70多年来纸坊沟小流域土壤侵蚀演变过程

为了系统研究黄土高原丘陵沟壑区土壤侵蚀演变过程及其规律,以黄土高原纸坊沟流域为例,在GIS的支持下,运用RUSLE估算了该流域1938-2010年间18个年份的年侵蚀量和侵蚀强度,分析了70多年来流域土壤侵蚀时空演变过程.结果表明:1)纸坊沟流域的土壤侵蚀随时间呈四次抛物线变化,侵蚀模数由1938年的7 584.39t/(km2·a)猛增到1958年的4万6 392.56 t/( km2 ·a),随后总体呈递减趋势,到2010年侵蚀模数降至5 150.80t/( km2·a).2)1938年中度以下侵蚀面积占流域总面积的52.99％;1958-1978年以剧烈侵蚀为主,占流域总面积的67.05％,其中1958年高达78.61％；1978-1998年侵蚀强度有所下降,微度侵蚀面积占流域总面积比例达到29.27％;1999年以来,微度侵蚀面积达到3.85 km2,剧烈侵蚀面积仅占流域总面积的8.96％.经过30多年的综合治理,该流域生态环境明显改善,但沟谷陡荒坡侵蚀依然严重,是今后水土流失治理的重点区域.

Soil erosion dynamics of Zhifanggou Watershed during the past 70 years

In order to explore the dynamic change of soil erosion in Loess Hilly-gully Area of Loess Plateau,this paper,taking Zhifanggou Watershed as a case study,evaluated the soil erosion change from 1938 to 2010.Combined with GIS technique,the revised universal soil loss equation(RUSLE) was used to evaluate spatial and temporal change of soil erosion.The results showed that: 1) The soil erosion modulus increased significantly from 7 584.39t/(km2·a) in 1938 to 46 392.56 t/(km2·a) in 1958,while it decreased to 5 150.80 t/(km2·a) in 2010.2) The area below moderate erosion account for 52.99% of the whole area in 1938.3) During the periods from 1958 to 1978,severe erosion account for a major part of the whole area,which was 67.05%,and the most severe erosion happened in 1958,which account for 78.61% of the whole area.4) Soil erosion intensity decreased slightly during the period from 1978 to 1998,the area with slight erosion accounted for 29.27% of the whole area;the area increased to 3.85 km2 since 1999,and area severe erosion only account for 8.96% of the watershed area.As the continuous ecological management over the past 30 years,the eco-environment in Zhifanggou Watershed was improved,but soil erosion in steep slope and gullies are still the key problems in the future conservation.