Groundwater contributions of flow and nitrogen in a headwater agricultural watershed

Nonpoint sources of nitrogen (N) and other nutrients are a major source of water pollution within the Chesapeake Bay watershed and other basins around the world. Human activities associated with agricultural practices can account for a large percentage of N loadings delivered to streams and rivers. This work aims to improve understanding of N transport from groundwater to surface waters, quantifying the principal hydrological processes driving water and N fluxes into and out of a headwater agricultural stream reach. The study site is a 175-m stream reach in a heavily cultivated 40-ha watershed in east-central Pennsylvania. This subwatershed is underlain by fractured shale bedrock, and receives most of its baseflow from groundwater, either by diffuse matrix discharge through the streambed or by localized discharge through riparian seeps. Samples of stream, seep, and shallow groundwater were collected approximately monthly under steady hydrologic conditions in 2017. Calculated matrix flow from hydraulic head and conductivity measurements paired with differential stream gauging was used to solve for the riparian seep flux using a mass balance approach. Riparian seep fluxes ranged from 45 to 217 m³/d, transporting 0.6–4.2 kg N d⁻¹ of nitrate-N from the fractured bedrock aquifer to the stream. Hydrochemical data suggest that the stream is mainly disconnected from the underlying aquifer and that seeps supply essentially all water and N to the system. Seeps are likely sourced with N in nearby agricultural fields and accelerated through the system with shorter residence times than shallow groundwater. Water isotope data reinforced this notion. This study underscores the importance of agriculture as a source of N to ground and surface waters. Identifying source areas that are causing groundwater enrichment of N and seep areas where N discharges to streams is beneficial for developing N pollution mitigation strategies and implementing management practices that aim to reduce nutrient loads to the Chesapeake Bay.     

User participation in watershed management and research

Many watershed development projects around the world have performed poorly because they failed to take into account the needs, constraints, and practices of local people. Participatory watershed management—in which users help to define problems, set priorities, select technologies and policies, and monitor and evaluate impacts—is expected to improve performance. User participation in watershed management raises new questions for watershed research, including how to design appropriate mechanisms for organizing stakeholders and facilitating collective action. Management of a complex system such as a watershed may also require user participation in the research process itself.     

Monitoring of organic micropollutants in Ghana by combination of pellet watch with sediment analysis: E-waste as a source of PCBs

Plastic resin pellets collected at 11 beaches covering the whole Ghanaian coastline were analyzed for polychlorinated biphenyls (PCBs). PCB concentrations (∑13 congeners) were higher in Accra, capital city, and Tema (39–69 ng/g-pellets) than those in rural coastal towns (1–15 ng/g-pellets) which are close to global background, indicating local inputs of PCBs. River sediments were also analyzed for PCBs together with molecular markers. Sedimentary PCBs concentrations were highest at a site (AR02) downstream of an electronic waste (e-waste) scrapyard. At the site (AR02), concentration of linear alkylbenzenes (LABs), a marker of municipal wastewater, was lower than another site (AR03) which is located at the downstream of downtown Accra. This result suggests that PCBs are introduced more to the river from the e-waste site than from activities in downtown Accra. PAHs concentrations were relatively higher in urban areas with strong petrogenic signature. Abundance of triphenylbenzenes suggested plastic combustion near e-waste scrapyard.     

Hydrologic trade-offs in conjunctive use management

An aquifer, in a stream/aquifer system, acts as a storage reservoir for groundwater. Groundwater pumping creates stream depletion that recharges the aquifer. As wells in the aquifer are moved away from the stream, the aquifer acts to filter out annual fluctuations in pumping; with distance the stream depletion tends to become equal to the total pumping averaged as an annual rate, with only a small fluctuation. This is true for both a single well and an ensemble of wells. A typical growing season in much of the western United States is 3 to 4 months. An ensemble of irrigation wells spread more or less uniformly across an aquifer several miles wide, pumping during the growing season, will deplete the stream by approximately one-third of the total amount of water pumped during the growing season. The remaining two-thirds of stream depletion occurs outside the growing season. Furthermore, it takes more than a decade of pumping for an ensemble of wells to reach a steady-state condition in which the impact on the stream is the same in succeeding years. After a decade or more of pumping, the depletion is nearly constant through the year, with only a small seasonal fluctuation: ±10%. Conversely, stream depletion following shutting down the pumping from an ensemble of wells takes more than a decade to fully recover from the prior pumping. Effectively managing a conjunctive groundwater and surface water system requires integrating the entire system into a single management institution with a long-term outlook.     

与东北冷涡相伴的高空急流诱发平流层重力波的数值模拟研究

使用中尺度数值模式WRF-ARW,针对2010年6月发生在中国东北地区一例伴随对流层高空西风急流（位于~9 km高度）演变过程出现的平流层重力波活动特征开展了数值模拟. 事件发生期间,对流层区域环流处在一个东北冷涡系统的控制之下. 模拟结果再现了该东北冷涡的发展和维持过程,以及与之相伴的高空急流的特征. 模拟结果揭示出在急流区域上空的平流层中存在显著重力波活动现象. 分析结果显示,重力波活动与急流存在紧密联系,在水平方向上,重力波呈显著的二维结构,出现在急流出口区上部并逆背景流向西传播. 功率谱分析结果表明盛行波动具有~700 km水平尺度、9~12 h时间尺度以及4~5 km垂直波长. 由于急流的存在,造成其与平流层中下部之间存在显著的水平风速垂直切变,与切变相伴的耗散使得上传的重力波动量通量数值随着高度升高而递减. 同时,在18~20 km高度间出现的西风-东风转换带极大地抑制了波动在垂直方向的传播,形成显著动量通量沉积效应. 估算结果表明,在11~20 km高度之间,这种效应的整体作用相当于对该层背景流施加强度为0.86 m·s^-1·day^-1的动力阻曳.     

Confounded by forgotten legacies: Effectively managing watersheds in the contemporary age of unknown unknowns

Contemporary watershed management practices can reflect oversimplifications of relationships between anthropogenic pressures and resource degradation. Remediation and restoration efforts often focus on recent land use practices as the primary driver of hydrologic regime changes. We present a case study that serves as an example to the scientific and watershed management communities of the lasting influences of historic land use practices and natural physical processes on a stream in the central United States listed as impaired by the federal government. Abnormal spatiotemporal streamflow relationships, determined by means of an experimental watershed study, alerted the authors to possible sink/source behavior in the upper‐watershed. Subsequent research uncovered archival evidence of coal mining, which may provide at least partial explanation. Additional investigation identified hydrologic processes associated with natural landscape evolution, noted by early‐20th‐century researchers, which are considered in the context of the current water quality and flow regime. Despite best‐intended management practices, regulatory agencies, scientists, and local decision makers have not accounted for such practices and processes, instead relying on recent development as the proximate cause of designated impairment. We present argumentation that historic land use (coal mining) and landscape processes comprise cumulative yet unconsidered legacy effects that contribute systemically to the observed hydrologic regime of the watershed. Results hold important implications for contemporary watershed management, and support rethinking the case‐by‐case appropriateness of federal and state water impairment listings, and the achievability of restoration efforts in many developing watersheds.     

Water safety: management,perception and health implications in Santa agricultural area,North-West Region,Cameroon

ABSTRACT

Santa agricultural area is a key production site for crops in Cameroon. This study aimed to look at the risk factors, knowledge and health implications of water pollution across 10 villages, in the area: 140 water points were visited and questionnaires randomly administered to water users, while health data were collected from the two local hospitals. Water sources are tap, stream, rain, well and spring and the water is used for agriculture, domestic activities, hygiene and sanitation. Pesticide pollution was illustrated by activities such as spraying, mixing and management of waste containers and purification methods are chlorination, boiling, sedimentation, filtration and refrigeration. Waterborne diseases are cholera, typhoid (the most prevalent), diarrhea, dysentery and skin diseases. Many water sources are close to toilets, farms and dumping sites. We found that 75% of respondents were not satisfied with the quality of water. Our results will be interest for water management, and to educate users on the risks linked to current practices.     

Impacts of urban headwater disturbances on downstream sediment loading where streamside management zones for forest harvesting activities are present downstream

Watershed disturbances caused by land use/land cover(LU/LC) change, intensive forestry practices, and other forms of watershed disturbance are known to negatively affect water quality, if best management practices(BMPs) are not present. Disturbances near or around headwaters where BMPs are absent or are inadequate may impact downstream water quality and stream ecology regardless of the presence of downstream BMPs. In this study, the recovery of two small forest-dominated watersheds(Ww and Ew) in Auburn, Alabama, USA, was monitored 6-years after a partial clearcut was done. The streamside management zone(SMZ) in Ww was also partially harvested shortly after the partial clearcut to improve its sediment trapping effectiveness over the long-term. The hydrology and sediment transport in these watersheds were expected to stabilize over this period, however, new disturbances in the headwaters of both watersheds changed the watershed dynamics. Streamflow and sediment load were examined over a15-month period from February 2014 to May 2015. The clearcut in Ww and Ew, and the partially harvested SMZ in Ww seemed to have recovered; however, substantial amount of sediment load were measured across all monitoring sites in both watersheds as a result of upstream disturbances. This study emphasizes the necessity of watershed management as a whole, and the importance of BMP applications within the entire watershed. It also highlights the fact that watershed management and BMP implementation is a dynamic process, thus, strategies and techniques need to be continuously adapted in response to environmental changes.     

Modelling stream acidification in afforested catchments: Long-term reconstructions at two sites in central Scotland

A conceptual model of the combined effects of afforestation and acidic deposition is applied to two forested sites in central Scotland. Refinements are made to the model inputs specifically to include: increased dry deposition to the forests (in excess of the dry deposition expected for moorland sites) as the forest canopy develops; uptake of ions by the growing forests; and increased evapotranspiration (and thus decreased water yield) as the forests mature. The model is calibrated using a fuzzy optimisation technique which incorporates uncertainty in target variables (stream base cation concentrations and soil exchangeable bases) and uncertainty in selecting values for fixed and adjustable parameters which describe the physico-chemical characteristics of the catchments. Simulated present-day stream and soil chemistry closely match observed values at both sites. The calibrated models indicate that while the patterns of acidification in the two catchments are broadly similar, some differences do exist between the sites in the responses of the soils to acidic deposition and afforestation. It is concluded that the calibrated models provide a tool for: (a) comparison of the relative effects of deposition and afforestation on soil and surface water acidification; (b) assessment of the likely effects of reductions in future deposition combined with future forestry management practices.     

冰川均衡调整(GIA)的研究

冰川均衡调整对固体地球物理学、大地测量学、地貌学、海洋学、冰川学、气候变化、水资源、天文学和考古学等学科具有重要的意义,通过其综述性介绍,以吸引我国地学界的注意和兴趣.本文结合作者和国内外研究成果,全方位地阐述了冰川均衡调整研究的完整内涵,首先给出了冰川均衡调整的完整概念,探讨了冰川均衡调整对冰后地壳运动、全球海平面变化、地球重力场、地球旋转运动和应力状态的影响,再分析了冰川均衡调整研究的科学目标和冰川均衡调整研究的历史与现状,最后指出了冰川均衡调整研究的未来发展方向.     

Ground Water Recharge and Chemical Contaminants: Challenges in Communicating the Connections and Collisions of Two Disparate Worlds

Our knowledge base regarding the presence and significance of chemicals foreign to the subsurface environment is large and growing — the papers in this volume serving as testament. However, complex questions with few answers surround the unknowns regarding the potential for environmental or human health effects from trace levels of xenobiotics in ground water, especially ground water augmented with treated waste water. Public acceptance for direct or indirect ground water recharge using treated municipal waste water (especially sewage) spans the spectrum from unquestioned embrace to outright rejection. In this paper, I detour around the issues most commonly discussed regarding ground water recharge and instead focus on some of the less-recognized issues—those that emanate from the mysteries created at the many literal and virtual interfaces involved with the subsurface world. My major objective is to catalyze discussion that advances our understanding of the barriers to public acceptance of waste water reuse with its ultimate culmination in direct reuse for drinking. I pose what could be a key question as to whether much of the public's frustration or ambivalence in its decision-making process for accepting, or rejecting, water reuse (for various purposes including personal use) emanates from fundamental inaccuracies, misrepresentation, or oversimplification of what water is and how it functions in the environment—just exactly what the water cycle is. These questions suggest it might behoove us to revisit some very elementary aspects of our science and how we are conveying them to the public.     

Monitoring and Mathematical Modeling of Contaminated Ground-Water Plumes in Fluvial Environments

Ground-water monitoring to delineate a contaminant plume in fluvial hydrostratigraphic units often is uncertain. Fluvial deposits consist typically of interbedded layers of sands, silts and clays, with buried stream channel deposits of sands or gravels. The channel deposits are often interpreted erroneously to be discontinuous between test holes and in cross section due to their sinuosity. Erroneous conclusions pertaining to the areal continuity of these geometrically complex deposits are inevitable unless the investigator thoroughly understands the depositional environment(s). The hydraulic conductivity of buried stream channel deposits may be several orders of magnitude higher than the matrix materials in which they are enclosed. The higher hydraulic conductivity of buried stream channel deposits has potentially significant ramifications with respect to ground-water monitoring to delineate the geometry of a contaminant plume migrating through these deposits. Ground-water monitoring at uranium mill waste disposal sites located in fluvial environments began on a significant scale in about 1977. A uranium mill tailing disposal site located in such an environment in central Wyoming is among the first sites monitored. Thirty-seven monitor wells were constructed at the site to delineate a seepage plume originating from one of the tailing ponds. This case history illustrates the need for a detailed under—standing of the hydrostratigraphy at a waste disposal site in order to interpret the meaning of ground-water quality data effectively. Water quality data from monitor wells located on a hit or miss basis often are misleading. The hydrostratigraphic horizon from which a water quality sample is collected must be well defined before the sample analyses can be interpreted quantitatively.     

Can we always ignore ship-generated food waste?

Considerable quantities of food waste can be generated at a rapid rate in ships, particularly those with large numbers of people onboard. By virtue of the amounts involved and its nature, food waste is potentially the most difficult to manage component of a ship's garbage stream, however, in most sea areas it may be dealt with by the simple expedient of direct discharge to sea. As a consequence, only minimal attention is paid to food waste management by many ship and port operators and advisory bodies, and there is a paucity of information in the available literature. The determination that management of ships' food waste is inconsequential is, however, incorrect in many circumstances. Disposal to sea is not always possible due to restrictions imposed by MARPOL 73/78 and other marine pollution control instruments. Effective management of food waste can be critical for ships that operate in areas where disposal is restricted or totally prohibited.     

Reuse of waste water: impact on water supply planning / Remploi de l'eau résiduaire: influence sur la planification des systèmes de distribution des eaux

Abstract

As the urban population of the world increases and demand on easily developable water supplies are exceeded, cities have recourse to a range of management alternatives to balance municipal water supply and demand. These alternatives range from doing nothing to modifying either the supply or the demand variable in the supply-demand relationship. The reuse or recycling of urban waste water in many circumstances may be an economically attractive and effective management strategy for extending existing supplies of developed water, for providing additional water where no developable supplies exist and for meeting water quality effluent discharge standards. The relationship among municipal, industrial and agricultural water use and the treatment links which may be required to modify the quality of a municipal waste effluent for either recycling or reuse purposes is described. A procedure is described for analysing water reuse alternatives within a framework of regional water supply and waste water disposal planning and management.     

SEDIMENT RETENTION AND WATER QUALITY ENHANCEMENT IN DISTURBED WATERSHEDS

lPRoBLEMSTATEMENTANDOVERVIEWQualitywateriswithoutdoubtalimitingsubstance,notonlyforhumansbutforalllife.Yet,ashumanpopulation,activity,andpollutioncontinuetoincrease,naturalsourcesofreadilyuseablewateraredecliningatanalarmingfate.Humanscurrentlydiveftorregulatemorethanhalfofgloballyavailablefreshwaterrunofffortheirownpurposes(Posteletal.,l996),includingtheuseoflargedamsordiversionsonriversandthewidespreadcreationofotherartificialcatchments.Additionally,groundwatersourcesarebecomingin…     

Inexact quadratic joint-probabilistic programming for water quality management under uncertainty in the Xiangxi River, China

An inexact quadratic joint-probabilistic programming model for water quality management (IQJWQ) is developed and applied to supporting multiple-point-source waste reduction in the Xiangxi River, China. The IQJWQ is a hybrid of interval quadratic programming, joint probabilistic programming and multi-segment water quality simulation. It has advantages in reflecting uncertainties expressed as joint probabilities of system risk, probability distributions of water quality standards, interval parameters and nonlinearities in the objective function. An interactive and derivative algorithm is employed for solving the IQJWQ model. The results indicate that the Pingyikou chemical plant and Liucaopo chemical plant contribute more to pollution of the main stream in the Xiangxi River, which should be the prior plants to reduce the wastewater discharge and enhance the wastewater treatment efficiencies. Meanwhile, the environmental agencies should choose the joint probability carefully to balance the tradeoff between production development and pollution control. Compared with the conventional chance-constrained programming method, the IQJWQ exhibits an increased robustness in handling the overall system risk in the optimization process. Although this study is the first application of the IQJWQ to water quality management, the proposed methods in the IQJWQ can also be applicable to many other environmental management problems under uncertainty.     

A multicatchment analysis of headwater and downstream temperature effects from contemporary forest harvesting

Stream temperature is a key physical water‐quality parameter, controlling many biological, chemical, and physical processes in aquatic ecosystems. Maintenance of cool stream temperatures during summer is critical for high‐quality aquatic habitat. As such, transmission of warm water from small, nonfish‐bearing headwater streams after forest harvesting could cause warming in downstream fish‐bearing stream reaches with negative consequences. In this study, we evaluate (a) the effects of contemporary forest management practices on stream temperature in small, headwater streams, (b) the transmission of thermal signals from headwater reaches after harvesting to downstream fish‐bearing reaches, and (c) the relative role of lithology and forest management practices in influencing differential thermal responses in both the headwater and downstream reaches. We measured summer stream temperatures both preharvest and postharvest at 29 sites—12 upstream sites (4 reference, 8 harvested) and 17 downstream sites (5 reference, 12 harvested)—across 3 paired watershed studies in western Oregon. The 7‐day moving average of daily maximum stream temperature (T_7DAYMAX) was greater during the postharvest period relative to the preharvest period at 7 of the 8 harvested upstream sites. Although the T_7DAYMAX was generally warmer in the downstream direction at most of the stream reaches during both the preharvest and postharvest period, there was no evidence for additional downstream warming related to the harvesting activity. Rather, the T_7DAYMAX cooled rapidly as stream water flowed into forested reaches ~370–1,420 m downstream of harvested areas. Finally, the magnitude of effects of contemporary forest management practices on stream temperature increased with the proportion of catchment underlain by more resistant lithology at both the headwater and downstream sites, reducing the potential for the cooling influence of groundwater.     

The effective management of national hydrometric data: experiences from the United Kingdom

Abstract

Access to hydrometric information underpins many areas of effective water management. This paper explores the operational practices of one national hydrological information service, the UK National River Flow Archive, in collating, managing and providing access to river flow data. An information lifecycle approach to hydrometric data management is advocated, with the paper detailing current UK procedures in the areas of: monitoring network design and development; data sensing and recording; validation and archival; synthesis and analysis; and data dissemination. The methods and policies outlined herein are widely transferable to other hydrological data archives around the world.

Editor D. Koutsoyiannis

Citation Dixon, H., Hannaford, J., and Fry, M.J., 2013. The effective management of national hydrometric data: experiences from the United Kingdom. Hydrological Sciences Journal, 58 (7), 1383–1399.     

Soil water balance scenario studies using predicted soil hydraulic parameters

Pedotransfer functions (PTFs) have become a topic drawing increasing interest within the field of soil and environmental research because they can provide important soil physical data at relatively low cost. Few studies, however, explore which contributions PTFs can make to land‐use planning, in terms of examining the expected outcome of certain changes in soil and water management practices. This paper describes three scenario studies that show some aspects of how PTFs may help improve decision making about land management practices. We use an exploratory research approach using simulation modelling to explore the potential effect of alternative solutions in land management. We: (i) evaluate benefits and risks when irrigating a field, and the impact of soil heterogeneity; (ii) examine which changes can be expected (in terms of soil water balance and supply) if organic matter content is changed as a result of an alternative management system; (iii) evaluate the risk of leaching to deeper horizons in some soils of Hungary. Using this research approach, quantitative answers are provided to ‘what if?’ type questions, allowing the distinction of trends and potential problems, which may contribute to the development of sustainable management systems. Copyright © 2005 John Wiley & Sons, Ltd.