USE OF STREAMFLOW INCREASES FROM VEGETATION MANAGEMENT IN THE VERDE RIVER BASIN1

ABSTRACT: Although the effects of vegetation management on streamflow have been studied in many locations, the effects of augmented streamflow on downstream water users have not been carefully analyzed. This study examines the routing of streamflow increases that could be produced in the Verde River Basin of Arizona. Reservoir management and water routing to users in the Salt River Valley around Phoenix were carefully modeled. Simulation of water routing with and without vegetation modification indicates that, under current institutional conditions, less than one-half of the streamflow increase would reach consumptive users as surface water. Most of the remainder would accumulate in storage until a year of unusually heavy runoff, when it would add to reservoir spills. Under alternative scenarios, from 39 to 58 percent of the streamflow increase was delivered to consumptive users.     

围填海造成的海岸带生态系统服务损耗的货币化评估技术探讨

从围填海负面生态影响的货币化评估的必要性和重要性入手,基于国内外相关研究的分析,将海岸带生态系统服务划分为两大类,一类是提供物质性产品和条件的供给服务;另一类是提供其他非物质性的服务,包括调节、文化和支持服务,并对供给、调节、文化和支持四类服务各自包含的具体子服务加以识别.在此基础上,针对海岸带生态系统提供的各类服务自身的特点,运用直接市场法、替代市场法、调查评价法和成果参照法,提出了围填海造成的海岸带生态系统服务损害的货币化评估技术选择的基本框架,并构建了四类服务(子服务)损耗货币化的相应评估模型.     

污染地块VOCs源衰减对室内蒸气入侵风险的影响

我国挥发性有机物(VOCs)污染地块普遍采用J&E模型预测蒸气入侵风险,该模型假定污染源含量在整个暴露周期内恒定,与其在地块中的客观变化规律不符.以某VOCs污染地块为例,采用J&E恒定源模型、 SD衰减源模型及RBCA衰减源模型,分别预测VOCs侵入建筑物室内的质量浓度及蒸气入侵风险.结果显示,J&E预测暴露期内的源含量及室内污染物质量浓度始终较高,SD和RBCA衰减源模型预测显示两者均呈指数下降.RBCA衰减源模型预测的源衰减更快,但其室内污染物质量浓度预测结果小于SD衰减源模型预测结果.SD模型中建筑物室内外压差是影响源衰减的关键参数,压差增大,污染物以对流方式侵入室内,源衰减速率增加.压差降低,污染物以扩散方式侵入室内,建筑物对源衰减的作用减弱,预测结果与J&E模型差异不明显. J&E模型预测的致癌风险和危害商最高,SD次之,RBCA最低.因此,J&E模型易高估暴露期内蒸气入侵风险,RBCA衰减源模型未考虑建筑物对源衰减的阻滞而低估风险,SD模型考虑了建筑物对源衰减的影响,更适用于评估实际场地的室内蒸气入侵风险.     

Spatial and Temporal Patterns of Low Streamflow and Precipitation Changes in the Chesapeake Bay Watershed

Spatial and temporal patterns in low streamflows were investigated for 183 streamgages located in the Chesapeake Bay Watershed for the period 1939–2013. Metrics that represent different aspects of the frequency and magnitude of low streamflows were examined for trends: (1) the annual time series of seven‐day average minimum streamflow, (2) the scaled average deficit at or below the 2% mean daily streamflow value relative to a base period between 1939 and 1970, and (3) the annual number of days below the 2% threshold. Trends in these statistics showed spatial cohesion, with increasing low streamflow volume at streamgages located in the northern uplands of the Chesapeake Bay Watershed and decreasing low streamflow volume at streamgages in the southern part of the watershed. For a small subset of streamgages (12%), conflicting trend patterns were observed between the seven‐day average minimum streamflow and the below‐threshold time series and these appear to be related to upstream diversions or the influence of reservoir‐influenced streamflows in their contributing watersheds. Using multivariate classification techniques, mean annual precipitation and fraction of precipitation falling as snow appear to be broad controls of increasing and decreasing low‐flow trends. Further investigation of seasonal precipitation patterns shows summer rainfall patterns, driven by the Atlantic Multidecadal Oscillation, as the main driver of low streamflows in the Chesapeake Bay Watershed.     

Modelling future copper ore grade decline based on a detailed assessment of copper resources and mining

The concept of “peak oil” has been explored and debated extensively within the literature. However there has been comparatively little research examining the concept of “peak minerals”, particularly in-depth analyses for individual metals. This paper presents scenarios for mined copper production based upon a detailed assessment of global copper resources and historic mine production. Scenarios for production from major copper deposit types and from individual countries or regions were developed using the Geologic Resources Supply-Demand Model (GeRS-DeMo). These scenarios were extended using cumulative grade-tonnage data, derived from our resource database, to produce estimates of potential rates of copper ore grade decline.The scenarios indicate that there are sufficient identified copper resources to grow mined copper production for at least the next twenty years. The future rate of ore grade decline may be less than has historically been the case, as mined grades are approaching the average resource grade and there is still significant copper endowment in high grade ore bodies. Despite increasing demand for copper as the developing world experiences economic growth, the economic and environmental impacts associated with increased production rates and declining ore grades (particularly those relating to energy consumption, water consumption and greenhouse gas emissions) will present barriers to the continued expansion of the industry. For these reasons peak mined copper production may well be realised during this century.