hydrologie.orghydrologie.org/redbooks/a334/P334 Description, contents, abstrac… · Web viewEdited by Richard Taylor, Callist Tindimugaya, Michael Owor & Mohammad Shamsudduha. IAHS

Groundwater and Climate in Africa Edited by Richard Taylor, Callist Tindimugaya, Michael Owor & Mohammad ShamsudduhaIAHS Publ. 334 (2009) ISBN 978-1-907161-05-6, 276 + xii pp. Price £65.00

Current assessments of the impacts of climate variability and change on water resources commonly exclude groundwater. This omission is of particular concern in Africa where current water usage and future adaptations in response to climate variability and change, together with population growth, place considerable reliance upon groundwater to meet domestic, agricultural and industrial water needs. The Groundwater and Climate in Africa conference, held in Kampala, Uganda, in June 2008, was the first such conference in Africa, and one of the first globally to focus on the interactions between groundwater and climate variability and change.

This collection of papers selected from the conference includes the Kampala Statement, and addresses five themes: Impact of climate variability and change on

groundwater-based livelihoods Impact of climate variability and change on

groundwater and groundwater-fed ecosystems Monitoring and modelling groundwater use and

replenishment Estimation of groundwater resources and demand

under a changing climate Groundwater management in Africa

Contents

Preface by Richard Taylor, Callist Tindimugaya, Michael Owor & Mohammad Shamsudduha

v

Groundwater and Climate in Africa – The Kampala Statement vii

1 Impact of Climate Variability and Change on Groundwater-Based Livelihoods

Groundwater resources assessment under the pressures of humanity and climate change (GRAPHIC) M. Taniguchi, A. Aureli, J. L. Martin & H. Treidel

3

Water supply provision for poverty alleviation in rural areas of Zambia D. C. W. Nkhuwa

9

Increased risk of diarrhoeal diseases from climate change: evidence from urban communities supplied by groundwater in Uganda R. Taylor, M. Miret-Gaspa, J. Tumwine, L. Mileham, R. Flynn, G. Howard & R. Kulabako

15

The influence of hydrochemistry on the distribution of pathogenic strains of Escherichia coli in urban groundwater of Yaoundé, Cameroon M. E. Nougang, M. Nola, T. Njine, S. H. Zebaze Togouet, M. Djaouda & M. Djah

20

Groundwater quality monitoring in collaboration with rural communities in Bénin Stephen Silliman, Pamela Crane, Moussa Boukari, Nicaise Yalo, Felix Azonsi & Flavien Glidja

27

Chemical quality of groundwater drawn from boreholes in the Ashanti region of Ghana M. A. Nkansah & J. H. Ephraim

36

Reliability of interview data for monitoring and mapping groundwater D. R. Lightfoot, N. Mavlyanov, D. Begimkulov & J. C. Comer

40

2 Impact of Climate Variability and Change on Groundwater and Groundwater-Fed Ecosystems

Climate variability and change in Africa: a review of potential impacts on terrestrial water resources Ogallo Laban

47

Variations in intensity of the westerly monsoon-like flow from the tropical Atlantic and summer rainfall over equatorial and tropical southern Africa N. Vigaud, M. Rouault, Y. Richard & N. Fauchereau

52

Groundwater–surface water interactions and the ecohydrology of arid regions: evidence from the Tafilalt Oasis of southern Morocco Mohamed Messouli, Asma El Alami El Filali, Bahia Ghallabi, Saloua Rochdane, Abdelkrim Ben Salem & Fatima Ezzahra Hammadi

61

Monitoring groundwater–surface water interactions in the Upper Nile Basin of Uganda M. Owor, R. Taylor, J. Thompson, C. Mukwaya & C. Tindimugaya

68

An isotopic study of surface water and groundwater in a semi-arid environment: Souss-Massa basin in SW Morocco L. Bouchaou, T. Tagma, Y. Hsissou, M. Ikenne, S. Boutaleb, L. Bouragba, J. Mudry & J. L. Michelot

76

Seasonal variability in groundwater resources available to rural communities in western Kenya Gelas Simiyu, Tom Esipila & Donald Dick Adams

82

Modelling freshwater availability in Africa: projected changes in groundwater recharge Jürgen Schuol, Karim C. Abbaspour & Hong Yang

88

Impact of a groundwater reservoir on simulated extreme hydroclimatic conditions: case study from the United States Richard O. Anyah

94

3 Monitoring and modelling groundwater use and replenishment

Monitoring groundwater resources in Sub-Saharan Africa: issues and challenges S. M. A. Adelana

103

The global groundwater monitoring network in Africa: an introduction and invit-ation N. Kukuric & M. T. H. Van Vliet

114

Design of an issue-based groundwater monitoring network in Uganda D. Mwesigwa & C. Tindimugaya

119

Groundwater recharge mechanisms and water management in the coastal sedi-mentary basin of Benin H. S. V. Totin, M. Boko & M. Boukari

127

Impacte des changements climatique sur le renouvellement des ressources en eau souterraines: Cas du Bassin Hydrographique Chéliff-Zahrez / Impact of climate change on groundwater recharge in the Chéliff-Zahrez Basin of Algeria M. Meddi & A. Boucefiane

135

Application of a semi-distributed SWAT model to estimate groundwater recharge in the Lake Kyoga basin of Uganda M. Kigobe

143

Climate change impacts on groundwater recharge in semi-arid Uganda and the role of groundwater in livelihood adaptation and peacebuilding J. Gavigan, R. Mackay & M. O. Cuthbert

153

4 Estimation of groundwater resources and demand under a changing climate

Impacts of climate change on groundwater recharge and salinization of ground-water resources in Senegal S. Faye, M. Diaw, S. Ndoye, R. Malou & A. Faye

163

The impact of climate change on groundwater recharge: a case study from the Ethiopian Rift T. A. Abiye, D. Legesse & H. Abate

174

Climate variability and its impact on groundwater recharge to the Table Moun-tain Group aquifers in South Africa Anthony A. Duah & Yongxin Xu

181

Impacts du changement et de la variabilité climatiques sur les eaux souterraines en zone tropicale humide: Cas de la Côte d’Ivoire / Impact of climate change and variability on groundwater resources in humid tropical areas: a case study from the Ivory Coast B. T. A. Goula, F. W. Kouassi, V. Fadika, K. E. Kouakou, G. B. Kouadio, K. Koffi, K. Bamory, D. Inza & I. Savane

190

Staged development of a model to evaluate climate change impacts on ground-water in Benin Antoine Kocher & Barbara Reichert

203

Quantifying the impact of climate change on groundwater recharge to fractured-rock aquifers: a case study from Canada E. K. Appiah-Adjei & D. M. Allen

210

5 Groundwater management in Africa under variable climates

Urban water-supply security – making the best use of groundwater to meet the demands of expanding population under climate change Stephen Foster

221

Episodic recharge to the Quelo-Luanda aquifer in Angola: anticipating the im-pacts of climate change G. L. Miguel, L. F. Rebollo & M. Martín-Loeches

229

Carbon-14, Chlorine-36 and noble gases in deep groundwaters from northeastern Sahara (Algeria): palaeoclimatic implications A. Guendouz, A. S. Moulla & J. L. Michelot

234

Development of groundwater resources to adapt to climate variability in Dar es Salaam, Tanzania Praxeda Kalugendo

241

Recent improvements in the conceptual model of hard rock aquifers and its ap-plication to the survey, management, modelling and protection of groundwater P. Lachassagne, Sh. Ahmed, B. Dewandel, N. Courtois, J. C. Maréchal, J. Perrin & R. Wyns

250

Trade-off analysis between economic development and climate change adapta-tion strategies for River Nile Basin water resources E. M. Fathelrahman, J. C. Ascough, T. R. Green, M. H. Babiker & K. M. Strzepek

257

Key word index 271

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Groundwater and Climate in Africa (Proceedings of the Kampala Conference, June 2008) IAHS Publ. 334, 2009, 3-8.

Groundwater resources assessment under the pressures of humanity and climate change (GRAPHIC)

M. TANIGUCHI1, A. AURELI2, J. L. MARTIN2 & H. TREIDEL2

1Research Institute for Humanity and Nature, Kyoto, [email protected]

2UNESCO-IHP, Paris, France

Abstract UNESCO-IHP initiated the project “Groundwater Resources Assessment under the Pressures of Humanity and Climate Change (GRAPHIC)”. The project promotes and advances sustainable groundwater management in the face of climate change and linked human effects. GRAPHIC provides a platform for exchange of information through case studies, thematic working groups, scientific research, and communication. In this paper, the vision, aims, structure, theme, and methods of the GRAPHIC are shown. Two case studies in Tokyo and the use of satellite GRACE data are introduced. There are urgent and ongoing needs to address the expected coupled effects of human activities and climate change on global groundwater resources in Africa and many other areas of the globe. Key words groundwater resources; climate change; human activities

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Water supply provision for poverty alleviation in rural areas of Zambia

D. C. W. NKHUWASchool of the Built Environment, Copperbelt University, PO Box 21692, Jambo Drive, Riverside, Kitwe, [email protected]; [email protected]

Abstract Zambia has invested substantially in rural water supply since the early 1970s, but the actual number of people effectively provided with safe drinking water remains very low. It is estimated that only 37% of the population had access to safe water supply in 2000, a deprivation that has characterised and entrenched poverty in Zambia’s rural areas. Attempts to alleviate this poverty require a policy that favours a shift in emphasis from provision of safe water supplies to that encompassing productive water. The latter enables families to increase income and reduce costs of healthcare services for water-related illnesses. Gains in income generation will further enable communities to take care of their safe water needs, addressing the systematic challenge of sustainability in the delivery of rural water supply programmes. Under such favourable conditions rural communities can enjoy a life of quality and dignity.Key words appropriate rural water supply; productive water; income generation; poverty alleviation; sustainability; Zambia


mailto:[email protected]


Increased risk of diarrhoeal diseases from climate change: evidence from urban communities supplied by groundwater in Uganda

R. TAYLOR1, M. MIRET-GASPA2, J. TUMWINE3, L. MILEHAM1, R. FLYNN2,4, G. HOWARD5 & R. KULABAKO6

1Department of Geography, University College London, London, [email protected]

2Centre for Hydrogeology, Université de Neuchâtel, Switzerland3Medical School, Makerere University, Kampala, Uganda4School of Planning, Architecture and Civil Engineering, Queen’s University, Belfast, UK 5Climate Change Group, Department for International Development, East Kilbride, UK6Department of Civil Engineering, Makerere University, Kampala, Uganda

Abstract Faecal-oral transmission of pathogenic microorganisms is widespread in rapidly urbanising areas of sub-Saharan Africa where access to adequate sanitation is limited and there is a range of contaminant pathways between faecal sources and the consumption of household water derived from groundwater. High-frequency sampling of a protected spring in Kampala, Uganda, reveals gross but ephemeral contamination by thermotolerant (faecal) bacteria in response to heavy rainfall events (>10 mm·day -1) during the rainy season. At this time, the incidence of diarrhoeal diseases is observed to increase substantially. Dynamical downscaling of climate projections from the HadCM3 general circulation model (SRES A2 forcing scenario) indicates a rise in the frequency of heavy rainfall events over the 20th century in Uganda. Climate change is, therefore, expected to increase the risk of diarrhoeal diseases in Kampala and similar environments. Significant correlations between sanitary risk scores and bacteriological contamination of groundwater-fed sources in Kampala highlight the critical role of improved community hygiene in reducing this risk. Key words groundwater; diarrhoea; climate change; hygiene; urban


The influence of hydrochemistry on the distribution of pathogenic strains of Escherichia coli in urban groundwater of Yaoundé, Cameroon

M. E. NOUGANG, M. NOLA, T. NJINE, S. H. ZEBAZE TOGOUET, M. DJAOUDA & M. [email protected] of Yaoundé I, Laboratory of General Biology, PO Box 812 Yaoundé, Cameroon

Abstract Bacteriological and hydrochemical studies of 10 springs, 4 wells and 13 surface waters in Yaoundé (Cameroon) were conducted to assess the influence of hydrochemistry on the abundance of pathogenic strains of Escherichia coli. Microbiological analyses were carried out by membrane filtration; physico-chemical analyses used standard analytical techniques. The concentration of thermotolerant coliforms, E. coli and pathogenic E. coli exhibit spatial and temporal fluctuations. The relationship between abundances of these microorganisms and physico-chemical factors such as temperature, electrical conductivity or pH, are weak and variable. The distribution of these bacteria in these aquatic environments depends upon a range of environmental parameters. The presence of the pathogenic strains in groundwater and surface water fed water points exposes users to short-term health risks for which basic precautions like boiling must be considered. Key words Yaoundé, Cameroon; E. coli; hydrochemistry; streams; springs; groundwater




Groundwater quality monitoring in collaboration with rural communities in Bénin

STEPHEN SILLIMAN1, PAMELA CRANE1, MOUSSA BOUKARI2, NICAISE YALO2, FELIX AZONSI3 & FLAVIEN GLIDJA4

1Department of Civil Engineering and Geological Sciences, 156 Fitzpatrick Hall, University of Notre Dame, Indiana, [email protected]

2Université d’Abomey-Calavi, Cotonou, Bénin3Direction de l’Hydraulique, Cotonou, Bénin4Centre Afrika Obota, Cotonou, Bénin

Abstract We relate experiences in developing regional and local water-quality data sets in Bénin through collaborations with multiple participants, including rural communities impacted by the studies. Spatial sampling was performed regionally, allowing geostatistical analysis at the scale of hundreds of kilometres. Local (temporal) sampling was completed by teams from the local population trained to measure nitrate and associated parameters using test strips and colorimetry. Local sampling enabled collection of reliable, weekly data over a period of more than three years. Key obstacles to effective monitoring at this scale included communication, logistics, and reliability of field equipment. Results illustrate that collaboration among diverse participants can result in collection of high-value, water-quality data. We especially demonstrate the efficacy of relying on a local population with minimal formal education to collect reliable, high-frequency, time-series data on water quality over multiple years. Key words groundwater quality; sampling; Benin; Africa; local populations; collaboration


Chemical quality of groundwater drawn from boreholes in the Ashanti region of Ghana

M. A. NKANSAH1 & J. H. EPHRAIM2

1Department of Chemistry, KNUST, Kumasi, [email protected]

2Catholic University of Ghana, Fiapre, Ghana

Abstract In the Ashanti Region of Ghana, the physicochemical quality of groundwater sampled from 38 wells in 24 communities in Ejisu-Juaben and Bosomtwi-Atwima-Kwanwoma districts was surveyed between November 2004 and June 2005. Water samples were analysed for pH, electrical conductivity (EC), SO4

2-, Cl-, PO43-, NO2

- , Fe, Mn, Cu, Zn, Cd, Na, K and Pb. The results revealed wide variations in analysed parameters: pH (4.0–8.0); EC (44–1110 μs·cm-1), turbidity (0.1–45 NTU), colour (<5–60 HU), hardness (3–400 mg CaCO3·L-1), alkalinity (10–365 mg CaCO3·L-1), Cl-1 (5–92 mg·L-1), SO4

2- (0.5–17 mg·L-1), PO43-

(<0.01 to 2.4 mg·L-1) and NO2- (<0.01 to 0.08 mg·L-1). Elemental concentrations were Fe (0.06–3.4 mg·L-1),

Mn (<0.01–1.6 mg·L-1), Cu (0.01–1.3 mg·L-1), Zn (<0.01–3.3 mg·L-1), Cd (<0.001–0.006 mg·L-1), Pb (<0.001–0.038 mg·L-1), Na (4–87 mg·L-1) and K (0.2–80 mg·L-1). With the exception of isolated cases of


trace metal contamination and turbidity, water from the boreholes in the two districts had acceptable quality for domestic use.Key words groundwater; physicochemical; quality; trace metals


Reliability of interview data for monitoring and mapping groundwater

D. R. LIGHTFOOT1, N. MAVLYANOV2, D. BEGIMKULOV3 & J. C. COMER1

1Department of Geography, Oklahoma State University, Stillwater, Oklahoma, [email protected]

2State Committee on Geology and Mineral Resources, Tashkent, Uzbekistan3Department of Hydrogeology, Tashkent State Technical University, Tashkent, Uzbekistan

Abstract The impacts of human abstraction, as well as climate variability and change, on groundwater levels, are unknown in many regions of the world. Monitoring wells can be used to record these changes but are commonly limited in their distribution. Our critically limited understanding of magnitude and distribution of changes in groundwater levels inhibits sustainable management of groundwater resources. People who maintain personal or village wells are familiar with local groundwater conditions and can provide valuable information on changing groundwater conditions where monitoring infrastructure is absent. The reliability of data drawn from users is untested. In this study, we assess the accuracy of interview data on groundwater levels by comparing water table depths reported by users of traditional wells to data recorded independently from nearby monitoring wells for the years 1985, 1995, 2000, and 2005. In all cases, the correlation between well water depths is at least 0.9 and the regression coefficient is between 0.80 and 0.87, indicating that estimation of depths to the water table can be reliably made based on oral reporting from traditional wells in the absence of hydrological well monitoring. Key words groundwater; interview data; monitoring well; participatory development


Climate variability and change in Africa: a review of potential impacts on terrestrial water resources

OGALLO LABANIGAD Climate and Applications Centre (ICPAC), PO Box 10304 Nairobi, [email protected]

Abstract The climate in many parts of Africa may be classified as arid and semi-arid, with recurrences of severe droughts. The livelihoods of many in the society are largely nomadic pastoralist. The economies of many states in areas that receive reliable rainfall rely heavily on rain-fed agriculture. The Intergovernmental Panel on Climate Change (IPCC) assessment indicates that both droughts and floods have increased in frequency and severity in recent years, and are projected to increase in the future at many locations world wide, with far reaching implications on the demand and availability of quality freshwater resources. Increased recurrences of droughts in the future will force agriculture in Africa to introduce new demands for clean water through increased irrigation for sustainable agricultural production. IPCC (2007) has shown that the African continent is the most vulnerable continent to climate change. Other future challenges to freshwater availability in Africa include pollution by human activities, together with the ever-


increasing demand for clean water by the fast-increasing population of the continent. Climate change will thus introduce new challenges to sustainable freshwater availability, conflicts/security and the general sustainable development of the continent of Africa in the 21st century. This paper provides some highlights of the climate variability and change in Africa, and some of the potential impacts on terrestrial hydrology. Lessons and experiences from the African regional climate centres in integrated climate risk management for coping with current climate variability and adaptation to future climate changes are also reviewed. Key words terrestrial water resources; hydrology; ICPAC; regional centres; drought; climate variability; climate change


Variations in intensity of the westerly monsoon-like flow from the tropical Atlantic and summer rainfall over equatorial and tropical southern Africa

N. VIGAUD1, M. ROUAULT1, Y. RICHARD2 & N. FAUCHEREAU2

1Department of Oceanography, University of Cape Town, South [email protected]

2Centre de Recherches en Climatologie, UMR 5080 CNRS/Université de Bourgogne, Dijon, France

Abstract An empirical orthogonal function (EOF) of the onshore flow of moisture along the west coast of southern Africa using NCEP-DOE AMIP-2 re-analyses suggests two dominant modes of variability that are linked to: (a) variations within the circulation linked to the mid-latitude westerlies and the South Atlantic anticyclone, (b) the intensity of the westerly flow from the tropical Atlantic. The second mode, referred to as the Equatorial Westerly mode, contributes the most to moisture input from the Atlantic onto the subcontinent at tropical latitudes. This mode appears to be associated with large-scale rainfall anomalies over the upper lands surrounding the Congo basin in January–February, with potential impacts on land hydrology persisting until April–May to the east of the Great Rift valley. It is preceded in November–December by a strengthening/weakening of the South Atlantic anticyclone. Enhanced (reduced) advection of moisture over the Congo basin is accompanied by increased (inhibited) convection processes. In the positive phase of this mode, the excess water vapour is channelled from the Congo basin to the east and southeast at surface, while the southern extension of the African Easterly Jet (AEJ) could play a role in transporting more moisture southwards at mid-tropospheric levels, leading to above-normal rainfall. During its negative phase, often related to ENSO, an eastward shift of the ascending branch of the Walker-type circulation is found to reduce convection and thus rainfall over the upper lands surrounding the Congo basin. Further research into water vapour transport is required to better understand southern African rainfall variability.Key words Tropical Atlantic; Southern Africa summer rainfall; moisture transport; hydrology


Groundwater–surface water interactions and the ecohydrology of arid regions: evidence from the Tafilalt Oasis of southern Morocco

MOHAMED MESSOULI, ASMA EL ALAMI EL FILALI, BAHIA GHALLABI,


SALOUA ROCHDANE, ABDELKRIM BEN SALEM & FATIMA EZZAHRA HAMMADIDepartment of Biology, LHEA, Semlalia Faculty of Sciences, BP 2390 Marrakech, [email protected]

Abstract The interaction between groundwater and surface water is a critical component of the ecohydrology of arid regions. We assess dynamic interactions over a 4-year period between a small aquifer within the Ziz River basin and the Tafilalt Oasis, a Biosphere Reserve in southern Morocco. Changes in spatial and temporal flow patterns were observed under differing hydroclimatological conditions using both hydrological and hydrobiogeochemical methods. Strong positive correlations are observed between percentage saturation of dissolved oxygen in the hyporheic zones of all stations and both species richness and total invertebrate abundance. A significant disruption in the prevailing hydrological regime was caused by both construction of the Hassan Edakhil dam and groundwater abstraction for agriculture. Land clearances led to hill slumping and siltation, which bury lateral bars along the stream channels and render this habitat unsuitable for hyporheic invertebrates. Key words Sahara; hyporheic fauna; climate change; ecohydrology


Monitoring groundwater–surface water interactions in the Upper Nile Basin of Uganda

M. OWOR1,2, R. TAYLOR2, J. THOMPSON2, C. MUKWAYA2 & C. TINDIMUGAYA3

1Department of Geology, Makerere University, Kampala, Uganda [email protected]

2Department of Geography, University College London, London, UK3Directorate of Water Resources Management, Entebbe, Uganda

Abstract The role of groundwater in maintaining surface water levels during periods of low or absent rainfall on low relief surfaces of the Great Lakes Region of Africa has received little attention and remains very poorly understood. Neither a clear conceptual nor a numerical representation of the interaction between surface water and groundwater in this terrain exists. In the Upper Nile Basin of Uganda, interactions between groundwater and surface waters (lakes, wetlands) are commonly ignored and groundwater is excluded from estimations of the lake-water balance. Current research seeks: (1) to characterise the interface and hence pathways between groundwater and surface water, and (2) to assess the contribution of groundwater to surface waters under variable climatic conditions. Preliminary findings show that regionally, precipitation variations and changes affect shallow groundwater storage, which is also supported by large-scale monitoring of terrestrial water storage under the Gravity Anomaly and Recovery Experiment (GRACE). The lithological interface and dynamic hydrological gradients between groundwater and surface water are currently being examined at two sites on Lake Victoria (Jinja, Entebbe) and one site on Lake Kyoga (Bugondo). Groundwater discharges to surface water primarily via saprolite underlying a relatively thin (<5 m) lacustrine sand. Preliminary observations of the hydraulic gradient between groundwater and surface water indicate that the groundwater primarily discharges to the lake. The magnitude and direction of this flux is strongly influenced by variations in precipitation and dam-controlled levels of Lake Victoria. Key words groundwater–surface water interactions; rainfall; lithologic interface




An isotopic study of surface water and groundwater in a semi-arid environment: Souss-Massa basin in SW Morocco

L. BOUCHAOU1, T. TAGMA1, Y. HSISSOU1, M. IKENNE1, S. BOUTALEB1, L. BOURAGBA2, J. MUDRY2 & J. L. MICHELOT3

1Applied Geology and Geo-Environment Laboratory, Ibn Zohr University, Agadir, [email protected]

2Chrono Environnement, University of Franche Comté, Besançon, France3 IDES, University of Paris Sud, Orsay, France

Abstract We apply stable isotope ratios to characterize water resources in the Souss-Massa basin of south-western Morocco. The isotopic contents of waters range from –8‰ to –5.2‰ for δ18O and –52‰ to –34‰ for δ2H. Stable isotope ratios indicate substantial infiltration before evaporation, suggesting recent recharge from the Atlas Mountains and infiltration of surface water along the rivers (oueds) crossing the alluvial cones at the margin of the mountains. The upstream watershed shows more characteristic 2H and 18O -depleted waters. This finding can be explained by altitude and continental effects. Conversely, towards the ocean, 2H and 18O-enriched waters show an evaporation effect in the coastal and the irrigated areas. The rain isotope values indicate that the majority of recharge is from the Atlas Mountains, whereas the contribution of local rainfall is negligible in the watershed downstream.Key words isotopes; water resources; recharge; arid climate; Souss-Massa; Morocco


Seasonal variability in groundwater resources available to rural communities in western Kenya

GELAS SIMIYU1, TOM ESIPILA2 & DONALD DICK ADAMS1

1 School of Environmental Studies, Moi University, Eldoret, [email protected]

2 Department of Geography, Moi University, Eldoret, Kenya

Abstract The study assesses seasonal variability in groundwater resources (spring water and shallow wells) supplying rural communities in a seasonally humid catchment of western Kenya. The discharge of 16 springs and the water column depths of eight shallow wells from the River Nzoia catchment were monitored in March, May and August 2006. Spring discharges were measured using a stop watch and graduated cylinder; water column depths were monitored using a weighted cord and dip meter. Land use was characterised from LandSat imagery (2003) using a GIS. Our observations show that March to May (at the start of the first rainy season), the highest spring discharge was 2.85 L·s-1 but by August (at the end of the long rainy season), had increased to 5.40 L·s -1. For shallow wells, the greatest water column depth was 4.2 m in May but by August was 5.4 m. These observations highlight the seasonality of groundwater resources and their dependency upon seasonal precipitation. Key words groundwater resources; rainfall variability; vulnerability; Kenya


Modelling freshwater availability in Africa: projected changes in groundwater recharge

JÜRGEN SCHUOL, KARIM C. ABBASPOUR & HONG YANG

Swiss Federal Institute of Aquatic Science and Technology, PO Box 611, 8600 Dübendorf, Switzerland [email protected]

Abstract On a continental and annual basis Africa has abundant water resources. However, the problem is that many people and large areas suffer from insufficient water supply due to large spatial and temporal variability within and between African countries and river basins. Though of critical importance, detailed information on water resources and water scarcity in Africa is still limited, and this is especially true for the groundwater recharge. By applying the semi-distributed hydrological model SWAT (Soil and Water Assessment Tool), different freshwater components (i.e. water yield, groundwater recharge, actual evapotranspiration, soil water) were estimated for the African continent by dividing the area into 1496 sub-basins. Using the program SUFI-2 (Sequential Uncertainty Fitting Algorithm), the model was calibrated and validated at 207 discharge stations and the uncertainty quantified for all temporally and spatially aggregated water resources components. The presented model and its results can be used in various advanced studies on climate change, water and food security, and virtual water trade, among others. First results for implications of the projected climate change on the African sub-basin and country based groundwater recharge are shown and evaluated, considering in particular prediction uncertainty. Key words SWAT; SUFI-2; climate change; blue water; green water; African continent


Impact of a groundwater reservoir on simulated extreme hydroclimatic conditions: case study from the United States

RICHARD O. ANYAHDepartment of Natural Resources and the Environment, University of Connecticut, 1376 Storrs Road, Storrs, Connecticut 06269, USA [email protected]

Abstract A fully coupled regional climate-hydrological modelling system (RAMS-Hydro) that incorporates surface, sub-surface and groundwater processes is applied to investigate the importance of incorporating dynamic groundwater storage in the simulation of extreme hydroclimatic conditions in the United States. Based on the availability of model evaluation and validation data, the present study focuses on two most extreme drought and flood conditions experienced over Midwestern parts of the United States in 1988 and 1993, respectively. Two parallel simulations are performed: one with and one without the groundwater reservoir. The inclusion of the groundwater reservoir leads to substantially different simulations of land–atmosphere responses and feedbacks, compared to the scheme that allows free drainage at the bottom of the soil column. It is further shown that with groundwater storage the simulated precipitation is more consistent with observations in the semi-arid, water-limited regions over the western United States. In these areas, groundwater introduces stronger vertical interactions (coupling) between the land surface and overlying atmosphere. However, in relatively humid areas where the water table is shallow, evidence of influence of the water table on temporal and spatial variability in land surface and atmospheric fluxes is less clear. Instead, both lateral and vertical moisture transport appear to play complementary and, at times, competing roles in generating feedbacks associated with regional soil moisture, evapotranspiration and precipitation variability/anomalies. Inclusion of the groundwater reservoir also reproduces temporal patterns of soil moisture that are consistent with those observed during 1988 drought and 1993 flood conditions. Key words climate; groundwater; coupled modelling; droughts; floods; case study


Monitoring groundwater resources in Sub-Saharan Africa: issues and challenges

S. M. A. ADELANADepartment of Geology, University of Ilorin, Ilorin, [email protected]

Abstract Over the last five decades the growing demand for freshwater has created water shortages in many parts of the world. Reliable assessment of groundwater resources, required to supply rapidly growing populations in Africa under a changing climate, places extraordinary demands upon the field of hydrogeology. The limited knowledge of groundwater resources on a national scale hampers development and managed use of this resource in many countries of Africa. Effective management of Africa’s groundwater resources is therefore challenging under these conditions and requires improved monitoring of groundwater resources. While new solutions are needed to meet future water demands globally, critical shortfalls exist in Africa of sustained monitoring of basic hydrogeological parameters. This paper reflects on the shortfalls in the designs, construction and maintenance of groundwater databases and presents case studies that employ monitoring data with current challenges in modelling groundwater use in Africa. Prior to identifying possible strategies and cost-effective techniques for groundwater monitoring, cognizance of constraints and considerations such as responsibility and funding is considered in this study. Proposed strategies consider the level of information required at country- and continent-scale, available resources, monitoring frequencies, funding and the use of a pilot-scale study to initiate national or continent-wide monitoring networks.Key words groundwater database; resource monitoring; groundwater management; Sub-Saharan Africa


The global groundwater monitoring network in Africa: an introduction and invitation

N. KUKURIC & M. T. H. VAN VLIETIGRAC – International Groundwater Resources Assessment Centre, Utrecht, The [email protected]

Abstract This paper describes the Global Groundwater Monitoring Network (GGMN) and its introduction in Africa. Together with several partners, the IGRAC (International Groundwater Resources Assessment Centre) has started an initiative to improve groundwater monitoring in Africa. The initiative includes support of collaboration among groundwater specialists, improved access to relevant monitoring information and an interactive, online monitoring database. The simplicity of this web-based database (only a browser required) and its ownership structure (data provider retains a full control over data) will hopefully encourage groundwater specialists to engage with, and contribute to the network. Besides terrestrial monitoring, remote sensing observations and global hydrological modelling will also be used to provide an estimation of groundwater recharge on a regular basis. The estimation will be compared with terrestrial observations and made available via the common groundwater monitoring portal. Integration of the Groundwater Monitoring Network with remote sensing and regional hydrological modelling provides a multiple-scale approach for assessing the impacts of climate change and socio-economic developments on groundwater resources in Africa.Key words groundwater; Africa; monitoring network; IGRAC; portal



Design of an issue-based groundwater monitoring network in Uganda

D. MWESIGWA & C. TINDIMUGAYADirectorate of Water Resources Management, Ministry of Water and Environment, PO Box 19 Entebbe, [email protected]

Abstract Groundwater monitoring in Uganda was initiated in 1998 and was initially based on the adoption of existing boreholes. This initial network comprised 15 dedicated monitoring wells that were unevenly distributed across the country, yet the objective of the network was to give a picture of the changes in groundwater quantity and quality resulting from natural (climatic) and human impacts as a basis for national strategy for groundwater resources development and management. The monitoring network has since undergone continuous reviews in order to address the key water resources issues in the country. Systematic design of an issue-based monitoring network of surface water, groundwater and water quality was undertaken by Directorate of Water Resources Management through a participatory process of identification of issues nationally and at sub-basin level. Of the 93 water resources issues identified, those pertinent to groundwater include: impact of abstraction, long-term climatic change, seasonal variations, poor water quality, pathogenic contamination, pesticide pollution, nitrate pollution, and state of water resources. Identification of potential locations and parameters to be monitored, and classification of the potential sites in terms of whether they will be basic, specific or temporary networks followed. This process was then followed by integration of the old and proposed network. Prioritisation and ranking of the proposed sites based on three major factors, namely; water resources issues, geology and spatial distribution followed. A prioritized issue-based groundwater monitoring network consisting of 47 wells (including the old network), of which 25 are basic and 22 are specific stations, was designed and is undergoing phased implementation.Key words groundwater monitoring; groundwater quality; heterogeneous hydrogeological conditions


Groundwater recharge mechanisms and water management in the coastal sedimentary basin of Benin

H. S. V. TOTIN1, M. BOKO1 & M. BOUKARI2 1Laboratory of Climate, Water Resources and Ecosystem Dynamic Research, University of Abomey-Calavi - 03 BP

1122 Jericho Cotonou, [email protected]

2Laboratory of Applied Hydrogeology, University of Abomey-Calavi BP 526, Benin

Abstract Groundwater resources constitute the principal source of water supply to large cities in the coastal sedimentary basin of Benin. In the context of climate change, it is important to analyse aquifer recharge mechanisms to adapt water demand to changing water availability in this basin. We investigate the historical relationship between rainfall variability and groundwater recharge using borehole hydrographs. This study shows that groundwater recharge occurs via direct infiltration of rainwater as well as lateral infiltration and vertical drainage through the semi permeable sedimentary sequences in the coastal basin of Benin. Groundwater-level fluctuations are in the order of 1–3 m. Decreasing recharge and more intensive groundwater abstraction pumping accelerate saltwater intrusion from Lake Nokoue. Under these



conditions, it is essential to develop water supply strategies contributing towards an integrated and sustainable management of groundwater. Key words sedimentary coastal Basin; groundwater; rainwater infiltration; lateral flow; Water-Table Fluctuation method


Impacte des changements climatique sur le renouvellement des ressources en eau souterraines: Cas du Bassin Hydrographique Chéliff-Zahrez

M. MEDDI & A. BOUCEFIANEKhemis Milina Uuniversity, 44225 Khemis Miliana, [email protected]

Résumé L’eau souterraine, constitue une ressource très utilisée, dans le bassin hydrographique Chéliff- Zahrez, autant pour l’alimentation en potable que pour l’irrigation, malgré l’existence d’un important périmètre d’irrigation qui couvre la majorité de la vallée du Chéliff. Toutefois, suite à la sécheresse qui a touché toute l’Algérie du Nord, les agriculteurs de la région ont eu recours à la mobilisation intense des ressources en eau souterraine par le biais de forage souvent subventionnés par l’administration. Le travail a permis tout d’abord d’identifier les tendances générales des variations climatiques dans le bassin hydrographiques Cheliff-Zahrez et d'étudier la relation entre ces tendances et la fluctuation du niveau des nappes d'eau souterraines les plus exploitées dans la région (aquifères du Cheliff et de la Mina). Cette démarche nous mène vers la mise en évidence des impacts des changements climatiques sur la recharge des ces nappes, en vue d’identifier les indicateurs climatiques et surtout les introduire dans les plans de gestion et de planification à court terme des ressources en eau de la région. Mots clés changement climatique; eau souterraine; bassin du chéliff; Algérie

Impact of climate change on groundwater recharge in the Chéliff-Zahrez Basin of AlgeriaAbstract Groundwater constitutes a widely-used resource in the Cheliff-Zahra basin, both for drinking supply and for irrigation, despite the existence of a large irrigation scheme covering the majority of the Chéliff Valley. However, following the drought which affected the whole of northern Algeria, farmers in the region have used the intense mobilization of groundwater resources through drilling often subsidized by government. The work has first to identify the general trends of climate variability in the hydrographic Cheliff-Zahrez basin, and to study the relationship between these trends and the fluctuations of the most exploited groundwater in the region (aquifers of Chéliff and Mina basin). This leads us to highlight the impacts of climate change on groundwater recharge, to identify the climatic indicators and especially to introduce them into management plans and short-term planning of water resources in the region.Key words climate change; groundwater; Chéllif bassin; Algeria


Application of a semi-distributed SWAT model to estimate groundwater recharge in the Lake Kyoga basin of UgandaM. KIGOBE1,2

1Faculty of Technology, Department of Civil Engineering, Makerere University, PO Box 7062, Kampala, Uganda


[email protected] Building, Imperial College London, London SW7 2AZ, UK

Abstract Uganda, like many other developing countries, is faced with escalating challenges of raising sufficient resources to meet its water supply needs. Abstraction of groundwater for water supply, especially for rural communities, requires an understanding of its quantity and quality. In this study, groundwater recharge in a medium-sized catchment (River Mpologoma) in the Lake Kyoga Basin of Uganda is estimated using a semi-distributed hydrological model, SWAT (Soil-Water Assessment Tool). The model is calibrated against observed river discharge over the period 1970–1974. Mean modelled recharge is estimated to be 150 mm·year-1 but varies substantially in space and time across the basin. Observational data sets over longer periods and at higher resolution are required to constrain model parameterisation and thereby reduce uncertainty in future simulations of recharge.Key words groundwater; recharge; SWAT model; Uganda


Climate change impacts on groundwater recharge in semi-arid Uganda and the role of groundwater in livelihood adaptation and peacebuilding

J. GAVIGAN1, R. MACKAY1 & M. O. CUTHBERT1,2

1Hydrogeology Research Group, School of Geography Earth, and Environmental Sciences, The University of Birmingham, Edgbaston, Birmingham B15 2TT, [email protected]

2Christian International Peace Service, 35 Melton Rd, Birmingham B14 7DA, UK

Abstract Simulations of groundwater recharge in northeastern Uganda reproduce observed groundwater level fluctuations and provide estimates of recharge ranging from 140 mm·year -1 in Teso to 30 mm·year-1 in Karamoja. Simulations and available data strongly suggest that recharge occurs predominantly through indirect or localised mechanisms. If so, the impacts of higher air temperatures as a result of climate change may be more than offset by the projected increases in precipitation leading to a net increase in the available groundwater resources. Adaptive strategies to climate change in northeastern Uganda will likely depend on groundwater use if current environmental and socio-political trends continue. Further research is essential to confirm the mechanisms of recharge in these regions and sustainability of development activities relying upon groundwater. Given the role of natural resources within the current conflict dynamics, groundwater science may have a significant role to play in peacebuilding within this region for years to come. Key words groundwater recharge; semi-arid; Uganda; climate change; peacebuilding


Impacts of climate change on groundwater recharge and salinization of groundwater resources in Senegal

S. FAYE1, M. DIAW1, S. NDOYE2, R. MALOU1 & A. FAYE1

1Département de Géologie, Faculté des Sciences et Techniques, Université Cheikh Anta Diop (UCAD), PO Box 5005, Dakar-Fann, Séné[email protected]

2Département de Génie Civil, Ecole Supérieure Polytechnique, Université Cheikh Anta Diop, Dakar, Senegal BP 5085,


Dakar Fann, Sénégal

Abstract Climate variability and climate change affect groundwater resources through changes in the timing and magnitude of recharge, the interaction between groundwater and surface waters, and water withdrawals. Evaluation of these impacts is essential for long-term water resource management, especially in semi-arid regions where the availability of resources is often the key to economic development. In Senegal, hypersalinity occurs upstream in tidal estuaries with salinisation of groundwater in shallow aquifers up to 200 km inland. Recent studies on several aquifers (Senegal River Delta System, North Coast Littoral, Saloum Delta and the Casamance Delta) reveal high sensitivities to climate variability and climate change. Hydrochemical evidence together with numerical and analytical models informs regional groundwater recharge and flow. Sensitivity analyses involving reductions of 10–25% in mean annual recharge reveal only minor changes in the seasonality of water-table fluctuations. In the North Coast Littoral and Saloum Delta systems, changes (–1.2 to –3 m water table lowering) are more pronounced in the high water-level zone (corresponding to the high altitude zone) where recharge mostly occurs; whereas values are negligible to nil in the lower water-level region. In the Casamance catchment and the Senegal River catchments, recharge regimes deduced from the water-table fluctuation method and isotopic signatures suggest that climate change will impact these systems, but the magnitude of these impacts will vary under different geomorphological settings. Key words climate variability; climate change; recharge; salinization; estuary


The impact of climate change on groundwater recharge: a case study from the Ethiopian Rift

T. A. ABIYE1, D. LEGESSE2 & H. ABATE2

1School of Geosciences, University of the Witwatersrand, Private Bag X3, PO Box Wits 2050, Johannesburg, South [email protected]

2Department of Earth Sciences, Addis Ababa University, PO Box 1176, Addis Ababa, Ethiopia

Abstract PRMS (Precipitation–Runoff Modelling System) was applied to a river basin in the Main Ethiopian Rift in order to: (1) assess the impact of projected changes in rainfall due to climate change on basin water resources, and (2) to estimate groundwater recharge. Due to variable geological cover and physiography, climate and physical characteristics of the River Meki basin control the amount of water in the rivers and runoff in the basins, which are directly related to effective recharge. Climate varies locally as a result of topography. PRMS uses rainfall, temperature, evaporation, radiation and river discharge as an input variable, along with digital elevation model, land use and soil maps. The impact of six plausible scenarios of climate change on mean basin fluxes was evaluated. The results of the simulated scenarios reveal that an increase in ambient air temperature by 1.5°C reduces the recharge, whereas a rise in rainfall of 20% increases annual recharge by 27–50%. Further research will investigate inter-annual changes in water resources.Key words effective recharge; Main Ethiopian Rift; Meki River basin; PRMS


Climate variability and its impact on groundwater recharge to the Table Mountain Group aquifers in South Africa

ANTHONY A. DUAH & YONGXIN XU


Groundwater Group, Department of Earth Science, University of the Western Cape, P/Bag X17, Bellville 7535, South Africa [email protected]

Abstract The Table Mountain Group (TMG) aquifers lie within the Southwestern Cape (SWC) region of South Africa and are replenished by winter rainfall that exhibits substantial inter-annual variability. Projections of climate change in the SWC feature rising air temperatures and reduced precipitation over the next few decades. In this paper we relate rainfall time series within the TMG aquifer to groundwater levels in order to assess how rainfall variability as a result of climate change will impact groundwater recharge and sustainability of groundwater use. The expected decline in rainfall due to climate change implies a long-term reduction in recharge to groundwater and calls for sound management practices in groundwater-dependent economies.Key words climate variability; rainfall; recharge; aquifer; sustainability


Impacts du changement et de la variabilité climatiques sur les eaux souterraines en zone tropicale humide: Cas de la Côte d’Ivoire

B. T. A. GOULA, F. W. KOUASSI , V. FADIKA, K. E. KOUAKOU, G. B. KOUADIO, K. KOFFI, K. BAMORY, D. INZA & I. SAVANELaboratoire Géosciences et Environnement, UFR SGE – Université d’Abobo-Adjamé – 02 BP 801 Abidjan 02, Côte d’[email protected]

Résumé Cette étude vise à mettre en évidence le changement climatique en Afrique de l’ouest et évaluer les impacts de la variabilité climatique sur les eaux souterraines de la Côte d’Ivoire. D’abord, le modèle RegCM3 à mis en évidence sur l’Afrique de l’ouest par comparaison à la période 1991–2000 que les périodes 2031–2040 et 2091–2100 pourraient connaître des augmentations de température de 0.6°C–1.8°C à 3.2°C–5.8°C . Pour la période, 2031–2040, la pluviométrie de l’Afrique de l’ouest pourrait fluctuer entre –30% à 40%. Ensuite, la fluctuation des pluies annuelles a été caractérisée par la méthode de la variable centrée et réduite pour définir les périodes déficitaires 1970–1996, 1967–1997, 1969–1996, 1995–1997 et 1981–1997 respectivement sous le climat tropical de transition, le climat de montagne, le climat équatorial de transition atténué et le climat équatorial de transition. Enfin, l’impact de la variabilité climatique sur les eaux souterraines par l’analyse des coefficients de tarissement et les volumes d’eau mobilisés par les aquifères montrent que les nappes d’eau souterraines répercutent cette baisse des précipitations par celle des volumes d’eau mobilisés par les aquifères et l’augmentation des coefficients de tarissement. Les volumes d’eau mobilisés baissent pendant les périodes 1971–1999 pour la Comoé à Yendéré et Aniassué, 1980–1993 pour le N’zo à Kahin sur le bassin du Sassandra, 1971–1994 pour le N’zi à Dimbokro sur le Bandama, 1982–2000 pour le Tabou à Yaka et 1991–2002 pour le San Pédro à la station de pompage qui sont des bassins côtiers de l’ouest. Les déficits respectifs produits sont de 54, 47, 40, 31, 46 et 49%. Mot cles climat; eaux souterraines; impacts; zone tropicale

Impact of climate change and variability on groundwater resources in humid tropical areas: a case study from the Ivory CoastAbstract This study assesses the impact of climate change and climate variability on groundwater in the Ivory Coast. The climate model RegCM3, indicates the increase of temperatures for the periods 2031–2040 and 2091–2100 of approximately 0.6–1.8°C and 3.2–5.8°C, respectively; changes in precipitation for the period 2031–2040 are highly uncertain and range from –30% to +40%. Historical climate variability has affected groundwater resources. Using the recession coefficient of Maillet, groundwater fluxes mobilised by aquifers are estimated. Changing groundwater fluxes reflect variable rainfall and absolute deficits. Estimated groundwater fluxes decrease during the periods of rainfall deficit from 1971–1999 for the Comoe in Yendere and Aniassue, 1980–1993 for the N’zo in Kahin on the Sassandra basin, 1971–1994 for


the N’zi in Dimbokro on the Bandama, 1982–2000 for the Tabou in Yaka, and 1991–2002 for the San Pedro at the pumping station which are western coastal watersheds. Key words climate; groundwater; impacts; tropical zone


Staged development of a model to evaluate climate change impacts on groundwater in Benin

ANTOINE KOCHER & BARBARA REICHERTSteinmann Institute – Geology, University of Bonn, Nussallee 8, 53115 Bonn, [email protected]

Abstract An efficient assessment tool for groundwater resources is a central requirement in basin-wide integrated water resource management. We review a progressive, local- to regional-scale assessment of groundwater resources undertaken in Benin through the IMPETUS (an Integrated Approach to the Efficient Management of Scarce Water Resources in West Africa) project. The first phase assessed the main hydrogeological processes in a sub catchment (30 km2) to produce a conceptual hydrogeological model. In the second phase, a regional-scale (14 500 km2) finite element hydrogeological model was developed for the Upper Ouémé catchment. Currently, the project is developing a regional-scale (51 348 km2) numerical model for the whole Ouémé catchment to better understand the regional flow system. Key words Benin; assessment; local-scale; regional scale; IMPETUS


Quantifying the impact of climate change on groundwater recharge to fractured-rock aquifers: a case study from Canada

E. K. APPIAH-ADJEI1 & D. M. ALLEN2

1Department of Geological Engineering, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana [email protected]

2Department of Earth Sciences, Simon Fraser University, Burnaby, British Columbia, Canada

Abstract This study investigates the potential impact of climate change on groundwater recharge to a fractured bedrock aquifer. A case study area on the west coast of Canada is used to demonstrate a methodology that can be applied to estimate recharge under scenarios of climate change in other regions, including Africa. The Hydrologic Evaluation of Landfill Performance (HELP) hydrological model is used. This water-balance model derives estimates of vertical flux (recharge) at the base of a percolation column. Different percolation profiles, representative of the different combinations of soil type and thickness, depth to water table, and vadose zone fractured media are developed. Average estimates of media properties (thickness, hydraulic conductivity, field capacity, wilting point, and porosity), surface slope, and leaf area index are mapped in ArcGIS to generate recharge zones that allow spatial and temporal integration of the recharge results. The recharge model is driven by daily weather data downscaled from current and future global climate model (here Canadian Global Coupled Model 1) predictions using Statistical DownScaling Model (SDSM) and the Long Ashton Research Station Weather Generator (LARS-WG) stochastic weather generator that is calibrated to the observed local climate data. In our Canadian case study, recharge varies from 184 to 537 mm·year-1 and is projected to increase by up to 8% by 2070.Key words climate change; recharge; HELP model; Gulf Islands, Canada; SDSM and LARS-WG


Urban water-supply security – making the best use of groundwater to meet the demands of expanding population under climate change

STEPHEN FOSTERc/o British Geological Survey, Maclean Building, Wallingford OX10 8BB, [email protected]

Abstract In Sub-Saharan Africa the rate of urban population growth places heavy pressure on water-supply provision – a pressure that is likely to be exacerbated by reduced reliability of surface-water sources under most climate change scenarios. Where suitable aquifers are present, expansion of groundwater development is usually the preferred response, in terms of time taken, capital outlay and drought reliability. This is widely occurring, both by urban water utilities (at a variety of scales) and through the rapidly-growing phenomenon of “community and private self-supply”. This paper provides an overview primarily from World Bank experience of the social benefits, economic implications and quality hazards of urban groundwater use, as a stimulus for discussion of the role of groundwater in improving urban water-supply security.Key words urban water-supply; Sub-Saharan Africa; groundwater; climate-change adaptation


Episodic recharge to the Quelo-Luanda aquifer in Angola: anticipating the impacts of climate change

G. L. MIGUEL1, L. F. REBOLLO2 & M. MARTÍN-LOECHES2 1Departamento de Geología, Faculdade de Ciencias, Universidade Agostinho Neto, Luanda, Angola

[email protected] Departamento de Geología, Universidad de Alcalá, Alcalá de Henares, Madrid, Spain

Abstract The Quelo-Luanda aquifer system, which underlies Luanda (Angola), has a maximum depth of 500 m and comprises detrital formations of Middle Miocene to Pleistocene age. Mean annual precipitation is 370 mm and highly variable. Recharge is estimated to be 250 mm per decade. The aquifer system is characterised by deep water levels (60–70 m below ground), low hydraulic gradients (0.001–0.005) and high salinity (800–6000 µS·cm-1). The Quelo-Luanda aquifer system is productive but further development is constrained by salinity. A trend toward longer periods of absent recharge as a result of climate change is expected to severely restrict future groundwater use. Key words Angola; Quelo-Luanda aquifer; estimation of recharge; vulnerability; risk of salinity; regulation


Carbon-14, Chlorine-36 and noble gases in deep groundwaters from northeastern Sahara (Algeria): palaeoclimatic implications

A. GUENDOUZ1, A. S. MOULLA2 & J. L. MICHELOT3

1Blida University, Engineering Science Faculty, BP 270-Soummâa, Blida, [email protected]

2Centre de Recherche Nucléaire d’Alger, DAN/DDTI, BP 399, Alger-RP, Algiers, Algeria3Université Paris sud-UMR "IDES", Orsay Terre, Bat.504, F-91405, France

Abstract Underlying the northern part of the Sahara desert is a major aquifer system, the deep “Continental Intercalaire” (CI), extending over an area of approx. 1 000 000 km2. Groundwater in this aquifer system, a vital resource in such an arid region, is considered to be “fossil”, i.e. mainly inherited from previous climatic conditions, more humid than at present. Sampled groundwaters show a relatively wide range of 36Cl contents, ranging from 8 to 99 10-15 at·at-1, expressed as 36Cl/Cl atomic ratio. The spatial distribution of 36Cl contents fits fairly well with what is known about the piezometric contours of the aquifer: a decrease is observed from recharge to discharge zones. Assuming this decrease is due to radioactive decay, it can be interpreted in terms of groundwaters transit time. Maximum time intervals of about three half-lives (900 ka) may be computed using 36Cl specific activities (at·L-1). The residence time determined on the main flow line where the radiodecay is observed is expressed in terms of minimum ages (16–500 ka) and maximum ages (25–1200 ka). Noble gas data are presented to improve the palaeoclimatic and residence time interpretation for the considered aquifer system. The groundwater recharge temperatures (RT) were estimated from the averaged amounts of noble gases (Ne, Kr, Xe) corrected for the excess air effect. RTs for most groundwaters are generally lower than present-day recharge temperatures. Along the main flow direction, CI paleowaters (ages 20–40ka BP) have an average RT of 16.9°C, which is 5°C cooler than the present day. Recharge temperatures calculated in four samples from the overlying Complexe Terminal (CT) aquifer (30–150 m depth) average 19.7°C, close to the present day mean annual air temperature of 21°C.Key words isotopes; noble gases; chlorine-36; Sahara; palaeoclimate; palaeowater


Development of groundwater resources to adapt to climate variability in Dar es Salaam, Tanzania

PRAXEDA KALUGENDOWami Ruvu Basin Water Office, Ministry of Water and Irrigation, [email protected]

Abstract The city of Dar es Salaam, in Tanzania, depends upon the River Ruvu for its main supply of water for a growing population of 4 million people. Current climate variability undermines the reliability of this water supply derived from river discharge. During a period of prolonged drought (1996/1997), a large number of water users turned to groundwater sources to augment insufficient supplies derived from surface water. Groundwater is available locally from relatively shallow Quaternary deposits composed of sand, clay bound sand and weathered limestone. Since 1997, unplanned and non-regulated exploration and exploitation of groundwater has taken place in order to address water shortages. This ad hoc utilisation threatens the sustainability of groundwater abstraction in terms of both quantity and quality but goes unchecked as no groundwater monitoring network is in place. Recent work supported by the World Bank suggests that a deep aquifer (up to 1000 m) may occur in coastal areas to the north and south of the city. Sustainable development of this aquifer requires an understanding of the regional groundwater flow and replenishment; both of which depend upon groundwater observations.Key words climate variability; Tanzania; groundwater resources


Recent improvements in the conceptual model of hard rock aquifers and its application to the survey, management, modelling and protection of groundwater

P. LACHASSAGNE1, SH. AHMED2, B. DEWANDEL1, N. COURTOIS1, J. C. MARÉCHAL1, J. PERRIN3 & R. WYNS4

1BRGM, Water Division, Resource Assessment, Discontinuous Aquifers Unit, 1039, Rue de Pinville 34 000 Montpellier, FranceNow at: Danone Eaux France, BP 87, 11 Av. Général Dupas, 74500 Evian Cedex, France [email protected]

2National Geophysical Research Institute, Indo-French Centre for Groundwater Research, Uppal Road, 500 007 Hyderabad, India

3BRGM, Water Division, Resource Assessment, Discontinuous Aquifers Unit, Indo-French Centre for Groundwater Research, Uppal Road, 500 007 Hyderabad, India

4BRGM, Geology Division, BP 36009, 45060 Orléans, Cedex, France

Abstract Hard rocks (granites, metamorphic rocks) occupy large areas of Africa and India. Well yields from hard rock aquifers are modest, commonly 2–3 m3·h-1 compared to those from other types of aquifers. However, these resources are geographically widespread and well suited to scattered settlement and small- to medium-size cities. They contribute greatly to the economic development of such regions, especially in arid and semi-arid areas where the surface water resources are limited. Significant advances have recently been made regarding the genesis, geometry, and hydraulics of hard rock aquifers, particularly in India. The hydrodynamic properties of these aquifers appear to be mainly related to weathering processes. The weathering profile, up to more than 100 m thick, is mainly composed of two layers: saprolite which provides groundwater storage; and saprock (fissured bedrock) which affords adequate transmissivity to sustain well discharges. These two layers constitute an aquifer system. New geological and hydrogeological conceptual models enable the spatial distribution and remnants of such weathering profiles to be mapped at the catchment scale and give rise to numerous practical applications: (1) mapping of groundwater potential on a regional scale; (2) sustainable water resources management at the watershed scale through multilayer mathematical modelling tools; and (3) management of groundwater quality issues such as non-point source pollution. Key words conceptual model; saprock; hard rock; hydrogeology; mapping; saprolite


Tradeoff analysis between economic development and climate change adaptation strategies for River Nile Basin water resources

E. M. FATHELRAHMAN1, J. C. ASCOUGH1, T. R. GREEN1, M. H. BABIKER2 & K. M. STRZEPEK3

1 USDA- ARS, Agricultural Systems Research Unit, Fort Collins, Colorado, [email protected]



2 Massachusetts Institute of Technology, Cambridge, Massachusetts, USA3 University of Colorado, Dept. of Civil, Environmental, and Architectural Engineering, Boulder, Colorado, USA

Abstract This paper presents a conceptual, integrated modelling framework and provides an example tradeoff analysis between economic development goals and climate change adaptation strategies. Case study results for tradeoffs between water entering Egypt and predicted economic consequences are discussed and lessons learned (e.g. the nature and limitations of the tradeoff analysis) are summarized. Tradeoff analysis results were illustrated using Stochastic Efficiency with Respect to a Function (SERF) stochastic dominance methodology (including certainty equivalent measures of the GDP and the quantity of water), and used recent projected climate change scenarios and economic indicators. Results show that some climate change adaptation strategies may coincide with economic development agenda and objectives (such as more water release from the Aswan High Dam). Some strategies may, however, contradict existing regional economic development goals. The conceptual framework and methods developed and illustrated here have broad applications to trans-boundary water issues in Africa and elsewhere.Key words tradeoff framework; climate change; groundwater integration; risk

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