Groundwater Ensure Capacity Spatial-temporal Characteristics And Mechanism In Main Grain Producing Areas Of North China Plain Under Different Climatic Conditions

North China Plain (NCP)is the main winter wheat and summer maize production area in china, and groundwater is the main irrigation source in this area。 Irrigation water and groundwater over-exploitation density is closely related to climate change. So, It is of great significance to study the groundwater ensure extent in different climatic conditions.In this paper, aiming at the problems which the irrigation agriculture dependent and influence on groundwater is continuous rising, focus on further understanding groundwater ensure extent under climate change condition of next 30 years. Utilizing the methods of statistical analysis, penman formula, based on GCM predicted data of precipitation and air temperature data in 2011-2060, carried out the study of spatial and temporal characteristic and influence mechanism groundwater ensure extent. The main results as follows:(1) Climate change has significance influence on grain crop irrigation water requirement in NCP, and there is a great difference in different hydrological years, the reasonable utilization of this difference has great potential for water saving. In wet year, the main distribution area of winter wheat irrigation water demand index(IDI) was in between 0.6 and 0.7, and summer maize was in between 0.3 and 0.4. In normal flow years, the main distribution area of winter wheat IDI was in between 0.7 and 0.8, and summer maize was in between 0.4 and 0.5. under dry years, the main distribution area of winter wheat IDI was in between 0.8 and 0.85, and the summer maize was in between 0.6 and 0.7.(2)The influence climate impact on groundwater level in different regions is obviously different,which is closely related to the regional difference of the regional hydrogeological conditions. In the piedmont plain, in the combined climate conditions of wet-wet years, the groundwater level years will rebound sharply. In the combined climate conditions of normal flow-dry years, dry-dry year, the groundwater level years will significantly decline.In the Central Plains, under the combined climate conditions of normal flow-dry years, the groundwater level has the tendency of declining, in the combined condition of normal flow-normal flow year, the groundwater level can be recovered to the level of the beginning of the year. In the coastal plain, under the combined climate conditions of wet-wet years, the groundwater level was slightly downward trend, in the condition of normal flow-dry year, groundwater level will significantly decline.(3) Climate change has a great influence on groundwater ensure extent, and it is an important constraint for the rational exploitation of groundwater in irrigation agriculture. In wet years, the groundwater ensure extent of NCP is 81%, is belong to higher extent. In normal flow year, the groundwater ensure extent is 54%, is the state of basic ensure extent. In dry years, the groundwater ensure extent is 45%, is under inferior state.(4) Under the climate scenarios of RCP4.5, In Taihang Piedmont of North Henan plain, the groundwater ensure extent is in higher state, Yanshan Piedmont plain is under basic ensure extent, Taihang Mountain of Hebei Plain, Henan central plain and the coastal plain is in a state of inferior, and the Hebei central plain is under the state of difficult to ensure.Innovation point:Prominent the mechanism research of climate change and agriculture exploitation impact on groundwater ensure extent. Understanding the process, characteristics and law of groundwater evolution in NCP main grain producing area with the concept of system, Utilizing the methods of dynamic viewpoint and nonlinear dynamic theory, for the first time,clarified the characteristics and development trends of groundwater ensure extent of different regions of NCP in different hydrological years.