• Journal of The Korean Society of Agricultural Engineers
• /
• v.61 no.1
• /
• pp.95-105
• /
• 2019

Evapotranpiration (ET) is one of the important factor in Hydrological cycle and irrigation planning. In this study, temperature-based artificial neural network (ANN) model for daily reference crop ET estimation was developed and compared with reference crop evapotranpiration ($ET_0$) from FAO-56 Penman-Monteith method (FAO-56 PM) and parameter regionalized Hargreaves method. The ANN model was trained and tested for 10 weather stations (5 inland stations and 5 costal stations) and two input climate factors, maximum temperature ($T_{max}$), minimum temperature ($T_{min}$), and extraterrestrial radiation (RA) were used for training and validation of temperature-based ANN model. Monthly reference ET by the ANN model also compared with parameter regionalized Hargreaves method for ANN model applicability evaluation. The ANN model evapotranspiration demonstrated more accordance to FAO-56 PM evapotranspiration than the $ET_0$ from parameter regionalized Hargreaves method(R-Hargreaves). The results of this study proposed that daily reference crop ET estimated by the ANN model could be used in the condition of no sufficient climate data.

• Journal of The Geomorphological Association of Korea
• /
• v.24 no.1
• /
• pp.39-50
• /
• 2017

This study was conducted to analyze the variation of hydro-geomorphological environment along Baekgok wetland, which experiencing periodical inundation, in that water-level fluctuation of reservoir caused by irrigation. Since the field data is unavailable, modeling techniques, involving models such as HSPF and TELEMAC-2D, have been applied to simulate hydrological cycle in watershed and hydrodynamics in channel scale. The result of simulation indicates that the water-level of reservoir determines both the water surface extension and water depth in the wetland. Furthermore, it also shows that water-level functions as a spatial limit factor for a fluvial environment and woody vegetation such as willow. The fact of which the scale of water-level fluctuation being larger than an average topographical relief along the wetland can explain the result. While the water-level kept high, the wetland is submerged and waterbody becomes lentic. In contrast, while the water-level is lowered, fluvial phenomena of which being dependent on flow rate and channel shape become active. Hence, the valid fluvial process is likely to take place only for 4 months annually just near the channel, and it advances to a conclusion expecting a deposition to be dominant among the wetland except for such area. It is anticipated that such understanding can contribute to establishing plans to preserve the geomorphological and ecological value of the Baekgok wetland.

• Journal of Korean Society on Water Environment
• /
• v.36 no.6
• /
• pp.592-610
• /
• 2020

In South Korea, the concept of water environment was expanded to include aquatic ecosystems with the Integrated Water Management implementation. Watershed-scale modeling is typically performed for hydrologic component analysis, however, there is a need to expand to include ecosystem variability such that the modeling corresponds to the social and political issues around the water environment. For this to be viable, the modeling must account for several distinct features in South Korean watersheds. The modeling must provide reasonable estimations for peak flow rate and apply to paddy areas as they represent 11% of land use area and greatly influence groundwater levels during irrigation. These facts indicate that the modeling time intervals should be sub-daily and the hydrologic model must have sufficient power to process surface flow, subsurface flow, and baseflow. Thus, the features required for watershed-scale modeling are suggested in this study by way of review of frequently used hydrologic models including: Agricultural Policy/Environmental eXtender(APEX), Catchment hydrologic cycle analysis tool(CAT), Hydrological Simulation Program-FORTRAN(HSPF), Spatio-Temporal River-basin Ecohydrology Analysis Model(STREAM), and Soil and Water Assessment Tool(SWAT).

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.10 no.2
• /
• pp.1443-1453
• /
• 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 Korea Water Resources Association
• /
• v.55 no.5
• /
• pp.321-331
• /
• 2022

In this study, we tried to present a method for calculating the amount of regression using a watershed modeling method that can simulate the hydrological mechanism of water balance analysis and agricultural water based on watershed unit. Using the soil water assessment tool (SWAT), a watershed water balance analysis was conducted considering the simulation of paddy fields for the Manbongcheon Standard Basin (97.34 km²), which is a representative agricultural area of the Yeongsan river basin. Before evaluating return flow, the SWAT was calibrated and validated using the daily streamflow observation data at Naju streamflow gauge station (NJ). The coefficient of determination (R²), Nash-Sutcliffe Efficiency (NSE), Root-Mean-Square Error (RMSE) of NJ were 0.73, 0.70, 0.64 mm/day. Based on the calibration results for three years (2015-2017), the quick return flow and the return rate compared to the water supply amount for the irrigation period (April 1 to September 30) were calculated, and the average return flow rate was 53.4%. The proposed method of this study may be used as foundation data to optimal agricultural water supply plan for rational watershed management.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2006.05a
• /
• pp.1444-1449
• /
• 2006

Korea is about 70% of all country to mountain, and basin is consisted of various terrain, soil, vegetation, land use etc. because use land as intensive. Also, need basin hydrologic model that can analysis base outflow as well as outflow directly for calculation of discharge to establish irrigation plan. Inconvenient in use method and user interface offer side is causing by way that existing USGS WEASEL runs in PC Arc/Info, and ArcGIS with development of present GIS technology is applied in many fields offering convenience in analysis that use GIS. In this research, wished to develop suitable outflow parameter extraction system, For this, develop pre-processor and post-processor that effectively draw of hydrologic model input data from water resources DB through van example benchimarking, and developed input/output component of GIS base applicable to various hydrologic and water quality model.

• Journal of Environmental Science International
• /
• v.25 no.7
• /
• pp.1007-1016
• /
• 2016

Environmental policy implementation has been strengthened to protect the source waters in Korea and to improve their water quality. Increasing of non-point source caused water quality problem continuously. Research on runoff from forests, which occupy over 65% of the land in korea, is insufficient, and studies on the characteristics and influences of storm runoff are necessary. In this study, we chose to compare the effects of land use in the form of two types of forest distribution and then gathered data on storm characteristics and runoff properties during rainfall events in these areas. Furthermore, the significance and influences of the discharges were analyzed through correlation analysis, and multilateral runoff characteristics were examined by deducing a formula through $COD_{Mn}$ and TOC regression analysis. At two forest points, for which the basin areas differed from each other, flow changed according to storm quantity and intensity. The peak discharge at point A, where the basin area was big, was high, whereas water-quality fundamental items (BOD, $COD_{Mn}$, and SS) and TOC density were high at point B where the slope and storm intensity were high. Effects of dissolved organic matter were determined through correlation analysis, and the regression formulas for $COD_{Mn}$ and TOC were deduced by regression analysis. It is expected that the data from this study could be useful as basic information in establishing forest management measures.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.50 no.3
• /
• pp.31-41
• /
• 2008

There are many agricultural facilities (46.7%) that have been over 30 years in the Republic of Korea (the ratio of reservoirs built before 1945 is 53%, from 1946 to 1971 is 35%). In the case of reservoirs which do most important functions among these facilities, only 3,000 reservoirs are managed by Korea Rural Community & Agriculture Corporation (KRC) and the other 15,000 reservoirs are managed by local authorities (City and Gun). But, 15,000 reservoirs included in City. Gun have been built in more wide area than KRC and the reservoir management system has not been operated well because of shortage of budget and manpower of the local authorities. Particularly, the abnormal weather happened during every summer season recently has ruined a lot of rural community facilities. So flood control function have been more important than irrigation function in agricultural reservoir system and it may be required to introduce new safe, management and maintenance techniques in City Gun reservoirs. So we investigated landscapes and deteriorations of agricultural reservoirs managed by local small governments for revealing not only present usage but also future value. Survey shows that there are no structural managements except typical hydrological reportings and the deterioration of small darn is very serious. There are needs for more systematic management system and equipment methods. Therefore, this study may suggest that reservoir (that takes charge of the greatest deal of weight in all agricultural facilities) must be considered as new concept of the usage and the unification. On the other hand, reservoir must be also developed as amenity resources, natural circumstances and district values.

• KCID journal
• /
• v.18 no.2
• /
• pp.87-100
• /
• 2011

This study is to delineate the watershed hydrological parameters such as area, slope, rain gauge weight, NRCS-CN and time of concentration (Tc) by using the Geographic Information Sytem (GIS) technique, and estimation of design flood for an ungauged watershed. Especially, we attempted to determine the Tc of ungauged watershed and develop simple program using the cell-based algorithm to calculates upstream or downstream flow time along a flow path for each cell. For a $19km^2$ watershed of tributary of Nakdong river (Seupmoon), the parameters including flow direction, flow accumulation, watershed boundary, stream network and Tc map were extracted from 30m Agreeburn DEM (Digital Elevation Model) and landcover map. And NRCS-CN was extracted from 30m landcover map and soil map. Design rainfall estimation for two rainfall gauge which are Sunsan and Jangcheon using FARD2006 that developed by National Institute for Disaster Prevention (NIDP). Using the parameters as input data of HEC-l model, the design flood was estimated by applying Clark unit hydrograph method. The results showed that the design flood of 50 year frequency of this study was $8m^3/sec$ less than that of the previous fundamental plan in 1994. The value difference came from the different application of watershed parameter, different rainfall distribution (Huff quartile vs. Mononobe) and critical durations. We could infer that the GIS-based parameter preparation is more reasonable than the previous hand-made extraction of watershed parameters.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.36 no.3
• /
• pp.407-416
• /
• 2016

The purpose of this study is to develop regional regression models to estimate mean low flow for ungauged basins. The unregulated streamflow data observed at 12 multipurpose dams and 4 irrigation dams were analyzed for determining mean low flows. Various types of regression models were developed using the relationship between mean low flows and various sets of watershed characteristics such as drainage area, average slope, drainage density, mean annual precipitation, runoff curve number. The performance of each regression model for estimating mean low flows was assessed by comparison with the results obtained from the observed data. It was found that a regional regression model explained by drainage area, the mean annual precipitation, and runoff curve number showed the best performance. The regression model presented in this study also gives better estimates of mean low flow than the estimates by the drainage-area ratio method and the previous regression model.