Conservation and Management of Agricultural Watersheds in the Snowy-cold Region

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Agricultural farmland in watershed influences variously for all of the ecosystem. For example, farmland have a properly of buffer to the anti-ecological factors. On the other hand, pollutional loads occur according to the farming practices. For the sustainable agriculture, farmland have to harmonize as suitable system in the watershed. In this research, conservation and management of agricultural watersheds in the snowy-cold region investigated through soil loss. And the results may be summarized as follows :(1)Influences of the rainfall must be determine quantitatively for conservation of the sloping farmland. And rainfall-runoff factor R of USLE serves this purpose. But R value can't be calculated correctly by the rainfall data as offered from AMEDAS. And R, o is closely, correlated to the soil loss amount.(2)An estimate of subfactor Rs for thaw and snowmell may be obtained taking 1.0 times the local Dec. -Mar. precipitation, measured as cm of water. Rs values by this method is overestimated in Hokkaido. So modified values investigate by the slope-lysimeter that Rs is 0.113 in south-west district in Hokkaido.(3) For interception the eroded soil enter rivers, various prevention facilities set around the sloping farmland. But complete interception of suspended matter be almost impossible. In this research, behaviors of suspended sediment load in the river are investigated with hydrological conditions and land use in the watershed. Suspended sediment load in snowmell period indicated the closely correlation with temperature-snowmelt amount-river discharge. And this characteristics depends on cacti rivers, because the conditions of soil, land use and meteorology depend on each watersheds too.