最长的地下河The longest underground river
新疆的坎儿井是中国最长的地下河。坎儿，意为井穴，为荒漠地区一特殊灌溉系统，普遍于中国新疆吐鲁番地区。坎儿井与万里长城、京杭大运河并称为中国古代三大工程。吐鲁番的坎儿井总数近千条，全长约5 000千米，多为清代以来陆续修建，如今仍浇灌着 大片绿洲良田。 坎儿井结构大体上是由竖井、地下渠道、 地面渠道和“涝坝”(小型蓄水池)4部分组成，吐鲁番盆地北部的博格达山和西部的喀拉乌成山，春夏时节有大量融化的积雪和雨水流下山谷，潜人戈壁滩下。人们利用山的坡度，巧妙地创造了坎儿井，弓I地下潜流灌溉 农田。坎儿井不因炎热、狂风而使水分大量蒸发，因而流量稳定，保证了自流灌溉。可见，它在吐鲁番盆地大量兴建的原因，是和当 地的自然地理条件分不开的。 正是因为有了这独特的地下水利工程把地下水引向地面，灌溉盆地数十万亩良田，才孕育了吐鲁番各族人民，使沙漠变成了绿洲。林则徐当年途经吐鲁番时，见到了坎儿井，并在他的日记中赞曰：“见沿途多土坑，询其名 曰：‘卡井’，能引水横流者，由南而北，渐引渐高，水从土中穿穴而行，诚不可思议之事! ”Xinjiang Karez is China the longest underground river. Kaner, meaning well points, for the desert area special irrigation systems, ubiquitous in XinjiangTurpan area Chinese. With the Great Wall Karez, Beijing Hangzhou the Grande Canale and known as the China three great ancient engineering projects. The total number of Karez in Turpan nearly a thousand lines, total length of about 5000 km, most of the Qing Dynasty has been built, is now a large oasis farmlandirrigation. Karez structure largely consists of shafts, underground channels,terrestrial channels and "Laoba" (small reservoir) is composed of 4 parts, Turpanbasin of the northern Bogda mountain and west of Karawushen mountain, spring and summer season there are a large number of melting snow and rain flow down the valley, dived under the Gobi. People use the mountain slope, artfully createdKarez, bow I underground irrigation. Karez not due to the hot, the wind so that water evaporation, thus the flow stability, ensure the gravity irrigation. Visible,causes it to build a large number in the Turpan basin, and the natural and geographical conditions inseparable. It is because of this unique underground water into the ground, hundreds of thousands of acres of farmland irrigation basin, only gave birth to the people of all ethnic groups in Turpan, the desert into an oasis. When Lin Zexu passed through Turpan, saw the Karez, and Chan saidin his diary: "see more along the pit, with its name says: 'card well', can bring water cross flow, from south to north, gradually lead to high gradually, water from the soil to wear point line, sincerity incredible things!"