黄河下游历史泥沙灾害的宏观特征及其与流域因素和人类活动的关系（Ⅱ）：—人类活动、历史地震及地形因子的影响

以历史上黄河下游的决溢频率为泥沙灾害的代用指标,研究了人类活动,历史地震及地形因子对黄河下游历史泥沙灾害的影响,研究表最,人类活动是影响黄河下游泥沙灾害的重要因素,历史上人口的增加使下游决溢频率增大,人口低谷与决溢频率的低值时段相应,历史上农牧交错带的南移与下游决溢频率的减小相伴发生。北移则导致决溢频率的增大,历史地震对黄河下游历史泥沙灾害有一定的影响,黄河下游历史泥沙灾害表现出明显的空间分异,这种分异与平原地貌条件的沿程变化有密切的关系。     

At the intersection of disaster risk and religion: interpretations and responses to the threat of Tsho Rolpa glacial lake

Over the last several decades, the scientific community has replaced the ‘acts of god’ explanations for disasters with a view that disasters are actually ‘acts of nature,’ and more recently, ‘acts of human behavior and decision making.’ Despite the secular orientation of contemporary disaster research, religious beliefs still govern people’s interpretations of natural events across many continents and cultures. Using a case study of a rural Sherpa community in Nepal, this paper responds to the challenge of linking religion and disaster risk in the context of a climate change-induced glacial lake outburst flood hazard. Data collection employed ethnographic techniques including participant observation and 53 interviews with community members. Results indicate that the case study community’s religious belief system influences how they interpret and respond to the glacial lake hazard, although their beliefs co-exist with more scientific interpretations of risk. Rather than being immobilised by their belief system, we found that religious aspects like rituals and prayer can enhance social cohesion and contribute to capacities for coping with fear and uncertainty in this community. We assert that religion can yield valuable resources to glacial lake risk reduction strategies, which will benefit from incorporating social-cultural factors more profoundly.     

DETECTION OF FRESH WATER AQUIFERS IN THE GLACIAL DEPOSITS OF NORTHWESTERN MISSOURI BY GEOELECTRICAL METHODS1

Geoelectrical investigations in Grundy County of northwestern Missouri, where the groundwater resources of the glacial deposits have already been examined through an extensive drilling program by the Missouri Geological Survey and Water Resources, indicate that water-bearing gravel deposits can be distinguished from glacial deposits containing appreciable amounts of clay and limited amounts of water. The Schlumberger method used for the geoelectric depth soundings in the vicinity of the Survey's drillholes demonstrates the exploratory usefulness of the method in that it can partly replace the more expensive procedure of drilling. The method also provides improved interpretation between drillholes. Results of the investigation show that, in the area, clay has a resistivity below 20in, that the fresh water-bearing gravel at the bottom of the buried glacial stream channels has a resisitivity of 40 to 50fim, and that the near surface glacial gravel deposits have a resistivity above lOOfim. Interpretation of the depth soundings and the conductivity of water obtained from a local well implies that its water is drawn from the saline water of the bedrock. A recommendation is made for the quality improvement of this particular well.     

Sediment Production From Forest Roads in Western Montana1

Abstract: Unpaved roads are a primary sediment source in forested watersheds. Validation of erosion models and improvements to road management require information on road erosion rates and the factors controlling erosion. This study measured sediment yields from twenty ～0.05 ha unsurfaced (native) road plots in Belt Supergroup and glacial till parent materials of western Montana, and investigated the factors controlling erosion. Annual sediment yields for individual plots ranged from 0 to 96.9 Mg/ha/yr over 3 years (2002‐2004). Annual mean sediment yield ranged from 2.1 Mg/ha in 2003 to 9.9 Mg/ha in 2004 with an overall mean of 5.4 Mg/ha/yr. The mean of log‐transformed sediment yields for sites in glacial till parent materials was higher than Belt Supergroup parent materials (p = 0.063). A regression model with road slope, time since last grading, roadbed gravel content, and precipitation as predictive variables explained 68% of the variability in sediment yield (F = 28.2; p < 0.0001). Road erosion in western Montana is limited by low erodibility of the dominant parent materials and low rainfall. Management procedures such as reducing the frequency of grading can significantly reduce sediment yields from forest roads.     

THE DEPENDENCE OF THE RESIDUAL GRAVITY ON HYDRAULIC CONSTANTS IN GLACIAL DEPOSITS1

ABSTRACT: Buried glacial stream channels contain large and easily accessible groundwater resources. Gravity surveys have been frequently applied for their location. A gravity survey in the geohydrologically explored Wood River Valley Area of southern Rhode Island shows extreme lows of -2 mgals over channel depths of maximal 300 feet. Three gravity profiles were observed in east-west direction across a north-south striking stream channel. The bedrock depth increases rapidly towards the south from 130 to 300 feet. The gravity lows observed across each profile are not related to the bedrock depth but rather to the saturated thickness of the main quifer and its hydraulic transmissivity. Well logs indicate that the large change of bedrock depth is solely due to an increase of till of low permeability. The volume of the glacial outwash, which is the major groundwater resource, changes little underneath the three profiles. The gravity lows apear to be directly related to the density contrast between glacial outwash and till. The response to the hydraulically more pertinent units renews the interest in the gravity method as it may have a potential to estimate yields of hydrologically complex aquifers     

EVALUATION OF AN INDUCED INFILTRATION MODEL AS APPLIED TO GLACIAL AQUIFER SYSTEMS1

ABSTRACT: Numerical models were used to examine the limitations of the assumptions used in an analytical induced infiltration model. The assumptions tested included negligible streambed effects, negligible areal recharge, two-dimensional ground water flow, fully penetrating rivers and wells, and constant surface water stage. For situations that deviate from the underlying assumptions, the analytical model becomes a less reliable predictor of induced infiltration. The numerical experiments show that streambed effects cannot be neglected if the streambed conductivity is more than one order of magnitude lower than the aquifer hydraulic conductivity. Areal recharge cannot be neglected if the ground water basin receives more than 5 in/yr of areal recharge. Three-dimensional flow effects due to well partial penetration cannot be neglected if the ratio of horizontal hydraulic conductivity to vertical hydraulic conductivity (K_h/K_u) is greater than 10. Surface water elevation fluctuations can significantly influence the induced infiltration rate, depending on the degree of fluctuations and the ground water hydraulic gradient.     

Effect of biogeographic history on population vulnerability in European amphibians

The genetic diversity of populations, which contributes greatly to their adaptive potential, is negatively affected by anthropogenic habitat fragmentation and destruction. However, continental‐scale losses of genetic diversity also resulted from the population expansions that followed the end of the last glaciation, an element that is rarely considered in a conservation context. We addressed this issue in a meta‐analysis in which we compared the spatial patterns of vulnerability of 18 widespread European amphibians in light of phylogeographic histories (glacial refugia and postglacial routes) and anthropogenic disturbances. Conservation statuses significantly worsened with distances from refugia, particularly in the context of industrial agriculture; human population density also had a negative effect. These findings suggest that features associated with the loss of genetic diversity in post‐glacial amphibian populations (such as enhanced fixation load or depressed adaptive potential) may increase their susceptibility to current threats (e.g., habitat fragmentation and pesticide use). We propose that the phylogeographic status of populations (i.e., refugial vs. post‐glacial) should be considered in conservation assessments for regional and national red lists.     

青藏高原冰川雪冰微生物研究进展

微生物作为青藏高原冰川研究的一个参数,不仅能提供丰富的物种和嗜冷基因资源作用于冰川的能量和化学物质平衡,而且还与气候和环境相关联.近年来,青藏高原冰川雪藻的研究主要在南部的Yala冰川开展,细菌的研究集中在北部冰川.这些研究主要针对冰川雪冰微生物与环境的关系.未来除在研究方法上加以改进外,还应该在微生物多样性、生态意义、嗜冷机制及其与气候和环境的关系等方面进一步深入研究.参36     

黄土高原沟壑区小流域土壤有机碳与环境因素的关系

研究不同环境要素共同作用下的土壤有机碳分布特征及其与环境因素的关系对于全面准确评估黄土高原地区土壤有机碳状况和土壤碳循环具有重要意义.结合野外调查和室内分析,研究了黄土高原沟壑区典型小流域土壤不同组分有机碳分布特征及其与地形条件、土地利用方式和土壤类型之间的关系.结果表明,黄土沟壑区小流域土壤总有机碳变异较小(变异系数为34%),高活性有机碳变异较大(变异系数为43%),有机碳的变异性随其活性的增强而增大.各组分有机碳之间极显著正相关,而且在不同环境条件下的含量顺序一致.各组分有机碳在不同地形条件下以塬面土壤最高,沟道土壤最低:在不同土地利用方式下以林地和农田土壤较高,草地土壤较低;在不同土壤类型中则以黑垆土最高,红土最低.不同环境条件下各组分有机碳之间的关系分析表明,环境条件不但直接影响有机碳的分布,还通过影响有机碳不同组分之间的关系来改变其分布特征.研究区总有机碳与活性有机碳之问的关系受环境条件影响最大,中活性与高活性有机碳之间的关系受环境条件影响最小.     

冰川水资源资产负债表编制实践

冰川是自然资源重要组分。因受认知所限,当前水资源资产负债表编制中尚缺乏对冰川资源的考虑。参考水资源资产负债表编制案例,结合冰川水资源自身特征,构建了冰川水资源资产负债表。研究表明：冰川水资源的独特性使其资产负债核算与其他类型水资源存在差异;冰川水资源资产包括水量资产和水域资产,即冰川冰储量和冰川融水径流量,冰川面积和冰川融水水域面积;冰川水资源负债主要来源于人类活动造成的冰川水资源消退和过耗、冰川融水环境损害和由此导致的冰川水资源服务衰退。青藏高原大江大河源区是冰川水资源负债区,而其负债却成为中下游的收益。应建立国家或下游为主导的水资源补偿机制,以冰川水资源流量变化为依据,统筹管理青藏高原大江大河源区流域水资源,适度对源区进行冰川水资源价值补偿。