Evaluation of Automatic Irrigation System for Rice Cultivation and Sustainable Agriculture Water Management

The water-resource policy of South Korea has been changing from that of securing water to that of saving water through sustainable water management. Moreover, population aging in rural areas is leading to agricultural water-management problems. In this study, an automatic irrigation system for rice crops was investigated and compared with conventional irrigation, and changes in water productivity and required labor power were quantified. The effect of the proposed system on economic feasibility was verified on farmland by monitoring irrigation water and rice yields for three years. Under the automatic irrigation system, on-site water productivity improved by an average of 12.7% and the labor power required for paddy water management decreased by an average of 21.8% compared to the conventional irrigation system. The internal rate of return was 8.6% higher than the discount rate of 4.5%. The net present value was 406,411 KRW, and the benefit-cost ratio was 1.23. The results can serve as a reference for the on-site introduction of irrigation water-supply automation for sustainable water management and are expected to benefit farmers in saving water and reducing labor demands through sustainable agricultural activities

Assessment of Future Climate Change Impact on an Agricultural Reservoir in South Korea

Drought has been frequently occurring in South Korea due to climate change. Analyzing the water supply capacity of the water resource system provides essential information for water resource management. This study evaluates the future water supply capacity of the Gwanghye (GH) agricultural reservoir based on the representative concentration pathways 4.5 and 8.5 climate change scenarios. We performed a reservoir simulation by reflecting the full water level of the reservoir before and after reservoir heightening. Climate change is expected to decrease the GH reservoir’s future available water resources due to the overall reduction in the reservoir’s runoff. After the reservoir-heightening project, an overall improvement was observed in the stability of the future irrigation water supply. Moreover, the remaining water after the supply of the irrigation water could supply 0.6–7.2 × 103 m3 of daily instream water. Thus, flexible reservoir operations are necessary according to climate change scenarios and the reservoir operation period. The use of climate change information should be expanded to establish reasonable water management policies for future climate change scenarios

Agricultural Reservoir Operation Strategy Considering Climate and Policy Changes

Agricultural water is affected by climate change and water management. Agricultural reservoirs are increasing demand on the environmental water supply because the Korean government has recently implemented an integrated water resource management policy. However, agricultural reservoirs are still in operation solely to supply agricultural water. To examine sustainable agricultural water management under climate change, we analyzed the strategy of operating regulations to efficiently distribute agricultural water as environmental water. We simulated the agricultural reservoir operation, analyzing its water supply capacity by applying operation regulations. The simulation predicted that future water supply capacity would decrease if the existing operation were maintained, and agricultural reservoir operation will be necessary in the future. The proposed reservoir operating strategy decreased the maximum water shortage and number of water shortage days compared with the existing operation with the required water supply. Our results can contribute to agricultural reservoir operation strategies and sustainable water management in response to climate change and provide decision-making guidance on water distribution for environmental use in response to water management policy changes

A Strategy to Quantify Water Supply of an Agricultural Reservoir for Integrated Water Management Policy

A data-driven approach is required to scientifically manage agricultural water resources in accordance with the integrated water management policy of South Korea. In this study, a quantification strategy is presented to calculate reservoir supply by comparing the results with the actual reservoir water storage. Strategies considering current calculation methods were divided into canal flow measurement (S1), theoretical flow rate (S2), water storage decrease in field practice (S3), and water demand in design practice (S4), utilizing water levels of the reservoir and its canal and the level–flow rate curve obtained from surveying the canal flow. Each strategy was assessed through hydrological verification of reservoir water balance modeling. Based on the determination coefficient (R2), Nash–Sutcliffe efficiency (NSE), and relative error (RE) values, the S1 method was found to be the most suitable. S2 had lower reliability than S1, while S3 and S4 satisfied neither R2 nor NSE and had a larger RE than S1 and S2. To accurately quantify agricultural water supplies, the importance of directly measuring reservoir canal flows must be emphasized using automatic water level and flow gauges in canals. This study provides insights into more scientific management of agricultural reservoir water supplies and more effective monitoring of agricultural water usage

Assessment of Agricultural Drought Vulnerability with Focus on Upland Fields and Identification of Primary Management Areas

Robust water management systems are crucial for sustainable water use, particularly considering rapidly changing, ever-improving water supply system technologies. However, the establishment of specific management standards in upland fields is challenging, as several types of crops are cultivated in upland fields. Hence, the timing and required amount of water vary greatly, further rendering drought response challenging. In this study, we evaluated the agricultural drought vulnerability of South Korean upland fields, considering the lack of water resources, to establish preliminary drought damage prevention measures. The Technique for Order of Preference method was used for the drought vulnerability assessment, and the assessment indicators used were annual rainfall, number of dry days, upland field area, available soil water capacity, and groundwater usage. The 20 areas of highest vulnerability comprised large cultivation areas with minimal subsurface-water usage, except for areas where the number of dry days appeared to be the major factor for drought vulnerability. Damage caused by recurring droughts accumulated over time; thus, upland-field-oriented management may be required and can even be used in cases where insufficient drought information is available. Future studies can use the proposed method while considering assessment factors that describe upland field conditions.Y

An Approach to Drought Vulnerability Assessment Focused on Groundwater Wells in Upland Cultivation Areas of South Korea

This study aimed to present an approach that identifies priority management areas to drought focused on field crops and groundwater wells using the MCDM method. Groundwater wells are the primary source of water during drought for field crops. Nevertheless, the systematic management of groundwater wells has not been achieved. Thus, this paper intends to establish a plan that can manage groundwater wells through a vulnerability assessment. This study used TOPSIS, a widely applied multi-criterion decision-making algorithm, to evaluate 158 cities and counties in Korea. This study chose the assessment factors by focusing on drought and classifying the positive and negative elements of the wells. Precipitation, groundwater level, and pumping capacity were considered to have positive effects, while cultivated area, the number of consecutive days without rain, and the proportion of private groundwater wells were considered as negative factors. As a result, the pumping capacity per cultivation area is the major factor affecting management priorities and groundwater well vulnerability. This study presents an approach to assess the drought vulnerability of field crops focused on groundwater wells and select a priority management area, which facilitates efficient well management and reduces damage to crops caused by local droughts

Comparing Water Quantity between Korean and Japanese River

To compare water quantity and quality on the Korean and Japanese rivers, two watersheds with similar watershed area were selected. The one from Korea is called the Yongdam dam watershed in the Geum river basin with watershed area of 930 km2, the other from Japan is called the Nakama watershed in the Onga river basin with watershed area of 925 km2. The 3 discharge, 2 water quality stations from Korea and 14 discharge, 2 water quality stations from Japan were selected and analyzed to determine flow durations. Korean data were collected during 2000 to 2013 from water management information system. Japanese rainfall and discharge data were collected during 1980 to 2013 from water information system. Numbers of station–year were 38 on Korea and 436 on Japan. Annual rainfalls were averaged to 1418.1 mm ranged from 778.2 mm to 2061.9 mm on Korea and 1972.5 mm ranged from 845.0 mm to 3623.0 mm on Japan, from which Japanese showed more 1.39 times than Korean. Streamflow data were generated daily by the ONE (One parametric New Exponential) hydrological model. Simulated annual streamflows were averaged to 854.2 mm ranged from 273.6 mm to 1571.4 mm on Korea and 1481.6 mm ranged from 360.6 mm to 3177.4 mm on Japan, from which Japanese showed 1.73 times more than Korean. The flow durations with 10 year frequency were compared, in which the 1st flows were 18.77 mm in Korea and 88.27 mm in Japan, the 95th flows of 0.43 and 3.97, the 185th of 0.13 and 1.92, the 275th of 0.06 and 0.93, and the 355th of 0.05 and 0.30, respectively. Japanese flows were 4 to 15 times more than Korean. On the other hand, mean flow durations showed the 1st flows of 67.11 mm and 88.27, the 95th of 1.58 and 3.97, the 185th of 0.51 and 1.92, the 275th of 0.21 and 0.93, and the 355th of 0.08 and 0.30, respectively. Japanese flows also showed 1.3 to 4.4 times more than Korean. Mean annual runoff ratios were 58.2% ranged from 35.2% to 76.2% on Korean river, and 73.7% from 42.6% to 90.0% on Japanese river. Japanese runoff ratio also showed 1.27 times more than Korean. This result shows some more necessities and difficulties on low flow management in Korean river than in Japanese river