小流域防治体系中沟坡兼治的量化指标

Quantitative Index for Erosion Controlfor Both Slope and Gully of Small Watershed ControlSystem

水平梯田可拦蓄降水600 ～800 m m ,而甘肃省黄河流域实测一次短历时最大雨量为166-1 m m ,长江流域为216m m ,即水平梯田可拦蓄径流量是田面承接雨量的3 ～5 倍,靠田面自身的雨量满足不了作物生长的需要,因此在布设坡面工程措施时,可考虑隔坡布设,以增加梯田的深层土壤水分。治沟工程建成后因逐年淤积,其有效拦蓄能力即有效控制面积逐年递减,相邻两年有效控制面积的差值,即为当年坡面治理的最小面积。

Leveledterracefields can hold 600 ～800 m m rainfall, whilethe observed maximum precipitation ofshortdura tion in the Yellow River basin of Gansu Provinceis 166 - 1 m m and the Yangtze River216 m m .Itcan beseen thatthe retaining volume ofrunoff ofleveledterrace fieldsis 3 ～5 times offarmland surface and the rainfallretained bytheland surface can not meetthe requirement ofcrop growth. Therefore,itshould considerthe way oflayout withslope whileconducting engineering measuresforslopesforincreasing soil moisture at a deeplayer ofterraced fields.Aftercompleting gully control works and because of deposition year by year,the effective capacity of retaining andstoring ,i. e.the effective control area will be reduced annually and the difference of effective controlarea of twoneighbouring yearsisthe minimum controlled area ofslope ofthe same year.