在全球变暖的背景下,系统分析气候变化及其对农田水分平衡的影响,对西北地区,乃至全国的生态环境和社会经济可持续发展具有重要的现实意义。论文从水分平衡的角度出发,以县域为基本单元,在10a尺度下,通过构建农田水分平衡模型,全面刻画了气候变化下近40年来西北地区天然状态下农田水分平衡的基本特征及演变态势。结果表明:水分亏缺是西北地区天然状态下农田水分平衡的主要特征,全区亏水量呈现由东南向西北、由高山向盆地递增的空间分布格局;40年来,西北地区农田水分平衡呈现西降东升的态势,新疆大部及河西走廊西部的部分县市,农田亏水量显著降低;西北中部及东部地区大部分县市,40年间农田亏水量呈"W"状波动,近10年亏水最为严重;河西走廊以及新疆大部分县域农田水分平衡年际间变幅较小,中东部地区变幅较大;西北地区降水与农田水分平衡呈显著的正相关,最高温度、最低温度与农田水分平衡的相关性不明显,蒸散量与农田水分平衡呈显著的负相关。

Global warming affects regional sustainable development but there has been lacking in an appropriate approach to assess the impacts. By applying Arc/GIS and Visual Foxpro technologies, this study performs systematical simulation and analysis of the variations in the monthly cropland water balance for 12 major crops in Northwest China over the last 40 years (1960-2000). For 313 counties in the region, it shows that the precipitation and soil water are generally unable to meet the water requirements of the crops. The deficit of cropland water tends to increase from the southeast to the northwest and from mountains to lower basins. By analyzing the anomaly percentage of cropland water balance, this study shows that during the last 40 years, the western part of Northwest China, mainly the Xinjiang Uygur Autonomous Region, has shown a moderate increase both in temperature and precipitation, a slight shift to a warm-wet pattern in climate, and a moderate decrease in water deficit. In contrast, the central and eastern parts of the region have encountered a moderate increase in temperature, a relatively significant decrease in precipitation (especially in recent 10 years), and a moderate increase in water deficit. Furthermore, this study classifies the region into 13 agro-ecological zones and examines the variance of cropland water balance over the last 40 years through analyzing the variation of C_v in these zones. It is shown that in Hexi Corridor of Gansu and Xinjiang Uygur Autonomous Region, C_v is the lowest (<0.10), while in hilly areas around Sichuan Basin C_v takes the highest value of 2.1. In most parts of Northwest China, a significant positive correlation between cropland water balance and precipitation can be identified (r=0.85), indicating that precipitation has been a dominant factor affecting cropland water balance. The correlations of cropland water balance with the maximum and minimum temperature are less significant, particularly the latter. Cropland water balance is also closely related with evapotranspiration (r=-0.88), demonstrating the impact of climate change on cropland water balance.