Regions:Chad/Guéra/Bitkine/Water points

2026-09-20T22:56:13Z

Samuel: Created page with "{{AI-Generated | tool = ChatGPT | date = 2026-09-21 | scope = full page }} {{DISPLAYTITLE:Water points around Bitkine}} This page documents '''actual known wells, boreholes and other water sources''' around Bitkine. It is intended as a field inventory. Geological interpretation and proposed future drilling locations are documented separately under Groundwater prospecting. Water-po..."

{{AI-Generated | tool = ChatGPT | date = 2026-09-21 | scope = full page }}

{{DISPLAYTITLE:Water points around Bitkine}}

This page documents '''actual known wells, boreholes and other water sources''' around [[Regions:Chad/Guéra/Bitkine|Bitkine]].

It is intended as a field inventory. Geological interpretation and proposed future drilling locations are documented separately under [[Regions:Chad/Guéra/Bitkine/Groundwater_prospecting|Groundwater prospecting]].

Water-point information should distinguish clearly between:

* measured values;
* information reported by owners or operators;
* approximate or historical values;
* observations that still require confirmation.

== Inventory ==

{| class="wikitable sortable"
! Name
! Type
! Location
! Depth
! Yield
! Water quality
! EC
! Current use
! Status
|-
| Restaurant Complex
| Borehole / well
| ''coordinates to add''
| ''unknown''
| ~3 m³/h during March–June
| ''to confirm''
| ''not yet measured''
| Local use
| Existing
|-
| Djaborona Church
| Borehole / well
| ''coordinates to add''
| ''unknown''
| ~2 m³/h during March–June
| ''to confirm''
| ''not yet measured''
| Local use
| Existing
|-
| Elie Tchere
| Borehole / well
| ''coordinates to add''
| ''unknown''
| ~3 m³/h during March–June
| ''to confirm''
| ''not yet measured''
| Local use
| Existing
|}

The reported yields above are field information and should be replaced or supplemented by measured pumping-test data where available.

Additional known water points should be added as their location and ownership are confirmed.

== Water quality ==

Local observations indicate that both potable and noticeably saline groundwater occur around Bitkine.

At present, water described as ''salty'' is primarily a field description. The actual hydrochemical type has not yet been established for most local sources.

Electrical conductivity should therefore be measured for every accessible water point.

A minimal field record should include:

* electrical conductivity (µS/cm);
* temperature;
* pH;
* pumping rate;
* duration of pumping before sampling;
* taste or other field observations;
* current use of the water.

For selected representative wells, laboratory analysis should include:

* sodium;
* potassium;
* calcium;
* magnesium;
* chloride;
* sulfate;
* bicarbonate / alkalinity;
* nitrate;
* fluoride;
* iron;
* manganese;
* microbiological parameters.

Different dissolved salts do not necessarily produce the same taste. A water described as salty may be dominated by sodium chloride, sodium bicarbonate, calcium or magnesium salts, or a mixture of several major ions.

== Electrical conductivity ==

Electrical conductivity is one of the most useful rapid measurements for comparing local groundwater.

Conductivity is recorded in '''microsiemens per centimetre (µS/cm)''' and provides an indication of the total concentration of dissolved ions.

Repeated measurements are preferable to a single value, particularly in fractured-rock boreholes.

A useful pumping record is:

{| class="wikitable"
! Time
! Pumping rate
! Water level
! EC
! Temperature
! pH
! Notes
|-
| Before pumping
|
|
|
|
|
|
|-
| 5 min
|
|
|
|
|
|
|-
| 15 min
|
|
|
|
|
|
|-
| 30 min
|
|
|
|
|
|
|-
| 1 h
|
|
|
|
|
|
|-
| 2 h
|
|
|
|
|
|
|-
| 4 h
|
|
|
|
|
|
|-
| 8 h
|
|
|
|
|
|
|}

Changes in EC during pumping can indicate changing contributions from different fractures.

A decreasing EC may indicate displacement of stagnant or more mineralised water by a fresher source.

An increasing EC may indicate that continued drawdown is recruiting a more mineralised fracture or groundwater body.

Such interpretations require repeated measurements and should not be inferred from taste alone.

== Seasonal behaviour ==

Water-point yield should be recorded throughout the year.

The late dry season is particularly important because a well that performs well shortly after the rainy season may provide substantially less water several months later.

For each important water point, useful seasonal observations include:

{| class="wikitable"
! Date
! Season
! Static water level
! Pumping rate
! Pumping duration
! EC
! Notes
|-
|
|
|
|
|
|
|
|}

Where possible, the same pumping method should be used for repeated measurements so that results remain comparable.

== Individual water-point pages ==

Water points with sufficient information may receive dedicated subpages.

Suggested structure:

:'''Regions:Chad/Guéra/Bitkine/Water_points/Restaurant_Complex'''
:'''Regions:Chad/Guéra/Bitkine/Water_points/Djaborona_Church'''
:'''Regions:Chad/Guéra/Bitkine/Water_points/Elie_Tchere'''

An individual page can contain:

* precise coordinates;
* photographs;
* owner or operator;
* construction date;
* borehole depth;
* casing and screen information;
* pump type;
* measured yield;
* seasonal behaviour;
* EC measurements;
* laboratory chemistry;
* pumping-test results;
* current use;
* maintenance history;
* nearby water points;
* field notes.

== Data quality ==

Field information should retain its source.

Values reported verbally by an owner should be marked as reported values until they are independently measured.

Approximate coordinates should not be presented as survey-quality positions.

Water described as potable should not be considered microbiologically safe without appropriate testing.

== Related pages ==

* [[Regions:Chad/Guéra/Bitkine|Bitkine]]
* [[Regions:Chad/Guéra/Bitkine/Groundwater_prospecting|Groundwater prospecting]]
* [[Regions:Chad/Guéra|Guéra]]

[[Category:Bitkine]]
[[Category:Water points]]
[[Category:Groundwater]]
[[Category:Water supply]]

2026-09-18T00:43:24Z

Samuel:

Regions:Chad/Guéra

2026-09-18T00:43:00Z

Samuel:

{{AI-Generated
| model = ChatGPT
| date = 2026-09-18
| scope = full page
}}

'''Guéra''' is a province in central [[Regions:Chad|Chad]]. Its provincial capital is '''Mongo'''. The province includes the town of [[Regions:Chad/Guéra/Bitkine|Bitkine]], where AOWIS is currently involved in local water-supply work and groundwater assessment.

Guéra lies across the transition from the Sahelian zone in the north to more humid Sudanian conditions in the south. Its mountainous crystalline basement, strongly seasonal rainfall, lack of permanent rivers, and highly variable groundwater productivity make water supply a major engineering challenge.

== Geography and administration ==

The 2022 ''Schéma Provincial d'Aménagement du Territoire du Guéra'' gives an area of approximately '''61,279 km²'''. Following the 2021 administrative restructuring, the province consists of five departments:<ref name="spat">[https://apef-conservation.org/ressources-documentaires/ APEF / Republic of Chad, ''Schéma Provincial d'Aménagement du Territoire du Guéra 2022–2032'', 2022.]</ref>

* '''Guéra''', capital Mongo;
* '''Abtouyour''', capital [[Regions:Chad/Guéra/Bitkine|Bitkine]];
* '''Mangalmé''', capital Mangalmé;
* '''Barh Signaka''', capital Chinguil;
* '''Garada''', capital Melfi.

The same planning document gives a projected population of '''635,822 inhabitants in 2020''', based on the 2009 national census and subsequent INSEED projections. The population is concentrated particularly in Guéra and Abtouyour.<ref name="spat" />

== Terrain and surface water ==

The landscape is dominated by plains interrupted by large granitic massifs, inselbergs, plateaus, and exposed bedrock.

The central Chadian massif reaches some of its highest elevations in Guéra. The Mont Guéra reaches approximately '''1,613 m''' in the Bitkine area, while Mont Guédi east of Mongo reaches approximately '''1,506 m'''.<ref name="spat" />

There are no major permanent rivers across most of the province. Surface drainage is dominated by seasonal watercourses, locally known as '''barhs''' or '''ouadis''', which flow during the rainy season and may retain water temporarily in depressions and ponds.

Seasonal streams draining the Guéra massif include the Bolong, Bang-Bang, Zilla, Zerzer and Melmele systems. Water from some northern catchments ultimately contributes toward Lake Fitri.<ref name="spat" />

Surface-water availability therefore changes strongly between the rainy and dry seasons, increasing dependence on groundwater for permanent water supply.

== Climate ==

Guéra spans several climatic zones. The north is predominantly Sahelian, the centre is Sahelo-Sudanian, and the southern part of the province approaches Sudanian conditions.

The main seasons are:

* '''rainy season:''' approximately May to September;
* '''dry season:''' approximately October to April.

July and August account for a large fraction of annual rainfall in hydrogeological studies of the central and northern part of the province.<ref name="palomar">[https://nextcloud.aowis.org/s/j7Gy7bMrFr5Gsew Pierre Palomar, ''Conceptualisation hydrogéologique et recommandations pour les prospections géophysiques et l'implantation des forages — Province du Guéra, Tchad'', SEVES, 2024.]</ref>

The provincial planning document reports annual precipitation increasing broadly from around '''800 mm in the north to 1,100 mm in the south'''. Hydrogeological studies covering more restricted parts of Guéra use lower ranges, including approximately '''430–867 mm/year'''. These values refer to different geographic extents and datasets and should not be treated as a single uniform rainfall value for the province.<ref name="spat" /><ref name="palomar" />

Mean annual temperature is around '''28 °C''', with high temperatures and long dry periods contributing to evaporation, drying of seasonal ponds, and strong seasonal pressure on water supplies.<ref name="spat" />

== Geology ==

Much of the Guéra massif consists of '''crystalline basement rock'''. Nouradine's regional hydrogeological work describes the study area as being dominated by granitoids and metamorphic rocks.<ref name="nouradine">[https://nextcloud.aowis.org/s/tCJgPAa2G6Lws83 Haroun Nouradine, ''Évaluation des ressources en eau dans les aquifères de socle dans la région du Guéra (Tchad) : combinaison d'approches géologiques, hydrogéologiques, géophysiques, géochimiques et d'apprentissage automatique'', doctoral thesis, Sorbonne Université, 2023.]</ref>

Around Bitkine, the basement includes:

* granite;
* biotite granite;
* diorite;
* granodiorite;
* dolerite.

The lithology strongly influences groundwater productivity. Biotite granites can develop permeable weathered and fractured horizons, while alteration of diorites, granodiorites and dolerites can produce larger amounts of clay, reducing infiltration and hydraulic conductivity.<ref name="palomar" />

== Hydrogeology ==

Groundwater in Guéra does not occur as one large continuous regional aquifer. The principal groundwater resources are associated with:

* weathered crystalline basement;
* fractured and fissured bedrock;
* alluvial deposits;
* sands and sediments along seasonal drainage systems.

The basement aquifers are therefore '''heterogeneous and discontinuous'''. Two boreholes located relatively close to one another can encounter substantially different conditions.

A simplified basement-aquifer structure consists of:

# superficial material and soil;
# weathered basement, or '''alterites''';
# a fractured basement horizon;
# progressively less fractured competent bedrock at greater depth.

The weathered horizon can provide substantial groundwater storage. Hydraulic transmissivity is often associated particularly with the upper fractured basement beneath it.<ref name="nouradine" />

Nouradine's regional analysis found that important water inflows commonly occur at approximately '''30–60 m depth'''. Productivity generally decreases where drilling continues far into relatively unfractured basement.<ref name="nouradine" />

Groundwater occurrence and borehole productivity depend on the combined effects of:

* lithology;
* thickness and permeability of the weathered zone;
* development of the fractured horizon;
* geomorphology;
* recharge conditions;
* local drainage;
* position within the landscape.

Low-lying areas and locations favourable to infiltration and recharge can provide substantially better groundwater conditions than nearby elevated or poorly weathered basement.

== Borehole productivity ==

Obtaining productive boreholes is a major difficulty in Guéra.

Data analysed for boreholes constructed between 2010 and 2016 show that, among '''137 boreholes''' considered by the SEVES study:

* '''47%''' were unsuccessful during drilling and were not equipped;
* '''42%''' produced too little water for connection to an AEP water-supply network;
* only '''11%''' provided an exploitable yield of approximately '''4 m³/h for 8 hours per day'''.<ref name="palomar" />

The broader dataset analysed by Nouradine contains technical information from '''798 boreholes''', together with approximately '''700 EM34 profiles''' and '''592 electrical-resistivity tomography profiles'''.<ref name="nouradine" /><ref name="article">[https://doi.org/10.1007/s10040-024-02766-2 H. Nouradine et al., ''Integrating geological, hydrogeological and geophysical data to identify groundwater resources in granitic basement areas (Guéra Massif, Chad)'', Hydrogeology Journal 32, 759–784, 2024.]</ref>

The mean borehole yield in the analysed basement-aquifer dataset is approximately '''1 m³/h'''. More productive boreholes are associated particularly with well-developed weathered and fractured horizons and favourable granite or biotite-granite formations.<ref name="nouradine" />

The difficulty is therefore not simply drilling deep enough. Successful groundwater development requires identifying favourable combinations of geology, weathering, fractures, topography and recharge.

== Groundwater recharge ==

Recharge is closely linked to the short rainy season.

Direct infiltration across exposed or poorly permeable uplands can be limited, while runoff concentrates water in lower terrain, seasonal drainage channels, alluvial deposits and favourable fractured zones.

The strongly seasonal rainfall regime means groundwater recharge can vary substantially between years. Quantifying long-term recharge remains an important uncertainty for sustainable groundwater development in Guéra.<ref name="palomar" />

Groundwater availability must therefore be evaluated not only in terms of instantaneous borehole yield, but also in terms of seasonal variation and sustainable long-term abstraction.

== Groundwater quality ==

Regional groundwater studies generally describe Guéra groundwater as relatively weakly mineralised compared with strongly saline groundwater systems elsewhere in Chad.

Earlier regional studies cited by Nouradine reported dissolved mineral content generally below approximately '''250 mg/L''', with bicarbonate-dominated groundwater and relatively low chloride and sulfate concentrations.<ref name="nouradine" />

More recent geochemical work by Nouradine analysed '''211 groundwater samples''', principally in and around the Mongo study area. Electrical conductivity ranged from approximately '''83 to 1,183 µS/cm''', with an overall mean of approximately '''427 µS/cm'''.<ref name="nouradine" />

Mineralisation increases in some deeper or fractured groundwater systems. Mean conductivity in the study was approximately:

{| class="wikitable"
! Water source
! Mean electrical conductivity
|-
| Shallow rural wells
| ~175 µS/cm
|-
| Rural boreholes in fractured basement
| ~445 µS/cm
|-
| Urban boreholes in fractured basement
| ~526 µS/cm
|-
| Wells intersecting both weathered and fractured horizons
| ~677 µS/cm
|}

These figures describe the sampled areas around Mongo and should '''not''' be assumed to represent every groundwater body in Guéra.

Local groundwater chemistry can vary strongly because individual boreholes may intercept different weathered zones, fracture systems and groundwater residence times.

=== Local salinity ===

Saline or noticeably mineralised boreholes occur locally in the Guéra region, including around Bitkine.

AOWIS field observations around Bitkine indicate substantial local variation in water quality, with potable and saline groundwater occurring within the same general area. Some saline wells are unsuitable for drinking but remain in use for washing, construction, irrigation or other non-potable purposes.

This local variability is consistent with the discontinuous fractured-basement hydrogeology of the area. Salinity at one borehole does not establish that neighbouring groundwater will have the same composition.

Electrical conductivity, TDS and full chemical analysis should therefore be measured individually for each water point before treatment requirements or desalination systems are designed.

== Bitkine and Abtouyour ==

[[Regions:Chad/Guéra/Bitkine|Bitkine]] is the capital of the Abtouyour department and one of the main current areas of groundwater investigation in Guéra.

The 2023–2024 work carried out by SEVES, UMR METIS of Sorbonne Université and ANTEA concentrated specifically on the Bitkine area. Pierre Palomar reinterpreted '''61 existing electrical-resistivity tomography surveys''' and associated borehole information to develop a local hydrogeological model and improve future borehole siting.<ref name="palomar" />

The work builds directly on Nouradine's regional research, which had concentrated particularly on the Mongo and Barlo areas.

The Bitkine study found that geology and weathering pattern are critical to borehole performance and that geophysical anomalies cannot be interpreted reliably as fractures without considering the geological and geomorphological context.<ref name="palomar" />

A dedicated page covers the local conditions and water-supply work:

:'''[[Regions:Chad/Guéra/Bitkine]]'''

== Water supply ==

Much of Guéra depends on boreholes, hand-pumped wells and small piped drinking-water systems.

The combination of low borehole yields, high drilling failure rates, seasonal demand and uncertain recharge makes reliable water supply difficult, particularly during the dry season.

The provincial development plan reported substantial deficits in both rural hand-pump coverage and piped AEP systems.<ref name="spat" />

In the Bitkine area, '''SEVES''' and its Chadian partner '''ADES''' have been working with the Commune of Bitkine and the regional water authorities through the '''REAVIA''' programme.

Recent groundwater-development work reported by SEVES included:

* a new borehole at Bitkine producing approximately '''6 m³/h''';
* rehabilitation of a borehole at Koubo Adougoul producing approximately '''4 m³/h''';
* a new borehole at Koubo Adougoul producing approximately '''7 m³/h'''.<ref name="reavia">[https://www.asso-seves.org/tchad-mobilisation-de-la-ressource-en-eau-pour-les-services-d-eau-potable-de.html SEVES, ''Mobilisation de la ressource en eau pour les services d'eau potable de Bitkine et Koubo Adougoul dans la province du Guéra — REAVIA''.]</ref>

These yields are high relative to many of the boreholes represented in the regional datasets.

== Hydrogeological research ==

Recent groundwater research in Guéra has produced an unusually large combined hydrogeological and geophysical dataset for a crystalline-basement region.

=== Nouradine 2023 ===

Haroun Nouradine's doctoral research combined:

* geological analysis;
* hydrogeology;
* electrical geophysics;
* groundwater chemistry;
* stable isotopes;
* piezometric monitoring;
* machine learning.

The underlying datasets include:

* 798 boreholes;
* 700 EM34 profiles;
* 592 electrical-resistivity tomography profiles;
* 211 geochemical and isotopic groundwater samples.

The work established a conceptual model of Guéra's crystalline-basement aquifers and identified factors controlling borehole productivity.<ref name="nouradine" />

'''Full thesis:'''
:[https://nextcloud.aowis.org/s/tCJgPAa2G6Lws83 ''Évaluation des ressources en eau dans les aquifères de socle dans la région du Guéra (Tchad)'', Haroun Nouradine, 2023]

=== Palomar / SEVES 2024 ===

Pierre Palomar's study, carried out within SEVES in collaboration with Sorbonne Université's UMR METIS and ANTEA, applies the regional hydrogeological model specifically to the Bitkine area.

It includes:

* a review of basement-aquifer hydrogeology;
* evaluation of geophysical prospecting methods;
* reinterpretation of existing ERT surveys;
* comparison with borehole results;
* a hydrogeological conceptual model for the Bitkine area;
* recommendations for future groundwater prospecting and borehole siting.

'''Full report:'''
:[https://nextcloud.aowis.org/s/j7Gy7bMrFr5Gsew ''Conceptualisation hydrogéologique et recommandations pour les prospections géophysiques et l'implantation des forages — Province du Guéra, Tchad'', Pierre Palomar / SEVES, 2024]

== AOWIS work ==

Guéra is a current AOWIS field region, with initial work concentrated around [[Regions:Chad/Guéra/Bitkine|Bitkine]].

Current work includes documentation of existing water points, seasonal borehole yields, water quality, groundwater salinity, opportunities for cooperation between existing well operators, and options for additional storage, treatment and distribution infrastructure.

The combination of highly variable groundwater productivity and local differences in groundwater chemistry makes the region particularly relevant to integrated water-resource monitoring and planning.

== References ==

<references />

== External resources ==

* [https://nextcloud.aowis.org/s/tCJgPAa2G6Lws83 Nouradine 2023 doctoral thesis — AOWIS-hosted PDF]
* [https://nextcloud.aowis.org/s/j7Gy7bMrFr5Gsew Palomar / SEVES Guéra and Bitkine hydrogeology report — AOWIS-hosted PDF]
* [https://doi.org/10.1007/s10040-024-02766-2 Nouradine et al. 2024 — Hydrogeology Journal]
* [https://www.asso-seves.org/implantation-des-forages-dans-la-province-du-guera-autchad.html SEVES — hydrogeology and borehole siting in Guéra]
* [https://apef-conservation.org/ressources-documentaires/ Schéma Provincial d'Aménagement du Territoire du Guéra 2022–2032]

[[Category:Chad]]
[[Category:Guéra]]
[[Category:Groundwater]]
[[Category:Hydrogeology]]
[[Category:Water supply]]

Regions:Chad/Guéra

2026-09-18T00:40:52Z

Samuel: Created page with " {{AI-generated | model = ChatGPT | date = 2026-09-18 | scope = full page }} '''Guéra''' is a province in central Chad. Its provincial capital is '''Mongo'''. The province includes the town of Bitkine, where AOWIS is currently involved in local water-supply work and groundwater assessment. Guéra lies across the transition from the Sahelian zone in the north to more humid Sudanian conditions in the south. Its mountai..."

{{AI-generated
| model = ChatGPT
| date = 2026-09-18
| scope = full page
}}

'''Guéra''' is a province in central [[Regions:Chad|Chad]]. Its provincial capital is '''Mongo'''. The province includes the town of [[Regions:Chad/Guéra/Bitkine|Bitkine]], where AOWIS is currently involved in local water-supply work and groundwater assessment.

Guéra lies across the transition from the Sahelian zone in the north to more humid Sudanian conditions in the south. Its mountainous crystalline basement, strongly seasonal rainfall, lack of permanent rivers, and highly variable groundwater productivity make water supply a major engineering challenge.

== Geography and administration ==

The 2022 ''Schéma Provincial d'Aménagement du Territoire du Guéra'' gives an area of approximately '''61,279 km²'''. Following the 2021 administrative restructuring, the province consists of five departments:<ref name="spat">[https://apef-conservation.org/ressources-documentaires/ APEF / Republic of Chad, ''Schéma Provincial d'Aménagement du Territoire du Guéra 2022–2032'', 2022.]</ref>

* '''Guéra''', capital Mongo;
* '''Abtouyour''', capital [[Regions:Chad/Guéra/Bitkine|Bitkine]];
* '''Mangalmé''', capital Mangalmé;
* '''Barh Signaka''', capital Chinguil;
* '''Garada''', capital Melfi.

The same planning document gives a projected population of '''635,822 inhabitants in 2020''', based on the 2009 national census and subsequent INSEED projections. The population is concentrated particularly in Guéra and Abtouyour.<ref name="spat" />

== Terrain and surface water ==

The landscape is dominated by plains interrupted by large granitic massifs, inselbergs, plateaus, and exposed bedrock.

The central Chadian massif reaches some of its highest elevations in Guéra. The Mont Guéra reaches approximately '''1,613 m''' in the Bitkine area, while Mont Guédi east of Mongo reaches approximately '''1,506 m'''.<ref name="spat" />

There are no major permanent rivers across most of the province. Surface drainage is dominated by seasonal watercourses, locally known as '''barhs''' or '''ouadis''', which flow during the rainy season and may retain water temporarily in depressions and ponds.

Seasonal streams draining the Guéra massif include the Bolong, Bang-Bang, Zilla, Zerzer and Melmele systems. Water from some northern catchments ultimately contributes toward Lake Fitri.<ref name="spat" />

Surface-water availability therefore changes strongly between the rainy and dry seasons, increasing dependence on groundwater for permanent water supply.

== Climate ==

Guéra spans several climatic zones. The north is predominantly Sahelian, the centre is Sahelo-Sudanian, and the southern part of the province approaches Sudanian conditions.

The main seasons are:

* '''rainy season:''' approximately May to September;
* '''dry season:''' approximately October to April.

July and August account for a large fraction of annual rainfall in hydrogeological studies of the central and northern part of the province.<ref name="palomar">[https://nextcloud.aowis.org/s/j7Gy7bMrFr5Gsew Pierre Palomar, ''Conceptualisation hydrogéologique et recommandations pour les prospections géophysiques et l'implantation des forages — Province du Guéra, Tchad'', SEVES, 2024.]</ref>

The provincial planning document reports annual precipitation increasing broadly from around '''800 mm in the north to 1,100 mm in the south'''. Hydrogeological studies covering more restricted parts of Guéra use lower ranges, including approximately '''430–867 mm/year'''. These values refer to different geographic extents and datasets and should not be treated as a single uniform rainfall value for the province.<ref name="spat" /><ref name="palomar" />

Mean annual temperature is around '''28 °C''', with high temperatures and long dry periods contributing to evaporation, drying of seasonal ponds, and strong seasonal pressure on water supplies.<ref name="spat" />

== Geology ==

Much of the Guéra massif consists of '''crystalline basement rock'''. Nouradine's regional hydrogeological work describes the study area as being dominated by granitoids and metamorphic rocks.<ref name="nouradine">[https://nextcloud.aowis.org/s/tCJgPAa2G6Lws83 Haroun Nouradine, ''Évaluation des ressources en eau dans les aquifères de socle dans la région du Guéra (Tchad) : combinaison d'approches géologiques, hydrogéologiques, géophysiques, géochimiques et d'apprentissage automatique'', doctoral thesis, Sorbonne Université, 2023.]</ref>

Around Bitkine, the basement includes:

* granite;
* biotite granite;
* diorite;
* granodiorite;
* dolerite.

The lithology strongly influences groundwater productivity. Biotite granites can develop permeable weathered and fractured horizons, while alteration of diorites, granodiorites and dolerites can produce larger amounts of clay, reducing infiltration and hydraulic conductivity.<ref name="palomar" />

== Hydrogeology ==

Groundwater in Guéra does not occur as one large continuous regional aquifer. The principal groundwater resources are associated with:

* weathered crystalline basement;
* fractured and fissured bedrock;
* alluvial deposits;
* sands and sediments along seasonal drainage systems.

The basement aquifers are therefore '''heterogeneous and discontinuous'''. Two boreholes located relatively close to one another can encounter substantially different conditions.

A simplified basement-aquifer structure consists of:

# superficial material and soil;
# weathered basement, or '''alterites''';
# a fractured basement horizon;
# progressively less fractured competent bedrock at greater depth.

The weathered horizon can provide substantial groundwater storage. Hydraulic transmissivity is often associated particularly with the upper fractured basement beneath it.<ref name="nouradine" />

Nouradine's regional analysis found that important water inflows commonly occur at approximately '''30–60 m depth'''. Productivity generally decreases where drilling continues far into relatively unfractured basement.<ref name="nouradine" />

Groundwater occurrence and borehole productivity depend on the combined effects of:

* lithology;
* thickness and permeability of the weathered zone;
* development of the fractured horizon;
* geomorphology;
* recharge conditions;
* local drainage;
* position within the landscape.

Low-lying areas and locations favourable to infiltration and recharge can provide substantially better groundwater conditions than nearby elevated or poorly weathered basement.

== Borehole productivity ==

Obtaining productive boreholes is a major difficulty in Guéra.

Data analysed for boreholes constructed between 2010 and 2016 show that, among '''137 boreholes''' considered by the SEVES study:

* '''47%''' were unsuccessful during drilling and were not equipped;
* '''42%''' produced too little water for connection to an AEP water-supply network;
* only '''11%''' provided an exploitable yield of approximately '''4 m³/h for 8 hours per day'''.<ref name="palomar" />

The broader dataset analysed by Nouradine contains technical information from '''798 boreholes''', together with approximately '''700 EM34 profiles''' and '''592 electrical-resistivity tomography profiles'''.<ref name="nouradine" /><ref name="article">[https://doi.org/10.1007/s10040-024-02766-2 H. Nouradine et al., ''Integrating geological, hydrogeological and geophysical data to identify groundwater resources in granitic basement areas (Guéra Massif, Chad)'', Hydrogeology Journal 32, 759–784, 2024.]</ref>

The mean borehole yield in the analysed basement-aquifer dataset is approximately '''1 m³/h'''. More productive boreholes are associated particularly with well-developed weathered and fractured horizons and favourable granite or biotite-granite formations.<ref name="nouradine" />

The difficulty is therefore not simply drilling deep enough. Successful groundwater development requires identifying favourable combinations of geology, weathering, fractures, topography and recharge.

== Groundwater recharge ==

Recharge is closely linked to the short rainy season.

Direct infiltration across exposed or poorly permeable uplands can be limited, while runoff concentrates water in lower terrain, seasonal drainage channels, alluvial deposits and favourable fractured zones.

The strongly seasonal rainfall regime means groundwater recharge can vary substantially between years. Quantifying long-term recharge remains an important uncertainty for sustainable groundwater development in Guéra.<ref name="palomar" />

Groundwater availability must therefore be evaluated not only in terms of instantaneous borehole yield, but also in terms of seasonal variation and sustainable long-term abstraction.

== Groundwater quality ==

Regional groundwater studies generally describe Guéra groundwater as relatively weakly mineralised compared with strongly saline groundwater systems elsewhere in Chad.

Earlier regional studies cited by Nouradine reported dissolved mineral content generally below approximately '''250 mg/L''', with bicarbonate-dominated groundwater and relatively low chloride and sulfate concentrations.<ref name="nouradine" />

More recent geochemical work by Nouradine analysed '''211 groundwater samples''', principally in and around the Mongo study area. Electrical conductivity ranged from approximately '''83 to 1,183 µS/cm''', with an overall mean of approximately '''427 µS/cm'''.<ref name="nouradine" />

Mineralisation increases in some deeper or fractured groundwater systems. Mean conductivity in the study was approximately:

{| class="wikitable"
! Water source
! Mean electrical conductivity
|-
| Shallow rural wells
| ~175 µS/cm
|-
| Rural boreholes in fractured basement
| ~445 µS/cm
|-
| Urban boreholes in fractured basement
| ~526 µS/cm
|-
| Wells intersecting both weathered and fractured horizons
| ~677 µS/cm
|}

These figures describe the sampled areas around Mongo and should '''not''' be assumed to represent every groundwater body in Guéra.

Local groundwater chemistry can vary strongly because individual boreholes may intercept different weathered zones, fracture systems and groundwater residence times.

=== Local salinity ===

Saline or noticeably mineralised boreholes occur locally in the Guéra region, including around Bitkine.

AOWIS field observations around Bitkine indicate substantial local variation in water quality, with potable and saline groundwater occurring within the same general area. Some saline wells are unsuitable for drinking but remain in use for washing, construction, irrigation or other non-potable purposes.

This local variability is consistent with the discontinuous fractured-basement hydrogeology of the area. Salinity at one borehole does not establish that neighbouring groundwater will have the same composition.

Electrical conductivity, TDS and full chemical analysis should therefore be measured individually for each water point before treatment requirements or desalination systems are designed.

== Bitkine and Abtouyour ==

[[Regions:Chad/Guéra/Bitkine|Bitkine]] is the capital of the Abtouyour department and one of the main current areas of groundwater investigation in Guéra.

The 2023–2024 work carried out by SEVES, UMR METIS of Sorbonne Université and ANTEA concentrated specifically on the Bitkine area. Pierre Palomar reinterpreted '''61 existing electrical-resistivity tomography surveys''' and associated borehole information to develop a local hydrogeological model and improve future borehole siting.<ref name="palomar" />

The work builds directly on Nouradine's regional research, which had concentrated particularly on the Mongo and Barlo areas.

The Bitkine study found that geology and weathering pattern are critical to borehole performance and that geophysical anomalies cannot be interpreted reliably as fractures without considering the geological and geomorphological context.<ref name="palomar" />

A dedicated page covers the local conditions and water-supply work:

:'''[[Regions:Chad/Guéra/Bitkine]]'''

== Water supply ==

Much of Guéra depends on boreholes, hand-pumped wells and small piped drinking-water systems.

The combination of low borehole yields, high drilling failure rates, seasonal demand and uncertain recharge makes reliable water supply difficult, particularly during the dry season.

The provincial development plan reported substantial deficits in both rural hand-pump coverage and piped AEP systems.<ref name="spat" />

In the Bitkine area, '''SEVES''' and its Chadian partner '''ADES''' have been working with the Commune of Bitkine and the regional water authorities through the '''REAVIA''' programme.

Recent groundwater-development work reported by SEVES included:

* a new borehole at Bitkine producing approximately '''6 m³/h''';
* rehabilitation of a borehole at Koubo Adougoul producing approximately '''4 m³/h''';
* a new borehole at Koubo Adougoul producing approximately '''7 m³/h'''.<ref name="reavia">[https://www.asso-seves.org/tchad-mobilisation-de-la-ressource-en-eau-pour-les-services-d-eau-potable-de.html SEVES, ''Mobilisation de la ressource en eau pour les services d'eau potable de Bitkine et Koubo Adougoul dans la province du Guéra — REAVIA''.]</ref>

These yields are high relative to many of the boreholes represented in the regional datasets.

== Hydrogeological research ==

Recent groundwater research in Guéra has produced an unusually large combined hydrogeological and geophysical dataset for a crystalline-basement region.

=== Nouradine 2023 ===

Haroun Nouradine's doctoral research combined:

* geological analysis;
* hydrogeology;
* electrical geophysics;
* groundwater chemistry;
* stable isotopes;
* piezometric monitoring;
* machine learning.

The underlying datasets include:

* 798 boreholes;
* 700 EM34 profiles;
* 592 electrical-resistivity tomography profiles;
* 211 geochemical and isotopic groundwater samples.

The work established a conceptual model of Guéra's crystalline-basement aquifers and identified factors controlling borehole productivity.<ref name="nouradine" />

'''Full thesis:'''
:[https://nextcloud.aowis.org/s/tCJgPAa2G6Lws83 ''Évaluation des ressources en eau dans les aquifères de socle dans la région du Guéra (Tchad)'', Haroun Nouradine, 2023]

=== Palomar / SEVES 2024 ===

Pierre Palomar's study, carried out within SEVES in collaboration with Sorbonne Université's UMR METIS and ANTEA, applies the regional hydrogeological model specifically to the Bitkine area.

It includes:

* a review of basement-aquifer hydrogeology;
* evaluation of geophysical prospecting methods;
* reinterpretation of existing ERT surveys;
* comparison with borehole results;
* a hydrogeological conceptual model for the Bitkine area;
* recommendations for future groundwater prospecting and borehole siting.

'''Full report:'''
:[https://nextcloud.aowis.org/s/j7Gy7bMrFr5Gsew ''Conceptualisation hydrogéologique et recommandations pour les prospections géophysiques et l'implantation des forages — Province du Guéra, Tchad'', Pierre Palomar / SEVES, 2024]

== AOWIS work ==

Guéra is a current AOWIS field region, with initial work concentrated around [[Regions:Chad/Guéra/Bitkine|Bitkine]].

Current work includes documentation of existing water points, seasonal borehole yields, water quality, groundwater salinity, opportunities for cooperation between existing well operators, and options for additional storage, treatment and distribution infrastructure.

The combination of highly variable groundwater productivity and local differences in groundwater chemistry makes the region particularly relevant to integrated water-resource monitoring and planning.

== References ==

<references />

== External resources ==

* [https://nextcloud.aowis.org/s/tCJgPAa2G6Lws83 Nouradine 2023 doctoral thesis — AOWIS-hosted PDF]
* [https://nextcloud.aowis.org/s/j7Gy7bMrFr5Gsew Palomar / SEVES Guéra and Bitkine hydrogeology report — AOWIS-hosted PDF]
* [https://doi.org/10.1007/s10040-024-02766-2 Nouradine et al. 2024 — Hydrogeology Journal]
* [https://www.asso-seves.org/implantation-des-forages-dans-la-province-du-guera-autchad.html SEVES — hydrogeology and borehole siting in Guéra]
* [https://apef-conservation.org/ressources-documentaires/ Schéma Provincial d'Aménagement du Territoire du Guéra 2022–2032]

[[Category:Chad]]
[[Category:Guéra]]
[[Category:Groundwater]]
[[Category:Hydrogeology]]
[[Category:Water supply]]