小流域岩土侵蚀规律研究——以子洲县周家圪崂乡桥沟小流域为例

桥沟小流域位于子洲县周家圪崂乡东部,系黄河四级支流,面积19km^2。桥沟主沟长5．75km,坡降12．8％,沟谷切深100m左右。流域内地貌为黄土梁峁及沟壑,出露地层主要有侏罗系砂泥岩、新近系（原为第三系）红土和第四系黄土。黄土层中下部含地下水,在黄土与基岩接触带,多有下降泉溢出。从地层岩性上看,第四系黄土分布广,厚度大,结构松散,遇水易解体。岩土侵蚀环境地质类型有三：一是降雨对谷坡面的面状冲刷一坡面侵蚀;二是地表径流对谷底的侧蚀一沟谷侵蚀,三是滑塌对谷坡坡体的破坏一重力侵蚀。三种侵重力蚀的防治措施各有侧重点,对于坡面侵蚀的防治措施主要是退耕还林种草,改造微地貌;对于沟谷及重力侵蚀的防治措施主要是沟道坝系建设,即在重力侵蚀及沟谷侵蚀发育区下游,修建淤地坝,从而抬高侵蚀基准,减少重力侵蚀的发生。     

基于数学形态学的IKONOS多光谱图像分割方法研究

利用数学形态学方法,研究与探讨了IKONOS多光谱图像的分割技术.提出一种结合图像边缘特征和纹理特征的混合分割新算法.在高分辨率多光谱遥感图像K-L变换的基础上,采用多尺度多方向形态学梯度算子提取边缘特征.应用数学形态学滤波及局部方差统计特征对图像对象进行标记,最后采用强制最小过程,进行标记控制的分水岭分割.研究结果表明,提出的分割算法优于仅利用边缘特征的分水岭分割算法,同时,该算法能较好地解决分割过程中存在的过分割与欠分割问题,是一种适合高分辨率多光谱遥感图像的分割算法.     

The contribution of gully erosion to total sediment production in a small watershed in Southwest China

Determining the contribution of gully erosion to the total sediment yield is important for enhancing decision-making regarding sediment abatement and soil conservation measures. The dry-hot valley region of the Jinsha River is one of the most intensive areas of gully erosion in China. However, the contribution of gully erosion to total sediment production in this region is unclear. Instead of using the source tracing technique commonly employed in other studies, this study provides a method of rapidly reconstructing historical sediment yields based on the properties of sediment that accumulated in an undrained pond at a small gully watershed outlet. We produced a three-dimensional model in geographical information system software to calculate the volume of each layer of accumulated pond deposits from 2006 to 2011. Moreover, we estimated sheet erosion amounts using the Universal Soil Loss Equation. The results showed that sheet erosion accounted for between 14.28 and 23.39% of the total sediment yield in the watershed in the case that the sediment delivery ratio was 100%. Therefore, gully erosion is the major source of total soil loss in this area, and effective soil measures of gully erosion mitigation are crucial for managing the sediment yield.     

俄罗斯西伯利亚与远东地区城镇化发展水平测度及空间分异研究

构建城镇化评价指标体系,研究俄罗斯西伯利亚与远东地区2005~2015年人口、经济、社会城镇化发展水平及空间分异。研究表明：俄罗斯西伯利亚与远东地区城镇化综合发展水平呈小幅上升,西伯利亚城镇化发展水平高于远东,两联邦区人口城镇化水平下降、经济与社会城镇化发展缓慢,多数联邦主体的城镇化发展低于平均水平;空间上,城镇化发展水平高值区集中在西伯利亚联邦区西部（鄂木斯克-新西伯利亚-阿尔泰边疆区-克麦罗沃-克拉斯诺亚尔斯克-伊尔库茨克联邦主体）,低值区分布在远东联邦区东部（马加丹-楚科奇-勘察加联邦主体）,西高东低格局特征显著;最后探讨了促进西伯利亚与远东人口、经济、社会城镇化发展的具体对策。     

北方半干旱快速城镇化流域径流变化的驱动因素分析

通过社会经济发展对于流域水文过程产生的影响,分析城镇化流域的径流变化对于水资源管理保护和促进社会经济发展具有重要的作用。利用乌兰木伦河流域1997-2015年的水文气象、土地利用和社会经济等数据,以降水-径流双累积曲线、改进的Mann-Kendall检验和主成分分析等方法从不同时间尺度分析了流域径流、城镇化、气候和社会经济的变化趋势,揭示了气候、社会经济快速发展和城镇化过程对于流域径流的影响,发现了研究区年、季尺度下径流变化的主要驱动因素,并建立与不同时间尺度径流的映射函数关系。结果表明：在鄂尔多斯市快速城镇化影响下,研究区径流深呈现下降趋势,在2005年出现拐点变化; 2005年之后的平均径流深小于之前的平均径流深;降水、蒸发、气温等气候因素没有显著变化趋势,但城镇化面积、GDP和人口明显增加,城镇化为2005年后研究区径流减少的主要驱动因素;城镇化对于枯水季径流的影响更为显著。     

长三角典型城郊流域溶解性有机质的分子特征:以浙江樟溪为例

溶解性有机质(DOM)在流域水环境中广泛存在,参与各种生物地球化学循环过程。快速的城镇化过程和人类活动显著改变了流域水体DOM含量和特性,从分子层面上解析DOM在流域尺度上的时空分异特征对流域水质管控具有重要的理论和应用价值。以长三角地区樟溪流域为研究对象,依据土地利用和人类活动强度布设采样点,于2022年7月采集水样。结果表明,樟溪流域水体溶解性有机物主要的分子式元素组成为CHO、CHON、CHOS,其中木质素/富羧酸脂环分子类有机物相对占比最高。在子流域空间分布上,人类活动强的子流域CHON、CHONS类型化合物含量更高。选取采样点距城镇距离、距源头距离以及土地利用类型所占采样点缓冲区的比例来表征人类活动的影响。结果表明,流域内DOM杂原子受人类活动强度影响,距源头的距离与水体DOM分子中氮原子的强度加权平均值(N_wa)和CHON化合物百分呈显著正相关,与碳、氢原子和荷质比的强度加权平均值(C_wa、H_wa、m/z_wa)呈显著负相关。CHON分子的相对丰度与林地面积比例呈显著负相关,与农业用地比例呈显著正相关。比较具有典型土地利用类型的水体DOM:典型农田、城镇土地利用类型DOM含有更多独特的CHON分子式,农田DOM在木质素/富羧酸脂环分子区域出现CHON分子式的富集,城镇DOM在脂肪类和木质素/富羧酸脂环分子区域均出现了CHON分子式富集。研究表明在城郊流域中,人类活动显著改变了水体DOM的分子特征,增加了分子多样性,促进了特定分子式的富集。     

怒江小流域土地利用变化及人文驱动力分析--以茶山小流域为例

通过实地调查和两期土地利用现状数据对比以及对农户的访谈,分析研究怒江茶山小流域土地利用现状及时空变化特征,从人文地理视角研究人地关系地域系统,分析导致土地利用变化的驱动力,为确立可持续发展背景下土地利用优化模式及产业结构的优化提供重要前提和科学依据。     

人工沟渠对流域水文格局的影响研究

人工沟渠是指以排水和灌溉为主要目的的人工挖掘的水道。目前,国内外对人工沟渠的研究主要集中在控制沟渠对农田或斜坡影响的水文过程上,而有关人工沟渠对流域水文格局影响的研究比较少,并且缺乏人工沟渠景观及其所携带污染物管理的研究。在流域的尺度上,从人工沟渠对流域径流、污染物传输和水文连通性的影响三方面,详细阐述了人工沟渠对流域水文格局的影响;并对目前人工沟渠对流域水文格局影响研究中存在的问题进行了讨论,同时指出了需要进一步开展的相关研究工作。     

Nitrogen fluxes in a high elevation colorado rocky mountain basin

Measured, calculated and simulated values were combined to develop an annual nitrogen budget for Loch Vale Watershed (LVWS) in the Colorado Front Range. Nine-year average wet nitrogen deposition values were 1·6 (s=0·36) kg NO₃-N ha⁻¹, and 1·0 (s=0·3) kg NH₄-N ha⁻¹. Assuming dry nitrogen deposition to be half that of measured wet deposition, this high elevation watershed receives 3·9 kg N ha⁻¹. Although deposition values fluctuated with precipitation, measured stream nitrogen outputs were less variable. Of the total N input to the watershed (3·9 kg N ha⁻¹ wet plus dry deposition), 49% of the total N input was immobilized. Stream losses were 2·0 kg N ha⁻¹ (1125 kg measured dissolved inorganic N in 1992, 1–2 kg calculated dissolved organic N, plus an average of 203 kg algal N from the entire 660 ha watershed). Tundra and aquatic algae were the largest reservoirs for incoming N, at approximately 18% and 15% of the total 2574 kg N deposition, respectively. Rocky areas and forest stored the remaining 11% and 5%, respectively. Fully 80% of N losses from the watershed came from the 68% of LVWS that is alpine. © 1997 John Wiley & Sons, Ltd.     

Application of the geographical information systems approach to watershed mass balance studies

This study was undertaken to test the utility of a geographical information systems (GIS) approach to problems of watershed mass balance. This approach proved most useful in exploring the effects that watershed scale, lithology and land use have on chemical weathering rates, and in assessing whether mass balance calculations could be applied to large multilithological watersheds. Water quality data from 52 stations were retrieved from STORET and a complete GIS database consisting of the watershed divide, lithology and land use was compiled for each station. Water quality data were also obtained from 7 experimental watersheds to develop a methodology to estimate annual fluxes from incomplete data sets. The methodology consists of preparing a composite of daily flux data, calculating a best fit sinusoid and integrating the equation to obtain an annual flux. Comparison with annual fluxes calculated from high resolution data sets suggests that this method predicts fluxes within about 10% of the true annual flux. Annual magnesium fluxes (moles km⁻² yr⁻¹) were calculated for all stations and adjusted for fluxes from atmospheric deposition. Magnesium flux was found to be a strong function of the amount of carbonate in the watershed, and silica fluxes were found to increase with the fraction of sandstone present in the watershed. All fluxes were strongly influenced by mining practices, with magnesium fluxes from affected watersheds being 6–10 times higher than fluxes from comparable pristine watersheds. Mining practices enhance chemical weathering by increasing the surface area of unweathered rock to which water has access and by increasing acidity and rate of mineral weathering. Fluxes were also found to increase with watershed size. This scale dependence is most likely caused by the sensitivity of weathering fluxes to even minor quantities of carbonates, which are likely to be found in all lithologies at larger scales. Mass balances were carried out in watersheds where gauged sub-watersheds made up more than 95% of the area. The calculations show large magnesium flux and water balance discrepancies. These errors may be a result of significant groundwater inputs to streams between gauges. The results suggest that improvements in how we measure discharge and estimate fluxes may be required before we can apply mass balance techniques to larger scales. © 1997 John Wiley & Sons, Ltd.