Now showing 1 - 10 of 50
  • Publication
    ESManage Programme: Irish Freshwater Resources and Assessment of Ecosystem Services Provision
    Freshwater is vital for all forms of life and it is a key requirement in almost all human activities. The societal importance of water has been highlighted by the United Nations, with access to clean water and sanitation regarded as a universal human right. Consequently, the sustainable management of freshwater resources has gained importance at regional, international and global scales. However, the activities of humankind affect freshwater resources extensively, in terms of both quantity and quality, through a variety of activities ranging from abstraction of water for drinking and irrigation to waste disposal. Today, worldwide freshwater ecosystems are undergreat pressure and are one of the most endangered ecosystems. Furthermore, climate change, especially in relation to precipitation patterns and flooding, will result in the traditional norms being replaced with increased variability and unpredictability, with knock-on effects for human societies and well-being.
  • Publication
    Evaluation of the EV1 distribution for different low flow series in the Shannon river basin in Ireland
    (European Geosciences Union, 2009-04) ;
    The 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.
  • Publication
    Understanding Hydrological Flow Paths in Conceptual Catchment Models To Improve Water Quality Modelling
    Increasing pressures on water quality due to intensification of agriculture have increased the need for environmental modelling to accurately simulate the movement of diffuse (nonpoint) nutrients in catchments. As hydrological flows drive the movement and attenuation of nutrients, individual hydrological processes in models should be adequately represented for water quality simulations to be meaningful. In particular, the relative contribution of groundwater and surface runoff to rivers is of interest, as, for example, higher nitrate concentrations in surface waters are strongly linked to catchments with proportionately larger groundwater contributions to the river. In this study, uncertainty analysis was used to investigate parameter sensitivities and flow partitioning of three conceptual hydrological models simulating 31 Irish catchments. We compared two established conceptual hydrological models (NAM and SMARG) and a new model (SMART), produced especially for water quality modelling. In addition to the criteria that assess streamflow simulations, a ratio of average groundwater contribution to total streamflow was calculated for all simulations over the 16 year study period. As measured time-series of groundwater contributions to streamflow are not available at catchment scale, the groundwater ratios were evaluated against average annual indices of base flow (from the OPW) and estimates of deep groundwater flow (from the Geological Survey of Ireland) for each catchment. The exploration of sensitivities of internal flow path partitioning was a specific focus to assist in evaluating model performances. Results highlight that model structure has a strong impact on simulated groundwater flow path contributions. Sensitivities to the internal pathways in the models are not reflected in the usual (flood forecasting) performance criteria results. This demonstrates that simulated groundwater contribution should be constrained by independent data to ensure results within realistic bounds if such models are to be used in the broader environmental sustainability decision making context.
  • Publication
    Developing an independent, generic, phosphorus modelling component for use with grid-oriented, physically-based distributed catchment models
    Grid-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.
  • Publication
    CCT: A simple prioritisation tool for identifying critical source areas for managing waterborne pollutants
    Catchment characterisation integrates an understanding of the physical characteristics, sources, pathways and pressures in a catchment, and provides a scientific basis for evaluation of mitigation measures required by the EU Water Framework Directive. In Ireland, the Catchment Characterisation Tool (CCT) has been developed to assess the potential risk posed by nitrate and phosphate from diffuse agricultural sources to surface and groundwater receptors, and to delineate critical source areas in Irish sub-catchments (typically from 10 – 200 km2 in size) as a means of facilitating the targeting of mitigation measures. The CCT for nitrate, which is presented in this paper, is a steady-state model based on annual average nitrate loadings transported from their land sources along near surface and subsurface pathways to each receptor. The GIS-based model links spatial datasets, such as land-use, soil and geological properties with transport and delivery factors derived from field and literature data. The model can distinguish between the contaminant loads transported through each of the major hydrological pathways. The CCT calculates the nitrate loading to surface waters following the source-pathway-receptor methodology, and results are displayed in pollution impact potential maps. A key issue with such export models is how they can be validated. This paper describes the validation methodology which compared a national dataset of measured nitrate concentrations in Irish water bodies with values predicted by the CCT. More detailed comparisonswith local test catchments that are more intensively monitored showed satisfactory correlation between the CCT predictions and measured concentrations. This paper thus shows both the potential of the CCT approach, the likely range of the uncertainty to be expected, and the issues that arise from its validation.
  • Publication
    Estimating the parameters of the extreme value type 1 distribution for low flow series in Ireland
    (Civil-Comp Press, 2009-09) ;
    In 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.
  • Publication
    FloodWarnTech: Flood warning technologies for Ireland
    (Environmental Protection Agency, 2019-04) ;
    Flooding occurs when a body of water rises to overflow land that is not normally submerged (Ward, 1978). While this definition explicitly includes all types of surface inundation, floods are typically classified into four categories, viz., riverine (fluvial), coastal, groundwater and urban (often called pluvial) flooding. This study is limited to riverine floods, which occur when a river discharge exceeds its bankfull capacity (Leopold et al., 1964).
  • Publication
    Catchment Management Support Tools for Characterisation and Evaluation of Programme of Measures
    (Environmental Protection Agency, 2018-05) ;
    Nutrient enrichment and eutrophication can negatively impact on freshwater ecosystems, estuarine and coastal waters. As a result of improvements in nutrient management and regulation, there has been a large reduction in total phosphorus, total ammonia and total nitrogen emissions from Irish catchments in recent decades. However, half of Irish river water bodies still require improvements to bring them to Good status, as required by the Water Framework Directive (WFD) (2000/60/EC). The Catchment Management Support Tools for Characterisation and Evaluation of Programme of Measures project, or CatchmentTools project, developed data analysis tools and models for assessing nutrients in Irish catchments to support catchment scientists and managers to (1) characterise nutrient sources, pathways and receptors in catchments and (2) assess potential mitigation measures.
  • Publication
    The 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
    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.