poster - International Conference of Agricultural Engineering

water maintenance. At the same time, thess systems are equipped with estimation
procedures to determine appropriate environmental water levels according to the levels of
the observed performance data. In other words, the previous case shows that on-site
monitoring is extremely important (KRCC, 2010). It shows the importance of systematic onsite
monitoring. Therefore, the purpose of this study was to monitor the stream flow of rural
streams in order to investigate the status of stream depletion located downstream from
irrigation reservoirs.
Ⅱ. Materials and Methods
2.1 Watershed Study
The Bonghyun and Hai reservoirs, located in Hai-myeon, which is in the city of Gosung in
the Gyeongnam Province, Korea were selected for watershed and stream study. The Seokji
stream has a length of approximately 2,600 m from the Hai reservoir spillway. The Seokji and
Bonghyeon streams meet downstream. The flow goes into the southern sea. The Bonghyeon
reservoir has a watershed area of 2.80 km 2 and the irrigation area is 0.38 km 2 . The Hai
reservoir has a watershed area of 13.42 km 2 , and the irrigation area is 1.67 km 2 . The scale of
the land use data by the Ministry of Environment is 1:25,000 which indicates that paddies
cover 62.3% of the total area or 4.40 km 2 . Cropland has an area of 0.71 km 2 and the
residential area is 0.75 km 2 . The remaining area covers 17% of the total area. Stream water
is released regularly from the reservoirs to use as irrigation water because most of the area
is covered with paddies.
2.2 Meteorological data
It is important to have a steady water supply to prevent stream depletion. The outflow
discharge, the amount of evapotranspiration, and reservoir flood routing should be
considered in order to maintain stream environment. The weather data was collected from
the Jinju weather station from 1970 through 2011. The rainfall data is divided into irrigation
periods and non-irrigation periods (FIGURE 1). The city of Jinju's annual average
precipitation was 1,503 mm, higher than Korea's annual average precipitation. In 1989,
Jinju's annual average precipitation reached a record high. It reached a low 784.9 mm in
1994. According to the weather data, the mean wind velocity in Jinju was the fastest at 2.9
m/s. The lowest was when the relative humidity was 45.2% in February, 2000. The mean
wind velocity was lowest at 0.8 m/s in 1977, 2006, 2007, and 2008. 284 hours of recorded
sunshine were the most recorded in July, 1994 and the lowest of 32.2 hours were recorded
in July, 1984.
FIGURE 1 Compared rainfall of irrigation periods (May-Oct.) and non-irrigation periods (Nov.-Apr.)
2.3 Reservoir Storage Capacity Assessment and Investigation
A selection of watersheds was made for the study after considering their accessibility, their
storage amount, stream lengths, and the usages of riverbeds from the reservoirs. The Hai
reservoir (Standard code, 4882010042), located in Hai-myeon, which is in the city of Gosung
in the Gyeongnam Province, Korea was completed in 1971. Now it is managed and operated
by the Goseong and Geoje offices of the Korean Rural Corporation. The Hai reservoir is a fill
dam. It has 1,000 m 3 in volume, is more than 23.2 m tall and has a length that just reaches
2