Article

Mapping the combined risk of agricultural fine sediment input and accumulation for riverine ecosystems across England and Wales

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Fine sediment inputs from agricultural sources are a potential threat to freshwater ecosystems and may impact on the ability of EU members’ states to achieve environmental targets under the Water Framework Directive (WFD). An index (the Agricultural Sediment Risk index or ASR) representing the risk of agricultural fine sediment accumulation in rivers was produced using estimates of sediment inputs from the process-based PSYCHIC model and predictions of fine sediment accumulation using River Habitat Survey data. The ASR was mapped across the entire river network of England and Wales. The ASR map and index were combined with a national dataset of fisheries surveys using logistic regression to test its relevance to freshwater biota. The ASR was strongly associated with a group of species sensitive to fine sediment inputs including salmon and trout. Another group of species including roach and perch showed a positive association with low levels of agricultural sediment inputs potentially due to their impacts on predators and competitors. The proposed approach demonstrates how existing national monitoring data and sediment pressure models can be combined to produce an assessment of risk to aquatic ecosystems from agricultural fine sediment sources at a national scale that can be used alongside WFD classification tools to identify potential causative pressures and design remedial actions.
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A hierarchical Bayesian model is described for mapping the abundance of fish throughout a watershed from single- and multiple-pass removal sampling. A geographic information system (GIS) was used to generate a raster-based model of the river network, which provided three benefits for estimating fish density. Firstly, the horizontal resolution of the raster (50 m) provided an approximation to the statistical sampling frame and allowed correction for the finite number of potential sampling sites in a reach. Secondly, the modelled river network generated explanatory variables for every site in the network, facilitating the mapping of predicted densities and providing the basis for stratified or regression estimators for reach-specific densities. Finally, the spatial autocorrelation of fish densities was modelled in terms of the distance along the river network. A similar Bayesian model was also developed for the wetted width of the river network, and this was combined with the density model to provide estimates of the total stock size. The model was implemented using Markov chain Monte Carlo simulation in the statistical package WinBUGS. Application of the hierarchical model is illustrated with electrofishing data for age-1+ sea trout (Salmo trutta) in a small tributary of the River Conwy, Wales.
Article
The sustainable use of water resources requires clear guidelines for the management of diffuse pollution inputs to rivers. Without informed guidelines, management decisions are unlikely to deliver cost-effective improvements in the quality of rivers as required by current water policy. Here, we review the evidence available for deriving improved guidelines on the loading of fine sediment to rivers based on the impact on macro-invertebrates. The relationship between macro-invertebrates and fine sediments is poorly defined. Studies of the impacts of fine sediment on macro-invertebrates have been undertaken at various scales, which has an influence on the range of responses displayed and the reliability of the results obtained; results obtained from investigations at smaller scales may not manifest at the scale required to manage rivers and vice versa. Many of the identified effects of increased loading of fine sediment on macro-invertebrates occur as a consequence of deposition on the river bed, yet many current management guidelines are based on suspended sediment targets. On this basis, existing water quality guidelines for sediment management are unlikely to be appropriate. Copyright © 2011 John Wiley & Sons, Ltd.
Article
Concern for sediment problems in the Upper River Piddle, Dorset, including accumulation of fine sediment on the channel bed and elevated turbidity levels during periods of stable flow, provided the stimulus for a detailed field investigation of the sediment dynamics of this chalk stream system undertaken during the period November 1991 to April 1993. Two monitoring stations were established at South Farm, Piddletrenthide and Lawrence Mede, Piddlehinton and estimates of suspended sediment load were obtained for these two sites. In addition, suspended sediment concentrations and bed sediment loadings were regularly sampled at several other sites, sediment traps were deployed at ten representative sites along the river channel, field observations of sediment sources and pathways were made during storm events and a sediment source fingerprinting study was undertaken. Estimates of annual suspended sediment yield provided values of 9–12 t km−2 year−1, which must be seen as low by UK standards. Elevated suspended sediment concentrations were not restricted to storm events, but occurred throughout the monitoring period in response to remobilisation of sediment stored in the channel. The evidence provided by the sediment loads recorded at the two monitoring stations, by the sediment traps and by the measurements of bed sediment loading, indicated that substantial amounts of sediment accumulated in the channel of the upper and middle reaches of the river during the winter months and that this ‘slug’ of sediment was slowly transmitted downstream during the following summer. Fingerprinting of the transported sediment and of potential sources indicated that the dominant source of suspended sediment was likely to be surface soil from cultivated areas. Field reconnaissance surveys undertaken during storm events indicated that substantial inputs of surface runoff and suspended sediment entered the stream. Much of this sediment is, however, stored within the channel system and slowly transmitted downstream. Copyright © 1999 John Wiley & Sons, Ltd.
Article
The interplay between erosion and deposition are fundamental characteristics of river basins. These processes result in the delivery, retention and conveyance of sediment through river systems. Although the delivery of sediment to rivers is a natural phenomenon, in recent years there has been increasing concern about the enhancement of sediment loadings as a result of anthropogenic activities. The presence of macrophytes in river channels tends to increase the retention of fine sediment leading to changes in bed composition. However, a complex relationship exists between macrophytes and fine sediment: macrophytes affect the conveyance of fine sediment and are, in turn, affected by the sediment loading. This review deals with these two reciprocal effects and, in particular, summarizes the available evidence base on the impact of fine sediment on macrophytes. Increased inputs of fine sediment appear to have both direct and indirect impacts on the macrophyte community, altering light availability, and the structure and quality of the river bed. The nature of these impacts depends largely on the rate of deposition and the nature of the material deposited. Changes in macrophyte community composition may ensue where the depositing material is more nutrient rich than the natural river bed. Many of the changes in macrophyte flora that occur with increased fine sediment inputs are likely to closely parallel those that occur with increased dissolved nutrient availability. If attempts to manage nutrient inputs to rivers are to achieve their goals, it is critical that fine sediment-associated nutrient dynamics and transfers are considered. Copyright © 2011 John Wiley & Sons, Ltd.
Article
Sediment plays a pivotal role in determining the physical, chemical and biological integrity of aquatic ecosystems. A range of factors influences the impacts of sediment pressures on aquatic biota, including concentration, duration of exposure, composition and particle size. In recognition of the need to assess environmental status for sediment and mitigate excessive sediment pressures on aquatic habitats, both water column and river substrate metrics have been proposed as river sediment targets. Water column metrics include light penetration, turbidity, sediment concentration summary statistics and sediment regimes. Substrate metrics include embeddedness, the fredle index and riffle stability. Identification of meaningful numeric targets along these lines has, however, been undermined by various issues including the uncertainty associated with toxicological dose-response profiles and the impracticalities of deploying statistically robust sampling strategies capable of supporting catchment-scale targets. Many of the thresholds reported are based on correlative relationships that fail to capture the specific mechanisms controlling sediment impacts on aquatic habitats and are stationary in nature. Temporal windows represented by the key life stages of specific species must be given greater emphasis. Given such issues and the need to support the revision of sediment targets for river catchment management, it is proposed that greater emphasis should be placed on developing generic modelling toolkits with the functionality for coupling current or future projected sediment regimes with biological response for a range of biota. Such tools should permit the identification of river catchment-specific targets within a national context, based on biological effect and incorporate sufficient flexibility for utilizing updated physical, chemical, biological and catchment attribute data. Confidence will continue to be required in compliance screening to ensure cost-effective management programmes for avoiding disproportionate investment in impacted river catchments. Copyright © 2011 John Wiley & Sons, Ltd.
Article
Elevated fine sediment input from terrestrial and aquatic sources as a result of anthropogenic activity is widely recognized to impact negatively on aquatic ecosystems. In rivers, freshwater fish are exposed to a range of impacts resulting from fine sediment pressures. To date, research on the effects of fine sediments on fish has been concentrated within relatively few families, notably the salmonidae. This paper reviews the literature describing indirect and direct impacts of fine sediment on freshwater fish as a contribution towards enhancing the understanding of the impacts of anthropogenic activities on freshwater ecosystems. We identify the causal mechanisms that underpin the observed negative response exhibited by fish populations to enhanced fine sediment loads, and the variability across different fish species. Copyright © 2011 John Wiley & Sons, Ltd.
Article
A model was developed to predict evapotranspiration and soil moisture changes, which could be used either for scheduling irrigation or crop water-use studies. The general form of the model is reported here, and its validation for sugarbeet and potatoes is described in a subsequent paper. The soil characteristics required are depth of topsoil, texture or available water capacity of topsoil and subsoil, and whether a significant slope exists. The plant characteristics required are species and planting date. Meteorological data used to calculate potential evapotranspiration are obtained from the Meteorological Office synoptic network, but local rainfall data are preferred. The model estimates potential evapotranspiration of a reference crop, and uses this to model canopy and root development for all crops at each location. Available options allow for observed data on canopy or root development to be incorporated into the simulations. Estimates of potential evapotranspiration for each crop are then adjusted to allow for the effects of water stress, taking soil characteristics, root depth and evapotranspiration demand into account. The model enables growers to reduce the risks of under- or over-watering their crops and has proved successful in irrigation management.
Article
Fine sediment (<63 µm) storage in river channels frequently represents a significant term in catchment sediment budgets and plays an important role in diffuse pollution problems. A combination of a sediment remobilization technique and the fingerprinting approach was used to examine the storage and provenance of fine sediment on the channel bed of two contrasting lowland permeable catchments in the UK. In the upper Tern (∼231 km2) study catchment, estimates of mean fine sediment storage on the channel bed ranged between 860–5500 g m−2, with an overall average of 2391 g m−2, compared to 470–2290 g m−2 and 1065 g m−2 in the Pang (∼166 km2) and 770–1760 g m−2 and 1255 g m−2 in the Lambourn (∼234 km2) sub-catchments. Mean total fine sediment storage on the bed of the main channel was equivalent to 37% (upper Tern), 38% (Pang) and 21% (Lambourn) of the mean annual suspended sediment loads measured at the catchment outlets. Over the study period, the total gain (1427 t) and loss (1877 t) to fine sediment storage on the channel bed in the upper Tern catchment were equivalent to 82% and 108% of the mean annual suspended sediment load, respectively, compared to 149% (740 t) and 136% (678 t) in the Pang sub-catchment, and 39% (422 t) and 49% (528 t) in the Lambourn sub-catchment. The source of the fine sediment stored on the channel bed within each study area varied. In the upper Tern catchment, the weighted mean relative contributions from individual source types were estimated to be 35 ± 5% (pasture), 51 ± 5% (cultivated) and 14 ± 3% (channel banks and subsurface sources). The corresponding estimates were 49 ± 8%, 33 ± 5% and 18 ± 5% for the Pang sub-catchment, compared to 19 ± 6%, 64 ± 5% and 17 ± 5% for the Lambourn sub-catchment. These sediment source estimates have important implications for the design and implementation of targeted sediment control policies within the study areas. Copyright © 2007 John Wiley & Sons, Ltd.
Article
The England Catchment Sensitive Farming Delivery Initiative has recently identified 40 priority catchments where stakeholders require assistance with tackling harmful diffuse pollution, including that associated with phosphorus (P) and sediment. Newly appointed Catchment Sensitive Farming Officers require appropriate means of targeting P and sediment mitigation methods. In this context, the prototype PSYCHIC (Phosphorus and Sediment Yield CHaracterization In Catchments) model was used to characterize three pilot catchments in England, namely: the Derwent-Cocker (626 km2), Teme (1623 km2) and Wensum (689 km2). Modelled annual total P export from the Derwent-Cocker catchment is 1.2 kg ha−1 year−1, compared with 0.6 kg ha−1 year−1 from the Teme catchment and 0.9 kg ha−1 year−1 from the Wensum catchment. Corresponding sediment export is predicted at 271 kg ha−1 year−1, 124 kg ha−1 year−1 and 70 kg ha−1 year−1, respectively. The findings highlight the importance of factors including P application rates, soil types and the increased connectivity provided by assisted drainage in determining pollution ‘hotspots’. Model output is being used to engage stakeholders and devise abatement strategies.
Article
1. Submerged macrophytes have important physical and structural effects on lowland streams. This study investigated the ability of submerged macrophytes to modify the near-bed flow and to retain mineral and organic particles in patches of four common macrophytes in shallow Danish streams during mid-summer. 2. In dense patches of Callitriche cophocarpa and Elodea canadensis, where near-bed velocity was reduced, the sediment surface was markedly raised and enriched with fine particles. In dense patches of Ranunculus peltatus, fine sediments were deposited among rooted shoots in the upstream part of the patches, while erosion and coarse sediments prevailed in the downstream part of the patches because of the strong vortices that formed at the rear and moved up under the trailing canopy. The open canopy of Sparganium emersum, with its streamlined leaves, had little effect on flow and sediment. 3. Patterns of sediment deposition and composition were closely related to the morphology and canopy structure of plant species and the presence of low velocity above the sediment among the rooted shoots. The mineral particles retained probably originate from bed-load, and the enrichment with finer particles within the patches probably results mainly from size-selective processes during erosion and transport of particles rather than during deposition. The mixed sediment composition within patches suggests that the flow-resistant shoots generate an environment conducive to deposition of all transported particles. 4. Fine sediments within macrophyte beds contained high concentrations of organic matter, carbon, nitrogen and phosphorus. The wide scatter in the relationships between mineral grain size and the content of organic matter and nutrients reflects the spatial and temporal complexity of erosion, transport and sedimentation of mineral and organic particles. 5. Enrichment of sediment within macrophyte beds relative to the surrounding substratum ranged from 780 g organic matter m–2, 30 g N m–2 and 25 g P m–2 for the flow-resistant dense canopies af Callitriche cophocarpa to 150 g organic matter m–2, 6.6 g N m–2 and 3.4 g P m–2 for the open canopies of Sparganium emersum. Retention of nutrient-rich particles within the macrophyte beds is probably of limited importance for plant growth in most lowland European streams, because macrophyte growth is rarely nutrient limited.
Article
Lowland permeable catchments in the UK are particularly prone to sedimentation problems, on account of the increased fine sediment loadings generated by recent land-use change and their stable seasonal hydrological regimes, which are frequently depleted by groundwater abstraction. Fine-grained sediment storage on the bed of the main channel systems of the Frome (437 km2) and Piddle (183 km2) catchments, Dorset, UK, has been examined at 29 sites using a sediment remobilization technique. Measurements encompassed the period February 2003–July 2004. At individual sites in the Frome, average values ranged between 410 and 2630 g m−2, with an overall mean of 918 g m−2. In the Piddle, the average values for individual sites varied between 260 and 4340 g m−2, with an overall mean of 1580 g m−2. Temporal variations in fine bed sediment storage at each site were appreciable, with the coefficients of variation ranging between 43 and 155% in the Frome and between 33 and 160% in the Piddle. Average reach-scale specific bed sediment storage increased markedly downstream along each main stem from 2 to 29 t km−1 (Frome) and from 4 to 19 t km−1 (Piddle). Total fine sediment storage on the channel bed of the Frome varied between 479 t (5 t km−1) and 1694 t (17 t km−1), with a mean of 795 t (7 t km−1), compared with between 371 t (5 t km−1) and 1238 t (14 t km−1) with a mean of 730 t (9 t km−1) in the Piddle. During the study period, fine bed sediment storage was typically equivalent to 18% (Frome) and 57% (Piddle) of the mean annual suspended sediment flux at the study catchment outlets. Copyright © 2006 John Wiley & Sons, Ltd.
Article
1. Rivers are subject to thresholds of several types that define significant changes in processes and morphology and delimit distinctive riverine landscapes and habitats. Thresholds are set by the conditions that govern river channel process and form, amongst which the most important are the flow regime, the quantity and calibre of sediment delivered to the channel, and the topographic setting (which determines the gradient of the channel). These factors determine the sediment transport regime and the character of alluvial deposits along the channel. 2. Changes occur systematically along the drainage system as flow, gradient and sediment character change, so a characteristic sequence of morphological and habitat types - hence of riverine landscapes - can be described from uplands to distal channels. The sequence is closely associated with stream competence to move sediment and with bank stability. 3. The paper proposes a first order classification of river channel and landscape types based on these factors. The riverine landscape is affected seasonally by flow thresholds, and further seasonal thresholds in northern rivers are conditioned by the ice regime. 4. It is important to understand geomorphic thresholds in rivers not only for the way they determine morphology and habitat, but because human activity can precipitate threshold crossings which change these features significantly, through either planned or inadvertent actions. Hence, human actions frequently dictate the character of the riverine landscape.
Article
This paper describes the preliminary evaluation of the PSYCHIC catchment scale (Tier 1) model for predicting the mobilisation and delivery of phosphorus (P) and suspended sediment (SS) in the Hampshire Avon (1715 km2) and Herefordshire Wye (4017 km2) drainage basins, in the UK, using empirical data. Phosphorus and SS transfers to watercourses in the Wye were predicted to be greater than corresponding delivery in the Avon; SS, 249 vs 33 kg ha−1 yr−1; DP, 2.57 vs 1.26 kg ha−1 yr−1; PP, 2.20 vs 0.56 kg ha−1 yr−1. The spatial pattern of the predicted transfers was relatively uniform across the Wye drainage basin, whilst in the Avon, delivery to watercourses was largely confined to the river corridors and small areas of drained land. Statistical performance in relation to predicted exports of P and SS, using criteria for relative error (RE) and root mean square error (RMSE), reflected the potential shortcomings associated with using longer-term climate data for predicting shorter-term (2002–2004) catchment response and the need to refine calculations of point source contributions and to incorporate additional river basin processes such as channel bank erosion and in-stream geochemical processing. PSYCHIC is therefore best suited to characterising longer-term catchment response.
Article
The need to understand and mitigate diffuse water pollution from agriculture (DWPA) using a range of monitoring or modelling techniques and abatement methods has never been greater. In response to the widely reported detrimental environmental impacts of such pollution and the desire to safeguard water resources, a number of important legislative drivers have been introduced, including the Water Framework Directive (WFD) for EU member states. Efforts to commission research and introduce policy options that address the key requirements of over-arching legislation, increasingly point to a number of common and important issues for policy makers. Whereas our understanding of, and ability to predict, pollutant loadings is reasonably well developed, coupling such pressures to ecological impacts remains a difficult task due to the limited functionality of available toolkits. It is important for mitigation programmes to consider multiple pollutants especially given the risks of pollution swapping and to support the uptake of abatement options that are economically and socially acceptable to the stakeholders involved. Appropriate spatial targeting of mitigation methods will continue to come under scrutiny, especially in the context of additional environmental pressures like climate change. Given its key role in governing the transfer and fate of priority nutrients and contaminants and its well-documented negative habitat impacts, sediment must be given a higher profile in diffuse pollution policy. The latter does, however, require further investigation of background sediment loads necessary for healthy habitats and associated sediment standards or thresholds, in order that catchment compliance can be more reliably assessed. Delayed water quality response to the mitigation of DWPA must be assessed and understood, as a means of informing stakeholders and policy options. A further challenge is posed by the need to place DWPA in the context of pollution from alternative sectors so that a more holistic approach to understanding and managing pressures and impacts and engaging stakeholders can be encouraged.
Article
This paper is concerned with estimating the gap between current and compliant losses of suspended sediment from the agricultural sector in England and Wales in relation to achieving ‘good ecological status’ (GES) in freshwaters by 2015. Given the emphasis on strategic information for policy support, the assessment necessitated a novel modelling methodology for predicting mean annual total suspended sediment loads (SSL) and time-weighted suspended sediment concentrations (SSC). GES was defined as the guideline annual average SSC of 25 mg l−1 cited by the EC Freshwater Fish Directive. Total suspended sediment inputs to all rivers across England and Wales were estimated using a national sediment source apportionment exercise detailing the contributions from diffuse agricultural and urban sources, eroding channel banks and point sources. The total SSL estimated for each Water Framework Directive (WFD) sub-catchment (n = 7816) across England and Wales was used in conjunction with predicted flow exceedance to derive corresponding SSC time-exceedance plots. Spatial variations in modelled time-averaged SSC compared well with available monitoring data. Given the focus upon national scale, the predictive power of the SSC model (r2 = 33%) was considered realistic. The modelling approach provided a means of mapping the probability of annual average SSC being less than the 25 mg l−1 standard for GES due to sediment losses from all potential, as well as from agricultural sources only. In order to meet GES in non-compliant catchments, suspended sediment losses from diffuse agricultural sources will typically need to be reduced by up to 20%, but by as much as 80% in isolated cases.
Article
Riparian vegetation, particularly trees and shrubs, can play a crucial role in the construction and turnover of fluvial landforms, but aquatic plants may also act as river ecosystem engineers.Macrophyte and environmental data from 467 British river reaches are used to explore associations between aquatic plant morphotypes and the physical characteristics of the reaches. The abundance of five plant morphotypes (mosses, linear-submerged, patch-submerged, linear emergent, branched emergent) is estimated for each river reach. Cluster analysis is applied to the abundances of the five morphotypes across the 467 reaches to identify six typical assemblages or clusters of the morphotypes. These clusters are found to be associated with statistically significantly different values of seven physical variables (altitude, slope, median annual flood discharge, channel width, mean bed sediment size, percentage cover of sand and silt on the river bed, and unit stream power). Associations between the morphotype clusters and combinations of the physical variables are explored using Canonical Correspondence Analysis and standard slope–discharge–sediment calibre–channel style graphs.Several of the morphotype clusters are discriminated by unit stream power and bed sediment size. In particular, morphotype clusters dominated by emergent and submerged macrophytes are associated with granules, sand, and finer bed sediments and are rarely found where unit stream power exceeds 100 W m− 2. One cluster characterised by branched emergent species with relatively low cover of submerged morphotypes is confined to sites with unit stream power below 20 W m− 2; and another cluster characterised by linear emergents with low cover of submerged morphotypes is associated with particularly extensive, fine bed sediments, suggesting possible smothering of submerged plants. In contrast, mosses reach their highest abundance in two clusters associated with the highest unit stream power and coarsest bed sediments, with the patch-submerged morphotype reaching relatively high abundance in the slightly lower energy cluster of these two.British rivers have been modified over hundreds of years such that the sample of study reaches have predominantly single-thread channels. However, the plotting positions of these reaches on established graphs describing slope–discharge–sediment calibre–channel style associations, illustrates the potential of some of these sites to develop wandering or braided forms and, in lower energy situations, the potential for aquatic plants to trap fine sediments and contribute to landform building and channel change if maintenance (cutting and dredging) of the emergent and submerged morphotypes were reduced.
Article
The research examines the incompatibility between resolution and scale of spatial data in a spatial modelling environment and the resolution and scale of human spatial decision-making. This incompatibility is rarely considered when a geographic information systems (GIS) is applied to natural hazard risk assessment. However, the ultimate success of a risk management project should be assessed in the context of improved decision-making. Decision utility is an emerging theme in GIS literature that focuses on cognitive issues of GIS and human interactions. The research presents a technique for flood risk modelling using GIS and digital elevation models to map relative risk in urban communities. The study is based on Cairns located in far northern Australia. The risk model accounts for uncertainties inherent in the elevation data by adapting an existing error simulation technique. Techniques for making spatial model assumptions and model error explicit to flood risk managers are introduced and evaluated for risk management decision-making.
Article
Le développement des activités humaines a conduit dans de nombreuses régions à une augmentation du transfert de sédiments fins vers les cours d’eau, multipliant les phénomènes de colmatage. Le colmatage fait référence au dépôt de sédiments organiques ou minéraux et à leur infiltration dans le benthos et l’hyporhéos. Dans cet article de synthèse, le colmatage par les sédiments minéraux est présenté du point de vue de ses mécanismes et de sa variabilité spatio-temporelle dans un schéma d’organisation global du cours d’eau. Le colmatage entraîne une modification des habitats benthique et interstitiel, ainsi que des échanges d’eau et de matières entre la surface et l’hyporhéos. Il affecte la structure du peuplement d’invertébrés en modifiant la structure et la stabilité du substrat, la disponibilité des ressources trophiques et de l’oxygène, ainsi que de la pression de prédation. Les conséquences à court terme sont une augmentation de la dérive et une réduction de l’abondance totale des organismes. Sur le long terme le colmatage affecte la survie, le développement et la croissance des invertébrés ainsi que la biomasse et la productivité du peuplement. Les espèces sensibles adaptées aux substrats grossiers disparaissent au profit des espèces adaptées aux sédiments fins. Les conséquences sur la faune hyporhéique sont peu connues mais l’importance de l’hyporhéos dans le fonctionnement du cours d’eau suggère que son altération pourrait avoir des conséquences importantes en terme de capacité de résilience du peuplement face aux perturbations.
Article
Geostatistics is essential for environmental scientists. Weather and climate vary from place to place, soil varies at every scale at which it is examined, and even man-made attributes - such as the distribution of pollution - vary. The techniques used in geostatistics are ideally suited to the needs of environmental scientists, who use them to make the best of sparse data for prediction, and top plan future surveys when resources are limited. Geostatistical technology has advanced much in the last few years and many of these developments are being incorporated into the practitioner's repertoire. This second edition describes these techniques for environmental scientists. Topics such as stochastic simulation, sampling, data screening, spatial covariances, the variogram and its modeling, and spatial prediction by kriging are described in rich detail. At each stage the underlying theory is fully explained, and the rationale behind the choices given, allowing the reader to appreciate the assumptions and constraints involved.
Article
Grass vegetation has been recommended for use in the prevention and control of soil erosion because of its dense sward characteristics and stabilizing effect on the soil. A general assumption is that grassland environments suffer from minimal soil erosion and therefore present little threat to the water quality of surface waters in terms of sediment and sorbed contaminant pollution. Our data question this assumption, reporting results from one hydrological year of observations on a field-experiment monitoring overland flow, drain flow, fluxes of suspended solids, total phosphorus (TP), and molybdate-reactive phosphorus (<0.45 mum) in response to natural rainfall events. During individual rainfall events, 1-ha grassland lysimeters yield up to 15 kg of suspended solids, with concentrations in runoff waters of up to 400 mg L(-1). These concentrations exceed the water quality standards recommended by the European Freshwater Fisheries Directive (25 mg L(-1)) and the USEPA (80 mg L(-1)) and are beyond those reported to have caused chronic effects on freshwater aquatic organisms. Furthermore, TP concentrations in runoff waters from these field lysimeters exceeded 800 mug L(-1). These concentrations are in excess of those reported to cause eutrophication problems in rivers and lakes and contravene the ecoregional nutrient criteria in all of the USA ecoregions. This paper also examines how subsurface drainage, a common agricultural practice in intensively managed grasslands, influences the hydrology and export of sediment and nutrients from grasslands. This dataset suggests that we need to rethink the conceptual understanding of grasslands as non-erosive landscapes. Failure to acknowledge this will result in the noncompliance of surface waters to water quality standards.
A model for estimating soil moisture changes as an aid
  • R J Bailey
  • E Spackman
Bailey, R.J., Spackman, E., 1996. A model for estimating soil moisture changes as an aid
A reconnaissance survey of deposited fine 641 sediment in the headwater streams of agricultural catchments across England and Wales
  • D D Naura
  • M Sear
D.D., Naura, M., Sear, D.A., submitted. A reconnaissance survey of deposited fine 641 sediment in the headwater streams of agricultural catchments across England and Wales.
Cross sector 678 contributions to river pollution in England and Wales: Updating waterbody scale
  • Y Zhang
  • A L Collins
  • N Murdoch
  • D Lee
  • P S Naden
Zhang, Y., Collins, A.L., Murdoch, N., Lee, D., Naden, P.S., 2014. Cross sector 678 contributions to river pollution in England and Wales: Updating waterbody scale