吉兰泰盐湖防护体系的防风阻沙效应

Windbreak and sand-blocking effects of Jilantai Salt Lake protection system

[目的]定量描述防护体系防风阻沙能力及地表蚀积变化,揭示盐湖防护体系的防风阻沙作用规律,为吉兰泰盐湖防护体系防护效果评估提供数据支撑,为中国西北风沙区及荒漠盐湖沙害治理提供理论依据。[方法]选择吉兰泰盐湖防护体系为研究对象,通过野外原位监测,对3,10月两场典型强风沙尘天气下不同下垫面0—30 cm高度内输沙以及逐月地表蚀积情况进行观测。[结果](1)2 m高度处风速由流动沙垄到盐湖湖心表现为衰减—急剧衰减—恢复阶段,到盐湖湖心时风速恢复至旷野风速。从白刺灌丛至盐碱滩地风速均较流动沙垄降低了70%~90%。(2)从白刺灌丛至盐湖湖心输沙量呈现为急剧降低—降低—缓慢增加的状态,整体较流动沙垄降低了83.89%~94.90%。(3)防护体系对两种主害风的防风阻沙效果明显,其风速及输沙量分别较流动沙垄降低了98.71%,91.79%,且西北风向下的防风阻沙效果优于西南风向。(4)6—9月白刺灌丛至盐湖湖心地表呈现为风积状态,且净蚀积强度较流动沙垄最高可降低157.04%。[结论]虽然受季节和风向影响,但防护体系防风阻沙效果仍保持较好状态,它对风沙流的阻滞作用使地表由风蚀转为堆积,并使风速及输沙量均降低了90%以上,从而有效避免盐湖湖面积沙。

[Objective]The ability of a salt lake protection system to protect against wind and sand damage quantitatively and the changes to surface erosion and deposition induced by the system were described in order to reveal the wind-proof and sand-resistant action law of the protection system.The purpose of this study is to provide data support for the evaluation of the protection effect of the Jilantai Salt Lake protection system,and to provide a theoretical basis for sand damage control in the sandstorm area and desert salt lake in Northwest China.[Methods]The Jilantai Salt Lake protection system was chosen as the research object.Sand transporting(at 0—30 cm height)and surface erosion sediment intensity(monthly)were observed in situ by field positioning monitoring in different parts of the Jilantai Salt Lake protection system.[Results]①The wind speed at 2 m height from the moving sand ridge to the center of the salt lake passed through three phases(attenuation,rapid attenuation,recovery).The wind speed from the Nitraria tangutorum shrub to the saline-alkali beach decreased by 70%~90%compared with the moving sand ridge.②The sediment discharge from N.tangutorum to the center of the salt lake passed through three states(sharp decrease-decrease-slow increase),and was 83.89%~94.90%lower than the sediment discharge of the moving sand ridge.③The effect of the protection system on wind prevention and sand resistance from the two main harmful wind periods was obvious.Wind speed and sediment discharge decreased by 98.71%and 91.79%,respectively,compared with the moving sand ridge.In addition,the effect on wind and sediment prevention for the northwest wind direction was better than that for the southwest wind direction.④The surface showed sedimentation from N.tangutorum to the center of the salt lake from June to September,and the net erosion intensity could be reduced by up to a maximum of 157.04%compared with the moving sand ridge.[Conclusion]Although the protection system was affected by season and wind direction,the windbreak and sand-blocking effects still maintained a good state,and its blocking effect on wind-sand flow can change the state of the surface from wind erosion to sedimentation,thereby reducing wind speed and sediment discharge by more than 90%,and thus effectively avoiding sand accumulation on the salt lake surface.