离子型稀土矿区小流域级地表水氨氮治理工程效果分析及建议

我国南方离子型稀土矿山采用原地浸矿工艺,使用硫酸铵和碳酸铵作为浸矿剂和沉淀剂,导致离子型稀土矿区普遍出现地表水质氨氮超标.为了解决包含历史遗留矿山和停产稀土矿山的矿区地表水污染治理问题,赣州稀土集团有限公司自2018年起开展了国内首次针对离子型稀土矿山小流域级地表水氨氮污染的治理工程并长期运行.根据运行监测数据分析,在...     

The effect of beaver ponds on the nonpoint source water quality of a stream in Southwestern Wyoming

Currant Creek, a second order stream in southwestern Wyoming, has three large complexes of beaver ponds midway along its 32 km length. To determine whether these ponds improve the quality of water flowing through them, during spring and summer of 1984 and 1985 water samples were taken upstream from, within, and downstream from the pond complexes. During periods of high flow (i.e. spring runoff), concentrations of suspended solids (SS), total phosphorus (TP), sodium hydroxide-extractable phosphorus (NaOH-P, an index of biologically available P) and total Kjeldahl nitrogen (TKN) were reduced in water flowing through the beaver ponds. During low flow, beaver ponds had less effect on these parameters. Concentrations of nitrate nitrogen (NO₃-N) were reduced during both high and low flows, while concentrations of ortho-phosphate (ortho-P) did not appear to be affected by beaver ponds. Ammonia nitrogen almost always was at the limit of detection. Regression of NaOH-P versus [SS plus ortho-P] suggested that the primary source of NaOH-P was SS. In general, SS explained a large portion of the variation in TP, TKN, and NaOH-P, and often ortho-P was significantly correlated to TP. The increase in the concentration of most parameters below the area with dam complexes appears to reflect input from bank and channel erosion, and export of SS, TP, TKN and NO₃-N from beaver dam complexes was calculated to be less than that from stream sections above or below the dams. Thus the location of dams should be considered before using them to try and improve water quality. The apparent importance of bank and channel erosion as the primary source of nutrients to Currant Creek contrasts with many watersheds in agricultural areas.     

Impacts of climate and land‐cover changes on water resources in a humid subtropical watershed: a case study from East Texas,USA

This study investigates the response of water resources regarding the climate and land‐cover changes in a humid subtropical watershed during the period 1970–2009. A 0.7°C increase in temperature and a 16.3% increase in precipitation were observed. Temperature had a lower increase trend, and precipitation showed definite increasing trend compared to previous studies. The main trend of land‐cover change was conversion of vegetation and barren lands to developed and crop lands affected by human intervention, and forest and grass to bush/shrub which considered to be caused by natural climate system. Hydrologic responses to climate and land‐cover changes resulted in increases of surface run‐off (15.0%), soil water content (2.7%), evapotranspiration (20.1%) and a decrease in groundwater discharge (9.2%). We found that surface run‐off is relatively stable with precipitation, whereas groundwater discharge and soil water content are sensitive to changes in land cover, especially land cover brought about by human intervention.     

HEC-HMS模型在紫荆关流域水文模拟中的应用

水文模拟对于流域防洪减灾、水资源规划管理有重要意义。基于Aster GDEM2提取紫荆关流域特征,并利用HEC-GeoHMS构建流域HEC-HMS模型。采用初损后损法、Clark单位线、马斯京根法和指数退水曲线法进行产汇流计算,模拟紫荆关流域1980~1988年16场次洪,其中前11场次洪用于率定,其余5场次洪作为验证。结果表明,HEC-HMS模型在紫荆关流域水文模拟中模拟效果较好,率定期的确定性系数在0.762~0.932之间,验证期的确定性系数在0.706~0.890之间,验证了该模型在我国半湿润地区大中流域应用的可行性。     

基于投影覆盖法的小流域模型地貌分形特征

针对流域地貌所具有的明显各向异性和三维立体特征,将投影覆盖法引入其三维表面分形特征的直接量化,结合投影覆盖法计算三维表面分形维数基本原理和GIS技术,提出了基于投影覆盖法的计算流域地貌三维表面分形维数的GIS实现过程,并对9次摄影测量所得小流域模型地貌三维表面分形维数进行了计算。结果表明,投影覆盖法可实现流域地貌三维表面分形特征的直接量化,计算出的地貌三维表面分形维数准确反映了模拟降雨驱动下小流域模型地貌总体特征的动态变化过程;与计盒维数法相比,投影覆盖法更有利于揭示小流域模型不同发育阶段地貌特征的差异性,对于流域水土流失预报模型中地貌因子量化参数的选择具有重要意义。     

基于调查评价数据的永善县山洪灾害危险评价

基于近年来的山洪灾害调查评价数据,以云南省永善县为例,在要素评价框架下提出了一种县域尺度山洪灾害危险评价方法。该方法以小流域为基本统计单元,从河道形态、小流域属性等方面细化指标体系,并综合主成分分析、层次分析法和熵值法进行指标权重设计。结果表明,永善县山洪灾害危险分布主要受褶皱山系控制、区域特征明显,高危险区约占全县小流域总量的59%,主要沿五莲峰山系贯穿县境南北,低危险区集中在县域东南低地势起伏地区。通过对比历史资料,认为该方法精度较高,可为山洪灾害调查评价工作提供补充,为小流域山洪灾害监测预警设施布设、优化山区村镇居民点和开发建设项目布局等提供指导。     

应用区域颜色分割的机采棉杂质检测方法

机采棉中的杂质繁杂,而杂质类型及含量对后期棉花加工工艺的影响很大。为此,提出一种应用区域颜色分割方法以检测棉花中的杂质。在图像分割中,先对滤波后的机采棉图像进行彩色梯度运算,通过扩展极小变换运算获得标记图像,在修改后的梯度图像上运用分水岭算法获得初始分割图像,然后对初始分割图像进行区域合并。区域合并过程中要综合考虑空间邻接性、颜色信息和区域面积3个因素。颜色信息主要采用饱和度、亮度、区域颜色向量模及颜色相似度4 个特征量。用层次递进的合并方法,迭代过程更新信息特征。最后通过支持向量机算法提取颜色、纹理、形状特征对杂质区域进行识别。结果表明,所提方法对机采棉中天然杂质的平均识别率为94%。     

基于GIS的青海湖流域水生态功能分区

湖泊型水生态功能分区是以流域数字高程模型(DEM)为底图,通过水文分析划分出目标流域的自然水文单元和水系,借助流域综合调查资料确定水生态功能分区,也是地学分区面向生态环境领域的发展和应用。基于GIS技术,将研究区7大主要河流水系图、DEM、生态系统服务价值总量图、归一化植被指数(NDVI)图、土地利用类型图等进行统一处理为栅格单元相同的栅格图,使用GS+软件计算各指标要素的空间自相关距离,从而得到各因子之间的空间自相关距离,确定青海湖流域水生态功能一二级分区主导指标和影响指标,运用ArcGIS 10.0软件中的空间叠加法对选定的指标栅格图进行模糊叠加,修正分区边界,确定青海湖流域水生态功能一级分区为8个。以青海湖流域水生态功能一级分区图为底图,在一级分区的基础上确定青海湖流域水生态功能二级分区为27个。青海湖流域水生态功能一、二级分区有助于丰富青海湖流域分异规律研究,为青海湖国家公园的建设提供理论与方法指导。     

以地形为基础的HSC产流模型在辽西半干旱丘陵流域的适用性

采用以地形为基础的HSC产流模型(HAND-based storage capacity curve),以典型半干旱丘陵区的辽宁省叶柏寿流域为研究区,检验模拟效果。在只改变产流模块的情况下,把HSC线型同HBV(hydrologiska byrans vattenbalansavedlning)模型的beta函数、新安江模型的蓄水容量曲线、基于雨强阈值的超渗模型进行比较后发现,在进行长时间序列模拟时,极端高洪峰流量过程对径流的模拟结果有很强的影响。传统模型依赖参数率定,普遍存在参数过拟合现象,即为了提高洪峰流量模拟精度,导致优化的产流参数严重背离物理意义和假设。研究提出的产流模型基于HSC线型并耦合根系区蓄水容量反演的MCT方法,参数物理意义明确且无需率定,可避免传统模型存在的为提高对少数洪峰流量的模拟精度而产生的参数过拟合现象,因此在率定期和验证期其洪水模拟精度表现更为可靠和稳定。     

于桥水库流域水源供给服务的空间分布格局

空间定量评估流域生态系统水源供给服务功能对水源区可持续发展及生态补偿机制的建立具有重要意义。基于研究区土地利用数据、气象数据和土壤数据,应用In VEST模型评估了于桥水库流域生态系统的水源供给量,并定量分析了流域水源供给能力的空间分布格局特征。结果表明:当Zhang系数为3.2时,流域的年径流深为161 mm,流域内年总产水量为3.14亿m~3。从空间分布格局来看,流域水源供给量存在显著的空间异质性;南部和中东部平原区单位面积水源供给量较高,水库南岸水源供给能力高于北岸;遵化市和蓟县对水源供给总量的贡献率达到85%;流域内不同景观类型的水源供给能力由大到小的排序为:耕地林地人工表面裸地灌草地,耕地、林地和人造表面对水源供给总量的贡献率达到82%。流域南部和中东部平原区是水源供给功能保护的重点区域,但同时也是防控城镇面源污染的关键地区。