| The Yellow River Basin plays a very important role on Chinese agriculture and the national economic development. However, the river interception, environment degradation, soil erosion, etc, which were caused by lacking water had taken much adverse influence on the people's living environment and regional economic development. Moreover, the situation of water scarcity has seriously restricted agricultural sustainable development in the Yellow River Basin. Therefore, high-efficient water resource utilization and modem water-saving agricultural construction are important stratagems to the food security, ecological security and resource security of the Yellow River Basin.In view of this, the Yellow River Basin was selected as the study area in this post-doctor research. The Geographical Information System, wavelet analysis and Surfer method are used to analysis the agricultural climate resource, the spatial and temporal structure of soil moisture and the distribution rule of main crops' water situation in the Yellow River Basin. Based on above mentions, the author constructed the index system to regionalize agricultural types in the Yellow River Basin and put forward the water-saving scheme on agricultural divided area. The results and conclusions of this report will provide scientific basis for other key researches related with water saving agriculture such as agricultural water resource utilization and monitoring of soil moisture, etc. In conclusion, some important results are obtained as follows:①Through analyzing the climatic changes of the Yellow River Basin in the past 40 years, it is showed that the distribution of rainfall in the Yellow River Basin has obviously regional difference, which is influenced not only by the weather system but also by the geographical environment such as topography, etc. The main distribution trend is that there is more in the Southeastern and less in the Northwestern, and the rainfall in mountain areas exceeds the plains; Based on the monthly and annual rainfall data of 1961～2000, the multi-time scales characteristics of seasonal and annual rainfall in the past 40 years in the Yellow River Basin have been analyzed using Mexican Hat wavelet analysis in this report. The periodic oscillation of rainfall variation and the points of abrupt change at different time scales along the time series are discovered and the main periods of every serial are confirmed. The results indicate that there are obvious periodic oscillation of 8-12 years and 4-6 years for the seasonal and annual rainfalls variation. The variation trend of the summer rainfall is similar in some degree with that of the annual rainfall and both of them have the comparable main periods. The localization characteristics of time-frequency for wavelet analysis can demonstrate the detailed structures of rainfall. The wavelet analysis can be an alternative approach to analyze climate multi-time scales characteristics and forecast short-term climate variations.The whole distribution trend of the temperature in the Yellow River Basin is that the temperature is reducing gradually from the south to the north and from the east to the west. In respect to annual change, the temperature has an increasing tendency year by year since 1960. Furthermore, the temperature in January is the lowest and July is the highest; the evaporation capacity in the Yellow River Basin is high, the annual average evaporation is about 1100mm, and the spatial distribution is contrary to the distribution of the rainfall, which increases progressively from the Southeastern to the Northwestern.②Through analyzing the spatial and temporal structure of soil moisture in the Yellow River Basin, it is showed that the spatial distribution of soil moisture is mainly influenced by the natural climate characteristics and the anthropogenic influence (such as irrigation). The seasonal variation of soil moisture in the Yellow River Basin can be roughly divided into 4 stages: Relatively stable stage in winter (from last November to the first ten days of March), fast evaporation stage in spring (from midMarch to the last ten days of June), the stage of soil moisture's resuming (July, August and the first ten days of September), the stage of soil moisture's slow evaporation in autumn (from mid-September to the last ten days of November). Because of the regional difference of soil and climatic conditions, the division of 4 stages of soil moisture circulation is not all the same between different areas; the soil moisture dynamics between different dry farming areas in the Yellow River Basin is contrasted in this report. The results indicate that soil moisture increases gradually from dry semi-arid area to semi-arid area, dry semi-humid area and semi-humid area, and the high value district generally appears during soil moisture resuming period in rainy season or soil melting period. While the low value district appears at the stage of fast evaporation in spring or slow evaporation in autumn; in views of vertical changes of soil moisture, it is showed that the variation range of upper lays is larger than that of lower among the different dry farming areas in the Yellow River Basin. Moreover, the variation range from 0～5cm to 50～100cm reduce gradually from dry area, dry semi-arid area, semi-arid area, dry semi-humid area to semi-humid area. The variation tendency of soil moisture from top to bottom can be divided into three kinds situations, such as increasing type, reducing type and fluctuating type; The vertical changing range of soil moisture in the Yellow River Basin can be conclude as: the active changing layer lies in between 0cm and 30cm roughly, while the slow changing layer lies in between 30cm and 100cm, and the relatively stable layer lies in undersurface of 100cm; In respect to the dynamic changes of soil moisture in different precipitation years in typical stations, no matter the vertical change, or the horizontal change, the variation range of soil moisture is larger in typical abundant rainfall year than in typical lacking rainfall year.③Climate water balance in different dry fanning areas and main crops rainfall balance in the Yellow River Basin are analyzed in this report. The results indicate that: climate water in the Yellow River Basin increase gradually from south to north and from west to east in the space, which change between 200mm and 600mm in most areas; In views of the seasonal changes of climate water, water shortage happens in spring and early summer, which is exposed to being between 180mm and 300mm generally.As far as the matching degree of the water requirement of main crops with precipitation in the whole growing period, the water requirement of winter wheat in the whole growing period varies from 400mm to 700mm in most areas in the Yellow River Basin, and it increases from the Southeastern to the Northwestern in the space, but the water shortage amount of winter wheat varies from 250mm to 500mm in the whole growing period, and it increases gradually from the south to the north, which reflects the double influences of precipitation and water requirement of winter wheat in the whole growing period; The water requirement of summer maize changes from 300mm to 500mm in the whole growing period in the Yellow River Basin, which has a small change in whole basin relatively and is much different with the water requirement of winter wheat, which was caused mostly by the short growth period and little difference of heat condition for summer maize. Guanzhong area of Shaanxi Province is the place where the summer maize has a big water lack amount in its whole breeding time and which can reach about 200mm and reduces gradually to the east. The water requirement of spring wheat in its whole growing period in the Yellow River Basin varies from 400mm to 700mm and increases gradually from the south to the north and from the west to the east. While its lacked-water amount increases gradually from the south to the north, and normally between 200mm and 500mm, which is mostly influenced by the rainfall and water requirement obviously; the water requirement of spring maize is usually between 400mm and 500mm in the Yellow River Basin. The maximum value appears in Yulin and Suide of Shaanxi Province and reduces gradually from this to both sides. While the water shortage amount of spring maize in its whole growing period varies from 0mm to 400mm which increases gradually from the south to the north. ④Based on selecting index and using relevant methods, classification of water-saving agriculture in Yellow River Basin is carried on in this report. The result indicates that the water-saving agriculture in the Yellow River Basin can be zoned into 5 first-class areas and 18 second-class areas. The 5 first-class is that dry and extremely lacked water area, dry semi-arid and severe lacked water area, semi-arid and moderate lacked water area, dry semi-humid and tiny lacked water area and semi-humid and none-lacked water area. Based on the natural conditions and agricultural production status of the 5 first-class areas and the 18 second-class areas, the water-saving agricultural development modes for each are discussed in this report in order to improve the high-efficient utilization of water resources such as natural rainfall, surface water, soil water and groundwater. Therefore, it is very significant to realize sustainable development of the modern water-saving irrigation agriculture and modern drought water-saving agriculture in the Yellow River Basin.
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