黄河主要产沙区近年降水变化的空间格局

采集整理了1966—2014年黄河潼关以上主要产沙区604个雨量站的逐年逐日降水,并基于GIS制作了1966—2014年不同时期的年降水量和日降水大于10、25、50、100 mm的年降水总量空间分布图,进而分析了该区不同雨强量级的年降水总量和大暴雨发生频次等降水因子的变化。研究认为,该区日降水大于50 mm的降水总量占年降水量的比例为2.3%~7.8%,其产洪产沙量占年水沙量的比例分别为20%和44%;在潼关来沙较天然时期减少约88%的2005—2014年,河龙间大部、泾河上中游和汾河上游等日降水大于10、25、50 mm的年降水总量总体偏丰;2010—2014年,日降水大于25 mm和50 mm的年降水总量偏丰程度更高,其偏丰程度大于5%的面积占研究区总面积的比例分别为76.9%和69.6%;近年降水偏枯区主要分布在祖厉河和渭河上游西北部。2012—2013年几乎是1966年以来研究区降水最丰的时段。2001年以来,河龙间大部和泾河上中游地区大暴雨发生频次偏高,其它区偏低。

Spatial pattern of precipitation change in the main sediment-yielding area of the Yellow River basin in recent years

Based on daily precipitation data from 604 rainfall stations during 1966-2014 in the main sedi-ment-yielding areas in the upper reaches of Tongguan of Yellow River, the spatial distributions of annual precipitation and the annual accumulated precipitation where daily precipitation was larger than 10, 25, 50 and 100 mm (P10, P25, P50 and P100) for different periods during 1966-2014 were drawn based on Arc-GIS, and changes of total annual precipitation in different rainfall intensity magnitude and frequency of heavy rainstorm were analyzed in the study area. The results indicate that P50 accounted for 2.3%~7.8% of annual rainfall,while the corresponding runoff and sediment yield amount was 20% of the annual flood vol-ume and 44% of annual sediment yield amount, respectively. For the period from 2005 to 2014, when the incoming sediment amount has been reduced by approximately 88% compared with the natural period,P10, P25 and P50 of the main sediment-yielding areas in the most area from Hekou to Longmen and the upper reaches of Fenhe river as well as the upper and middle reaches of Jinghe river were larger than the annu-al average values overall; P25 and P50 were much more larger than the annual average values during 2010 to 2014, the areas where the abundance degree were larger than 5% reached 76.9% and 69.6% of the to-tal study area respectively; and precipitation in the Zuli River and northwest region of the upstream of the Weihe River is less than annual average values. Precipitation of 2012 and 2013 were almost the most abun-dant period since 1966. Since 2001, the frequency of heavy rainstorm is higher in most area from Hekou to Longmen and the upper and middle reaches of the Jinghe River basin,and it is lower in other areas.