The multi-functionality of paddy field and irrigation water has become a hot issue recently in Asian monsoon regions. Asian people know why they have to conserve the paddy farm where the sustainable functions have been historically inherited and maintain the rural community where the unique cultures have been traditionally created. But, the real value of multi-functionality has not been clearly highlighted as much worthy as it has. We should evaluate the characteristics of multi-functionality of paddy farming correctly and transmit them to the people of Western countries under quite different conditions of upland fields. In Korea, several studies on the multi-functionality of paddy farming have been performed with positive and negative viewpoints. This paper shows the results and the discussion of the researches to get global recognition on the multi-functionality of paddy farming.

Return flow rate of irrigation water was estimated by water balance method. Daepyeong pumping district to irrigate 75.8 ha of rice paddy in the Geum river basin was selected to install gauging instruments to collect data such as weather, water levels, infiltration rate and evapotranspiration during irrigation season (May 27 to Sept. 20) in 2003 and 2004. Irrigation and drainage discharge were calculated from the rating curve and evapotranspiration was estimated both by the modified Penman formula and by the lysimeter. The results were as followed : 1. Total amounts of pumping water during irrigation season were 1,076,000 m

Riparian buffers play an important role in improving water quality, providing wildlife habitat, and reducing suspended sediments and pollutants entering the water body. The efficiency of pollutant reduction by a riparian buffer is greatly influenced by the width of the riparian buffer. In this study, the Soil and Water Assessment Tool (SWAT) model was applied to the Yudeung Stream watershed, Daejeon Stream watershed, and Gap Stream watershed to determine the most effective width of the riparian buffer. These three largest streams in the Daejeon metropolitan area in South Korea were selected to evaluate the effects on nutrient reduction of various riparian buffer widths ranging from 15 to 1,000 m. The decision criterion for the optimum size of the riparian buffer was a 10% reduction in nutrient load based on the water pollution management plan for Daejeon. Total nitrogen and total phosphorus were reduced by 10% with an 80m deciduous riparian buffer and a 70-m evergreen riparian buffer in the Yudeung Stream watershed. Also, this diminishing was also done with a 70m deciduous and 60m evergreen buffer in the Daejeon Stream watershed, and by 9.8% and 16.3% with a 300m deciduous buffer in the Gap Stream watershed, while a 100m evergreen buffer was needed for 10% reduction. Thus, the effects of riparian buffers on flow and nutrient reduction depend on the type of trees and the width of the buffer, as well as the location of the urban area and land uses in the watershed. These results may be useful in developing economical watershed-specific riparian buffer management practices.

This study was performed to suggest a soil loss reduction skill through estimating soil erosion from a small watershed including each type of sloping agriland by using GEOWEPP model. Experimental watershed at Gangwon province was selected for very typical sloping fields of highland agriculture in Alpine area. Runoff discharge and sediment load, hourly rainfall amount occurred during storm event were gauged, and weather data were obtained from Daegwallyeong meteorological station. The results of GEOWEPP model estimation showed that relative error values for total runoff discharge and sediment load were 3 %, -14.5 % respectively. Based on the result, soil erosion and waterway path map for each hillslope were made to select target hillslope. Several hillslopes of severe soil erosion were analyezed and then the optimal vegetative filter strip construction width and waterway path to plant grass were decided by using GEOWEPP Model.