It is necessery that the total consumptive use of water in the rotation period is equal to the total effective precipitation(pre- cipitation minus runoff depth)in the loess hilly region.
在黄土丘陵区要求林草与农作物地在轮作周期内的总耗水量与有效雨量（降雨量与径流深之差）持平。
Leung is located in the Loess hilly and gully region, an Qinba Mountain West Qinling Mountains in the north, the continental cold sub-humid climate and a half.
地处黄土梁峁沟壑区，属秦巴山区西秦岭北部，大陆性半高寒半湿润气候。
West limestone dry stone mountain, central as the Loess Plateau hilly region and the Taiwan area, the eastern plains area, 731-1716 m above sea level in between.
西部为石灰岩干石山区，中部为黄土丘陵区和台塬区，东部为平原区，海拔高度在731-1716米之间。
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