control soybean (Taekwangkong). Two different stresses were applied to the cultivars as the restricted irrigations of 200 and 50 ml water $pot^{-1}\;d^{-1}$ for 5 days for a control and a drought stress, respectively, and a sodium chloride solution of 200 mmol for 6 days for a salt stress. The intact leaves of the two cultivars after treatment were used to measure chlorophyll fluorescence parameters, maximum efficiencies of photosystem II photochemistry (Fv/Fm), efficiencies of photosystem II photochemistry (${\Phi}_{PSII}$), $CO_2$ assimilation rate ($P_N$), and NPQ. Leaf water potentials of the two cultivars decreased from - 0.2 to - 0.8MPa by a drought treatment and from - 0.7 to - 1.7MPa by a salt treatment. Leaf water content of Shinpaldalkong 2 after a salt treatment was less decreased than that of Taekwangkong. $F_v/F_m$ values of both cultivars were not changed, while ${\Phi}_{PSII}$ and $P_N$ were decreased proportionally to leaf water potential decrease. The response of NPQ was occurred in Shinpaldalkong 2 under the drought and salt stresses. With Taekwangkong cultivar, only drought stress referred NPQ response. The cultivar differences on chlorophyll fluorescence parameters were found in the relationships between ${\Phi}_{PSII}$ and $P_N$, and between NPQ and ${\Phi}_{PSII}$. Although the positive relationships between ${\Phi}_{PSII}$ and $P_N$ were established on all treatments of both cultivars, the decreasing rate of ${\Phi}_{PSII}$ to $P_N$ was smaller in Shinpaldalkong 2 than Taekwangkong. The NPQ was increased according to the decrease of ${\Phi}_{PSII}$ by osmotic treatments in Shinpaldalkong 2. The complementary relationships between NPQ and ${\Phi}_{PSII}$ were well maintained at all treatments in Shinpaldalkong 2, while these relationships were lost at a salt treatment in Taekwangkong. Taken together, the results suggest that analysis of complementary relationships between ${\Phi}_{PSII}$ and NPQ could be more valuable and applicable for determining osmotic tolerance than single analysis of each parameter such as $F_v/F_m$, ${\Phi}_{PSII}$ and NPQ.

• Magazine of the Korean Society of Agricultural Engineers
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• v.15 no.2
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• pp.2949-2967
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• 1973

The purpose of this study is to find out and determine the minimum consumptive use of water for Korean cabbage and turmp, so that the minimum water requirement can be secured always for a stable cultivation of these vegetables regardless of weather conditions. The experiment was conducted in two periods; first one from May to July and second one from August to October, each experiment with two varieties of cabbage and two varieties of radish with 2 replicants and 15 treatments. The results found from the above are briefly as follows: 1. Since the mean soil moisture equivalent 64 days after the treatment was 28.5% and the soil moisture content at the time was 2.67% which is far less than that of the wilting point, the crop seemed to be extremely caused by a drought. 2. The rate of 51 days after the seeding, soil moisture content of plot No.2 where irrigation has been continuous was the highest or 21.3%, whereas the plot No.14 without irrigations was 11.2% and the lowest. Therefore, the soil moisture content for the minimum qrowth seemed to be 20%. 3. The consumptive coefficient of Blaney and Criddle on cabbage in two periods were K=1.14 and 0.97 respectively, and on radish in two periods were K=1.06 and 0.86 respectively, thus, cabbage was higher than radish. The consumptive coefficient in the first experiment (May-July) was 0.17 to 0.20 higher than the 2nd experiment(August-October). 4. Nomally, cabbage and radish germinate within one week, however, the germination ot these crops which were treated with a suspended water supply from the beginning took two full weeks. 5. When it elapsed 30 days after seeding, the conditions in plot 1,2 and 3 were fairly good however, the crops in the plops other than these showed a withering and the leaves were withered and changed into high green due to an extrem drought. Though it was about same at the beginning, the drought damage on cabbage was worse than that on radish period, and the reasos for this appears in the latter that the roots are grown too deep. 6. The cabbage showed a high affinity between treated plots and varieties. Consequently, it can be said that cabbage is very suseptive to drought damage, and the yield showed a difference of 35% to 56% depending on the selection oe varieties. 7. The radish also showed a high affinity between the treated plots, however, almost us affinity existed between varieties. Therfore, the yield of radish largely depends on the extent of drought, and the selection of variety does not affect at all. 8. The normal consumptive use on cabbage is $0.62{\ell}/sec$, while that on radish is $0.64{\ell}/sec$, and the minimum optimum water requirement that was obtained in this study is $4,000cc/day/m^3$ or $0.462{\ell}/sec/ha$.