The Land Use Characteristics In Northeast Part Of Jinghe River Basin During The Past30Years

In NorthWest China, there is a serious shortage of water resources; however, theannual runoff had decreased dramatically such as that in Jinghe River baisn during lastdecades. It was found by recent studies that climate change and land use change i.e.forestation were not enough to cause so strong reduction of runoff. We speculated thatland use intensity increasing e.g. terracing probraly would be the key reason of thisrunoff reduction. In order to test this hypothesis, Rouyuanchuan small catchmentlocated in Northeast part of Jinhe River basin, China was chosen as research area bythis study. Land use changes i.e. intensity changes in last three decades were evaluatedbased on the data of QuickBird image in2009of Rouyuanchuan catchment, its landuse maps in1986and1999. The results were shown as following:1. The key types of land use in the Rouyuanchuan catchment has been kept asgrassland and farmland during the past30years. Only the area of construction landwas increased by28%during1986-1999and1999-2009. There was no big change onthe area of other land use type except construction land.2. In2009, grassland and cropland were the key types of land use with69.8%and21.7%of basin area, respectively in the Rouyuanchan catchment. Forests accountedfor3.4%of basin area and shrubs accounted for1.5%of basin area. The other typesonly distributed with small area.Forests belonged to open forest with mean crown density of0.1and mean treedensity of260trees/hm~2. Canopy width in forests varied in the range of1.4-6.5m,with an average of3.4m.Hippophae rhamnoides shrub was key shrub with the largest area. Compared withthe forests, shrubs need better conditions on light.There were three types of artifical grassland, i.e. alfalfa (Medicago sativaLinn)plantation, grassland within ditches and grassland within small pits, which accounted for6%,4%and2%of basin area, respectively. But natural grassland wasstill key type of grassland as57.8%of basin area. Grassland with medium coverage(20-50%) accounted for44.2%of basin area, which included all of grassland withinditches and grassland within small pits and parts of natural grassland. Grassland withhigh coverage (>50%), which was consisted of alfalfa plantation, amounted to only2.8%of basin area.The micro-landform in cropland has being changed strongly by terracing.Terraces can be grouped as sloping terraces and level terraces, which accounted for6.5%and4.6%of basin area, respectively. The terraces area was more than that oftraditional cropland on natural slopes, which accounted for9.3%of basin area.The area of industrial land was1.2km~2. Wells fields, which located in the middlepart of the basin (the vicinity of the county), had the area of??. The area of rural roadswas4.1km~2, much of which were built following field well construction.3. There were no big change of land use i.e. conversion among forests, shrub,grassland and cropland in Rouyuanchuan. But there are strong change of land use e.g.terracing, artifical grassland. This would also impact on the runoff.