In snowy regions,the seasonal runoff pattern is greatly influenced by winter season temperature and precipitation which determines the accumulation and melt of seasonal snowpack.Climate change therefore has the potential to impact dramatically on the natural storage and release of water in seasonal snowpacks.The Niigata Plain is one of the most important rice-producing areas of Japan,and it currently relies heavily on spring snowmelt runoff to irrigate the rice paddies.Snowmelt water is released from mountain snowpack primarily during April and May,supplying the vast quantities of water needed for transplanting rice seedlings to irrigated paddy fields.Snowmelt continues to be a vital water resource up until the arrival of the rainy season in late June,especially as April to late-June is a period of relatively little precipitation in Niigata.