Current, these were many researches on impact of climate change on active field and human life. The results of the researches shown that the climate change would effect roughly production,human life and environment on the wold scale, especially agricultrural field will be the best vulnerability. In Viet Nam, over the past years, the climate changes in the extreme direction. Namely, precipitation has increased roughly in the rainy season and decreased in the dry season together with average temperature has increased. The climate change addes to more foods and droughts intense. Impact of both climate change and economic development on water demand is very serious in the fi/ture. In recent years, the phenomenon of supplied water shortage for the economic fields occurs frequently with severity at Chi Linh district. Hence, it is need to have study on assessment of impact of climate change and economice development on water balance in the irrigation system. This paper introduces results of the assessment of impact of climate change and economic development on water requirement of households and change of inflow of Phu Loi reservoir, Chi Linh district, Hai Duong province. Results showed that, agricultural water demand will increases significantly, combined with the decrease of inflow in the dry season, water shortage of Phu Loi reservoir will be serious in the future for medium emission scenario (B2). Name,ly, by the year 2020, water demand is expected to further increase by 3,09 percent relative to background period of 1980-1999
by the year 2050, it will be 10,7 percent. The water deficit is expected to increase quitely high with an increase of water deficit of 17,9 percent by the year 2020 and it will be 40,2 percent by the year 2050.