Consistency Analysis And Forecasting Of Agricultural Water Demand In Jianghan Plain

The amount of agricultural water accounts for about 62%of the total in China.With the changes in climate,land use and socio-economy,the agricultural structure is greatly changing.How to accurately predict agricultural water demand considering these changes is worth studying.It has a great significance to deeply reveal the rules in agricultural water using under changes,formulate scientific and reasonable water allocation and irrigation schemes,ensure agricultural irrigation and high-quality grain production,promote agricultural water saving and improve water efficiency.Taking Jianghan Plain as the backgroundand,this paper makes a systematic study on agricultural water demand including relative factors and consistency of agricultural water demand as well as its prediction methods,by means of field test monitoring,mathematical modeling,scenario analysis and statistical analysis.The main contents and conclusions are as follows:(1)Rainfall has a direct impact on irrigation to influence regional agricultural water use.Selecting four regions respectively as a small irrigation area scale,medium-sized irrigation scale,large scale irrigation area and greater regional scale,the relationship between the regional rainfall and irrigation water is analyzed.The results show that there is a significant negative correlation between annual rainfall and annual irrigation water amount while a significant positive correlation between annual rainfall frequency and annual irrigation water amount.Under the same regional area,the higher the rainfall frequency is,the larger the irrigation water amount in per unit area is.Under the same rainfall frequency,with the continuous increase of the area scale,the irrigation water amount in per unit area is decreasing.(2)The consistency of crop water demand and rainfall is tested based on the hydrological variation diagnosis system.Crop water demand has significant jump variation and trend variation at the same time,while annual rainfall sequence has no significant trend variation,but has significant jump point.The agricultural water demand under different rainfall types was predicted by the Monte-Carlo-Penman method,which was 5.148～7.200 billion m~3 in wet years,5.634～8.202 billion m~3 in partial wet years,6.560～9.057 billion m~3 in normal flow years,6.797～10.106 billion m~3 in partial dry years,and 7.607～10.657 billion m~3 in dry years.The forecasting result is proved to be reliable to a certain extent though the rationality analysis based on the agricultural water uses in the past years.(3)Some rules are uncovered.The agricultural water demand in 2030 in wet years and normal flow years is less than that in the present situation,while the demand in dry years is greater.Based on the analysis of regional agricultural water demand and water productivity under different scenarios,it is suggested to increase the planting area of organic rice,shrimp rice and facility agriculture in study areas in pursuit of economic benefits.