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Nasr, Ahmed Elssidig
Preferred name
Nasr, Ahmed Elssidig
Official Name
Nasr, Ahmed Elssidig
Research Output
Now showing 1 - 9 of 9
- PublicationMulti-criteria and Decision Support Systems in support of the Water Framework Directive in Ireland(2006-04)
; The current challenge in the implementation of the Water Framework Directive in Ireland is to introduce programmes of measures that will address the targeted environmental objectives in each River Basin District (RBD). Introduction of such programmes requires that proposed measures be thoroughly evaluated and that decisions will involve multiple criteria and must include stakeholders preferences and opinions. Decision Support Systems (DSS) facilitate this process. Many such systems have been developed and used in relation to water quality. In addition to their technical, modeling, benefits, DSS can also form the basis of systems to communicate options, benefits and damages to stakeholders and to receive feedback on their attitudes and preferences. Such systems could also be involved in facilitating the subsequent negotiations and resulting compromises. In Ireland, a new research project, Wincoms, has commenced which will address these aspects and will provide recommendations for suitable systems to be used in Ireland.860 - PublicationCoupling system model with fuzzy logic rules for use in runoff and total phosphorus load prediction in a catchment(2007-05)
; Tackling the problem of eutrophication in fresh waters is at the top of the agenda for the implementation of the Water Framework Directive (WFD) in Europe. The problem is caused primarily by an increase in phosphorus loading from diffuse sources. Therefore there is a need to apply appropriate measures, which are able to reduce the phosphorus diffuse pollution, at a catchment scale in each River Basin District (RBD). As the implementation of such measures disturbs the existing system in the catchment it is important to be able to predict their impact and this requires a reliable mathematical model to represent the system. In this study, a new, lumped catchment, methodology to improve on an existing diffuse phosphorus pollution model, the Grid Oriented Phosphorus Component (GOPC) model, is proposed. This methodology consists of two elements; (i) the Soil Moisture Accounting and Routing (SMAR) hydrological model was used to provide the required hydrological variables to the GOPC model; and (ii) fuzzy logic rules were formulated with the notion that each rule corresponds to a sub-model representing a particular hydrological behaviour in the catchment and the combined results of all rules give the total response. Sixteen modelling cases, each of which uses different numbers of fuzzy sub-sets for the rainfall and the evaporation, were compared for their discharge and total phosphorus (TP) simulations in a catchment in Northern Ireland. The comparison was based on the validation results as they allow testing the applicability of the models for conditions different from those used in the calibration period. Using 2 fuzzy sub-sets for the rainfall and a single fuzzy sub-set for the evaporation produced the best simulation for the discharge whereas the best TP simulation was obtained from the case of 4 rainfall fuzzy sub-sets and 3 evaporation fuzzy sub-sets.862 - PublicationThe significance of the differences in soil phosphorus representation and transport procedures in the SWAT and HSPF models and a comparison of their performance in estimating phosphorus loss from an agriculture catchment in Ireland(TWRI, 2003-07)
; ; ; ; Phosphorus transported from agriculture land has been identified as a major source of water pollution in a large number of Irish catchments. Models of this process are required in order to design and assess management measures. This paper reports on the comparison and assessment of two of the most promising physically-based distributed models, SWAT and HSPF, with particular emphasis on their suitability for Irish conditions. The representation of the overall soil phosphorus cycle is similar in both models but there is a significant difference in the level of detail in describing the chemical and biochemical processes in each model. Also there are differences in modeling the mechanisms by which phosphorus is removed from the soil column and either transported in dissolved form with the runoff water or in particulate form attached to eroded or detached sediment. These differences could have a significant influence on performance when using either of the models to simulate phosphorus loss from any catchment. Both models are applied to estimating the phosphorus concentration at the outlet of the Clarianna catchment in north Tiperrary (Ireland). This catchment is small (23km2) and the landuse is mainly pasture on grey brown podozilic soils. The results of model calibration are presented along with an assessment of the usefulness of the model outputs as a water quality management tool.326 - PublicationComparison of physically based catchment models for estimating Phosphorus lossesAs part of a large EPA-funded research project, coordinated by TEAGASC, the Centre for Water Resources Research at UCD reviewed the available distributed physically based catchment models with a potential for use in estimating phosphorous losses for use in implementing the Water Framework Directive. Three models, representative of different levels of approach and complexity, were chosen and were implemented for a number of Irish catchments. This paper reports on (i) the lessons and experience gained in implementing these models, (ii) compares the performances of the individual models and (iii) assesses their sensitivities to the main parameters and to spatial scales.
405 - PublicationEvaluation of the EV1 distribution for different low flow series in the Shannon river basin in IrelandThe Shannon river basin is the largest in Ireland and it encompasses a number of urban and rural towns. The water of this river provides the demand for drinking, agriculture, ecology, industry, etc. Therefore it is essential to ensure that such demands are available during dry season where the rainfall ceases and the source of water is the baseflow from groundwater. In this study a frequency analysis of the time series of different low flow events have been carried out. The results of this analysis allow of assessing the availability of water to satisfy the required demands during the case of any drought period which may occur in the future. The EV1 distribution, which has been adopted in Ireland, has been fitted to each time series using three methods: (i) method of moments; (ii) method of maximum likelihood; and (iii) method of probability weighted moments. Time series of six low flow events including (1) annual minimum; (2) 3-day sustained low flow (3-SLF); (3) 7-SLF; (4) 10-SLF; (5) 15-SLF; and (6) 30-SLF have been extracted for 55 hydrometric stations in the basins. These stations have been selected because of the availability of flow records which allow of having enough points in each time series. They are also representative for the basin since their catchments cover wide area in the basin.
301 - PublicationModelling phosphorus loss from agricultural catchments : a comparison of the performance of SWAT, HSPF and SHETRAN for the Clarianna catchment(IWA Publishing, 2003-08)
; ; ; ; ; Much research in Europe at present has been directed at generating and assessing modelling tools for use in catchment management, driven by the requirements and schedule of the Water Framework Directive. A logical first step is to assess the suitability of existing models for this task so that any resources used in generating new models can be targeted at actual modelling needs. Crucial questions, relating to the model structure and complexity and spatial and temporal scales required must also be addressed. This paper reports a comparison of the performance and suitability of three "off-the-shelf" distributed catchment models, each with a different level of complexity, applied to modelling phosphorous losses from the Clarianna catchment in Ireland. In this paper, the performance of three such models (SWAT, HSPF and SHETRAN/GOPC) is compared, both in estimating discharges and phosphorous loads in the Clarianna catchment. The flow comparison has showed that the HSPF model was the best in simulating the mean daily discharges. However, the best calibration results for daily total phosphorus loads in the study catchment has been achieved by the SWAT model.633 - PublicationEstimating the parameters of the extreme value type 1 distribution for low flow series in IrelandIn this study two different models have been developed and tested with data from 55 hydrometric stations in the Shannon River Basin in Ireland for estimating the location and the scale parameters of the EV1 distribution of the Minimum, 3-, 7-, 10-, 15-, and 30-days sustained low flow series at ungauged locations. The first is a simple linear model while the other is a fuzzy clustering model. Both models have been calibrated using the unconstrained and the constrained least squares methods. Moreover five different input scenarios including various combinations of some explanatory variables have been investigated with the two models. The results showed that: (i) the simple linear model calibrated by the constrained least squares method was the best model to estimate the EV1 location parameter using catchment area, mean annual rainfall, mean elevation, mean slope, and soil as explanatory variables, and (ii) the fuzzy clustering model calibrated by the unconstrained least squares method was the best for the EV1 scale parameter using only the first four above mentioned explanatory variables.
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651 - PublicationDeveloping an independent, generic, phosphorus modelling component for use with grid-oriented, physically-based distributed catchment modelsGrid-oriented, physically based catchment models calculate fields of various hydrological variables relevant to phosphorous detachment and transport. These include (i) for surface transport: overland flow depth and flow in the coordinate directions, sediment load, and sediment concentration and (ii) for subsurface transport: soil moisture and hydraulic head at various depths in the soil. These variables can be considered as decoupled from any chemical phosphorous model since phosphorous concentrations, either as dissolved or particulate, do not influence the model calculations of the hydrological fields. Thus the phosphorous concentration calculations can be carried out independently from and after the hydrological calculations. This makes it possible to produce a separate phosphorous modelling component which takes as input the hydrological fields produced by the catchment model and which calculates, at each step the phosphorous concentrations in the flows. This paper summarise the equations and structure of Grid Oriented Phosphorous Component (GOPC) developed for simulating the phosphorus concentrations and loads using the outputs of a fully distributed physical based hydrological model. Also the GOPC performance is illustrated by am example of an experimental catchment (created by the author) subjected to some ideal conditions.
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