Analysis of temporal-spatial precipitation variations during the crop growth period in the Lancang River basin, southwestern China

In recent years, droughts and upstream/downstream water conflicts (such as those between water supply and demand) have been occurring frequently in the Lancang River basin, threatening local food security. In this research, the empirical orthogonal function (EOF) analysis and the rotated empirical orthogonal function (REOF) analysis were employed to investigate the temporal and spatial characteristics of precipitation variations during the crop growth period over 1960 to 2009. The results indicated the following: (1) annual precipitation increased slightly over the period of 1960-2009 but decreased significantly (at the 5% significance level) since 2001. An increasing trend was observed in the northern region, while a decreasing trend was observed in the southern region; (2) five regions with different precipitation variation patterns were identified in the crop growth period, including the northern, the northeastern, the southwestern, the western, and the southernmost end patterns; (3) overall, a slightly increasing trend was identified in summer over the study period. Over the period of 2000-2009, precipitation in the summer and autumn decreased, (the strongest decreasing trend was observed in the autumn). Unlike that of the whole area, precipitation in the northern region decreased insignificantly in summer and increased slightly in autumn. Results of this study may facilitate the prevention of potential disasters (e.g., abnormal precipitation) and the reduction of the associated losses through early warning and forecasting of variation trends of regional precipitation. The approach could provide a support for decision-making related to international rivers and agricultural water resources management under global climate change.