松花江流域不同空间尺度典型流域泥沙输移比及其影响因素

Sediment delivery ratios of typical watersheds on different spatial scales in Songhua River Basin and its affecting factors

为在不同空间尺度上对东北黑土区流域侵蚀产沙建立宏观认识,以松花江流域为研究区,选择不同尺度的典型流域,通过收集降水、遥感影像和土地利用资料,计算不同尺度流域土壤流失量;采用流域出口量水堰和水文站径流泥沙观测资料,计算流域输沙量,从而得出不同空间尺度典型流域悬移质泥沙输移比（SDR）。研究区小尺度流域全年SDR为0.33,大中尺度流域SDR变化于0.005~0.365之间,平均仅0.051。本区SDR存在显著的季节差异：小尺度流域雨季SDR为0.38,春季融雪侵蚀期仅为0.17;流域面积（A）和主河道比降（SLP）是影响大中尺度流域SDR的重要因素;SDR与A呈幂函数递减关系,这在丘陵漫岗区更为显著;山区的流域的SDR随SLP的增加而递增。研究成果有助于建立本区土壤侵蚀与流域产沙之间的定量关系,为流域水土保持规划提供科学依据。

[ Background] There is widespread concern about the severe soil loss in the black soil region of Northeastern China. To date, however, few studies have examined the relationships between soil loss and sediment yields of different watersheds in this area. In this contribution, we calculated sediment delivery ratios of the suspended load （SDR） for selected watersheds of different sizes to obtain an overview of sedimentation and erosion in this region. [ Methods] We chose a total of 36 watersheds of different sizes, small, medium, and large, in the Songhua River Basin for our study. Nineteen of the 36 watersheds were in hilly region, where the altitudes ranged from 200 to 500 m; while the other 17 watersheds were in mountainous region, where the altitudes exceeded 500 m. The SDR of each watershed was the ratio of the sediment yields to the amount of soil loss. We used rainfall and land use data, and remote sensing images to calculate amount of soil loss for the different watersheds, with the adoption of the Chinese Soil Loss Equation （CSLE）. We calculated sediment yields for the different watersheds from runoff and sediment yields data from 36 corresponding hydrological stations. [ Results ] The results indicated that the annual average SDR for the small watershed was 0. 33. The SDR values for the medium- and large-scale watersheds ranged from 0. 005 to 0. 365, and the average was only 0.051. The drainage area （A） and slope of the main channel （SLP） were the two main controls on the SDR values in the medium-and large-scale watersheds： SDR decreased by a power function as A increased, and the relationship for the tested watersheds in the Songhua River Basin was SDR = 1.25A^-0.41 In the watersheds of the hilly region, this relationship was more obvious, the formula was SDR = 4.01A^-0.52. In the mountainous region, SDR increased as SLp increased and the relationship was expressed as： SDR = 0. 007SLP ＋0. 004; however, this relationship did not apply to the hilly region. The slopes in the hilly region generally had gradients that were less than 5° and the slope lengths varied between 500 and 2 000 m, meaning that the eroded particles were easily deposited at the foot of the slope. The SDR values in the Songhua River Basin were clearly lower than those of the Yellow （0.5 - 1.0） and the Yangtze （0.3 - 0.7） River Basins. There were sizeable seasonal differences in the values of the SDR. The SDR for the rainy season in the small watersheds was 0. 38 but was only 0. 17 in the snowmelt season, probably because the eroded particles transported in the snowmelt season were larger than those transported in the rainy season. [ Conclusions ] The results of this study will support the establishment of statistical relationships between soil loss and sediment yields at the watershed and basin scale, and will hopefully provide a robust scientific basis for soil conservation in this region.