青藏高原东缘三江流域生态功能区建设的措施与影响

三江流域生态环境极度脆弱,严重威胁着中下游地区的社会安全和经济发展。随着西部开发和生态建设的推进,尤其是本地区“香格里拉”旅游热潮的兴起,三江流域已经成为西部开发的重要地区。通过三江流域的生态环境功能区的界定和划分,科学制定研究区的生态环境建设目标,并进行生态环境质量的动态监测和退化过程的预警报,从而在宏观上实现生态环境质量动态管理;通过退化生态系统的恢复重建模式的研究,特别是功能区的建设示范,把目前的生态恢复工程提高到一个新的水平;为保护生物多样性资源,实现区域生态、经济、社会可持续发展提供理论支撑。     

Land cover and land use changes in a Brazilian Cerrado landscape: drivers,processes, and patterns

The Cerrado is one of the most threatened biomes in South America. To create protection actions on any scale, understanding drivers and consequences of land cover and land use (LC and LU) is essential. This study defines the composition and configuration of a Cerrado landscape watershed from 1975 to 2011. Using Landsat images and socioeconomic census data, we determined the forces acting on LC and LU change processes and their consequences. LC classes differ from LU classes for landscape dominance and processes. Economic opportunities drove LU change and its spatial distribution was related to soil, streams, and roads. Deforestation was the main cause of forest loss but forest degradation was also important, with both presenting different patterns. The spatial distribution of bare soil was related to pasture in degradation and streams. Bare soil distribution was related to pasture in degradation and streams. We concluded that broad scale factors drove changes, but local features determined distribution, and that watershed conservation plans should act on different scales, with management being spatially explicit.     

Hot Spots and Hot Moments in Riparian Zones: Potential for Improved Water Quality Management1

Vidon, Philippe, Craig Allan, Douglas Burns, Tim P. Duval, Noel Gurwick, Shreeram Inamdar, Richard Lowrance, Judy Okay, Durelle Scott, and Steve Sebestyen, 2010. Hot Spots and Hot Moments in Riparian Zones: Potential for Improved Water Quality Management. Journal of the American Water Resources Association (JAWRA) 46(2):278-298. DOI: 10.1111/j.1752-1688.2010.00420.x Abstract: Biogeochemical and hydrological processes in riparian zones regulate contaminant movement to receiving waters and often mitigate the impact of upland sources of contaminants on water quality. These heterogeneous processes have recently been conceptualized as “hot spots and moments” of retention, degradation, or production. Nevertheless, studies investigating the importance of hot phenomena (spots and moments) in riparian zones have thus far largely focused on nitrogen (N) despite compelling evidence that a variety of elements, chemicals, and particulate contaminant cycles are subject to the influence of both biogeochemical and transport hot spots and moments. In addition to N, this review summarizes current knowledge for phosphorus, organic matter, pesticides, and mercury across riparian zones, identifies variables controlling the occurrence and magnitude of hot phenomena in riparian zones for these contaminants, and discusses the implications for riparian zone management of recognizing the importance of hot phenomena in annual solute budgets at the watershed scale. Examples are presented to show that biogeochemical process-driven hot spots and moments occur along the stream/riparian zone/upland interface for a wide variety of constituents. A basic understanding of the possible co-occurrence of hot spots and moments for a variety of contaminants in riparian systems will increase our understanding of the influence of riparian zones on water quality and guide management strategies to enhance nutrient or pollutant removal at the landscape scale.     

Herbicide Transport in Goodwater Creek Experimental Watershed: II. Long‐Term Research on Acetochlor,Alachlor, Metolachlor,and Metribuzin1

Lerch, R.N., E.J. Sadler, C. Baffaut, N.R. Kitchen, and K.A. Sudduth, 2010. Herbicide Transport in Goodwater Creek Experimental Watershed: II. Long‐Term Research on Acetochlor, Alachlor, Metolachlor, and Metribuzin. Journal of the American Water Resources Association (JAWRA) 1‐15. DOI: 10.1111/j.1752‐1688.2010.00504.x Abstract: Farmers in the Midwestern United States continue to be reliant on soil‐applied herbicides for weed control in crop production, and herbicide contamination of streams remains an environmental problem. The main objective of this study was to analyze trends in concentration and load of acetochlor, alachlor, metolachlor, and metribuzin in Goodwater Creek Experimental Watershed (GCEW) from 1992 to 2006. A secondary objective was to document the effects of best management practices (BMPs) implemented within GCEW on herbicide transport trends. Median relative herbicide loads, as a percent of applied, were 3.7% for metolachlor, 1.3% for metribuzin, 0.36% for acetochlor, and 0.18% for alachlor. The major decrease in alachlor use and increase in acetochlor use caused shifts in flow‐weighted concentrations that were observed over the entire concentration range. The smaller decrease in metolachlor use led to a consistent decreasing time trend only for the upper end of the concentration distribution. Metribuzin also showed moderate decreases in concentration with time since 1998. Annual loads were generally correlated to second quarter discharge. Despite extensive education efforts in the watershed, conservation BMPs within GCEW were mainly implemented to control erosion, and therefore had no discernable impact on reducing herbicide transport. Overall, changes in herbicide use and second quarter discharge had the greatest effect on trends in flow‐weighted concentration and annual load.     

The Regionalization of National‐Scale SPARROW Models for Stream Nutrients1

Schwarz, Gregory E., Richard B. Alexander, Richard A. Smith, and Stephen D. Preston, 2011. The Regionalization of National‐Scale SPARROW Models for Stream Nutrients. Journal of the American Water Resources Association (JAWRA) 47(5):1151‐1172. DOI: 10.1111/j.1752‐1688.2011.00581.x Abstract: This analysis modifies the parsimonious specification of recently published total nitrogen (TN) and total phosphorus (TP) national‐scale SPAtially Referenced Regressions On Watershed attributes models to allow each model coefficient to vary geographically among three major river basins of the conterminous United States. Regionalization of the national models reduces the standard errors in the prediction of TN and TP loads, expressed as a percentage of the predicted load, by about 6 and 7%. We develop and apply a method for combining national‐scale and regional‐scale information to estimate a hybrid model that imposes cross‐region constraints that limit regional variation in model coefficients, effectively reducing the number of free model parameters as compared to a collection of independent regional models. The hybrid TN and TP regional models have improved model fit relative to the respective national models, reducing the standard error in the prediction of loads, expressed as a percentage of load, by about 5 and 4%. Only 19% of the TN hybrid model coefficients and just 2% of the TP hybrid model coefficients show evidence of substantial regional specificity (more than ±100% deviation from the national model estimate). The hybrid models have much greater precision in the estimated coefficients than do the unconstrained regional models, demonstrating the efficacy of pooling information across regions to improve regional models.     

基于氮磷指数的小流域氮磷流失风险评价

识别区域氮磷流失综合风险分布状况并对氮磷流失进行综合调控是控制非点源污染的有效措施。但传统的研究往往局限于氮或磷流失风险的单独评估和调控,以密云水库沿湖集约化农区东庄小流域为例,应用氮指数、磷指数及氮磷综合指数法,对区域氮磷流失风险进行综合评价。结果表明:流域氮、磷流失风险总体上较小,80%以上的区域均处于氮、磷流失的无风险或低风险区,但氮、磷流失的空间分布存在较大差异。其中氮流失的高度风险区集中在山地中土壤侵蚀指数较大的果园;而磷流失的高风险区域主要分布在河流沿岸的农业用地。氮磷综合风险指数显示,93.1%的区域处于无风险和低风险区,中度以上风险区占总面积的6.9%,主要集中在流域中部有着较高的肥料施用、地势陡峭且处在河流沿岸的农业用地或山地中。单独考虑氮指数或磷指数都难以反映区域氮磷流失的综合风险状况,容易忽略磷指数高氮指数低、氮指数高和磷指数低以及氮、磷风险在中等的区域。因此,在氮、磷流失风险评估基础上,进行氮磷流失风险的综合评价,可为氮磷流失的综合调控提供指导。     

A conceptual framework of agricultural land use planning with BMP for integrated watershed management

Land use planning is an important element of the integrated watershed management approach. It not only influences the environmental processes such as soil and stream bed erosion, sediment and nutrient concentrations in streams, quality of surface and ground waters in a watershed, but also affects social and economic development in that region. Although its importance in achieving sustainable development has long been recognized, a land use planning methodology based on a systems approach involving realistic computational modeling and meta-heuristic optimization is still lacking in the current practice of integrated watershed management. The present study proposes a new approach which attempts to combine computational modeling of upland watershed processes, fluvial processes and modern heuristic optimization techniques to address the water-land use interrelationship in its full complexity. The best land use allocation is decided by a multi-objective function that minimizes sediment yields and nutrient concentrations as well as the total operation/implementation cost, while the water quality and the production benefits from agricultural exploitation are maximized. The proposed optimization strategy considers also the preferences of land owners. The runoff model AnnAGNPS (developed by USDA), and the channel network model CCHE1D (developed by NCCHE), are linked together to simulate sediment/pollutant transport process at watershed scale based on any assigned land use combination. The greedy randomized adaptive Tabu search heuristic is used to flip the land use options for finding an optimum combination of land use allocations. The approach is demonstrated by applying it to a demonstrative case study involving USDA Goodwin Creek experimental watershed located in northern Mississippi. The results show the improvement of the tradeoff between benefits and costs for the watershed, after implementing the proposed optimal land use planning.     

降雨强度对洱海流域凤羽河氮磷排放的影响

降雨形成的径流携带各种陆面物质进入河流湖泊是导致水质变化的重要因素,而不同降雨强度下的河流氮磷输出特征均有所差异,因此,为阐明雨强对高原湖泊典型流域污染物排放的影响,本研究以洱海流域上游的凤羽河为研究对象,基于连续3 a(2011～2013年)的出口断面水质水量监测,分析了4种降雨强度(小雨、中雨、大雨、暴雨)对水体氮磷浓度和形态的影响.结果表明,降雨强度对凤羽河氮磷排放的影响显著,所有组分的氮和磷浓度平均值在小雨(10 mm)和中雨(10～25mm)时较低,在大雨(25～50 mm)和暴雨(50～100 mm)时较高;氨氮(NH_4+-N)(57. 14%～76. 85%)占总氮(TN)的质量分数大于颗粒态氮(PN)(23. 15%～42. 86%),溶解态总磷(TDP)(22. 73%～28. 00%)占总磷(TP)的质量分数小于颗粒态磷(PP)(72. 00%～77. 27%);不同形态的氮浓度比较为:TN NH_4+-N PN;不同形态的磷浓度比较为:TP PP TDP.     

九龙江流域河流磷输出对土地利用模式及水文状况的响应

本研究应用现场监测、地理信息技术（GIS）、模型模拟和数理统计等方法,基于2015年3月至2017年2月九龙江流域不同主导土地利用类型源头小流域和两条干流河流表层水总磷（TP）、总溶解态磷（TDP）和颗粒态磷（PP）的浓度监测,探究河流磷浓度与输出负荷的时空变化特征,揭示九龙江流域磷输出对土地利用模式及水文状况的响应.结果发现,九龙江流域河流磷浓度和磷输出负荷具有明显的时空变异性.在空间上,农业流域 > 城市流域 > 自然流域,西溪>北溪.在季节上,不同类型流域不同形态磷浓度总体表现为春、冬季节较高,而夏、秋季节较低.TP、TDP、和PP输出负荷春、夏季高于秋、冬季,与径流深度的变化趋势基本一致.磷浓度、输出负荷与林地和裸地面积百分比呈负相关关系,与耕地、果园面积百分比呈正相关关系.但不同季节,磷浓度和输出负荷对土地利用和水文状况的响应存在差异,在夏季的相关性最强.结果表明农业非点源污染是九龙江流域河流磷的关键源,提升林地比例有助于保持水土,改善河流水质,尤其在雨季.     

三峡库区典型紫色土小流域径流及氮磷流失特征

为了解三峡库区典型紫色土小流域径流污染特征,对新政小流域典型土地利用类型下降雨-径流时间过程和小流域集水区出口径流中氮磷浓度进行动态监测,监测分析库区小流域氮磷在降雨径流中的流失规律.结果表明,小流域径流氮磷损失量分别为13. 69 kg·(hm~2·a)-1和1. 50 kg·(hm~2·a)-1.农肥所含氮磷及降雨冲刷是小流域径流污染的主要原因.小流域的总氮(TN)和总磷(TP)平均浓度达10. 05 mg·L~(-1)和1. 10 mg·L~(-1),远超过富营养化发生标准,须引起关注.本研究观测的两场降雨中,8月15日降雨中硝态氮(NN)和颗粒态磷(PP)分别为69. 47 kg和6. 83 kg,分别占TN和TP的53. 91%和53. 78%; 8月26日降雨中NN、氨氮(AN)和PP分别为6. 68、5. 61和1. 36 kg,分别占TN和TP的37. 74%、31. 69%和57. 63%,表明氮素流失主要通过可溶态的方式,而磷素迁移则以颗粒态为主.小流域强降雨对于氮磷流失的影响显著.这与紫色土土层薄、耕作频繁、土壤相对疏松等性质有关.