The field survey for the elucidation of the mechanism and the control of the drought that occurs frequently in the agricultural zone of the yellow river basin in recent years

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In the agricultural area in the Yellow River basin in China, a water shortage occurred frequently in 1972 and continued until 1999. We clarified this mechanism and proposed a suitable agricultural form.Evaluation of water resources of the Yellow River basin was performed. The model with surface temperature and albedo by GMS presumes the precipitation of 14 points by multiple linear regression analysis. From this model, we concluded that the precipitation of the Yellow River basin does not have a downward tendency.We developed a model for the solar and net radiation by satellite data and applied to Shenmu and Yucheng form June 2000 to December 2002. The distribution of solar radiation is similar to the climate map by observation. We also developed a model for evapo-transpiration and applied to Ansai. The model showed there were 151 days of water shortage for crops. To keep sufficient water content, irrigation with 239mm of water was needed.The water use in the lower basin is affected the outflow from the upper and the middle basin and although the effort to effective water use was made, the situation is still unpredictable. We also investigated the change of the vegetation in the lower basin of Yellow River during the periods of dry-up of the river by satellite data and observational data in 1981-2000 and found the correlation between the water flow rate and NDVI. It came from the uptake of water from the Yellow River to irrigate the autumn.