EU Water Framework Directive : groundwater-dependent rivers and lakes in Northern Ireland

The EU Water Framework Directive (WFD) requires that those rivers and lakes that are dependent on groundwater be identified and the pressures on these analysed such that the risk of not meeting their environmental objectives by 2015, as set out in Article 4, can be assessed. This report describes the methodology for identifying and carrying out risk assessments for groundwater-dependent rivers and lakes in Northern Ireland, as part of the initial characterisation process. The methodology reflects UK Technical Advisory Group (UKTAG) guidance. The report details those river water bodies and lakes that are groundwater dependent and assesses which of these are at risk of being significantly damaged as a result of groundwater abstractions and potentially polluting point sources; diffuse pollution is addressed elsewhere. The report does not address quantitative impacts on rivers and lakes from groundwater abstractions outside specified assessment zones; the study addressed localised impacts rather than those due to cumulative groundwater abstractions which affect the overall groundwater body water balance, and the ‘available groundwater resource’. This is reported elsewhere. The risk assessment for lakes has been restricted to those with an area greater than 50 hectares, these being the reporting units agreed for the UK for initial characterisation. Lough Neagh and Upper and Lower Lough Erne, whilst obviously falling within this category due to their significant scale, are reported elsewhere. Of the 673 river water bodies considered, 564 are classified as groundwater dependent. Of the 17 lakes assessed, 10 are classified as groundwater dependent. None of the groundwater-dependent lakes are assessed as being affected by groundwater abstractions. Flows in four river water bodies are possibly at local risk due to groundwater abstractions, and one, the Breckagh Burn, is probably at risk. All groundwater-dependent lakes have been classified as risk category 2b in relation to potentially polluting point sources. Using an approach that assesses the equivalent categories for river water bodies based on the sum of the number of sources within the surrounding assessment zones, regardless of type, 113 river water bodies were classified as risk category 2a and the remainder risk category 2b. The report details data limitations and gaps in knowledge affecting the initial characterisation process used

EU Water Framework Directive : groundwater-dependent terrestrial ecosystems in Northern Ireland

The EU Water Framework Directive (WFD) requires those terrestrial ecosystems dependent on groundwater be identified and the anthropogenic pressures acting on the ecosystems analysed. Where significant damage is occurring or could occur due to groundwater factors, then the associated groundwater body is considered to be at risk of not attaining ‘good status’ as defined in the Directive. This report describes the methodology for identifying and carrying out risk assessments for groundwater-dependent terrestrial ecosystems (GWDTEs) in Northern Ireland as part of the initial characterisation process of the WFD. The methodology is based on UK Technical Advisory Group (UKTAG) guidance. 22 designated sites, all Special Areas of Conservation (SACs), have been identified in Northern Ireland as GWDTEs. The report details the level of risk to these GWDTEs from groundwater abstractions and potentially polluting point sources. With one exception, the occurrence of both types of groundwater pressure within the assessment zones of the GWDTEs set by the UKTAG guidance is negligible and hence Risk Category 2b has been determined for initial characterisation. Murlough SAC has been given a Risk Category of 2a for potentially polluting point sources, i.e. it is not at significant risk but confidence that the available information is comprehensive and reliable is low. This is because there are a number of controlled point sources on or close to the GWDTE, on geology that is likely to be in hydraulic connection with it, and some of these sources are concentrated in a small area. It is suggested that improved monitoring of this site would be advisable to increase confidence in the risk assessment. The report highlights a number of aspects that could improve the methodology for identification and assessment of risk for GWDTEs

Nitrogen sources, transport and processing in peri-urban floodplains

Peri-urban floodplains are an important interface between developed land and the aquatic environment and may act as a source or sink for contaminants moving from urban areas towards surface water courses. With increasing pressure from urban development the functioning of floodplains is coming under greater scrutiny. A number of peri-urban sites have been found to be populated with legacy landfills which could potentially cause pollution of adjacent river bodies. Here, a peri-urban floodplain adjoining the city of Oxford, UK, with the River Thames has been investigated over a period of three years through repeated sampling of groundwaters from existing and specially constructed piezometers. A nearby landfill has been found to have imprinted a strong signal on the groundwater with particularly high concentrations of ammonium and generally low concentrations of nitrate and dissolved oxygen. An intensive study of nitrogen dynamics through the use of N-species chemistry, nitrogen isotopes and dissolved nitrous oxide reveals that there is little or no denitrification in the majority of the main landfill plume, and neither is the ammonium significantly retarded by sorption to the aquifer sediments. A simple model has determined the flux of total nitrogen and ammonium from the landfill, through the floodplain and into the river. Over an 8 km reach of the river, which has a number of other legacy landfills, it is estimated that 27.5 tonnes of ammonium may be delivered to the river annually. Although this is a relatively small contribution to the total river nitrogen, it may represent up to 15% of the ammonium loading at the study site and over the length of the reach could increase in-stream concentrations by nearly 40%. Catchment management plans that encompass floodplains in the peri-urban environment need to take into account the likely risk to groundwater and surface water quality that these environments pose

Projected increases in potential groundwater recharge and reduced evapotranspiration under future climate conditions in West Africa

Study region West Africa, with a focus between 5°W and 5°E. Study focus The effects of changing climate and CO2 concentration (RCP8.5 between 2000 and 2100) on the West African monsoon are examined using the UPSCALE high-resolution (25 km) global climate model ensembles for present and future climate, combined with the JULES land-surface model. New hydrological insights Future climate is predicted to have an enhanced summertime Saharan heat low, changing large-scale circulation, causing monsoon rainfall generally to increase. The monsoon progresses further inland and occurs later in the year. UPSCALE rainfall projections indicate that the eastern Sahel becomes wetter (+ 12.2%) but the western Sahel drier (− 13.5%). Future evapotranspiration is reduced across most of West Africa due to the CO2 fertilisation effect causing lower transpiration. Potential groundwater recharge (soil drainage at the bottom of a 3 m deep soil column), is predicted to increase from 0% to 16% of rainfall under present climate, to 1–20% in the future, doubling from ~ 5% to ~ 10% in northern Ghana and the eastern Sahel. Potential recharge increases largely due to increased soil hydraulic conductivity, caused by higher soil moisture resulting from increased rainfall and reduced transpiration. Other factors have only a minor influence on the water balance and potential recharge, including rainfall intensity and land use type. A predicted increase in future potential groundwater recharge is significant as development of groundwater resources is seen as a key means to meet growing water demand in West Africa

Time of emergence of impacts of climate change on groundwater levels in sub-Saharan Africa

The impacts of climate change on groundwater are poorly constrained, particularly in regions such as sub-Saharan Africa where global circulation models (GCMs) project different directions of precipitation change. Moreover, the timing of when climate change impacts on groundwater can be differentiated from natural variability has not been quantified. Here, for the first time, we estimate the time of emergence (ToE) of climate change impacts on groundwater levels, using time series from eight sites across Burkina Faso, West Africa. We apply output data from historical and RCP8.5 runs of CMIP5 GCMs to lumped groundwater models for each site, and estimate ToE by calculating signal to noise ratios for each site and CMIP5 model. We show that in addition to inconsistent direction of climate change impacts across different GCMs, there is inconsistency in the ToE of climate change signals in future groundwater levels, particularly in drying GCMs. Across the eight sites, between 5 (4) and 13 (13) CMIP5 GCMs of a possible 23 show a ToE associated with decreases (increases) in groundwater levels. ToE from CMIP5 GCMs producing decreases in groundwater levels (i.e. drying) is highly variable between sites and GCMs (across all sites, median ToE = 2049, interquartile range = 48 years). For CMIP5 GCMs producing increases in groundwater levels (i.e. wetting), ToE appears to occur earlier and with less variability (across all sites median ToE = 2011, interquartile range = 11 years). These results underline the need for development of no-regrets adaptation measures in parallel with reductions in GCM uncertainty

Spatial and temporal scaling of sub-daily extreme rainfall for data sparse places

Global efforts to upgrade water, drainage, and sanitation services are hampered by hydrometeorological data-scarcity plus uncertainty about climate change. Intensity–duration–frequency (IDF) tables are used routinely to design water infrastructure so offer an entry point for adapting engineering standards. This paper begins with a novel procedure for guiding downscaling predictor variable selection for heavy rainfall simulation using media reports of pluvial flooding. We then present a three-step workflow to: (1) spatially downscale daily rainfall from grid-to-point resolutions; (2) temporally scale from daily series to sub-daily extreme rainfalls and; (3) test methods of temporal scaling of extreme rainfalls within Regional Climate Model (RCM) simulations under changed climate conditions. Critically, we compare the methods of moments and of parameters for temporal scaling annual maximum series of daily rainfall into sub-daily extreme rainfalls, whilst accounting for rainfall intermittency. The methods are applied to Kampala, Uganda and Kisumu, Kenya using the Statistical Downscaling Model (SDSM), two RCM simulations covering East Africa (CP4 and P25), and in hybrid form (RCM-SDSM). We demonstrate that Gumbel parameters (and IDF tables) can be reliably scaled to durations of 3 h within observations and RCMs. Our hybrid RCM-SDSM scaling reduces errors in IDF estimates for the present climate when compared with direct RCM output. Credible parameter scaling relationships are also found within RCM simulations under changed climate conditions. We then discuss the practical aspects of applying such workflows to other city-regions

The sustainable groundwater resources of the Deccan Basalts, India

In the semi-arid regions of the world, water for potable supplies and for supplementary irrigation is obtained mostly from shallow wells. Many of these areas are underlain by 'hard rocks', that is volcanic or ancient crystalline rocks, where groundwater most frequently occurs in aquifers within the shallow weathered and fractured layers. Yields from individual wells are usually low, less than 50 m3/d, and in addition the quantity of water stored in these aquifers is often relatively small, perhaps equivalent to only 2- 3 years average annual recharge, or even less. Further, the climatic conditions, low and variable rainfall, limit the quantity of recharge available to these aquifers and makes them susceptible to drought. The significance of these limitations are crucial as the aquifers often represent the only available source of water. In India, there has been a long tradition of using large-diameter shallow dug wells for both potable supplies and for irrigation. Since the 1950s traditional water-lifting devices have been progressively replaced by motorised pumps. In addition there has been a considerable increase in the number of shallow irrigation wells, 30,000 to 40,000 each year in Maharashtra state alone. The increased exploitation of water resources to meet the demand of a rising population has resulted in a decline in water levels within these wells. The nature of the decline is not fully understood. It is possibly: a long-term decline due to abstraction exceeding average annual recharge; a decline restricted to the vicinity of the well caused by abstraction exceeding the capacity of the aquifer to transmit water to the well; or a short-term decline due to a number of years of below average recharge, with water levels recovering once rainfall returns to normal

A manual for BGSPT : programs to simulate and analyse pumping tests in large diameter wells

Pumping tests are traditionally analysed using simple graphical or type-curve methods. Such techniques become impractical when more than two or three parameters have to be determined and then computer based techniques need to be employed. This manual describes two computer programs (the two elements of BGSPT): one for analysing pumping tests (PI'Ffl'), and the other to simulate time-drawdown behaviour for a specified set of parameters (PTSIM). The programs were developed for large-diameter wells but can be used for any size of well

Estimating groundwater recharge through glacial till at Bacon Hall, Shropshire

A study was undertaken to obtain estimates for recharge to groundwater through glacial till. The work was carried out in support of the Hydrogeological Classification of Superficial Clays programme; a cofunded programme of research between BGS and the National Rivers Authority. Estimates were made using data from Bacon Hall, one of a series of sites used to monitor the Shropshire Groundwater Scheme. The sites are instrumented to measure the effect on soil moisture due to the pumping of wells, installed to enhance flows in the River Severn during dry periods. Each site consists of two piezometers, two neutron probe access tubes and a nest of tensiometers. A value of 167 mm of groundwater recharge was obtained for 1989-90. This is 28.8% of the annual rainfall. However, doubts about the hydrogeological system at the site and the interval at which data was available, both in time and depth raises questions about the-accuracy of the estimates

Sustainability of yield from wells and boreholes in crystalline basement aquifers

Large areas of the world are underlain by crystalline basement rock of igneous or metamorphic origin (Wright, 1992). For many people in arid and semi-arid regions the groundwater stored in these rocks is the only source of water for long periods of the year. This is particularly true for the rural population without access to piped water. This project was undertaken to investigate the factors that control the yield from wells and boreholes in these aquifers and suggest methods of groundwater development to increase the probability that these yields are sustainable. The project concentrates on the crystalline basement aquifers of Zimbabwe, but many of the _conclusions are applicable to other regions of Africa and the-world. The project-highlighted general issues relating to the sustainability of yield from wells and boreholes as well as producing specific findings with relevance to groundwater development programmes