Browsing by Author "White, Sue"

Now showing 1 - 8 of 8
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    Estimating typical sediment concentration probability density functions for European rivers
    (Cranfield University, 2005-09) Becvar, Martin; White, Sue
    Sediment in rivers is linked with qualitative and quantitative water problems throughout Europe. Sediment supply and transfer are part of a natural process of minimising gradients in the landscape. However, since human activities have started to affect the equilibrium, sediment supply is often out of balance with the river system. Cases of either low or high concentration often mean an instability which may cause severe problems. Therefore it is highly important to gain knowledge about sediment patterns in catchments as a part of catchment management. This study was undertaken in order to improve sediment modelling in the GREAT-ER point source pollution river modelling package which currently uses suspended sediment concentration of 15 mg.l-1 for all rivers in Europe, which is an obvious oversimplification. There are three aims for this thesis; one to investigate the range of suspended sediment yields from major European catchments (44 catchments investigated), two the verification of sediment delivery equations and three to develop a methodology to predict suspended sediment concentration from sediment yield in these rivers. Coarse sediment and bed load are not investigated in this study. Monitored river sediment concentration data were analysed and compared to sediment yields obtained using the well established sediment delivery ratio (SDR) approach. Several SDR equations were tested. Equations where the area of the catchment was used as the sole variable provide the best results. In addition, sediment yields were estimated based on the recent PESERA soil erosion map for Europe. Annual sediment yields were finally predicted using three relationships between observed yields and catchment characteristics. A method to predict sediment concentration at different flow exceedance rates was successfully developed and provides satisfactory results. The basic principle of the method is redistribution of annual sediment yield into annual water volume using flow characteristics at the point of interest. Further investigations with an emphasis on sediment data and refining the methodology were suggested in order to improve concentration modelling.
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    Integrated catchment scale model of a lowland eutrophic lake and river system: Norfolk, UK
    (Cranfield University, 2006-02) Whitehead, Jodie; White, Sue
    Shallow lakes are ecologically and economically important; many users are interested in methods to assess their response to restoration measures and in tools to predict the impact of specific measures. These users include: local and governmental authorities, private companies or nature conservation organisations. This research is centred on the Broads. The Broads are shallow, eutrophic lakes, probably the result of medieval peat workings, concentrated in the Ant, Bure, Thurne and Yare river valleys. These man made lakes and their surroundings are unique in Europe in terms of both ecology and landscape, forming one of the few remaining large areas of lowland river grassland in the UK. A catchment scale model, SWAT, has been used to model past and future land use and climate scenarios for river basins supplying water and nutrients to the Broads. SWAT is a comprehensive model that requires a diversity of information including climate, topography, soil, land use, agricultural practices, water abstraction and discharge data. Future scenarios run with SWAT suggest that increases in rainfall and temperature through climate change and changed land use increase nutrient and sediment yields and runoff. Future scenarios therefore suggest increased eutrophication problems for both the rivers and Broads within the study area and an increase in the already high risk of ecological failure to the Broads. Various management scenarios based on erosion control measures were designed to alleviate nutrient and sediment yields and increased run-off to the system. SWAT modelling showed the best-case future scenario in terms of land management was to convert the area to grassland. Where land is still used for agriculture erosion control, measures such as cover crops and conservation tillage should be employed. Overall, the work has increased the understanding of water quality, water movement, nutrient and sediment dynamics and agricultural management practices within the study area. The environmental implications of different future scenarios and erosion control measures on the ecology of the Broads provide a basis for management of the area.
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    Investigation of the impact of land use management scenarios on diffuse source nutrients in the River Axe catchment
    (Cranfield University, 2007-09) Glavan, Matjaz; White, Sue; Holman, Ian P.
    The Water Framework Directive (WFD) (Directive 2000/60/EC) requires new ecological standards for rivers, lakes and coastal waters by 2015. In the United Kingdom the English Catchment Sensitive Farming Initiative has identified 40 catchments which are at risk of failing the European Commission WFD targets for good ecological status of water bodies because of a range of issues. The river Axe catchment situated in south-west part of the UK, with a mixture of diffuse and point sources of pollution, is one of these priority sites, as intensive dairy farming and cultivation of high risk crops (maize), cause problems with enhanced suspended sediment, nitrate and phosphorus levels in the river. For the purpose of this research the Soil and Water Assessment Tool (SWAT-2005) and ArcView GIS 3.2 interface AVSWAT-X were used. SWAT has been found to be a useful tool in numerous EU and UK studies addressing the objectives of the EU WFD, which requires identification of pollution sources, their influences and solutions for the studied catchment. The base scenario was based on field observation and interviews with the Environment Agency and farmers; it was run with and without point sources. Model was performing well; achieving hydrological calibration for Nash-Sutcliffe efficiency coefficient (ENS) of 0.62. Three different scenarios, field buffer strips (FBS), extensive land use management (ELUM) and sheep land use management (SLUM), were used to evaluate the ability of SWAT to represent the proposed mitigation methods and assess the effectiveness of the measures in reducing nutrient loads in the Axe. SWAT was found to be able to represent the proposed mitigation methods which were included in these three management scenarios. Management scenarios reduced the average annual loads at the main catchment outlet by 21.21% (FBS), 37.32% (ELUM) and 45.02% (SLUM), for total nitrogen; 47.72% (FBS), 60.58% (ELUM) and 62.41% (SLUM) for total phosphorus; and 3.49% (FBS), 7.34% (ELUM) and 5.58% (SLUM) for annual average sediment yield. To deliver the necessary water quality improvements for the river Axe both diffuse and point sources of pollution will have to be addressed as results show that reduction only in one type of source does not achieve the Environment Agency’s Environmental Quality Standard target values which were set to meet the objectives of the EU WFD.
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    Measuring, modeling and mapping ecosystem services in the Eastern Arc Mountains of Tanzania
    (V.H. Winston & Son, Inc., 2011-10-31T00:00:00Z) Fisher, Brendan; Turner, R. Kerry; Burgess, Neil D.; Swetnam, Ruth D.; Green, Jonathan; Green, Rhys; Kajembe, George; Kulindwa, Kassim; Lewis, Simon L.; Marchant, Rob; Marshall, Andrew R.; Madoffe, Seif; Munishi, P. K. T.; Morse-Jones, Sian; Mwakalila, Shadrack; Paavola, Jouni; Naidoo, Robin; Ricketts, Taylor; Rouget, Rouget; Willcock, Simon; White, Sue; Balmford, Andrew
    In light of the significance that ecosystem service research is likely to play in linking conservation activities and human welfare, systematic approaches to measuring, modeling and mapping ecosystem services (and their value to society) are sorely needed. In this paper we outline one such approach, which we developed in order to understand the links between the functioning of the ecosystems of Tanzania's Eastern Arc Mountains and their impact on human welfare at local, regional and global scales. The essence of our approach is the creation of a series of maps created using field-based or remotely sourced data, data-driven models, and socio-economic scenarios coupled with rule-based assumptions. Here we describe the construction of this spatial information and how it can help to shed light on the complex relationships between ecological and social systems. There are obvious difficulties in operationalizing this approach, but by highlighting those which we have encountered in our own case-study work, we have also been able to suggest some routes to overcoming these impediments
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    A robust methodology to predict diffuse source pollution in the aquatic environment : A case study for the Colworth catchment, Bedfordshire
    (Cranfield University, 2003-12-11) Kannan, Narayanan; White, Sue
    Throughout the world, increased use of agrochemicals, warrant urgent measures to minimise their impacts on the aquatic environment. Monitoring is the usual practice to identify and quantify pollutants, however, it is an after-the-fact occurrence, and monitoring over large spatial scales is not feasible. Mathematical models provide an alternative to monitoring and can be used both to forecast future pollution and to investigate the impacts of potential control measures. This thesis is therefore focussed on catchment scale modelling of pesticide pollution of rivers. Data from a 142-ha agricultural catchment on the Unilever Colworth estate, have been used to model pesticide pollution at the catchment scale. After a review of available models SWAT-2000 was selected as the modelling tool. An acceptable performance in hydrological modelling, along with correct simulation of the processes driving the water balance were essential first requirements. After modification of the SWAT-2000 source code, hydrological simulation, crop growth and evapotranspiration patterns were realistic when compared with monitored data SOUTCGS. Hydrological modelling was carried out using both daily and sub-daily data with Hargreaves and Penman-Montieth methods of evapotranspiration and the NRCS- Curve Number and Green-Ampt methods of runoff generation. A sensitivity analysis identified GWQMN, AWC and ESCO as the most sensitive parameters. These control baseflow, water content of soil layers, and depth distribution of evaporation from the soil respectively. The best combination of runoff generation and evapotranspiration components was identified as Curve Number with Hargreaves. Modelling of sediment and pesticide loss was carried out for four pesticides. Various management scenarios were designed and tested with the objective of reducing pesticide loss to streams and a web-based tool was developed to give advice on pesticide application. With the modifications implemented, it has been demonstrated that SWAT is a useful tool for modelling pesticide behaviour at catchment scale in UK conditions.
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    The use of geostatistics for hydromorphological assessment in rivers
    (Cranfield University, 2006-10) Rivas Casado, Monica; White, Sue
    Assessment of river rehabilitation and restoration projects, as well as the monitoring of morphological changes in rivers requires collection of hydromorphological parameter data (i.e. depth, velocity and substrate). Field data collection is highly time and cost consuming and thus, effective and efficient monitoring programmes need to be designed. Interpolation techniques are often used to predict values of the variables under study at non measured locations. In this way, it is not necessary to collect detailed data sets of information. The accuracy of these predictions depends upon (i)the method used for the interpolation and/or extrapolation procedure and (ii) the sampling strategy applied for the collection of data. Even though the design of effective sampling strategies are of crucial importance when applying interpolation techniques, little work has been developed to determine the most effective way to collect hydromorphological data for this purpose. This project aimed to define a set of guidelines for effective and efficient hydromorphological data collection in rivers and relate this to the type of river site that is being sampled and to the objective for which the data are being collected. The project is structured in three main sections: spatial problem, the scaling problem and the temporal problem. Spatial problem refers to the location and number of points that need to be collected. Scaling problems focus on the study of the river length that needs to be sampled to characterise the spatial variability of a river site, whilst temporal problems determine how often a river site needs to be sampled to characterise the temporal variability associated with changes in discharge. Intensive depth data sets have been collected at a total of 20 river sites. These data sets have been used to investigate the spatial, temporal and scaling problems through geostatistical theory.
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    Water cycle strategy process and its application
    (Cranfield University, 2008-09-20) Cvejic, Rozalija; Cook, Matthew; White, Sue
    Water Cycle Strategies (WCS) have been developed for various areas of the UK. WCSs gather an evidence base which should assist with the promotion of sustainable water management and compliance with important legislation such as the Water Framework Directive (WFD). WCSs also provide evidence which influences the development of local spatial planning policy. This research explored the WCS process undertaken for Milton Keynes (England). The intention of this research was to critically assess the WCS process and its current relevance to sustainable water management, namely WFD compliance. In order to critically assess the WCS process, and to assess its potential and implications for the future of sustainable water management within spatial planning, this research was conducted in three stages and included several organisations, both regulators and regulated. The WCS process is new in spatial planning in England and is rapidly evolving due to several factors identified by this thesis, such as reforming of the spatial planning process or compliance with the WFD. The WCS process affects the influence of different stakeholders, social learning, inter-sectoral joined-up work, and the need for catchment specific evidence base. These aspects influence the outcomes of the WCS process locally, and should also aid implementation of sustainable water management in growth areas regionally and nationally. This study has indentified and analysed the influence of the WCS process so as to critically assess and discuss it. The thesis provides the reader with an insight into how sustainable water management, namely WFD compliance, may be realised in integrated spatial planning in the case of urban growth areas in England.
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    Water for Everyone
    (Tanzania Forest Conservation Group, 2014-06) Ashagre, Biniam; White, Sue; Mwakalila, Shadrack; Platts, Philip; Schaafsma, Marije; Smith, Celina
    Around one in ten Tanzanians source their water from rivers originating in the Eastern Arc Mountains (EAM). In Dar es Salaam, the main water source is the Ruvu River, flowing from Uluguru Nature Reserve, from which around 300 million litres are extracted daily. Moreover, at least half of Tanzanian hydroelectricity is generated from EAM rivers. The EAM contain moist forest assemblages as well as large areas of miombo woodland at lower elevations and on drier leeward aspects. These biomes are believed to play significant roles in the regulation of hydrological flow, flood mitigation and soil conservation. Despite this hypothesised importance, the interactions between river flow, habitat type and land use are not well understood. To explore these complexities, the Valuing the Arc programme (VTA) parameterised a detailed, daily water model called SWAT to model the hydrology of two focal catchments: the Sigi in Tanga Region and the Ruvu in Morogoro region. In addition, we developed a broader scale, monthly model (WatR) to tentatively explore hydrological flow across the wider VTA region.