陕西关中西部作物生长季近70年旱涝指数分析——以杨陵为例

用 Bhalme和 Mooley提出的旱涝指数计算方法 ,计算分析了作物生长季 ( 3月～ 1 0月 )杨陵近 70年的旱涝指数。结果表明 ,作物生长季各月不同等级的干旱出现频率远大于涝等级的出现频率 ,其中重旱以 4月～ 5月和 9月～ 1 0月出现频率 >5 % ,中旱以 3月～ 4月 ,6月和 8月出现频率 >1 0 % ;1 930 s～ 1 940 s和 1 970 s～ 1 990 s旱多于涝 ,中旱～重旱出现频率分别比中涝～重涝高 9.9%～ 1 2 .1 %和 1 1 .2 %～ 30 .0 % ;1 95 0 s～ 1 960 s大旱大涝并存 ,涝略多于旱 ,中涝～重涝出现频率比中旱～重旱高 3.8%～ 7.5 %。旱涝指数在 1 95 2年和1

Analysis of Sediment Source of Watershed in Western Shanxi of the Loess Plateau

The paper analyzes the sediment source of watershed by means of studying watershed in westernShanxi of the Losses Plateau. On the basis of watersheds classification, 7 typical watersheds were chosen andobserved for 11 years. The result shows that the sediment at the small watershed mainly comes from gullies,which is 60% of the total sediment. Erosion modulus of valley (including gully head, gully bed, valley side)is 1.28~2.48 times as that of the area between channels(including hill slope and mound of the Loess Plateau).The main sediment source of slope erosion is cultivated land on slope without water and soil conservationmeasures.