农业小流域土地利用格局变化对氮素输出的影响——以丹江口库区胡家山小流域为例

流域土地利用格局对农业非点源污染氮素输出具有重要的影响。以丹江口库区胡家山小流域为研究对象,分析2008～2016年土地利用类型变化对流域总氮输出的影响,以期为丹江口库区生态清洁小流域建设提供参考。结果表明:2008～2016年,流域出口处总氮年平均浓度从5. 13±4. 2 mg/L降低为2. 06±0. 62mg/L;总氮输出负荷由49 025 kg/a降低至21 578 kg/a,总氮输出负荷减少56. 0%。对比分析流域生态治理工程实施情况,发现坡改梯、退耕还林等水土保持治理与植被恢复措施在有效控制水土流失的同时,还在减少流域氮素输出中发挥了重要作用。经相关分析,流域内林地、耕地、居民地的空间分布格局对流域氮素输出均有影响,其中100 m河岸带范围为流域总氮负荷输出的主要区域。有效控制胡家山小流域100 m河岸带尺度的氮素流失,可显著降低流域总氮输出负荷。     

LiDAR based hydro-conditioned hydrological modeling for enhancing precise conservation practice placement in agricultural watersheds

High resolution Light Detection and Ranging (LiDAR)-derived Digital Elevation Models (DEMs) improve hydrologic modeling and aid in identifying the targeted locations of best conservation practices (CPs) in agricultural watersheds. However, the inability of LiDAR data to represent the conveyance of water under or through the surfaces (i.e., bridges or culverts) impedes the simulated flow, resulting in false upstream pooling. Improper flow simulation affects the accuracy of pollutant load estimations and targeted locations delineated by watershed models or models built upon hydro-conditioned DEMs (hDEM). We propose a novel approach of Hydro-conditioning to modify LiDAR imagery through breach lines, which is essential to accurately replicate the landscape hydrologic connectivity. We compared variations in outcomes of Agricultural Conservation Planning Framework (ACPF), based on manual and automated hDEMs for Plum Creek watershed, Minnesota. The derived flow network, catchment boundaries, drainage areas, locations/number of practices depend on the chosen hDEM. Locations, size and shape of bioreactors, drainage management, farm ponds, nutrient removal wetlands, riparian buffers are severely affected by hydro-conditioning. Shuttle Radar Topography Mission (SRTM) validation of hDEMs showed that Mean Average Percentage Deviation (MAPE) for automated and manual hDEMs is 1.34 and 0.998 respectively. Also, proximity analysis with a buffer of 200 m showed that CPs’ locations delineated by manual hDEM match better with the existing ones as compared to automated hDEM. Results indicate that coupled approach of using automated and manual ‘hDEM’ is best suited for guiding stakeholders towards the field-scale planning in a cost-saving manner.

     

The Contribution of Conservation Practices in Reducing Runoff, Soil Loss, and Transport of Nutrients at the Watershed Level

The lack of land use planning and the absence of conservation practices in a watershed can contribute to increased runoff, soil loss, and nutrient transport, which compromise the environmental quality in a watershed, especially the water resources. The objective of this study was to assess the contribution of conservation practices in reducing runoff and soil and nutrient losses using the Soil and Water Assessment Tool (SWAT) in the S?o Bartolomeu Stream Watershed, which is a significant watershed in Brazil. The modeling allowed us to identify critical areas regarding sediment yield, runoff, and nutrient loss. After that, conservation practices aimed at reducing the impacts of such processes were simulated. We also identified the most sensitive model parameters to simulate changes in management practices. Simulation results showed an average annual runoff (R) of 35?mm, average annual sediment yield (SY) of 51?t ha^-1?year^-1, 3.6?t ha^-1?year^-1 of total nitrogen (TN), and 1.6?t ha^-1?year^-1 of total phosphorus (TP). When considering the adoption of conservation practices, results showed an increase in water infiltration in the watershed and reductions of 18?%, 66?%, 25?%, and 30?% for R, SY, TN, and TP, respectively. Interventions which prioritize adequate management practices can be highly efficient and avoid changes in consolidated land uses.     

The uncertain search for the diffuse silver bullet: science, policy and prospects.

The overwhelming importance of diffuse sources as a determinant of receiving water quality has been recognised for over 30 years. Significant research and development on techniques for reducing inputs in the riparian zone has resulted in numerous guideline documents being produced. Yet despite this research effort, and the apparently successful transfer of key results to water resource managers, the public perception in New Zealand is that the quality of receiving waters continues to decline. In this paper we examine the veracity of that perception through examination of state-of-the-environment reporting, discussions with water resource managers, and published literature. Using a case study of Lake Taupo, New Zealand as an example, we discuss the difficulties faced by water resource managers in arresting declines in water quality. We compare the reduction in potential nutrient exports possible between 'non-invasive' mitigation techniques such as riparian buffer strips, constructed and natural wetlands and source control measures such as the use of nitrification inhibitors and wintering pads. Finally, we look at options available should voluntary measures or best management practices fail to deliver the nutrient reductions that are necessary to maintain lake water quality.     

流域尺度的河流生态修复

在对河流生态修复相关理念进行阐述的基础上，讨论了河流连续体概念和河流四维模型．从人类活动影响的大尺度特征、河流特性、河流水污染、水陆交错带几个方面对在流域尺度下进行河流生态修复的必要性进行了分析探讨，并指出我国现阶段河流修复中的首要任务是遏制流域内引起生态系统退化的水污染．     

Simulation of Agricultural Management Alternatives for Watershed Protection

The Bosque River Watershed in Texas is facing a suite of water quality issues including excess sediment, nutrient, and bacteria. The sources of the pollutants are improperly managed cropland and grazing land, dairy manure application, and effluent discharge from wastewater treatment facilities. Several best management practices (BMPs) have been proposed for pollution reduction and watershed protection. The overall objectives of this study were to demonstrate a modeling approach using Soil and Water Assessment Tool (SWAT) model to simulate various BMPs and assess their long-term impacts on sediment and nutrient loads at different spatial levels. The SWAT model was calibrated and validated for long-term annual and monthly flows at Valley Mills and for monthly sediment, total nitrogen (TN) and total phosphorus (TP) at Hico and Valley Mills monitoring locations. The BMPs including streambank stabilization, gully plugs, recharge structures, conservation tillage, terraces, contour farming, manure incorporation, filter strips, and PL-566 reservoirs were simulated in the watershed areas that met the respective practice’s specific criteria for implementation. These BMPs were represented in the pre- and post-conditions by modifying one or more channel parameters (channel cover, erodibility, Manning’s n), curve number (CN), support practice factor (P-factor), filter strip width, and tillage parameters (mixing efficiency, mixing depth). The BMPs were simulated individually and the resulting Hydrologic Response Units (HRUs), subwatershed, and watershed level impacts were quantified for each BMP. Sensitivity of model output values to input parameters used to represent the BMPs was also evaluated. Implementing individual BMPs reduced sediment loads from 3% to 37% and TN loads from 1% to 24% at the watershed outlet; however, the changes in TP loads ranged from 3% increase to 30% decrease. Higher reductions were simulated at the subwatershed and HRU levels. Among the parameters analyzed for sensitivity, P-factor and CN were most sensitive followed by Manning’s n. The TN and TP outputs were not sensitive to channel cover. This study showed that the SWAT modeling approach could be used to simulate and assess the effectiveness of agricultural best management practices.     

河流健康的概念及指标体系和评价方法

指出健康河流不但应当具有健康的生态系统,还应具有良好的社会服务功能;与生态河道和景观河道相比,健康河流兼有生态河道和景观河道的有益特征,具有更广泛的适用性;河流健康评价指标应当具备易于理解、便于定性或定量描述、便于监测、便于作为管理目标和拟定相应对策等特点。以此为依据,提出包括流量偏离率、水质综合污染指数、底栖大型无脊椎动物生物完整性指数、河流廊道连通性、河道稳定性、栖息地质量、缓冲带宽度、林草覆盖度、河流美景度和实际防洪能力等指标的河流健康评价指标体系及评价方法。     

长江经济带水资源保护带建设规划体系研究

针对长江经济带水资源保护面临的形势和要求,从水资源保护带建设的概念和内涵出发,研究提出了长江经济带水资源保护带建设规划体系框架,明确了规划的基本原则、战略格局、建设布局以及措施体系。同时,重点围绕饮用水水源地、重要江河湖库的水资源保护,分别提出了包含陆域隔离防护带、滨水缓冲带、水域净化带的水资源保护带建设布局,以及包含有入河排污控制带、水生态系统保护与修复带、生态防护林带、面源污染阻控带的水资源保护带建设布局,形成“远近结合、层次分明、从陆域到水域”的规划措施体系。研究成果对于指导长江经济带水资源保护建设规划的编制和水资源保护措施的落实具有重要的意义。     

Modelling Watershed Scale Soil Loss Prediction and Sediment Yield Estimation

Computer simulation models are becoming increasingly popular in predicting soil loss for various land use and management practices. A GIS-based system, GeoUSLE, was developed in this study for soil loss prediction and sediment yield estimation in the watershed scale. The Universal Soil Loss Equation (USLE) and watershed analysis models are incorporated in the system. The required watershed information and USLE factors are derived from digital elevation models (DEMs) and remote sensing data. The GIS-based system can flexibly delineate drainage networks and watersheds and rapidly query the sediment yield at any point or watershed outlet via the point-and-click interface. The study presents an example application of the system to an agricultural reservoir watershed in central Taiwan. The estimated result shows that the developed system scales up USLE applications from the slope to the watershed, which can be used to assess the erosion hot spots in a watershed for the management decision making.     

Influences of land use/cover on water quality in the upper and middle reaches of River Njoro, Kenya

Data from 10 sampling sites along the River Njoro are used to examine the contribution of nutrients from upstream land uses draining each of the sampling sites. The data also are used to assess whether both the proportion of land uses and the size of the subwatersheds account for the variability in water quality in the River Njoro watershed. Geographical Information System analysis was used to determine the spatial distribution of land‐cover types and subwatersheds contributing run‐off to the sampling sites in the River Njoro. Standard Digital Elevation Model‐based routines were used to establish the watershed area contributing run‐off to each sampling site. Water and sediment samples were collected for chemical analysis, and the nutrient levels were related to the upstream land‐use types and the size of the subwatersheds. The mid‐stream portion of the River Njoro (near Egerton University) accounts for the highest nutrient contributions. The percentage contribution is magnified by additions from industrial, human settlements and agricultural land uses around the University. There is a significant decrease in nutrient levels downstream, however, indicating natural purification as the river flows through an area of large‐scale farming with intense, well‐preserved riparian and in‐stream vegetation. Steep slopes of the land upstream of Egerton University enhance erosion and nutrient losses from those subwatersheds. Mixed small‐scale agricultural and bare lands contribute over 55% of the phosphorus load to the upper and mid‐reaches of the River Njoro. The size of the subwatershed accounts for about 53% of the variability in the soluble phosphorus in the river. The land‐use subwatershed proportions are important for characterizing and modelling water quality in the River Njoro watershed. Upland land uses are as important as near‐stream land uses. We suggest that conservation of intact riparian corridor along the river and its tributaries contributes significantly to natural purification processes and recovery of the ecological integrity of the River Njoro ecosystem.     

Evaluation of atmospheric deposition of nitrogen to the Feitsui reservoir in Taipei.

This research studied how the air pollutants of urban areas affect a neighboring reservoir and its water quality. Through the atmospheric dispersion process, air pollutants move from the Taipei metropolitan to the Feitsui reservoir and enter the water body through dry and wet depositions. ISCST3 (Industrial Source Complex Short Term Model), an air quality model, was used to simulate dispersion, dry deposition and wet deposition of the air pollutants. Then the nitrogen loadings to the Feitsui Reservoir were evaluated. The results indicate that wet deposition places a greater burden than dry deposition does on the water body. Wet and dry deposition of NH4+ together make up a rather large proportion of the total pollution. The ranged from 21.9 to 25.2%. Those of nitrate make up a smaller proportion, ranged from 2.0 to 2.3%. If we take indirect deposition into account and calculate the NO3- and NH4+ together, the proportion is 15.9-17.6%.     

Watershed management

Water management has increasingly been realized to be an essential component of sustainable water development. While no‐one argues with the desirability of proper watershed management, achieving it has not been an easy task. It requires concurrent accomplishment of many tasks, among which are strict control of land‐use practices, afforestation and forest management, and implementation of appropriate soil and water conservation practices. Two main impacts of inadequate watershed management are discussed. These are increased reservoir sedimentation which reduces storage capacity which may in turn render water projects uneconomic, and changing patterns of stream flow. It is argued that watershed management should not be viewed exclusively from the narrow perspective of benefits to water projects alone. It should be considered essential for soil and water conservation and forest management, which in the long run will enhance the prospect of self‐reliance of nations in terms of food, fibre and energy.     

我国水土保持的理论与方法

通过对我国近几十年水土保持实践经验的分析，总结了推动我国水土保持事业进一步发展的理论与方法。水土保持的理论基础即土壤侵蚀学原理、流域水文学原理、生态经济学原理、恢复生态学原理、系统科学原理，以及流域可持续经营原理。水土保持的技术体系及方法为：以小流域为单元进行综合调查分析、综合规划、综合治理、综合开发利用，以实现水土保持综合效益。     

水源地保护及突发性水污染事件预警应急的研究与实施进展

从保护水源地和建立突发性水污染事件预警应急系统的重要性出发,综述了国内外在水源地保护立法、管理体制、水源地保护现状和突发性水污染事件预警应急系统建设方面的研究与实施进展。提出了从加强立法、规划,严控污染源,强化流域管理,鼓励公众参与,对水源地进行经济补偿,采用先进技术,加强水源地保护教育等方面加强水源地保护工作以及加强水源地突发性水污染事件应急的预警体系的一些建议。     

河岸植被缓冲带生态功能及其过滤机理的研究进展

河岸植被缓冲带作为河岸生态系统的重要组成部分,是控制水土流失和面源污染、改善水环境的关键措施,对河岸生态系统的生态及水文过程具有重要的影响。概述了国内外关于河岸植被缓冲带研究的现状,总结了河岸植被缓冲带的主要功能、影响其功能发挥的主要因素和作用机理,并对河岸植被缓冲带的设计、管理和效益评估进行阐述,提出了我国在未来关于河岸植被缓冲带研究的发展趋势及后续研究中仍需加强和关注的重要方向,为今后河岸植被缓冲带的研究提供参考和借鉴,具有一定的理论价值和实际意义。     

Economic analysis of water temperature reduction practices in a large river floodplain: an exploratory study of the Willamette River,Oregon

This paper examines ecosystem restoration practices that focus on water temperature reductions in the upper mainstem Willamette River, Oregon, for the benefit of endangered salmonids and other native cold‐water species. The analysis integrates hydrologic, natural science and economic models to determine the cost‐effectiveness of alternative water temperature reduction strategies. A temperature model is used to simulate the effects of combinations of upstream riparian shading and flow augmentations on downstream water temperatures. Costs associated with these strategies are estimated and consist of the opportunity costs of lost agricultural production and recreation opportunities due to flow releases from an up‐stream reservoir. Temperature reductions from another strategy, hyporheic flow enhancement, are also examined. Restoration strategies associated with enhanced hyporheic cooling consist of removal/reconnection of current obstacles to the creation of dynamic river channel complexity. The observed reduction of summer water temperatures associated with enhanced channel complexity indicates that restoring hyporheic flow processes is more likely to achieve cost‐effective temperature reductions and meet the total maximum daily load (TMDL) target than conventional approaches that rely on increased riparian shading or/and combinations of flow augmentation. Although the costs associated with the hyporheic flow enhancement approach are substantial, the effects of such a long‐term ecological improvement of the floodplain are expected to assist the recovery of salmonid populations and provide ancillary benefits to society. Copyright © 2008 John Wiley & Sons, Ltd.     

Evaluation of Non-point Source Loads in the Reservoir Watershed using the GIS/GPS/RS Information Technologies and Numerical Models

Abstract

One of the recent concerns of reservoir eutrophication issues focuses on a fast assessment of the non-point sources pollution impact. It frequently requires an initial evaluation of the land use pattern and the reservoir assimilative capacity. This information is useful for estimating the non-point source loads, assessing the proper uses of natural resources in the watershed, and generating the essential control strategies when required. To achieve this goal, the state-of-the-art 3S information technologies, which properly integrates the skills of geographic information system (GIS), global positioning system (GPS) and remote sensing (RS), is viewed as an integrated means for reservoir land use assessment and watershed management. Substantial efforts in this study are placed upon identifying seven types of land use patterns in the watershed of the Tseng-Wen Reservoir in Southern Taiwan, which would directly assist in the required estimation of non-point sources pollution impact. With the aid of SPOT satellite images, Erdas Imagine⁰ image processing system, and ArcView⁰ GIS, the numerical model based on the export coefficient method yields an estimation of non-point source loads on a yearly basis with respect to four target constituents. These constituents of interest consist of total phosphorus (TP), total nitrogen (TN), biochemical oxygen demand (BOD), and total suspended solid (TSS). The analysis of assimilative capacity of the Tseng-Wen Reservoir based on various types of numerical models is also included for the evaluation of the eutrophication issue. Advanced management strategies with regard to the proper use of assimilative capacity of the Tseng-Wen Reservoir and the land resources in the watershed are then discussed in terms of three classified impact levels of non-point sources in the watershed. The methodology is proved practical, promising, and effective for assessing the eutrophication issue in the reservoir watershed within a short period of time     

Development of a GIS method to localize critical source areas of diffuse nitrate pollution

The present study aimed at developing a universal method for the localization of critical source areas (CSAs) of diffuse nitrate (NO3-) pollution in rural catchments with low data availability. Based on existing methods, land use, soil, slope, riparian buffer strips and distance to surface waters were identified as the most relevant indicator parameters for diffuse agricultural NO3- pollution. The five parameters were averaged in a GIS-overlay to localize areas with low, medium and high risk of NO3- pollution. A first application of the GIS approach to the Ic catchment in France, showed that identified CSAs were in good agreement with results from river monitoring and numerical modelling. Additionally, the GIS approach showed low sensitivity to single parameters, which makes it robust to varying data availability. As a result, the tested GIS-approach provides a promising, easy-to-use CSA identification concept, applicable for a wide range of rural catchments.     

水土保持措施防治面源污染效益研究——以河南省淅川县坡地柑橘种植为例

为保护丹江口水库水质,探索河南丹库汇水流域特色作物生态种植与氮磷污染负荷削减技术,在河南省淅川县建立坡地柑橘试验小区,采取室外人工模拟降雨,对微地形改造和植物篱的试验小区开展试验观测。结果表明,与对照小区对比,种植柑橘具有一定的水土保持效果,采取树盘等微地形改造措施能显著减少泥沙流失,而采取植物篱措施则可同时大幅度减少泥沙、全氮及全磷流失。为该类地区调整土地利用结构、扩大柑橘种植面积提供科学依据。     

Reducing current and future risks: Using climate change scenarios to test an agricultural conservation framework

Evaluating the potential effects of changes in climate on conservation practices can help inform strategies to protect freshwater biodiversity that are robust, even as conditions change. Here we apply a climate change “test” to a framework for estimating the amount of agricultural conservation practices needed to achieve desired fish conservation outcomes for four watersheds in the Saginaw Bay region of Michigan, USA. We developed three climate scenarios from global climate model outputs (high emissions scenario, “2080s” timeframe) to provide insight on potential impacts of a climate driver that represents a key uncertainty for this management system, the amount and timing of spring and summer precipitation. These scenarios were used as inputs to agricultural watershed models, which produced water quality outputs that we compared to thresholds in fish biodiversity metrics at the subwatershed scale. Our results suggest that impacts of climate change on evaporation rates and other aspects of hydrology will shift the relative importance of key stressors for fish (i.e., sediment loadings vs. nutrient concentrations) across these different watersheds, highlighting the need to design resilient implementation plans and policies. Overall, we found that changes in climate are likely to increase the need for agricultural conservation practices, but that increasing the implementation rate above current levels will likely remain a good investment under current and future climate conditions.