Phosphorus export from an agricultural watershed: linking source and transport mechanisms

Many source and transport factors control P loss from agricultural landscapes; however, little information is available on how these factors are linked at a watershed scale. Thus, we investigated mechanisms controlling P release from soil and stream sediments in relation to storm and baseflow P concentrations at four flumes and in the channel of an agricultural watershed. Baseflow dissolved reactive phosphorus (DRP) concentrations were greater at the watershed outflow (Flume 1; 0.042 mg L(-1)) than uppermost flume (Flume 4; 0.028 mg L(-1)). Conversely, DRP concentrations were greater at Flume 4 (0.304 mg L(-1)) than Flume 1 (0.128 mg L(-1)) during stormflow. Similar trends in total phosphorus (TP) concentration were also observed. During stormflow, stream P concentrations are controlled by overland flow-generated erosion from areas of the watershed coincident with high soil P. In-channel decreases in P concentration during stormflow were attributed to sediment deposition, resorption of P, and dilution. The increase in baseflow P concentrations downstream was controlled by channel sediments. Phosphorus sorption maximum of Flume 4 sediment (532 mg kg(-1)) was greater than at the outlet Flume 1 (227 mg kg(-1)). Indeed, the decrease in P desorption between Flumes 1 and 4 sediment (0.046 to 0.025 mg L(-1)) was similar to the difference in baseflow DRP between Flumes 1 and 4 (0.042 to 0.028 mg L(-1)). This study shows that erosion, soil P concentration, and channel sediment P sorption properties influence streamflow DRP and TP. A better understanding of the spatial and temporal distribution of these processes and their connectivity over the landscape will aid targeting remedial practices.     

Riparian buffer strips as a multifunctional management tool in agricultural landscapes: introduction

Catchment riparian areas are considered key zones to target mitigation measures aimed at interrupting the movement of diffuse substances from agricultural land to surface waters. Hence, unfertilized buffer strips have become a widely studied and implemented "edge of field" mitigation measure assumed to provide an effective physical barrier against nitrogen (N), phosphorus (P), and sediment transfer. To ease the legislative process, these buffers are often narrow mandatory strips along streams and rivers, across different riparian soil water conditions, between bordering land uses of differing pollution burdens, and without prescribed buffer management. It would be easy to criticize such regulation for not providing the opportunity for riparian ecosystems to maximize their provision for a wider range of ecosystem goods and services. The scientific basis for judging the best course of action in designing and placing buffers to enhance their multifunctionality has slowly increased over the last five years. This collection of papers aims to add to this body of knowledge by giving examples of studies related to riparian buffer management and assessment throughout Europe. This introductory paper summarizes discussion sessions and 13 selected papers from a workshop held in Ballater, UK, highlighting research on riparian buffers brought together under the EU COST Action 869 knowledge exchange program. The themes addressed are (i) evidence of catchment- to national-scale effectiveness, (ii) ecological functioning linking terrestrial and aquatic habitats, (iii) modeling tools for assessment of effectiveness and costs, and (iv) process understanding enabling management and manipulation to enhance pollutant retention in buffers. The combined understanding led us to consider four principle key questions to challenge buffer strip research and policy.     

Phosphorus loss from an agricultural watershed as a function of storm size

Phosphorus (P) loss from agricultural watersheds is generally greater in storm rather than base flow. Although fundamental to P-based risk assessment tools, few studies have quantified the effect of storm size on P loss. Thus, the loss of P as a function of flow type (base and storm flow) and size was quantified for a mixed-land use watershed (FD-36; 39.5 ha) from 1997 to 2006. Storm size was ranked by return period (<1, 1-3, 3-5, 5-10, and >10 yr), where increasing return period represents storms with greater peak and total flow. From 1997 to 2006, storm flow accounted for 32% of watershed discharge yet contributed 65% of dissolved reactive P (DP) (107 g ha(-1) yr(-1)) and 80% of total P (TP) exported (515 g ha(-1) yr(-1)). Of 248 storm flows during this period, 93% had a return period of <1 yr, contributing most of the 10-yr flow (6507 m(3) ha(-1); 63%) and export of DP (574 g ha(-1); 54%) and TP (2423 g ha(-1); 47%). Two 10-yr storms contributed 23% of P exported between 1997 and 2006. A significant increase in storm flow DP concentration with storm size (0.09-0.16 mg L(-1)) suggests that P release from soil and/or area of the watershed producing runoff increase with storm size. Thus, implementation of P-based Best Management Practice needs to consider what level of risk management is acceptable.     

Guild management: an evaluation of avian guilds as a predictive tool

The use and applicability of the guild concept to management is evaluated and questioned. Ecological problems are never as simple as implied in using one or two guild axes. A close examination of bird communities in a ponderosa pine forest reveals little relationship between guilds or guild blocks and the responses exhibited by individual bird species or bird species groups. Response guilds changed from year to year without any obvious changes in vegetation. A three-year composite analysis shows a clearer picture of the responses of ponderosa pine forest birds to the overall interactions between structure, weather, competition, and so on. The six response groups in the composite analysis are species that (1) were absent in 1973 on most or all study plots and showed no preference for any forested site; (2) had their highest densities on the medium cut and light cut plots; (3) were absent in 1973 on most or all study plots and had their highest densities on the medium cut and light cut plots; (4) had their highest densities on the untreated, light cut, and medium cut plots; (5) had their highest densities on the untreated and light cut plots and were either absent or had greatly reduced densities on all other plots; and (6) were present only on the clearcut, except for the Rock Wren which was also on the medium cut and heavy cut plots. The overall correlation between species density and guild density was significantly higher for response guilds ( <0.05) than for any of the structural or functional guilds. The whole concept of guild management needs much more research and development before it can be recommended as a management tool.     

Using the soil and water assessment tool to estimate achievable water quality targets through implementation of beneficial management practices in an agricultural watershed

Runoff from crop production in agricultural watersheds can cause widespread soil loss and degradation of surface water quality. Beneficial management practices (BMPs) for soil conservation are often implemented as remedial measures because BMPs can reduce soil erosion and improve water quality. However, the efficacy of BMPs may be unknown because it can be affected by many factors, such as farming practices, land-use, soil type, topography, and climatic conditions. As such, it is difficult to estimate the impacts of BMPs on water quality through field experiments alone. In this research, the Soil and Water Assessment Tool was used to estimate achievable performance targets of water quality indicators (sediment and soluble P loadings) after implementation of combinations of selected BMPs in the Black Brook Watershed in northwestern New Brunswick, Canada. Four commonly used BMPs (flow diversion terraces [FDTs], fertilizer reductions, tillage methods, and crop rotations), were considered individually and in different combinations. At the watershed level, the best achievable sediment loading was 1.9 t ha(-1) yr(-1) (89% reduction compared with default scenario), with a BMP combination of crop rotation, FDT, and no-till. The best achievable soluble P loading was 0.5 kg ha(-1) yr(-1) (62% reduction), with a BMP combination of crop rotation and FDT and fertilizer reduction. Targets estimated through nonpoint source water quality modeling can be used to evaluate BMP implementation initiatives and provide milestones for the rehabilitation of streams and rivers in agricultural regions.     

TIM: Assessing the sustainability of agricultural land management

TIM (Threat Identification Model) is a framework for the ex ante assessment of agricultural land management sustainability at the land unit scale that identifies sources of unsustainability within agricultural land management systems. The model explicitly links defined hazards to land productivity and environmental integrity, land resource data and information, and land management practice options using expert and local knowledge on land management and its potential effects. The model was tested in the Crystal Creek Subcatchment, a narrow coastal strip of land situated in north Queensland, Australia. This area was chosen due to the expansion of the sugar industry onto increasingly marginal land in the area, which represents a threat to sustainable land use and a requirement for careful land-use planning and land management.TIM may be used in a relational database as a stand alone decision support system for land-management planning. Its usefulness in land-use planning is greatest when it is linked to a Geographic Information System (GIS) as shown in this paper. GIS allows TIM outputs, such as constraints to agriculture and site-specific best-management practices, to be identified in a spatially explicit manner.The main advantages of TIM are that it can be done ex ante, it removes the need to define sustainability assessment criteria and indicators, it utilises current understanding of the causes and effects of land degradation and how different land-management practices influence these, and links this knowledge to definite land-management options.     

Information as a management tool: An evaluation of the Pemigewasset Wilderness management plan

The newly instituted management plan for the Pemigewasset Wilderness area of New Hampshire, USA, which relies principally on providing information to visitors, represents a departure from traditional plans. Logit analysis of survey data indicates limited evidence of the plan having much direct impact on visitor behavior. There is evidence of success in information dissemination to area users; however, the type of information that is being relayed to backcountry users does not appear to be that which the management plan is attempting to promote.     

Evaluation of fire as a management tool for controllingSchinus terebinthifolius as secondary successional growth on abandoned agricultural land

Schinus terebinthifolius, native to South America, has become an aggressive woody weed in southern Florida, displacing native vegetation as well as rapidly invading disturbed sites. Studies to evaluate the effectiveness of fire as a management option for controllingSchinus on abandoned farmland in Everglades National Park, known as the “Hole-in-the-Donut,” began in 1979. Study plots were established to monitor any change(s) in herbaceous cover and in numbers and size ofSchinus stems. Except in the control plot (which was not burned), each site was burned as often as fuel conditions permitted (usually once every one or two years), through 1985. Results indicated that both the number and density ofSchinus stems increased over the course of the study. While plots that burned showed a reduction in the rate ofSchinus invasion, invasion still progressed rapidly with or without the occurrence of fire. The increase inSchinus stem density from 1980 to 1985 was highly significant in all transects except one. Herbaceous cover showed no clear trends relative to burning.     

Palaeoecology: A tool to improve the management of Australian estuaries

Addressing environmental problems in estuaries is a worldwide problem. Establishing benchmarks and targets for management is critical, whether the aim is conservation, restoration or sustainable use. Palaeoecological techniques have rapidly improved during the past decade, particularly with advances in methods that allow high resolution quantitative assessments of environmental change. Palaeoecology is a useful tool in environmental management as it allows pre-impact conditions, the rate, extent, direction and cause of change, and range of natural variability to be determined. Australian estuarine ecosystems are qualitatively different from the often more well-studied estuaries in North America and Europe, which means site-specific studies of Australian estuaries are needed to inform management. While a potentially useful and valuable tool, palaeoecological techniques have not yet been widely adopted and practically implemented as part of estuarine management strategies and policy frameworks in Australia.     

Phosphorus losses from agricultural areas in river basins: effects and uncertainties of targeted mitigation measures

In this paper we show the quantitative and relative importance of phosphorus (P) losses from agricultural areas within European river basins and demonstrate the importance of P pathways, linking agricultural source areas to surface water at different scales. Agricultural P losses are increasingly important for the P concentration in most European rivers, lakes, and estuaries, even though the quantity of P lost from agricultural areas in European catchments varies at least one order of magnitude (<0.2 kg P ha(-1) to >2.1 kg P ha(-1)). We focus on the importance of P for the implementation of the EU Water Framework Directive and discuss the benefits, uncertainties, and side effects of the different targeted mitigation measures that can be adopted to combat P losses from agricultural areas in river basins. Experimental evidence of the effects of some of the main targeted mitigation measures hitherto implemented is demonstrated, including: (i) soil tillage changes, (ii) treatment of soils near ditches and streams with iron to reduce P transport from source areas to surface waters, (iii) establishment of buffer zones for retaining P from surface runoff, (iv) restoration of river-floodplain systems to allow natural inundation of riparian areas and deposition of P, and (v) inundation of riparian areas with tile drainage water for P retention. Furthermore, we show how river basin managers can map and analyze the extent and importance of P risk areas, exemplified by four catchments differing in size in Norway, Denmark, and the Netherlands. Finally, we discuss the factors and mechanisms that may delay and/or counteract the responses of mitigation measures for combating P losses from agricultural areas when monitored at the catchment scale.     

填埋场评价指标筛选和评价体系中的权重研究

伴随垃圾填埋量逐年增加,环境污染问题愈发严重,垃圾填埋场地的适宜性评价也变的更加重要。采用层次分析法,综合考虑了工程建设、运行管理、生态建设3大因素,构建了一套填埋场适宜性评价指标体系,并应用于吴忠市垃圾填埋场。实例应用表明,该方法选取的评价因素较全面,客观反映了吴忠市垃圾填埋场的实际情况,具有借鉴意义。     

Result-oriented approaches to the management of drinking water catchments in agricultural landscapes

Management of water quality in drinking water catchments is of ongoing, high importance as nitrate concentrations are often still very high. We analysed the Augsburg catchment in Germany, a unique example where a result-oriented approach has been implemented. We investigated the historical evolution of the water protection programme, the result-oriented payment contracts with farmers, and farmer satisfaction with the contracts, based on interviews with the water utility and farmers as well as an analysis of the literature. Today, the water protection programme has been successfully implemented, and a significant reduction of nitrate concentration was achieved due to the following factors: (1) investment of non-negligible amounts of money for high compensation and remuneration payments, (2) different contract options, (3) farmers’ participation in the negotiation process for result-oriented payment contracts, (4) involvement of “outside” people and institutions in negotiation processes, (5) anticipation of starting a programme when nitrate levels were still far below legislative thresholds, and (6) a political and legislative framework allowing direct decisions by a water supplier.     

LCA: A decision support tool for environmental assessment of MSW management systems

Life cycle assessment (LCA) can be successfully applied to municipal solid waste (MSW) management systems to identify the overall environmental burdens and to assess the potential environmental impacts. In this study, two methods used for current MSW management in Phuket, a province of Thailand, landfilling (without energy recovery) and incineration (with energy recovery), are compared from both energy consumption and greenhouse gas emission points of view. The comparisons are based on a direct activity consideration and also a life cycle perspective. In both cases as well as for both parameters considered, incineration was found to be superior to landfilling. However, the performance of incineration was much better when a life cycle perspective was used. Also, landfilling reversed to be superior to incineration when methane recovery and electricity production were introduced. This study reveals that a complete picture of the environmental performance of MSW management systems is provided by using a life cycle perspective.     

JMarinas: A simple tool for the environmentally sound management of small marinas

A novel index for the preliminary evaluation of the distribution of pollutants in the harbor environment (Small Marinas Pollution Risk) is proposed. An associated Environmental Decision Support System (JMarinas) has been developed which implements the Multiple Attribute Decision Making theory (MADM) and uses the harbor’s map as geographical support for computations. The MADM matrix is built considering various attributes of the marina and is calculated using both qualitative and quantitative data.     

Adaptive management for mitigating Cryptosporidium risk in source water: A case study in an agricultural catchment in South Australia

Water-borne pathogens such as Cryptosporidium pose a significant human health risk and catchments provide the first critical pollution ‘barrier’ in mitigating risk in drinking water supply. In this paper we apply an adaptive management framework to mitigating Cryptosporidium risk in source water using a case study of the Myponga catchment in South Australia. Firstly, we evaluated the effectiveness of past water quality management programs in relation to the adoption of practices by landholders using a socio-economic survey of land use and management in the catchment. The impact of past management on the mitigation of Cryptosporidium risk in source water was also evaluated based on analysis of water quality monitoring data. Quantitative risk assessment was used in planning the next round of management in the adaptive cycle. Specifically, a pathogen budget model was used to identify the major remaining sources of Cryptosporidium in the catchment and estimate the mitigation impact of 30 alternative catchment management scenarios. Survey results show that earlier programs have resulted in the comprehensive adoption of best management practices by dairy farmers including exclusion of stock from watercourses and effluent management from 2000 to 2007. Whilst median Cryptosporidium concentrations in source water have decreased since 2004 they remain above target levels and put pressure on other barriers to mitigate risk, particularly the treatment plant. Non-dairy calves were identified as the major remaining source of Cryptosporidium in the Myponga catchment. The restriction of watercourse access of non-dairy calves could achieve a further reduction in Cryptosporidium export to the Myponga reservoir of around 90% from current levels. The adaptive management framework applied in this study was useful in guiding learning from past management, and in analysing, planning and refocussing the next round of catchment management strategies to achieve water quality targets.     

Aggregating high-priority landscape areas to the parcel level: an easement implementation tool

Landscape characteristics and parcel ownership information are often collected on different spatial scales leading to difficulties in implementing land use plans at the parcel level. This study provides a method for aggregating highly resolute landscape planning information to the parcel level. Our parcel prioritization model directly incorporates a Land Trust's conservation goals in the form of a compromise programming model. We then demonstrate the use of our approach for implementation decisions, including parcel selection under a budget constraint and the estimation of a total conservation budget necessary to meet specific conservation goals. We found that these cost constraints significantly alter the composition of the 'best' parcels for conservation and can also provide guidance for implementation. The model's results were integral to a local Land Trust's ability to further define and achieve their goals.     

Evaluating agricultural best management practices in tile-drained subwatersheds of the Mackinaw River, Illinois

Best management practices (BMPs) are widely promoted in agricultural watersheds as a means of improving water quality and ameliorating altered hydrology. We used a paired watershed approach to evaluate whether focused outreach could increase BMP implementation rates and whether BMPs could induce watershed-scale (4000 ha) changes in nutrients, suspended sediment concentrations, or hydrology in an agricultural watershed in central Illinois. Land use was >90% row crop agriculture with extensive subsurface tile drainage. Outreach successfully increased BMP implementation rates for grassed waterways, stream buffers, and strip-tillage within the treatment watershed, which are designed to reduce surface runoff and soil erosion. No significant changes in nitrate-nitrogen (NO-N), total phosphorus (TP), dissolved reactive phosphorus, total suspended sediment (TSS), or hydrology were observed after implementation of these BMPs over 7 yr of monitoring. Annual NO-N export (39-299 Mg) in the two watersheds was equally exported during baseflow and stormflow. Mean annual TP export was similar between the watersheds (3.8 Mg) and was greater for TSS in the treatment (1626 ± 497 Mg) than in the reference (940 ± 327 Mg) watershed. Export of TP and TSS was primarily due to stormflow (>85%). Results suggest that the BMPs established during this study were not adequate to override nutrient export from subsurface drainage tiles. Conservation planning in tile-drained agricultural watersheds will require a combination of surface-water BMPs and conservation practices that intercept and retain subsurface agricultural runoff. Our study emphasizes the need to measure conservation outcomes and not just implementation rates of conservation practices.     

Environmental accounting as a management tool in the Mediterranean context: the Spanish economy during the last 20 years

Although human presence is one of the main characteristics of the Mediterranean identity since ancient times, a false dialectic between conservation and social-economic development has emerged in recent decades. On the one hand, an economic growth policy is taken as the paradigm of social-economic development; on the other hand, there is a multi-scale conservation policy, in which natural protected areas, as patches of preserved nature, are used as one of the main tools to deal with the challenge of sustainability. The Mediterranean Basin is the habitat of many unique species and one of the 25 main biodiversity hotspots in the world, and as a consequence a strong conservation policy has been used to protect environmental values. At the same time, Mediterranean countries are deeply involved in promoting strong economic growth policies, which are not always compatible with environmental ones. In this paper, Spain has been studied as one model of this situation. Due to political reasons, Spanish economic growth and conservationist policies were pursued together during the last 20 years. As a result, Spain owns one of the largest networks of natural protected areas in Western Europe, and at the same time it has experienced one of the strongest periods of economic growths in the European and Mediterranean context during the 1980s and 1990s. An historical series of resource use in five annual periods in the last 20 years of conservation policy, and the effects on the preservation of natural capital have been investigated by means of the eMergy (spelled with an 'm') synthesis approach, which was used to characterize the flow of environmental services supplied by ecosystems, but not in monetary terms. This study shows that Spain is becoming less self-sufficient and more inefficient in resource use, comprehensively measured in eMergy terms. A large part of Spain's economy depends on imported goods and services, and most economic activities are based on tourist services and associated construction, which promotes intensification in the urban use of the territory and more intense environmental impacts and resource use intensification of those countries supplying the raw materials. The consequence is a decoupling of the Spanish economy from local environmental services and the increase of Ecological footprint of Spain, measured by means of eMergy-based indicators. In spite of the increase in number, area and associated budget of the natural protected areas and other conservation measures, the general sustainability of the nation is decreasing.     

Atmospheric deposition of pesticides to an agricultural watershed of the Chesapeake Bay

The Choptank River watershed, located on the Delmarva Peninsula of the Chesapeake Bay, is dominated by agricultural land use, which makes it vulnerable to runoff and atmospheric deposition of pesticides. Agricultural and wildlife areas are in close proximity and off-site losses of pesticides may contribute to toxic effects on sensitive species of plants and animals. High-volume air samples (n = 31) and event-based rain samples (n = 71) were collected from a single location in the watershed representing regional background conditions. Surface water samples were collected from eight stations in the tidal portion of the river on five occasions during 2000. Chlorothalonil, metolachlor, atrazine, simazine, endosulfan, and chlorpyrifos were frequently detected in the air and rain, with maximal concentrations during the period when local or regional crops were planted. The wet deposition load to the watershed was estimated at 150 +/- 16, 61 +/- 7, and 51 +/- 6 kg yr(-1) for chlorothalonil, metolachlor, and atrazine, respectively. The high wet deposition load compared with the estimated annual usage for chlorothalonil (13%) and endosulfan (14-90%) suggests an atmospheric source from outside the watershed. Net air-water gas exchange fluxes for metolachlor varied from -44 +/- 19 to 9.3 +/- 4.1 ng m(-2) d(-1) with negative values indicating net deposition. Wet deposition accounted for 3 to 20% of the total metolachlor mass in the Choptank River and was a more important source to the river than gas exchange. Estimates of herbicide flux presented here are probably a low estimate and actual rates may be significantly higher in areas closer to pesticide application.