Hydrological Connectivity Between Headwater Streams and Downstream Waters: How Science Can Inform Policy1

Abstract: In January 2001, the U.S. Supreme Court ruled that the U.S. Army Corps of Engineers exceeded its statutory authority by asserting Clean Water Act (CWA) jurisdiction over non‐navigable, isolated, intrastate waters based solely on their use by migratory birds. The Supreme Court’s majority opinion addressed broader issues of CWA jurisdiction by implying that the CWA intended some “connection” to navigability and that isolated waters need a “significant nexus” to navigable waters to be jurisdictional. Subsequent to this decision (SWANCC), there have been many lawsuits challenging CWA jurisdiction, many of which are focused on headwater, intermittent, and ephemeral streams. To inform the legal and policy debate surrounding this issue, we present information on the geographic distribution of headwater streams and intermittent and ephemeral streams throughout the U.S., summarize major findings from the scientific literature in considering hydrological connectivity between headwater streams and downstream waters, and relate the scientific information presented to policy issues surrounding the scope of waters protected under the CWA. Headwater streams comprise approximately 53% (2,900,000 km) of the total stream length in the U.S., excluding Alaska, and intermittent and ephemeral streams comprise approximately 59% (3,200,000 km) of the total stream length and approximately 50% (1,460,000 km) of the headwater stream length in the U.S., excluding Alaska. Hillslopes, headwater streams, and downstream waters are best described as individual elements of integrated hydrological systems. Hydrological connectivity allows for the exchange of mass, momentum, energy, and organisms longitudinally, laterally, vertically, and temporally between headwater streams and downstream waters. Via hydrological connectivity, headwater, intermittent and ephemeral streams cumulatively contribute to the functional integrity of downstream waters; hydrologically and ecologically, they are a part of the tributary system. As this debate continues, scientific input from multiple fields will be important for policymaking at the federal, state, and local levels and to inform water resource management regardless of the level at which those decisions are being made. Strengthening the interface between science, policy, and public participation is critical if we are going to achieve effective water resource management.     

长壁综采工作面覆岩采动变形破坏时空演化规律研究

回采工作面煤层被采出以后,上覆岩层产生离层、断裂、垮落等运动,形成的冒落带和裂隙带范围对煤矿安全生产影响极大.以顾桥煤矿1116(1)综采工作面为工程背景,采用数值模拟和井下电法测试技术,研究了淮南矿区11-2煤层开采时覆岩移动破坏的规律.结果表明:在垂直方向上,采空区上方覆岩破坏分区特征明显,由下而上依次为双拉应力破坏区、拉伸裂隙区、剪切破坏区和未破坏区域;冒落带最大高度11.5～14.5 m,裂隙带最大高度45～47.5 m;覆岩破坏最终形态类似于马鞍形,破坏在水平方向的范围要比开采区域大.     

Predicting the aquatic risk of realistic pesticide mixtures to species assemblages in Portuguese river basins

Although pesticide regulatory tools are mainly based on individual substances, aquatic ecosystems are usually exposed to multiple pesticides from their use on the variety of crops within the catchment of a river. This study estimated the impact of measured pesticide mixtures in surface waters from 2002 and 2008 within three important Portuguese river basins (‘Mondego’, ‘Sado’ and ‘Tejo’) on primary producers, arthropods and fish by toxic pressure calculation. Species sensitivity distributions (SSDs), in combination with mixture toxicity models, were applied. Considering the differences in the responses of the taxonomic groups as well as in the pesticide exposures that these organisms experience, variable acute multi-substance potentially affected fractions (msPAFs) were obtained. The median msPAF for primary producers and arthropods in surface waters of all river basins exceeded 5%, the cut-off value used in the prospective SSD approach for deriving individual environmental quality standards. A ranking procedure identified various photosystem II inhibiting herbicides, with oxadiazon having the relatively largest toxic effects on primary producers, while the organophosphorus insecticides, chlorfenvinphos and chlorpyrifos, and the organochloride endosulfan had the largest effects on arthropods and fish, respectively. These results ensure compliance with European legislation with regard to ecological risk assessment and management of pesticides in surface waters.     

白洋淀上覆水及沉积物中微塑料赋存特征

为探究我国白洋淀淡水环境中微塑料的赋存特征,于2021年10月通过野外采样、实验室预处理、显微镜观察和激光红外光谱测定等方法鉴定了淀区10份上覆水及10份沉积物样品中微塑料的丰度分布、形状、粒径和聚合物类型,并通过Stokes沉降公式研究了微塑料在上覆水-沉积物界面的沉降规律,对其污染特征及潜在来源进行分析.结果表明,淀区上覆水及沉积物中微塑料丰度范围分别为474～19 382 n·m^-3和95.3～29 542.5 n·kg^-1,平均值为6 255.4 n·m^-3和11 088 n·kg^-1.上覆水中的微塑料主要聚合物为聚对苯二甲酸乙二醇酯[PET,(17.20±0.26)%],沉积物中微塑料以氯化聚乙烯[CPE,(46.11±1.30)%]为主.淀区内微塑料的沉降速度从0.079 3～111.754 7 mm·s^-1不等,粒径大的颗粒沉降速度较高,易沉降并保留在沉积物中.研究区微塑料污染主要来源为洗涤废水产生的纺织纤维排放,船舶漆、船舶橡胶和建筑材料磨损等过程.     

基于三维荧光及平行因子分析的川西高原河流水体CDOM特征

川西高原草甸和高寒湿地是青藏高原重要土壤碳库之一,高原河流水体溶解性有机碳特征及其与土壤碳库关系研究,对于理解高寒区域土壤碳输出通量及强度具有重要意义.本文对川西高原高山峡谷区河流(岷江上游、杂谷脑河、抚边河)和高原夷平面河流(白河)水体有色溶解性有机质(CDOM)采用三维荧光及平行因子法(EEM-PARAFAC)进行了分析.结果表明:(1)高原河流中CDOM主要有3种组分,即C_1(260/480,UVC类腐殖质)、C_2[310/420(570),UVA类腐殖质]和C_3(280/370,类色氨酸);(2)河流沿程变化特征显示,高山峡谷区河流总荧光强度值较低,变化范围窄,高原夷平面河流(白河)与其相反;同时白河类腐殖质(C_1、C_2)荧光强度远高于其他3条河流,表明白河中源于沿岸草甸和湿地的陆源腐殖质高,而其余高山峡谷区3条河流陆源腐殖质输入相对低;(3)水体荧光特征参数(荧光指数FI、自生源指数BIX、腐殖化系数HIXb、新鲜度指数β:α)表明,高山峡谷区河流CDOM来源具有外源兼内源双重特征,腐殖化程度低;高原夷平面河流CDOM腐殖化程度相对较高且降解程度低;(4)相关性分析发现4条河流中C_1、C_2极显著正相关,且白河C_1、C_2、C_3呈极显著正相关;所有河流β:α与BIX呈极显著正相关,溶解性有机碳(DOC)与355 nm处吸收系数[a(355)]相关性不显著.     

物理和摇蚊幼虫组合扰动对内源磷再生和形态转化的协同作用

为探讨物理和摇蚊幼虫组合扰动对内源磷再生和形态转化的协同作用,选取了苏州某富营养化河道为研究对象.利用室内静态培养试验和Rhizon间隙水采样技术,着重对比了单纯的摇蚊幼虫扰动和组合扰动下,上覆水、间隙水、沉积物中磷形态数量分布的变化规律.结果表明,组合扰动下,上覆水中不同形态磷含量(TP、PP、DTP、DIP)均处于较高水平,明显高于摇蚊幼虫扰动.这可归因于微生物活性的显著增加.与摇蚊幼虫扰动相比,组合扰动下,间隙水中DIP和Fe2+浓度的降低幅度和降低范围明显更大.这主要是由于物理扰动和底栖生物扰动产生的叠加效应,导致溶解氧渗透深度增加.另外,0~2 cm沉积物中,NH4Cl-P含量明显降低,Fe/Al-P明显增加,并且,NH4Cl-P和Fe/Al-P的变化幅度均在组合扰动下最大.这暗示了物理扰动和底栖生物扰动对磷再生和迁移产生的叠加效应.     

SALINITY AND SEDIMENTATION STUDY–COOPER RIVER REDIVERSION,CHARLESTON, SOUTH CAROLINA1

The study was prepared in 1966 for the Bureau of Sport Fisheries and Wildlife, Department of the Interior, for presentation to the United States Army Corps of Engineers which had under study several routes for rediversion of the discharge from the Santee-Cooper Hydro Electric Plant, Steam Plant and Lock. Each rediversion was designed to by-pass the Charleston Harbor and this study and report was concerned with one of those routes–Rediversion Route “B.” The channel was to be designed for a maximum fresh-water flow of 27,500 cfs and a mean flow of 15,500 cfs. The objectives of the study and report were to make an estimate of: (1) the geographical extent of salt marsh waters of which the salinity will be measurably reduced, and (2) the probable accumulation of fresh-water borne sediments in those same waters. Special consultants were Dr. F. H. Kellogg, Memphis State University, and Mr. K. L. Drennan, Gulf Coast Research Laboratory, Mississippi.     

The Loch Fleet Project in the Context of Acidification Reduction Measures

At Loch Fleet, and in other liming studies in similar environments, catchment liming is successful if an adequate amount of lime is added to hydrological source areas. Geochemical modelling demonstrates that the relatively late acidification of L. Fleet is consistent with the ameliorating effect of an alkaline groundwater input: the presence of this input implies that had the Loch not been limed in 1985 it would have recovered to conditions suitable for fish in about 20 years, given current commitments to sulphur emission reductions. Lakes without similar alkaline groundwater are not likely to recover as quickly. the different consequences of liming and emission reduction as methods of restoring acid waters are reviewed and contrasted. Restoration of waters by liming may result in some undesirable effects on the terrestrial catchment: these are discussed but it is concluded that catchment liming, used with discrimination, can be an acceptable management tool.     

Titration Curves: A Useful Instrument for Assessing the Buffer Systems of Acidic Mining Waters (10 pp)

Background, Aims and Scope The acidification of mine waters is generally caused by metal sulfide oxidation, related to mining activities. These waters are characterized by low pH and high acidity due to strong buffering systems. The standard acidity parameter, the Base Neutralization Capacity (BNC) is determined by endpoint titration, and reflects a cumulative parameter of both hydrogen ions and all buffering systems, but does not give information on the individual buffer systems. We demonstrate that a detailed interpretation of titration curves can provide information about the strength of the buffering systems. The buffering systems are of importance for environmental studies and treatment of acidic mining waters. Methods Titrations were carried out by means of an automatic titrator using acidic mining waters from Germany and Canada. The curves were interpreted, compared with each other, to endpoint titration results and to elemental concentrations contained therein. Results and Discussion The titration curves were highly reproducible, and contained information about the strength of the buffer systems present. Interpretations are given, and the classification and comparison of acidic mining waters, by the nature and strength of their buffering systems derived from titration curves are discussed. The BNC-values calculated from the curves were more precise than the ones determined by the standard endpoint titration method. Due to the complex buffer mechanisms in acidic mining waters, the calculation of major metal concentrations from the shape of the titration curve resulted in estimates, which should not be confused with precise elemental analysis results. Conclusion Titration curves provide an inexpensive, valuable and versatile tool, by which to obtain sophisticated information of the acidity in acidic water. The information about the strength of the present buffer systems can help to understand and document the complex nature of acidic mining water buffer systems. Finally, the interpretation of titration curves could help to improve treatment measurements and the ecological understanding of these acidic waters.     

Modelling algal blooms in the Dutch coastal waters by integrated numerical and fuzzy cellular automata approaches

In this paper, an integrated numerical and fuzzy cellular automata model was developed to predict possible algal blooms in Dutch coastal waters basing on the irradiance, nutrients and neighbourhood conditions. The numerical module used Delft3D-WAQ to compute the abiotic conditions, and fuzzy cellular automata approach was applied to predict the algal biomass that was indicated by chlorophyll a concentration. The simulated results of year 1995 were compared with that from BLOOM II model, and the advantages, disadvantages as well as future improvement were presented. In general, through this study, it is seen that the integrated modelling deserves more research inputs because: (1) the hydrodynamic processes and nutrients concentrations can be simulated in details by numerical method; (2) the irregular and sparse water quality and biological data, and the empirical knowledge from experts can be explored by the fuzzy logic technique; (3) the spatial heterogeneity, local interactions and the emerge of patchiness could be well captured through the cellular automata paradigm.