Surface water quality in a sulfide mineral‐rich arid zone in North‐Central Chile: Learning from a complex past,addressing an uncertain future          下载免费PDF全文

Mauricio Flores  Jorge Núñez  Jorge Oyarzún  Gustavo Freixas  Hugo Maturana  Ricardo Oyarzún 《水文研究》2017,31(3):498-513

This study presents an analysis of up to 30 years of hydrological variables and selected water quality parameters (pH, SO₄, Fe, Cu, and As) in the upper area of the Elqui River basin in North‐Central Chile. A correlation analysis determined statistically significant positive relationship for SO₄‐Cu, Fe‐As, and Fe‐Cu. In terms of historical behaviour, no statistically significant trends were detected for precipitation or temperature. In contrast, for flow, there is an overall decreasing pattern for the entire area of study, although only in one case this trend was statistically significant. Along with the aforementioned analysis, a characterization of the flow‐water quality relationships is considered for the time period analyzed. Although erratic behaviours were confirmed, a negative (i.e., inverse) flow‐concentration relationship was identified for SO₄, a positive (i.e., direct) relationship for Fe, and undefined relationships for As and Cu were obtained. From these analyses and based on previous studies on projections regarding climate change for the Andean region, and in particular for the upper Elqui zone, an estimation of the possible effects of the change in water regimes on water quality in the area of study is developed. It is likely that a decrease in surface flow, as a consequence of climate change could translate into improvements in water quality in terms of Fe and eventually As and Cu, but into an impairment in the case of SO₄. In any case, this is a complex situation that demands special attention in the face of industrial activities that could be developed in tributaries like the Claro River, which currently play an important role in depurating or diluting contaminants in the waters of the Elqui River. Finally, it should be noted that this study addresses an issue that goes beyond the local interest and could be used as a reference to compare other transitional environments containing sulphide ores or areas of hydrothermal alterations, which are considered to be highly vulnerable to climate change and variability.  相似文献   

Headwater stream length dynamics across four physiographic provinces of the Appalachian Highlands          下载免费PDF全文

Carrie K. Jensen  Kevin J. McGuire  Philip S. Prince 《水文研究》2017,31(19):3350-3363

Understanding patterns of expansion, contraction, and disconnection of headwater stream length in diverse settings is invaluable for the effective management of water resources as well as for informing research in the hydrology, ecology, and biogeochemistry of temporary streams. More accurate mapping of the stream network and quantitative measures of flow duration in the vast headwater regions facilitate implementation of water quality regulation and other policies to protect waterways. We determined the length and connectivity of the wet stream and geomorphic channel network in 3 forested catchments (<75 ha) in each of 4 physiographic provinces of the Appalachian Highlands: the New England, Appalachian Plateau, Valley and Ridge, and Blue Ridge. We mapped wet stream length 7 times at each catchment to characterize flow conditions between exceedance probabilities of <5% and >90% of the mean daily discharge. Stream network dynamics reflected geologic controls at both regional and local scales. Wet stream length was most variable at two Valley and Ridge catchments on a shale scarp slope and changed the least in the Blue Ridge. The density and source area of flow origins differed between the crystalline and sedimentary physiographic provinces, as the Appalachian Plateau and Valley and Ridge had fewer origins with much larger contributing areas than New England and the Blue Ridge. However, the length and surface connectivity of the wet stream depended on local lithology, geologic structure, and the distribution of surficial deposits such as boulders, glacially derived material, and colluival debris or sediment valley fills. Several proxies indicate the magnitude of stream length dynamics, including bankfull channel width, network connectivity, the base flow index, and the ratio of geomorphic channel to wet stream length. Consideration of geologic characteristics at multiple spatial scales is imperative for future investigations of flow intermittency in headwaters.  相似文献   

Hydrologic impacts of subsurface drainage from the field to watershed scale          下载免费PDF全文

Ricardo Mantilla  Morgan Fonley  Nandita B. Basu 《水文研究》2017,31(17):3017-3028

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中国乡村振兴背景下的农业发展状态与产业兴旺途径   总被引：9，自引：1，他引：9  

陈秧分  刘玉  李裕瑞 《地理研究》2019,38(3):632-642

中国农业竞争力偏弱,农业发展关乎农业农村现代化目标的实现。本文引入“要素-结构-功能”分析框架,探讨了乡村振兴背景下中国农业发展与产业兴旺的理论基础,解析了中国农业发展特征、影响因素与兴旺路径。结果表明：① 农业乡村已由特别强调农产品生产与社会稳定,转向兼顾产品供应、社会稳定、文化传承、生态涵养等诸多功能。农业的多功能属性,支撑了中国农业的基础地位与广阔的发展空间。② 基于比较优势进行分工、通过产品差异化以提高农业附加值、加强政府支持以化解市场失灵、促进“人”“地”“业”协调耦合,是推动农业发展的主要理论选项。③ 中国农业发展过程中,间接利益相关者的获得感要强于农民群体,同时还面临农业劳动生产效率偏低等瓶颈问题。④ 考虑农业的多功能属性与现实问题,建议切实推动中国农业发展由增产导向转向提质增效,促进产镇融合、产村融合,建立农业要素功能显化增殖机制与“进得来、留得住、能受益”的生产要素配置机制,提高农业支持政策的针对性、协同性与联动性,推动中国农业发展与产业兴旺。  相似文献   

Cultural Landscape Evolution of Traditional Agricultural Villages in North China —— Case of Qianzhai Village in Shandong Province   总被引：1，自引：0，他引：1  

FANG Yangang LIU Jisheng 《中国地理科学(英文版)》2008,18(4):308-315

Agricultural village is an important rural type in China. The evolution process and mechanism of its cultural landscape are different from those of the industrialized village. The paper focuses this theme by a case study of Qianzhai Village of Qufu City, Shangdong Province. In the case of Qianzhai Village, the evolution of its settlement has experienced three stages： mechanical expansion, sprawling expansion and hollowing, and recentralization. The land- scape evolution of residents＇ houses has undergone three phases： traditional quadrangle house, one-storied house and multistoried house. The evolution of its land use has experienced three stages： circled stratification, fragment and intensive use, and concentration and extensive use. We can see that the main driving factors of cultural landscape evolution of agricultural village are the changes of rural population, society, economy and culture, which are influenced by the change of urban-rural relation, the national modernization process and economic development, the reform of family planning and land system, and the changes in governmental policies. In the future, the modernization, ecological trend, and individualization for residents＇ houses of agricultural villages in China will develop step by step. The recentralization of settlement and the scaled, sustainable, intensive land use are likely to be the trends of agricultural villages in China.  相似文献   

Twentieth century agricultural drainage creates more erosive rivers          下载免费PDF全文

Shawn P. Schottler  Jason Ulrich  Patrick Belmont  Richard Moore  J. Wesley Lauer  Daniel R. Engstrom  James E. Almendinger 《水文研究》2014,28(4):1951-1961

Rivers in watersheds dominated by agriculture throughout the US are impaired by excess sediment, a significant portion of which comes from non‐field, near‐channel sources. Both land‐use and climate have been implicated in altering river flows and thereby increasing stream‐channel erosion and sediment loading. In the wetland‐rich landscapes of the upper Mississippi basin, 20th century crop conversions have led to an intensification of artificial drainage, which is now a critical component of modern agriculture. At the same time, much of the region has experienced increased annual rainfall. Uncertainty in separating these drivers of streamflow fuels debate between agricultural and environmental interests on responsibility and solutions for excess riverine sediment. To disentangle the effects of climate and land‐use, we compared changes in precipitation, crop conversions, and extent of drained depressional area in 21 Minnesota watersheds over the past 70 years. Watersheds with large land‐use changes had increases in seasonal and annual water yields of >50% since 1940. On average, changes in precipitation and crop evapotranspiration explained less than one‐half of the increase, with the remainder highly correlated with artificial drainage and loss of depressional areas. Rivers with increased flow have experienced channel widening of 10–40% highlighting a source of sediment seldom addressed by agricultural best management practices. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

A stem‐branch topological codification for watershed subdivision and identification to support distributed hydrological modelling at large river basins          下载免费PDF全文

Jiajia Liu  Zuhao Zhou  Yangwen Jia  Hao Wang  Xiangdong Chen 《水文研究》2014,28(4):2074-2081

Watershed subdivision is a useful discretization method for distributed hydrological models at large river basins. A subwatershed codification method, which is able to identify the subwatershed uniquely and reflect the topological relationship is desired. According to the previous literatures, there are two types of coding methods suitable for the subwatershed codification: the Pfafstetter‐group rules and the modified binary tree codification method. But, both of them have some shortcomings in theory and application. A new coding method named stem‐branch topological codification is developed to overcome these shortcomings, which is based on the stem‐branch topological structure of the drainage networks and capable of reflecting the river hierarchy. The basic coding elements of the method are river reaches in the drainage networks, which are not only generated by the tributary junctions, but also by the splitting points of hydrological factors (e.g. hydrological gauge stations and reservoirs). Also, the method could handle complex confluences (e.g. river reaches with more than two upstream inflows), which are rare under natural conditions, but more frequent in the digital elevation model extracted or artificial drainage networks (e.g. sewage systems or irrigation drainage networks). With the stem‐branch topological codification codes, it is easy to identify the upstream (or downstream) relationship between any two subwatersheds and to calculate the directly connected subwatershed codes. Also, if some changes have occurred in the drainage network, there is no need to recode the whole watershed, but by modifying the existed codes to form the new ones. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Surface water and groundwater interactions in an extensively mined watershed,upper Schuylkill River,Pennsylvania, USA          下载免费PDF全文

Charles A. Cravotta III  Daniel J. Goode  Michael D. Bartles  Dennis W. Risser  Daniel G. Galeone 《水文研究》2014,28(10):3574-3601

Streams crossing underground coal mines may lose flow, whereas abandoned mine drainage (AMD) restores flow downstream. During 2005–2012, discharge from the Pine Knot Mine Tunnel, the largest AMD source in the upper Schuylkill River Basin, had near‐neutral pH and elevated concentrations of iron, manganese and sulphate. Discharge from the tunnel responded rapidly to recharge but exhibited a prolonged recession compared with nearby streams, consistent with rapid infiltration of surface water and slow release of groundwater from the mine complex. Dissolved iron was attenuated downstream by oxidation and precipitation, whereas dissolved CO₂ degassed and pH increased. During high flow conditions, the AMD and downstream waters exhibited decreased pH, iron and sulphate with increased acidity that were modelled by mixing net‐alkaline AMD with recharge or run‐off having low ionic strength and low pH. Attenuation of dissolved iron within the river was least effective during high flow conditions because of decreased transport time coupled with inhibitory effects of low pH on oxidation kinetics. A numerical model of groundwater flow was calibrated by using groundwater levels in the Pine Knot Mine and discharge data for the Pine Knot Mine Tunnel and West Branch Schuylkill River during a snowmelt event in January 2012. Although the calibrated model indicated substantial recharge to the mine complex took place away from streams, simulation of rapid changes in mine pool level and tunnel discharge during a high flow event in May 2012 required a source of direct recharge to the Pine Knot Mine. Such recharge produced small changes in mine pool level and rapid changes in tunnel flow rate because of extensive unsaturated storage capacity and high transmissivity within the mine complex. Thus, elimination of stream leakage could have a small effect on the annual discharge from the tunnel, but a large effect on peak discharge and associated water quality downstream. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.  相似文献   

A model for distributed GIUH‐based flow routing on natural and anthropogenic hillslopes          下载免费PDF全文

Dennis W. Hallema  Roger Moussa 《水文研究》2014,28(18):4877-4895

Attempts to reduce the number of parameters in distributed rainfall–runoff models have not yet resulted in a model that is accurate for both natural and anthropogenic hillslopes. We take on the challenge by proposing a distributed model for overland flow and channel flow based on a combination of a linear response time distribution and the hillslope geomorphologic instantaneous unit hydrograph (GIUH), which can be calculated with only a digital elevation model and a map with field boundaries and channel network as input. The spatial domain is subdivided into representative elementary hillslopes (REHs) for each of which we define geometric and flow velocity parameters and compute the GIUH. The catchment GIUH is given by the sum of all REH responses. While most distributed models only perform well on natural hillslopes, the advantage of our approach is that it can also be applied to modified hillslopes with for example a rectangular drainage network and terrace cultivation. Tests show that the REH‐GIUH approach performs better than classical routing functions (exponential and gamma). Simulations of four virtual hillslopes suggest that peak flow at the catchment outlet is directly related to drainage density. By combining the distributed flow routing model with a lumped‐parameter infiltration model, we were also able to demonstrate that terrace cultivation delays the response time and reduces peak flow in comparison to the same hillslope, but with a natural stream network. The REH‐GIUH approach is a first step in the process of coupling distributed hydrological models to erosion and water quality models at the REH (associated with agricultural management) and at the catchment scale (associated with the evaluation of the environmental impact of human activities). It furthermore provides a basis for the development of models for large catchments and urban or peri‐urban catchments. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

驱动山区农业产业遥感监测的GMG协同系统建设与应用     

孙俊英  刘吉  陈忠超  蔡忠亮  闫从政 《测绘通报》2020,(11):124-127

由于喀斯特山区地貌的支离破碎、地形的高低起伏及气候的多云与雾，难以通过常规遥感手段实现大范围农作物的快速监测，针对该情况，本文研发了内外业一体化的GMG协同系统。该系统利用GPS的精准定位、多媒体的丰富语义及GIS的数据处理优势，多向驱动贵州山区农业产业遥感监测。实践表明，该系统快速实现了省域监测中解译样本的多样性，有效弥补了局部区域内遥感监测的局限性，同时检验了解译数据的准确性。  相似文献