Water in Celtic Countries: Quantity

Key words aquifer vulnerability; groundwater protection; modelling; sea water intrusion
_____________________________________________________________________________________________________Water in Celtic Countries: Quantity, Quality and Climate Variability (Proceedings of the Fourth InterCeltic Colloquium on Hydrology and Management of Water Resources, Guimarães, Portugal, July 2005). IAHS Publ. 310, 2007, 172-180.
Assessing aquifer vulnerability to seawater intrusion using GALDIT method: Part 2—GALDIT Indicators Description

A. G. CHACHADI¹ & JOÃO PAULO LOBO FERREIRA²
1 Goa University, Dept. of Earth Science, Goa University, Goa – 403 206, India

[e-mail]

2 Laboratório Nacional de Engenharia Civil (LNEC), Hydraulics and Environment Department (DHA), Groundwater Division (NAS), Av. do Brasil, 101, 1700-066 Lisboa, Portugal
Abstract This paper is Part 2 of a paper submitted to the 4th InterCeltic Colloquium as Lobo-Ferreira et al. (2007). In this second part of the paper the method for assessing GALDIT index parameters is fully explained. The original development of the GALDIT index was done in the framework of the EU-India INCO-DEV COASTIN project, aimed at the assessment of aquifer vulnerability to seawater intrusion in coastal aquifers. The most important factors controlling seawater intrusion were found to be the following: Groundwater occurrence (aquifer type; unconfined, confined and leaky confined); Aquifer hydraulic conductivity; depth to groundwater Level above the sea; Distance from the shore (distance inland perpendicular from shoreline); Impact of existing status of seawater intrusion in the area; and Thickness of the aquifer, which is being mapped. The acronym GALDIT is formed from the highlighted letters of the parameters for ease of reference. These factors, in combination, are found to include the basic requirements needed to assess the general seawater intrusion potential of each hydrogeological setting. GALDIT factors represent measurable parameters for which data are generally available from a variety of sources without detailed examination. A numerical ranking system to assess seawater intrusion potential in hydrogeological settings has been devised using GALDIT factors. The system contains three significant parts: weights, ranges, and ratings. Each GALDIT factor has been evaluated with respect to the other to determine the relative importance of each factor. In this part we also present the first applications of the method developed for the Bardez aquifer in Goa, India.

Key words aquifer vulnerability; groundwater protection; modelling; seawater intrusion

_____________________________________________________________________________________________________Water in Celtic Countries: Quantity, Quality and Climate Variability (Proceedings of the Fourth InterCeltic Colloquium on Hydrology and Management of Water Resources, Guimarães, Portugal, July 2005). IAHS Publ. 310, 2007, 181-190.
On wellhead protection assessment methods:
a case study in Montemor-o-Novo, Portugal

MARIA JOÃO MOINANTE & JOÃO PAULO LOBO-FERREIRA

Laboratório Nacional de Engenharia Civil (LNEC), Hydraulics and Environment Department (DHA), Groundwater Division (NAS), Av. do Brasil, 101, 1700-066 Lisboa, Portugal

[e-mail]
Abstract Groundwater is vulnerable to several kinds of pollution usually related to the development of anthropogenic activities. Nowadays, wellhead protection areas and their associated restrictions are the most widely used instruments for protecting aquifers. After the description of the wellhead protection area and the presentation of Portuguese regulations that govern wellhead protection areas, a review of the methods applied to define wellhead protection areas in the case study is presented. The study area is briefly described, including the wells used for public water supply, and analytical methods for wellhead protection zone definition are applied, including the method suggested by the Portuguese legislation and the ASMWIN numerical model. Finally, some conclusions are made, based on the results achieved.

Key words analytical method; aquifer protection; groundwater; numerical modelling; pollution; stochastic modelling
_____________________________________________________________________________________________________Water in Celtic Countries: Quantity, Quality and Climate Variability (Proceedings of the Fourth InterCeltic Colloquium on Hydrology and Management of Water Resources, Guimarães, Portugal, July 2005). IAHS Publ. 310, 2007, 191-198.
A new method for groundwater plume detection under uncertainty

Luís Miguel Nunes¹, maria da conceição Cunha², luís Ribeiro³ & João Azevedo³

1 Faculty of Marine and Environmental Sciences, University of Algarve, Campus de Gambelas, 8000 Faro, Portugal

[e-mail]

2 Civil Engineering Department, University of Coimbra, Pinhal de Marrocos, 3030 Coimbra, Portugal

3 Instituto Superior Técnico, Lisbon Technical University, Av. Rovisco Pais, 1096 Lisboa Codex, Portugal
Abstract Groundwater contamination plume characterization is a very hard task to perform and usually requires a large number of sampling sites. In this article a method for optimizing a monitoring network for plume detection and delimitation is proposed. It is assumed that an extensive sampling campaign has already been conducted and that only a few sampling sites should be included in the optimal monitoring network. The objective function incorpor­ates the prior knowledge about concentration variability in the form of its density function, and also a measure of spatial coverage (space-filling method) in order to best distribute the stations over the field. The method was applied to a synthetic case study with 160 sampling locations, and a final optimal monitoring network with 40 stations was obtained. A simulated annealing optimization algorithm was used to solve this very difficult combinatorial problem, which has more than 8.6  10³⁷ possible solutions.

Key words groundwater; monitoring; optimization; plume
_____________________________________________________________________________________________________Water in Celtic Countries: Quantity, Quality and Climate Variability (Proceedings of the Fourth InterCeltic Colloquium on Hydrology and Management of Water Resources, Guimarães, Portugal, July 2005). IAHS Publ. 310, 2007, 201-210.
Mechanisms of flooding in the Mawddach catchment

GRAHAM HALL & ROGER CRATCHLEY

Centre for Arid Zone Studies and School of Agricultural and Forest Sciences, University of Wales, Bangor, UK

[e-mail]
Abstract Rainfall distribution across the Mawddach catchment recorded at 22 raingauges does not correlate well with ground elevation, instead suggesting that maximum precipitation is generated at valley heads where maximum uplift occurs. Streams within the Mawddach catchment have their sources in upland blanket bogs. Water table monitoring shows the water storage capacity of older humified peat to be very limited, with saturation possible during a single storm event—throughflow is concentrated in zones of younger Sphagnum peat. Large thicknesses of glacial and periglacial deposits infill river gorges in the catchment. Hillslope throughflow monitoring indicates that saturation of these deposits can create conditions for rapid runoff and flooding downstream. Temperature monitoring of river bed sediments has identified resurgence of groundwater after prolonged rainfall, further increasing river discharge. Computer modelling predicts that flood plain forestry within the catchment can provide significant temporary storage for peak discharge, reducing flood levels downstream.

Key words blanket bog; flooding; flood plain forestry; groundwater; North Wales; rainfall distribution
_____________________________________________________________________________________________________Water in Celtic Countries: Quantity, Quality and Climate Variability (Proceedings of the Fourth InterCeltic Colloquium on Hydrology and Management of Water Resources, Guimarães, Portugal, July 2005). IAHS Publ. 310, 2007, 211-223.
Le littoral des Bas-Champs soumis aux risques perpétuels d’inondation

Julia BASTIDE¹, Edward ANTHONY¹ & Franck DOLIQUE²

1 GéoDal, EA 35 99, Université du Littoral Côte d’Opale, F-59 140 Dunkerque, France

[e-mail], [e-mail]

2 Université de Reims, Champagne, Ardenne, F-51 100 Reims, France
Résumén Le littoral des Bas-Champs de Cayeux, en Picardie, France, dispose d’un patrimoine géomorphologique particulièrement riche et, offre de ce fait une remarquable diversité de paysages naturels et artificiels. A l’interface “terre–mer”, la frange littorale du cordon de galets de Cayeux est en perpétuelle évolution, soulignant l’interactivité des différents agents de la dynamique d’accumulation côtière. De Dieppe à Ault, le littoral est principale­ment constitué par les falaises crayeuses hautes de 60–80 m. L’estran large de 200–400 m est formé dans sa partie la plus haute par un cordon de galets large de 5–15 m devant le débouché des vallées. Le cordon littoral des Bas-Champs, composé de galets, graviers et sables se développe, depuis environ 2500 ans BP, sur 16 km entre Ault et le Hourdel. Il est constitué par des flèches élémentaires, les pouliers, qui en s’ajoutant les unes aux autres, ont assuré la progression du cordon jusqu’au Hourdel. La flèche de galets, associée à un important estran sableux plat, a pu connaître des rythmes d’accumulation perturbés par des actions naturelles (pénurie de galets) mais aussi par des actions humaines (ouvrages portuaires et extractions). L’alimentation (naturelle) en galets du cordon littoral s’est considérablement amenuisée, elle n’est plus que de 2000 à 3 000 m³ an^-1 au lieu de 20 000 à 30 000 m³ an^-1. Il en résulte un processus important d’érosion du cordon qui se propage peu à peu vers la Baie de Somme et atteint désormais la limite Sud de Cayeux (site touristique). Naturellement, le cordon était très fragile et des ruptures se produisaient antérieurement aux actions humaines. Sa sous-alimentation a encore fragilisé le cordon rendant les ruptures et les inondations qui s’ensuivent de plus en plus importantes (exemple de 1990 plus de 3000 ha sous l’eau). Les brèches se produisent principalement dans des secteurs fragilisés et avant 1980 elles s’ouvraient au voisinage de Ault, à l’enracine­ment du cordon. Lors de la tempête de 1990 le cordon a été quasiment détruit sur 800 m au nord des derniers épis, là où l’érosion été la plus forte. Au fur et à mesure de la mise en place de la protection par des épis jusqu’à l’Amer Sud la zone de formation des brèches, les plus importantes, s’est décalée vers le Nord. Cela montre que la mise en place d’épis accroît l’aptitude du cordon à résister aux attaques de la mer où ils sont implantés mais également que le cordon s’affaiblit au Nord immédiat de la zone protégée. Les apports, pour compenser le stockage des galets dans les casiers, restent insuffisants et la sécurité de Cayeux dépend des rechargements effectués ponctuellement sur le site en érosion. Selon certains élus locaux “tant que cet ouvrage (épis) restera inachevé devant la digue de Cayeux-sur-Mer, les 3000 habitants de la commune resteront sous la menace permanente d’un risque de submersion”. Le problème actuel est de définir jusqu’où les ouvrages de protection devront être réalisés afin de garantir la sécurité du secteur et quel type d’ouvrage favoriserait le transit des galets. Une question reste à poser: faut-il protéger ou laisser faire la nature?

Mots clefs cordon de galets; flèche de galets; dynamique sédimentaire; hydrodynamisme
The coast of Bas-Champs subjected to perpetual risks of flood

Abstract The French coast at Bas-Champs de Cayeux, in Picardie, has a very rich geomorphological history and offers a remarkable diversity of landscape, both natural and man-made. The sea–land interface at the pebbles coastal dunes of Cayeux is in a continuous evolution, highlighting the different factors of coastal dynamics. From Dieppe to Ault, the coast is mainly formed by cliffs 60–80 m high. Natural pebble accretion of the coastal dunes is considerably reduced today, not more than 2000 to 3000 m³ year^-1, instead of 20 000–30 000 m³ year^-1. This is causing an important process of erosion of the dunes that is spreading little by little in the direction of Somme Bay. Today it has already reached the south of Cayeaux. Naturally the dunes are very fragile and ruptures have already happened, even before the intervention of man. Man’s activities reduced accretion, exacerbating the problem and causing more frequent and bigger flooding problems (e.g. in 1990 more than 3000 ha were under water). The breaches happened mainly in the most sensitive areas that were weakened before 1980. During the storm of 1990 the dunes have been almost destroyed over an area of 800 m. The refilling was not enough to compensate the natural stock of pebbles, and security at Cayeux depends now on the refills done on the most problematic erosion spots. According to local people “as long as these coastal works of Cayeux-sur-Mer are not fully achieved, the 3000 inhabitants of the municipality will be in permanent sea flooding danger”. Today, challenges are the definition of the size of the protection works so that security can be achieved in the region, and what type of coastal works is most appropriate to allow the transit of pebbles. But one question will remain open: should we protect or let nature follow its path?

Key words dunes; hydrodynamics; pebbles; sedimentary dynamics
_____________________________________________________________________________________________________Water in Celtic Countries: Quantity, Quality and Climate Variability (Proceedings of the Fourth InterCeltic Colloquium on Hydrology and Management of Water Resources, Guimarães, Portugal, July 2005). IAHS Publ. 310, 2007, 224-231.
Water balance and observed flows in the Anllóns River basin (NW Spain)

M. ERMITAS RIAL RIVAS, MANUEL ALÍ ÁLVAREZ ENJO &
FRANCISCO DÍAZ-FIERROS VIQUEIRA

Departamento de Edafoloxía e Química Agrícola, Universidade de Santiago, CP15782 Santiago de Compostela, Spain

[e-mail]
Abstract During 2001, 2002 and 2003, several streamflow measurement surveys were carried out in the Anllóns River basin, as well as an integral study of its hydrological characteristics that has provided an important under­standing of its hydrological behaviour. The annual hydrographs for each hydrological year were obtained and their separation into the basic compo­nents: surface water and baseflow, were carried out. The baseflow component of streamflow was obtained by means of the HYSEP computer program (developed by USGS). The mean value of the groundwater recharge for the study period was 72% of the total streamflow of the river. At the same time, using the recorded precipitation and evapotranspiration values calculated with the data from the nearest meteorological stations, the soil water balance was calculated using the Thornthwaite and Mather methodology for each observed year. The results obtained have been compared with the observed data.

Key words actual evapotranspiration; groundwater component; hydrograph separation; observed flows; streamflow measurement; water balance
_____________________________________________________________________________________________________Water in Celtic Countries: Quantity, Quality and Climate Variability (Proceedings of the Fourth InterCeltic Colloquium on Hydrology and Management of Water Resources, Guimarães, Portugal, July 2005). IAHS Publ. 310, 2007, 232-241.
Influence of 7-year old Eucalyptus globulus plantation on the low flow of a small basin

B. SOTO¹, M. A. BREA², R. PÉREZ² & F. DÍAZ-FIERROS²

1 Departamento de Bioloxía Vexetal e Ciencias do Solo. Facultad de Ciencias de Ourense, Universidade de Vigo, Spain

2 Departamento de Edafoloxía e Química agrícola, Universidade de Santiago de Compostela, Spain

[e-mail]
Abstract In the hydrological year 1997/98, a plantation of Eucalyptus globulus was planted in a basin of 10.7 ha. Hydrological monitoring of the catchment was carried out until 2003/04. Precipitation, temperature, solar radiation and humidity were measured. Flows were measured continuously with a capacitive probe in a type “V” weir. For the seven years observed, the terms of the monthly water balance were determined. The results show that at the present time, with the trees grown to 16 m height (one half of their total growth time) the annual water balance is not sensitive to the growth of the forest mass. However, the water balance for the dry season months (June, July, August and September), that define the low flow in the basin, shows a clear and sustained decrease with a reduction in the flows by 30% from the initial value.

Key words eucalyptus plantation; forest hydrology; low flow; water balance
_____________________________________________________________________________________________________Water in Celtic Countries: Quantity, Quality and Climate Variability (Proceedings of the Fourth InterCeltic Colloquium on Hydrology and Management of Water Resources, Guimarães, Portugal, July 2005). IAHS Publ. 310, 2007, 242-256.
Marnage et biodiversite en etang peu profond: estimation et relations (Limousin, France)

D. BRUNAUD

UMR 6042 GEOLAB CNRS, 39E rue Camille Guérin, F-87036 Limoges, France

[e-mail]
Résumé Des études multivariées sont réalisées depuis 2002 sur un plan d’eau continental pelliculaire, l’étang de Landes, situé en Limousin. En rapport avec sa situation en tête de source et sa localisation dans une topographie très peu encaissée de bassin sédimentaire tertiaire, en rapport avec la variabilité climatique, cet étang connaît un fonctionnement hydrologique particulier qui se matérialise, à l’échelle annuelle, par une dynamique saisonnière des niveaux d’eau, en l’occurrence par un marnage. Sur le plan vertical, l’amplitude de ce dernier est tel qu’il permet, sur le plan horizontal, d’entretenir de larges marges mi-aquatiques, mi-palustres dont dépend en partie l’évolution de la biodiversité qu’il accueille. Secondée par des facteurs externes qui, comme le vent ou l’exposition, entretiennent une géographie spécifique de la vie, la morphologie et la bathymétrie de l’étang permettent surtout l’existence d’un gradient hydrique. De ce dernier découle un gradient biologique, avec des zones préférentielles d’évolution ou de croissance des espèces, qui, dans cette zone humide fragile, peut rapidement être remis en question, sans gestion réfléchie basée sur la connaissance globale du fonctionnement du plan d’eau, par les caprices de l’hydrosystème.

Mots cléfs étang pelliculaire; marnage; biodiversité; zonation; spatialisation

Water levels variations and biodiversity in a shallow pond: appreciation and relations (Limousin, France)

Abstract Since 2002 multivariate studies have been carried out on a continen­tal water body, the pond of Landes, in Limousin. In relation to its situation at the head of sources and its location in the lowland of the sedimentary Tertiary basin, with respect to the climate changeability, this pond shows a particular hydrological regime which shows yearly in dynamic changes of the water levels, more precisely by the variations of the water mass. On a vertical level, its amplitude is so important that, on a horizontal level, it allows broad margins on which the biodiversity develops. Besides, the amplitude is accentuated by external factors, such as the wind or exposure, which create a specific geography of life (fauna and flora), morphology and bathymetry of the pool result in a hydric gradient. On this gradient depends a biological gradient, with favourite zones of evolution or growth of species, which can be endangered by the chance of the hydrosystem. It can be endangered too, in this humid fragile place, if it is not wisely managed or without taking into account the global dynamics of the water body.

Key words shallow pond; water levels variations; dynamic aquatic zone; hydrological complex/working system; biodiversity; zonation; habitat; spatialization; specific localization
_____________________________________________________________________________________________________Water in Celtic Countries: Quantity, Quality and Climate Variability (Proceedings of the Fourth InterCeltic Colloquium on Hydrology and Management of Water Resources, Guimarães, Portugal, July 2005). IAHS Publ. 310, 2007, 259-266.
Using hydrological models and Geographic Information Systems for water resources evaluation: GIS-VISUAL-BALAN and its application to Atlantic basins in Spain (Valiñas) and Portugal (Serra da Estrela)

Javier Samper¹, Miguel Angel García Vera², Bruno Pisani¹, Diego Alvares¹, Jorge Espinha Marques³, Alberto Varela¹ & José Angel Losada²

1 Escuela de Caminos, Universidade da Coruña, Spain

[e-mail]

2 Confederación Hidrográfica del Ebro, Ministerio de Medio Ambiente, Spain

3 Dep. de Geologia (CGUP), Universidade do Porto, Portugal
Abstract This paper presents a distributed hydrological model for the evaluation of water resources, which has been obtained by extending the capabilities of VISUAL-BALAN V2, a lumped hydrological code developed by the University of La Coruña, and coupling it to a GIS. VISUAL-BALAN is a lumped hydrological model, which solves the water balance equations in the soil, the unsaturated zone and the aquifer. It requires only a few parameters and incorporates user-friendly interfaces for data input and post-processing of results. It evaluates hydrological components in a sequential manner. Besides the balance in the upper soil the code also solves the water balance equations in the unsaturated zone and the underlying aquifer. This allows the computa­tion of daily groundwater levels, as well as basin water discharge rates. Computed heads and streamflows can be compared to measured values for the purpose of model testing and calibration. VISUAL-BALAN accounts for irrigation sources and return flows. It also allows for snow precipitation, melting and runoff. Two advanced options have been developed: (1) automatic parameter estimation using groundwater level and streamflow data; and
(2) sensitivity analyses of the main components of the water balance with respect to model parameters.