天水罗玉沟流域梯田效益分析

<正> 罗玉沟流域地处天水市秦城区北部,属黄河中游黄土丘陵沟懿区第三副区,是渭河支流——藉河的一条支沟。流域总面积75.3km~2,海拔高程1190～1895m。流域内地貌形态以黄土梁状丘陵为主,地面较平缓,大于25°的坡面仅占23.6％,年土壤侵蚀模数达7500t/km~2。罗玉沟流域属温带季风气候,流域平均年降雨量537mm,年蒸发量1293.3mm;流域内冬春干旱,夏秋多暴雨。

Analysis on Benefits of Terraced Field in Luoyugou Gully Watershed in Tianshui City

The terraced field in Luoyugou gully watershed added up to 15800 mu, covering 24% of the total farmland by the end of 1989. According to the experimental data, the annual average yield of slopeland is 143.6 kg/mu , the annual output of the terraced fieId built in sixties and seventies can increase by 59.1 kg per mu, while that in eighties is 21.4 kg per mu, then 15800 mu terraced field in the watershed can increase the yield of cereal products by 77900 kg in 1989. The annual average soil and water lost from slope farmland are 1.31 t and 10.37 m 3 per mu respectively, while after the slope farmland was constructed into terraced field, the annual average soil and water retained are 1.2 t and 9.3m3 per mu respectively. For 27 years from 1963 to 1989, 15800 mu terraced field had reduced the capacity of run-off and sediment by 2108 thousand m3 and 272 thousand tons respectively. At the same time, physical and chemical pro-perties were improved, the quantities of organic matter, total Nitrogen and total Phosphorus in the soil were enhanced greatly and the utilization rate of precipitation was increased along with the improvement of the micro-climate.