Definition Procedures Have Little Effect on Performance of Environmental Classifications of Streams and Rivers

Mapped environmental classifications are defined using various procedures, but there has been little evaluation of the differences in their ability to discriminate variation in independent ecological characteristics. We tested the performance of environmental classifications of the streams and rivers of France that had been defined from the same environmental data using geographic regionalization and numerical classification of individual river valley segments. Test data comprised invertebrate assemblages, water chemistry, and hydrological indexes obtained from sites throughout France. Classification performance was measured by analysis of similarity (ANOSIM). Geometric regions defined by a regular grid and without regard to environmental variables and a posteriori classifications based on clustering the test datasets defined lower and upper bounds of performance for a given number of classes. Differences in classification performances were generally small. The ANOSIM statistics for the a posteriori classifications were around twice that of all environmental classifications, including geometrically defined regions. The hydro-ecoregions performed slightly better for the invertebrate data and the network classification performed slightly better for the chemistry and hydrological data. Our results indicate that environmental classifications that are defined using different procedures can be comparable in terms of their ability to discriminate variation of ecological characteristics and that alleged differences in performance arising from different classification procedures can be small relative to unexplained variation. We conclude that definition procedures might have little effect on the performance of large-scale environmental classifications and decisions over which procedures to use should be based primarily on pragmatic considerations.     

Watershed wash-off of atmospherically deposited radionuclides: a review of normalized entrainment coefficients

Radionuclide wash-off is the transport of activity by flowing water over the soil surface (runoff). To complete existing reviews on long-term removal rates, this paper focuses on short-term wash-off fluxes, quantified in the literature by soil-runoff transfer factors called normalized liquid and solid entrainment coefficients (noted K(l)(*), K(s)(*)). Compiled data concerned essentially (137)Cs and (90)Sr wash-off measured under simulated rainfalls on small experimental plots after Chernobyl fallout in the exclusion zone. K(l)(*) and K(s)(*) values span approximately one order of magnitude. Their validity is limited to a season, and their representativeness is limited by restricted studied situations, notably dominant unsoluble forms in fallout, light soils and intense rainfalls. Formulas based on a simplified representation of the soil-runoff system were proposed to generalize the existing values for other conditions. However, their implementation requires a more systematic compilation of the available information, including decisive influence factors such as the fraction of exchangeable form, distribution coefficient, suspended matter enrichment ratio. Entrainment coefficients K(l)(*) and K(s)(*) were mathematically related to the transfer function approach. The proposed relationships proved their complementarity in terms of time support and captured fluctuations. Both approaches should be used in assessments to estimate average fluxes and their variability.     

Derivation of a GIS-based watershed-scale conceptual model for the St. Jones River Delaware from habitat-scale conceptual models

Conceptual modeling is a useful tool for identifying pathways between drivers, stressors, Valued Ecosystem Components (VECs), and services that are central to understanding how an ecosystem operates. The St. Jones River watershed, DE is a complex ecosystem, and because management decisions must include ecological, social, political, and economic considerations, a conceptual model is a good tool for accommodating the full range of inputs. In 2002, a Four-Component, Level 1 conceptual model was formed for the key habitats of the St. Jones River watershed, but since the habitat level of resolution is too fine for some important watershed-scale issues we developed a functional watershed-scale model using the existing narrowed habitat-scale models. The narrowed habitat-scale conceptual models and associated matrices developed by Reiter et al. (2006) were combined with data from the 2002 land use/land cover (LULC) GIS-based maps of Kent County in Delaware to assemble a diagrammatic and numerical watershed-scale conceptual model incorporating the calculated weight of each habitat within the watershed. The numerical component of the assembled watershed model was subsequently subjected to the same Monte Carlo narrowing methodology used for the habitat versions to refine the diagrammatic component of the watershed-scale model. The narrowed numerical representation of the model was used to generate forecasts for changes in the parameters “Agriculture” and “Forest”, showing that land use changes in these habitats propagated through the results of the model by the weighting factor. Also, the narrowed watershed-scale conceptual model identified some key parameters upon which to focus research attention and management decisions at the watershed scale. The forecast and simulation results seemed to indicate that the watershed-scale conceptual model does lead to different conclusions than the habitat-scale conceptual models for some issues at the larger watershed scale.     

The Relative Importance of Road Density and Physical Watershed Features in Determining Coastal Marsh Water Quality in Georgian Bay

We used a GIS-based approach to examine the influence of road density and physical watershed features (watershed size, wetland cover, and bedrock type) on water quality in coastal marshes of Georgian Bay, Ontario. We created a GIS that included landscape information and water-quality data from a 9-year synoptic survey of 105 coastal marshes covering 28 quaternary watersheds. Multiple regressions and partial correlations were used to discern confounding effects of human-induced (road density) versus natural physical watershed determinants of water quality. Road density was the dominant factor influencing many water quality variables, showing positive correlations with specific conductivity (COND), total suspended solids (TSS), and inorganic suspended solids (ISS) and a negative correlation with overall Water Quality Index scores. Road density also showed positive correlations with total nitrate nitrogen (TNN) and total phosphorus (TP). By comparison, larger watershed area was the main factor leading to elevated TP concentrations. The proportion of the watershed occupied by wetlands explained the largest amount of variation in TNN concentrations (negative correlation) and was also negatively correlated with COND and positively correlated with TSS and ISS when we controlled for road density. Bedrock type did not have a significant effect in any of the models. Our findings suggest that road density is currently the overriding factor governing water quality of coastal marshes in Georgian Bay during the summer low-flow period. We recommend that natural variation in physical watershed characteristics be considered when developing water quality standards and management practices for freshwater coastal areas.     

香溪河流域人类活动净磷输入量及其影响因素

为了阐明三峡库区第一大支流香溪河流域人类活动对磷输入的影响程度,收集流域所涉及的2001~2019年的乡镇统计数据,运用改进的人类活动净磷输入（NAPI）模型,分析了该流域NAPI的发展趋势.结果表明：在时间尺度上,香溪河流域2001~2019年的NAPI整体呈下降趋势;在空间尺度上,NAPI呈现东北部高于西南部的趋势,影响香溪河流域NAPI的主要乡镇为黄粮镇、峡口镇和昭君镇,占香溪河流域NAPI的63.8%;河流磷输出占NAPI的百分比为10.7%~79.5%;从NAPI结构上看,影响香溪河流域NAPI主要的影响因素为磷肥施入量,占香溪河流域NAPI的46%~68%,次要影响因素为食物磷和磷化工及磷矿开采导致磷素释放量,分别占香溪河流域NAPI的14%~32%和16%~24%;从NAPI影响因素上看,NAPI与人口密度和耕地面积占比均呈极显著正相关（P<0.001）,而在小流域研究尺度上,NAPI与河流磷输出的相关性不显著（P>0.05）,不具有直接的响应关系.因此,香溪河流域磷素管理应优先考虑重点区域（黄粮镇、峡口镇和昭君镇）,控制化肥施用量,并提高工厂污染物排放标准.     

近50a人工灌排技术进步对玛纳斯河流域耕地格局变化的影响

分析绿洲人工灌排技术发展和耕地格局变化之间的关系,对研究干旱区灌溉农业发展具有重要的意义。论文选取玛纳斯河流域为研究区,利用RS和GIS技术,对玛纳斯河流域1960年地形图,1976、1989、1997、2006、2013年Landsat遥感影像和历史水利工程建设分布图等原始数据进行处理,获得5期人工灌排渠系矢量图和6期土地利用分类矢量图,并计算人工灌排渠系长度指数和表征耕地格局的绿洲垦殖率、净耕地系数、周长面积比;利用多元逐步回归法,分析干旱区绿洲人工灌排技术对耕地格局变化的影响。结果表明:滴灌技术应用前,玛纳斯河流域耕地分布格局由灌排渠系的空间分布决定,尤其是农渠的分布格局和长度,其与耕地面积的回归方程为y=0.43x+7.38(R~2=0.90,n=33,P=0);滴灌技术应用后,耕地分布格局的变化取决于滴灌系统管网的空间分布,尤其是干管和支管的分布格局与长度,导致流域灌溉水利用系数从1960年的0.38增长到2010年的0.65。     

An Optimization Method Based on Scenario Analysis for Watershed Management Under Uncertainty

In conjunction with socioeconomic development in watersheds, increasingly challenging problems, such as scarcity of water resources and environmental deterioration, have arisen. Watershed management is a useful tool for dealing with these issues and maintaining sustainable development at the watershed scale. The complex and uncertain characteristics of watershed systems have a great impact on decisions about countermeasures and other techniques that will be applied in the future. An optimization method based on scenario analysis is proposed in this paper as a means of handling watershed management under uncertainty. This method integrates system analysis, forecast methods, and scenario analysis, as well as the contributions of stakeholders and experts, into a comprehensive framework. The proposed method comprises four steps: system analyses, a listing of potential engineering techniques and countermeasures, scenario analyses, and the optimal selection of countermeasures and engineering techniques. The proposed method was applied to the case of the Lake Qionghai watershed in southwestern China, and the results are reported in this paper. This case study demonstrates that the proposed method can be used to deal efficiently with uncertainties at the watershed level. Moreover, this method takes into consideration the interests of different groups, which is crucial for successful watershed management. In particular, social, economic, environmental, and resource systems are all considered in order to improve the applicability of the method. In short, the optimization method based on scenario analysis proposed here is a valuable tool for watershed management.     

太湖流域水生态功能区土地利用变化的景观生态风险效应

以太湖流域及其一级水生态功能区为研究对象,以Landsat遥感影像解译获得的2005年和2008年土地利用分类图等为基础数据,基于土地利用类型比例变化、转移矩阵、GIS叠加分析、土地利用综合转换速率、景观生态风险指数和土地利用变化的景观生态风险效应系数等分析方法,综合分析了太湖流域及其不同一级水生态功能区的土地利用与景观格局及其变化特征,在计算相关中间参数的基础上,从景观尺度计算得到了太湖流域及其不同一级水生态功能区景观生态风险值,并在此基础上对太湖流域及其不同一级水生态功能区景观生态风险差异特征进行了比较分析,进而分析了各区景观生态风险与土地利用变化之间的效应关系,从而为流域不同水生态功能区差异化水生态保护决策提供依据。     

基于碳汇的县南沟流域退耕林地补偿标准研究

补偿标准是退耕还林生态补偿的核心与难点,为探讨黄土高原退耕林地合适的补偿标准,论文基于清洁发展机制的国际背景,通过理论分析、实地测量与室内实验,把碳汇价值与退耕农户的机会成本相结合,构建了禁伐政策下退耕林地补偿标准的动态模型;并选取黄土高原退耕的代表流域——县南沟进行实证分析,依据退耕刺槐（Robinia pseudoacacia）林特性确定退耕的一个补偿周期为37 a,退耕地补偿过程与补偿标准分为两个阶段：退耕1~17 a,通过机会成本的计算,补偿的可执行标准为1 997.26元/(hm²·a);退耕18~37 a,通过碳汇模型进行测算,补偿的可执行标准为3 692.35元/(hm²·a)。人工刺槐纯林在补偿周期之后会逐渐出现灌木层和衰败现象,因此,这一补偿期结束后,应根据林地生态群落的变化再行核算并完善其补偿标准。将碳汇价值纳入补偿体系,能促使农民为提高碳汇产量自觉增强林地管护,巩固退耕成果。     

基于水土保持下的纸坊沟流域农业产业-资源系统耦合效应评价

农业产业-资源系统耦合不仅表现为两子系统之间耦合协调作用的程度,而且表现为这种协调作用下系统的耦合效率。以黄土丘陵区典型流域纸坊沟流域为例,采用耦合协调度模型与DEA方法,揭示农业产业-资源系统耦合效应:一系列水土保持政策和措施显著改善了区域农业资源环境条件、促进了农业产业的发展,并提高了二者的耦合协调度,然而在此协调趋势下,资源环境条件向产业效益转化的效率却只在很小幅度的波动中变化,水土保持在提高系统的耦合效率方面作用甚微。究其原因主要是由于在林草地资源大量闲置和利用不充分的状况下,农业产业结构与资源结构尚存在较大偏差,系统的这种结构性矛盾影响了其耦合效率,系统演变过程中潜伏了较大危机。为此,需要保证现有林草资源得以充分利用、林果业和畜牧业得以有序发展的经济、政策环境,并在此基础上优化系统的资源与产业结构,转变资源利用和产业发展方式。