Volta Basin Authority


This report has been compiled by the Volta International Investigation Team for the Volta Basin Authority (VBA). It provides an assessment on the future development of the Volta Basin region with due regard to the effect of an increasing number of small reservoirs and climate change.

Having consulted various articles and journals on the current situation of the Volta Basin the authors of this report gathered data on precipitation, evaporation, urban-rural population, water-use, hydro-power generation, small reservoir capacities and irrigation to develop a base-model using the Water Evaluation and Planning (WEAP) software. The base model was used to look at future scenarios where the numbers of small reservoirs are seen to grow and patterns in precipitation are expected to change. These scenarios project the base-model up to the year 2050 and focus on the impact of small reservoir development and climate change scenarios on the discharge of the Volta River and on the other water uses of the river, primarily hydro-power generation.

This report hopes to use the results of the scenarios to provide the Volta Basin Authority recommendations on how it should act on the development of small reservoirs in the basin. It also hopes to be able to convince the VBA that an unregulated growth of small reservoirs would be detrimental to the hydro-power generation capacities of the lake Volta which are already under stress. Preliminary results from the software indicate that the rate of the population growth will be a much bigger factor in effecting the discharge of the Volta River and other uses of the river. Small reservoirs are simply a tool in aiding the collection and use of rain water in the region and the existence of a growing number of these does not contribute to an additional decrease in the discharge of the Volta River. While there will be an increasing rate of decrease in the discharge, it will be caused by the increasing growth in population and the resultant increase in the demand for water instead of resulting from the construction of another small reservoir. And the ensuing decrease in the discharge will result in major losses in hydro power generation capacity in Akosombo Dam.

The changing climate will contribute further to the decrease in the discharge of Volta River with a greater impact on the seasonal amounts of precipitation within a year as opposed to changes in the overall total amount of rainfall in a year. Rainfalls are predicted to become more intense and last for shorter durations hence greatly affecting the seasonal discharge of Volta River and all its uses.

The different changes in the number of small reservoirs and the climate will lead to different consequences to the various stakeholders. Any actions by the VBA will also have an impact on them. This report will also look into all of the various stakeholders affected by the scenarios and the actions taken by the government to control any adverse effects in the future. The information will allow the VBA to obtain a greater insight into the effects of their decisions on the common man and the environment.


The Volta basin lies in West-Africa where water scarcity in the region is an increasing concern. The region is dependent on hydropower for power generation and several hydropower dams have been build over the years of which the Akosombo dam is the most important.

A decrease in river discharge will lead to decreased power generation. This paper examines how and if climate change and the construction of small reservoirs will influence the river discharge. Small reservoirs are built to provide irrigation water and hence, the water availability for agricultural and domestic use is also examined.

It was found that the influence of the construction of small reservoirs on the discharge of the Volta river is minimal, however, the predicted overall decrease of rainfall over the next 50 years will significantly lower the amount of hydropower generation along with an ever increasing demand of water from the river due to the significant increase in population.

It is expected that the Volta river basin area will have to deal with increasing water shortages in the future leading to conflicts of interests between different stakeholders in the area.

Some of the measures that the Volta Basin Authority will need to take to deal with the issue of increasing water shortage which include:

1. trying to limit population growth,

2. more efficient irrigation,

3. use crops that are less water intensive,

4. find alternate means of power generation and,

5. stimulate water and power saving.

Chapter 1 Introduction

The Volta river basin lies in West Africa. Water resources in the area are coming under stress due to climate change and population growth. Several hydropower dams have been built in the area of which the Akosombo dam is the most significant. A decrease of the river flow due to possible climate change and perhaps the construction of small reservoirs for irrigation upstream of the dam will lead to less water in the Volta river for power generation. While changes in the climate are somewhat difficult to control, the use and development of small reservoirs can be curtailed, however, the reservoirs are important for growth of agricultural production and thus for economic growth.

The purpose of this report is to investigate the future influence of climate change and the construction of small reservoirs on the river discharge in the Volta river and on availability of water in general. This is done with the help of a model constructed in the Water Evaluation and Planning (WEAP) software. This is followed by a stakeholder analysis to identify important actors involved and to analyse how they are influenced by the problem.

Chapter 2 will give an overview of the current situation in the Volta river basin while Chapter 3 will describe the stake holder analysis. Chapter 4 will describe the specification of the model and modelling choices made and Chapter 5 will describe the various scenarios programmed into the WEAP model while chapter 6 will present the results of the various scenarios. Chapter 7 will give the conclusions and recommendations and finally, chapter 8 will include the limitations of the entire study conducted by our team in particular and the scope of applicability of integrated water management in general and its relevance for this case.

Chapter 2 Description of the current situation

This chapter gives a short introduction to the current situation in the Volta river basin. The information in this chapter has been compiled from more detailed information, all of which has been included in Appendix A with a detailed list of references. A separate part of the document at the end includes all the references used in the various chapters.

2.1 Population

The Volta Basin is spread across 73% of the total land surface in Ghana, and about 60% of Burkina Faso. Therefore, in the analysis of the population characteristics along with other data discussed in the following parts of this report, there will be a major focus placed on the two major riparian states of the Volta Basin.

The Volta Basin is one of the densest parts of Sub-Saharan Africa (SSA) with 90 inhabitants per km² in Ghana which is roughly three times the mean population density of the rest of the SSA. The per capita incomes of Volta Basin countries are generally lower than their counterparts in SSA although, Ghana, at USD 447, appears somewhat more prosperous when income is evaluated in Purchasing Power Parity (PPP) terms (USD 1,940). Much of Ghana's affluence is located in urbanized regions in the south, which lie outside the Volta Basin boundaries (<http://esa.un.org/unpp/index.asp>).

Today, 70% to 90% of the population in the Volta Basin depends on farming for meeting their own needs. Agricultural productivity is low in comparison to other regions in the world. Small scale irrigation schemes, established by small and medium sized farmers, are developing rapidly which places the agricultural sector increasingly in competition with the power generation sector(<http://esa.un.org/unpp/index.asp>).

The population of Ghana in 2003 was estimated by the United Nations at 20,922,000, which placed it at the 50th position in the population rankings with 193 nations of the world. According to the UN, the annual population growth rate for 2000–2005 is 2.17%, with the projected population for the year 2015 at 26,359,000. It was also estimated by the Population Reference Bureau that 38% of the population lived in urban areas in 2001. The growth rates of the population are different between urban and rural settings. The population in the rural area is expected to grow at a much less rate than the urban population. This is mainly due to rural emigration towards regions with increasing standards of living.

In Burkina Faso, the population growth rate between 2000 and 2005 was recorded at 3.27%, and for the years between 2005 and 2010 it was estimated at 3.39% and expected to rise to 5%. With these estimations the population in Burkina Faso in 2050 is expected to reach 80 million people. Although, in 2000 the population of Burkina Faso was only at 11 million, it is expected to surpass Ghana's population in 2050 due to higher predicted population growth rates(<http://esa.un.org/unpp/index.asp>; <http://www.nationsencyclopedia.com/Africa/Ghana-AGRICULTURE.html>)

2.2 Land use

Ghana produces a great variety of crops, mainly cocoa, cassava, maize, shorgum, plantain, yam, oranges and millet. About 85% of all agricultural land holders in Ghana are small scale operators who primarily farm with hand tools. The Ministry of Food and Agriculture in Ghana estimates that Ghanian agriculture may be operating at only 20% of its full potential. This leaves a lot of room for technological improvements in agricultural methods thereby considerably increasing its food production(<http://www.infoplease.com/ce6/world/A0857071.html>; Congress).

80% of the labour force in Burkina Faso is employed in the agriculture sector. The main crops here are shorgum, millet, maize, groundnuts and cotton. And like Ghana, Burkina Faso is also not self-sufficient in its production of food. Government attempts to modernize the agricultural sector have met with some success, especially with cotton, whose export accounted for 36% of total exports in 2001. In 1999, about 85% of the 136,000 tons of cotton produced was exported(<http://www.infoplease.com/ce6/world/A0857071.html>)

2.3 Climate

The climate of Ghana, as the rest of tropical West Africa is dominated by the movement of the Inter Tropical Convergence Zone (ITCZ) which is the region where the hot, dry and dust harmattan air mass from the Sahara in the North meets the cool, moist monsoon air from the South Atlantic. It has been observed that there has been a clear declining rainfall trend since the 1970s in both the forest and savannah zones of West Africa (Aka et al., 1996; Paturel et al., Opoku-Ankomah and Amisigo, 1998). Significant rainfall reductions of 19.3%, 20.6%, 20.2%, and 23.9% have been recorded at Kumasi, Sekondi/Takoradi, Accra, and Koforidua, respectively(Andreini et al., 2000).

Potential evapotranspiration in the basin also varies both spatially and temporally with an annual mean varying from 2500 mm in the north of the basin to 1800 mm in the coastal zone. Mean monthly potential evapotranspiration exceeds mean monthly rainfall for most of the year for the entire basin (Amisigo, 2005). In addition, when rain comes, it often comes in the form of thunderstorms. Rainfall intensities often exceed the soil's infiltration rates causing surface runoff, without replenishing soil moisture and groundwater (Liebe et. al., 2005). The onset of the rainy season is especially unpredictable. From an agronomic point of view, rainfall in the region can only be characterized as unreliable (Van de Giesen et al., 2001). (<http://www.infoplease.com/ce6/world/A0857071.html>; C. Leemhuis1 et al., 2009).

Generally, the mean temperature never falls below 25oC in the country. This is explained by the fact that no part of the country is really far from the equator. The hottest month of the year is March-April and the coolest is August. There is a variation of 5-6oC in the south and 7-9oC in the north(C. Leemhuis1 et al., 2009).

2.4 Small reservoirs

The presence of small reservoirs is vital for the semi arid regions in northern Ghana in which about one million inhabitants are living. These people are largely dependent on rain fed agriculture, livestock rearing, and to some extent, fisheries, dry season gardening and irrigation farming. Irrespective of this the upper east of the country has only three months of monomodal rainy season which occurs mostly as thunderstorms. The rainfall intensity often exceeds the infiltration capacity of the soil which leads to the surface runoff without replenishing the soil moisture and groundwater. The inhabitants store water from the runoff of the rainy season in a small reservoir to satisfy their needs for water for agriculture and home use. In addition the reservoir serves also as a mechanism for flash flood protection. There are more than 500 multipurpose reservoirs which were built for the past 50 years following the drought which occurred in 1980s which made the country suffer from water scarcity, food shortage and hunger.

The locations of the reservoirs are such that they are not affected by other reservoirs in the near vicinity. Thus, little consideration has been given to their collective impact on the natural environment and livelihoods of the local population in the long term. The reservoirs also suffer from a dearth of information regarding their design, capacity, operational schedule and structural conditions. (<http://www.glowa-volta.de/results_energy_modeling.html>; Andreini et al., 2000; Birner et al., 2005a; C. Leemhuis1 et al., 2009).

In Burkina Faso there are about 1053 small and medium reservoirs. Most of them were constructed during the drought which occurred in the early eighties. The level of water in the reservoirs is highly variable. The Institute for Water and Environmental Engineering in Burkina Faso reports the total maximum storage volume of all registered small and medium scale reservoirs to be about to 670×106 m3. Ghana has not yet determined the amount of water stored in the reservoir, however, it has been estimated using rough storage volume approximations.

Using applied storage calculation, the total maximum storage volume of small and medium reservoirs located in the Volta Basin of Ghana amounts to 120×106 m3(<http://www.glowa-volta.de/results_energy_modeling.html>).

2.5 Power generation

Ghana's first hydro plant, the Akosombo Generating Station in the Eastern Region started producing 588MW of power in 1965 from four generating units. The plant was formally commissioned by Ghana's first President, Osagyefo Dr. Kwame Nkrumah, in January 1966. In 1972, two additional generation units of 324 MW capacity were commissioned to bring Akosombo's total installed capacity to 912 MW. In 1982, a second hydro generating station was commissioned on the Volta River at Kpong, also in the Eastern Region. This added another 160 MW capacity to bring the total installed hydro generation capacity to the current level of 1,072 MW(<http://library.thinkquest.org/J002335/Ghana/Ghana.html>; Youkhana et al., 2006)

Ghana's demand for electricity has outstripped the capacity of the two hydro generation systems. The shortfall in demand has therefore been met through the development of thermal power systems. A 330 MW Combined Cycle Thermal Plant was commissioned at Aboadze near Takoradi in 1999. This was followed by the addition of a further 220 MW of simple cycle plant at the same site in 2000. The gradual development of the power sector also lead to the realization of the need for a governing authority to plan and manage the power demand and supply of the country. Hence, the Volta River Authority, VRA, was created in 1961 by an act of parliament (the Volta River Development Act 46)(<http://bch-cbd.naturalsciences.be/burkina/bf-eng/implementation/doc/monography/chap2-5.htm>; FAO, 2004).

Chapter 3 Stakeholder analysis

The Volta Basin Authority is one of the main stakeholders in this study. The VBA is established by the following six West African countries, that have territory inside the Volta Basing:

* Ghana

* Burkina Faso

* Cote d'Ivoir

* Mali

* Benin

* Togo(Charles and Atikpo, 2008)

Table 3.1 water resource of different countries

3.1 Problem formulation

The objective of this project is to identify the impact of the development of small reservoirs for irrigation in combination with the effects of climate change, for the area of Volta basin, taking into consideration every one of the stakeholders that might be affected by the change in water resources.

Besides, the relations between stakeholders and water resources have to be investigated, and also the goals and interests that might be covered in 2050 with the construction of the small reservoirs.

3.2 Inventory of stakeholders

3.2.1 Volta Basin Authority (VBA)

The Volta Basin Authority is one of the main stakeholders in this study. The VBA is established by the following six West African countries, that have territory inside the Volta Basin:

* Ghana

* Burkina Faso

* Cote d'Ivoir

* Mali

* Benin

* Togo

The most important objectives of the VBA are:

1. “Organize and reinforce consultations among the riparian countries and also between these riparian countries.

2. Mobilize human, technical, and financial resources necessary for undertaking studies, research activities and works aimed at sustainable management of water resources.

3. Coordinate studies, research activities and works initiated in the basin for the development of the water resources of the basin.

4. Create and or improve the tools and networks for the collection, processing, storage and dissemination of data and information;

5. Develop and implement institutional mechanisms and tools for monitoring, evaluation and planning for an efficient and sustainable management of the water resources.

6. Promote cooperation between the Authority and other similar regional and international organisations.” (Barry et al., 2005a).

The VBA has a mandate to:

1. “Promote permanent consultation tools among the parties for the development of the basin;

2. Promote the implementation of IWRM (Integrated Water Recources Management) and the equitable distribution of the benefits resulting from their various utilizations;

3. Authorize the development of infrastructure and projects planned by the stakeholders and which could have substantial impact on the water resources of the basin;

4. Develop joint projects and works;

5. Contribute to poverty alleviation, the sustainable development of the Parties in the Volta basin, and for better socioeconomic integration in the sub-region.”

The permanent administrative organs of the Authority are:

1. “The Assembly of Heads of State and Government

2. The Council of Ministers in charge of Water Resources

3. The Forum of the Parties involved in the Volta basin development

4. The Committee of Experts

5. The Executive Directorate of the Authority” (Eric and Yankah, 1999)

3.2.2 The Volta River Authority

The VRA is a state-owned organization that is responsible for generation and transmission of electricity. The VRA operates the hydroelectric plants of the Akosombo and Kpong dam.

The organizations that are responsible for the distribution of the electricity are the Electricity Company of Ghana (ECG) and the Northern Electrification Department (NED). The second one is only responsible for distribution in the northern part of Ghana.

In order to meet the demands of energy consumption the dams must operate the entire year. For a fully operating hydro electric plant the water in the reservoirs must meet the demands of a minimal height. In the wet season the reservoir is refilled with a water surplus of the river, but in the dry season the water depth can be critical. This is a consequence of evaporation and the production of electricity.

The Authority is also responsible for safe-guarding the health and socio-economic well being of the inhabitants of the communities alongside the lake, and management of any incidental issues including maintenance of the environment. (Birner et al., 2005b)

3.2.3 Urban Population

As we established in the Population and Land Use Chapter, there are many cities in the Volta Basin that are largely populated, like Accra, Kumasi and Tamale. As all developing countries, residents of Volta Basin are expected to grow in number and influence so water and electricity demand for urban areas will grow.

The goals for this stakeholder come from people needs. In future years it would be necessary to extract enough water, with the adequate and hygienic sanitary system, both sewerage and discharge of rain. The urban areas are developing so the need for electricity will increase, for example for charging mobile phones and an increased use of air-conditioning systems.

3.2.4 Farmers

This stakeholder probably would be the most affected by the introduction of new small reservoirs. In Ghana almost 60% of the population works in the agriculture and in Burkina Faso this is 80%. Regarding water consumption farmers are the main Stakeholder, but industry weight is probably superior. Industry has more influence than farmers.

In Ghana, at national level, the Ministry of Food and Agriculture (MOFA) represents the interests of the farmers and development of agriculture. The Ghana Irrigation Development Authority (GIDA) is responsible for the development of hydraulic structures to improve irrigation. On local scale there is a division between agriculture land that rely on irrigation and land that are not relying on irrigation(Youkhana et al., 2006).

The focus of these organizations is:

1. “Improve irrigation to increase harvests, with the notion that this includes also a higher efficiency of irrigated water.

2. Boost the development of livestock agriculture” (<http://www.nationsencyclopedia.com/Africa/Ghana-AGRICULTURE.html>)

In Burkina Faso the ministry of agriculture, hydrology and fishery is responsible for the policy on their sector at national level. At provincial level this is the Provincial Agricultural, Hydrological and Fishery Office (DPAHRH) which is in charge of the coordination and implementation of development activities. Several other directorates work on their field.

3.2.5 Industry

Some of the important industries of Ghana are aluminium, cocoa, rubber, textiles, cement, paper, chemicals, soap, beverages, and shoes(Ghana, 2004)

The production of steel and exploiting of mines consumes one third of the total energy consumption. In particular the aluminium company (VALCO) consumes a lot of energy and water for their production. These types of industries are a major employer and their existents results not only in water and electricity consumption, but also in land use(<http://www.epa.gov.gh/index.php?option=com_content&view=article&id=46&Itemid=109>, 2009)

3.2.6 Environmental organizations

The Environmental Protection Agency (EPA) is the leading public body for protecting and improving the environment in Ghana. This is a sub-department of the ministry of Environment, science and technology of Ghana. The EPA enforces the standard on wastewater discharge and they conduct environmental impact assessments. They are also responsible for monitoring projects.

The EPA´s corporate objectives are:

1. “Create awareness to mainstream environment into the development process at the national, regional, district and community levels.

2. Ensure that the implementation of environmental policy and planning are integrated and consistent with the country's desire for effective, long-term maintenance of environmental quality.

3. Ensure environmentally sound and efficient use of both renewable and non-renewable resources in the process of national development.

4. Guide development to prevent, reduce, and as far as possible, eliminate pollution and actions that lower the quality of life.

5. To apply the legal processes in a fair, equitable manner to ensure responsible environmental behaviour in the country.” (<http://www.epa.gov.gh/index.php?option=com_content&view=article&id=46&Itemid=109>, 2009)

3.2.7 Governments

In this analysis the national governments and it's departments from the concerning countries are included. Governments are taken into account because decisions concerning small reservoirs, for example investments, have to be made by them. Although VBA must investigate solutions for the problem, the national governments are implementing the laws to achieve that solutions.

Governments are highly involved within farmers and industry since these stakeholders are the major GNP contributors. Decisions made by the governments concerning farmers and industry will have an important effect on the welfare and economy of the Volta basin region.

Volta basin CT4450|Integrated water management

3.3 Goals, Aims and Interests


Interests in small reservoir development

Goals to reach through assisting with development of reservoirs

Perceptions of present – view about current situation

Perceptions of future – stakeholders requirements in future

Reasoning for perceptions

Possibilities on participation for solving the problem

Power of the stakeholder


Improvement of living standards, welfare and economy

Provide sufficient water for all stakeholders in future

Conflict about interests, lack of foresight

Under investigation

Uncertainty towards the future

Scientific investigation of future scenarios about basin use

Decide where the water is used, what for, and authorize the development of projects.


Negative interest in reservoir development

Provide sufficient electricity

Practically enough electricity production

Less energy production, more energy demand

Increasing population pressure makes demand higher

grow of industry

possible increase of small reservoirs

Improve efficiency of energy production

Investigate other (renewable) energy sources

Control of electricity production

Urban population

Mixed interests in reservoir development

+ increased food production

- less energy production, more power outages

Sufficient water flow for electricity production

Insufficient power supply

Even less power supply, more energy demand

Growing number of small reservoirs

Decrease of electricity consumption

Pressure in water demand (drinking water, electricity). Urban inhabitants are an important part of voters.


Better living conditions caused by increased access to water for irrigation

More food production

Access to reservoir water

Small reservoir water needed for irrigation, livestock

Availability of water during dry seasons for irrigation

Food production for feeding growing population in the basin

Increasing commercial activities, trading

Assist in construction, maintenance and involvement in an organization

Most people are involved in agriculture.

Importance in economy.


Negative interest in reservoir development

Sufficient water and energy supply

Sufficient energy supply

Enough energy supply

Increasing population and energy demand, so increasing energy supply

Look for other energy sources

Improve technology

One of the most important contributers on the economy

Environmental organizations

Increase the environmental situation

Protection of environment

Undeveloped protection of the environment

Improving or start the protection of the environment

Increase of environmental pressure

International pressure


Improvement of living standards, welfare and economy

Provide sufficient resources for all stakeholders in future

Needs of the stakeholders are almost covered

Not prepared for future demands of resources

Increase of water stress, caused by increase of population and clamate change

Governments are the main decision makers

Power to decide, influence by population and international authorities

Volta basin CT4450|Integrated water management

3.4 Relations between Stakeholders

In conclusion, 1 shows what each stakeholder tries to do over the other, being this pressure or control. There are also arrows stating the main points of conflict, between urban population, industry and farmers.

3.5 Conclusions; brief overview about WEAP model results regarding stakeholders

The general trend of the results obtained from the modelling is that for the different scenarios similar conclusions came up.

Regarding power generation from Akosombo dam the trend for all four scenarios come to a decrease from 6 TWh in 2000 to 5TWh by 2050. The increasing demand and the reduction in rainfall leads to a high reduction in power production, even in the reference scenario (best case scenario for power production).

Climate change scenarios A and B do not have major influence on the power generation but climate scenario C has a negative impact.

In reference to unmet demand, there are no major differences between the unmet water demand among the different scenarios. Hence it can be concluded that small reservoirs do not have major effect on the unmet water demand. Similar as mentioned above, climate scenario A and B

These results were not expected as reservoirs were supposed to solve some of the problems in water demand supply.

In the models, farmers will cover part of their water demand in the early years, but the construction of small reservoirs without any government control will lead to higher unmet demands by 2050.

Industry will get the worst effects of reservoir development, as power supply will decrease dramatically by 2050. The general economical growth of Volta Basin countries is expected to be based not only on farming in next years, but also in industrial growth. The energy lack will generate a lower welfare growth, since industry will be affected by negative boundaries.

Population will be also affected by more power outages.

With this future perspective, the construction of huge amounts of store water in small reservoirs will affect the economy of Volta Basin countries in a negative way.

The recommendations of the International Volta Investigation Team (Group 5) to the VBA are:

1. Regulate the building of small reservoirs by governing the type of structures, volumes and locations of the small reservoirs.

2. Reduce leakages in the entire supply system of water in to the demand sites.

3. Build smaller dams which generate electricity or focus on getting power from other energy sources.

4. Try to control population growth through family welfare schemes.

Chapter 4 WEAP Modelling: The Base Model

4.1 Introduction

This part of the report tries to describe the base model that has been programmed in WEAP[1] for the development of various scenarios predicted for the year 2050. The base model has been chosen to represent the year 2000 since various data on the Volta Basin was readily available for this year. It will also include a description of all the simplifications made in the input of the various numerical data gathered from different resources.

This will allow the reader to gather an idea of the scope of the project and the results that the authors of this report are interested in. It will also allow for a better understanding of the various results derived from developing the different scenarios and using these to make recommendations to the members of the Volta Basin Authority.

The real case is simplified by considering only three main branches of a river and one large tributary for White Volta in the entire Volta Basin. The information used in the base model such as precipitation, measurement, catchment sizes, population was obtained from different literatures. Some simplifications have been made on some of the data. The rain gauge stations at each of the sub basin are averaged and used for the three catchment areas. The other additional data such as evaporation rate is provided based on the countries of Burkina Faso and Ghana which takes the largest share of the basin.

4.2 River Discharge

The three main branches of the river and large tributary modelled in the Volta River Basin were the Black Volta, White Volta, Red Volta and the Oti as the main branches combining their flow towards the Volta Lake. The discharge of these branches of rivers is provided from the information available on the website of the Global Data Centre(Centre). This resource allowed us to take discharge measurements from stations located all over the Volta Basin.

Instead of using data from all different gauge stations around the major rivers, the base year model is simplified by averaging data of monthly discharge around the stations and using it for Black Volta, White Volta, the Red Volta and the Oti. The number of stations used for the averaging in each river counts from 7-10. For the purpose of modelling the base year scenario only the stations with the highest average annual discharge were chosen and the data of monthly discharge were taken from these (see 41).

4.3 Catchments: Banza, Wiasi and Nasia

As shown in 1, the catchments are modelled for each sub basin as green circles. This was used to model information about rainfall in the Volta Basin and the catchment area. The information used was gathered from a Msc thesis by B.A. Amisigo(See Appendix 1)(Amisigo, 2006).

Different data about the Volta basin was provided in the literature. The annual average monthly rainfall, runoff and potential evapotranspiration series at various stations around the Volta Basin was taken from the literature and adapted on the basic model. The rainfall data for major rivers, Black Volta, White Volta and Oti are averaged for different stations for the base year 2000 and included in the model under the name of Banzo ,Wiasi and Nasia. Assuming that there is no overlap between the drainage area of different gauge stations, the catchment of the sub basin is taken as the sum of the area under each gauging stations. The drainage area of the rain gauge stations and their names used for the three sub basin, Black Volta, White Volta and Oti is shown in Table 2.1

Table 4.1: The area influenced by the rain gauge stations under each sub basin Black volta

Drainage aera

White volta

Drainage aera


Drainage aera





































4.4 Calibration of the Model

Many factors which affect the discharge of the river as well as the simulation like land use, evaporation, infiltration e.t.c is not modelled exactly as the real case. In order to correct such discrepancy, the base model data was calibrated using the catchment area till the output result from the model matches the data of the base year from the literature. The data in Table 2.1 was used as a catchment area for the first trial.

4.5 Small Reservoirs

Rainfall in the catchment area of the Volta basin occurs mostly over three months, from July to the end of August(Amisigo, 2006). Farmer use water from Small reservoirs during dry season which lasts from November to march. Besides being a means of water supply during the rainy season, the reservoirs protect the people against rainfall uncertainty. As it was estimated in phase 1 study by CPWF (CPWF-C5) there are about 1700 small reservoirs marked under the landscape of the northern Ghanaian and Southern Burkina Faso.

Small reservoirs were initially built as water holes for cattle latter the people started to use the reservoirs for different purposes such as small scale irrigation, domestic water supply for washing and limited aquaculture (CPWF-C5). Hence the data about storage capacity of small reservoir is unavailable, it is analysed and used in the modelling by considering their use in relation to the population and water demand of the above activities mentioned (Appendix 1)

Hence, under the above calculation the volume of small reservoir in Black and white Volta is estimated to be 697 and 307m3 while in Oti is 281m3.

Table 0‑1: The Number of Population in the cities and villages of the Volta Basin

Town and village dependent on the Black Volta


Town and village dependent on the White Volta


Town and village dependent on the Black Volta













Lama Kara





4.6 Demand Sites: Urban and Irrigation

The demand sites were divided into total water demand for Ghana and Burkina Faso. Under each country, the total demand was divided into different activities such as irrigation and all other types of demands which include water use for domestic purposes (Appendix 1).

4.7 Lake Volta, Akosombo Dam and Kpong Dam

Data' presented in varies literature on the capacity of lake Volta varies a little bit. In order to remain consistent with the other data , the evaporation and storage data was taken from the thesis work done by Amisigo (Amisigo, 2006). The capacity of the dam in each sub basin is provided after summing up the dams that exist in on each sub basin. Besides a minimum turbine flow of zero was assumed. The value will represent the lower limit for power generation. If there is zero turbine flow there will be no power generation. For the maximum turbine flow a highest discharge was selected from the historical data of average monthly discharge. Accordingly the data used in the model for the highest discharge.

Chapter 5 The scenario's

5.1 Small reservoirs

From the information given in the introduction and the appendix we can gather that small reservoirs are built in locations where there are not enough water supplies for irrigation from the main rivers in the Volta Basin. The development of the small reservoirs saw a dramatic increase during the droughts of the 1980s when the situation became so poor that the levels in the Volta Lake have not yet been able to recover fully.

In such conditions the majority of populations both in Ghana and Burkina Faso have begun to rely on small reservoirs to fulfill their irrigation and domestic needs. These reservoirs are obviously located in regions where water supply from the rivers is inadequate hence these reservoirs are filled solely with rain water runoff and are either completely used for their intended purposes and suffer from evaporation or both.

Keeping the nature of the small reservoirs in mind, modeling them in WEAP has to be done in a manner that it does not affect water flows in any of the major rivers. It also has to be influential in meeting the demands of the rural population of Burkina Faso and Ghana. And finally it has to represent a loss of water from Lake Volta.

In order to fulfill all of these conditions all of the rainfall catchments contributing to the flow in the Volta basin were grouped together according to their geographical location around the major rivers. Hence, each of the major rivers modeled in WEAP i.e the Black and White Volta and the Oti have their own catchments taking into account the rain falling in and around the rivers contributing to their stream flow.

Instead of complicating the model by locating separate catchments which contribute solely to the small reservoirs we use the influence from the same catchments by linking the flow from the rivers to these small reservoirs. In this way we avoid complicating the model and remove the chances of double counting by adding any separate catchment data. Even if we had all the necessary data it would have been a waste of time to try and locate the different small reservoirs and try to add rainfall specifically in that region. It would not have given us better results nor would it have contributed in any other way.

The small reservoirs in the WEAP model were also linked to the irrigation demand sites in Burkina Faso and Ghana. While those demand sites were also being supplied by the rivers, the preference for the supply was given to the small reservoirs. Since the irrigation sites are representing all the irrigation demands of the entire country and most of the water from the small reservoirs are always utilized in real life; this is not an incorrect simplification.

The biggest facility that this manner of modeling brings with it is that it directly links the volume capacity of the small reservoirs to the storage levels in Lake Volta and thus the power generation capacity.

Some of the data being used is as follows (see appendix):

1. Population growth in Rural Burkina Faso: 3.3%

2. Population growth in Urban Burkina Faso: 6.2%

3. Population growth in Rural Ghana: 2.2%

4. Population growth in Urban Ghana: 4.2%

5. Storage Capacity of combined small reservoirs in Burkina Faso: 670 million m3

6. Storage Capacity of combined small reservoirs in Ghana: 120 million m3

For the scenarios the growth rates of the rural parts carried more importance.

5.1.1 Scenario A

This was our reference scenario in WEAP. The only change between the year 2000 and 2015 was the population in the rural areas i.e. the increasing demand for irrigation from small reservoirs. It is important to note that factors related to climate i.e. precipitation in the Volta basin region was also kept constant.

5.1.2 Scenario B

In this scenario the population growth rates were the same as above while the number of small reservoirs in Burkina Faso i.e. the total capacity of storage for all the small reservoirs in the region was increased while keeping everything else the same as Scenario A. The increase was modeled such that the total volume storage increased linearly from the year 2000 to 1340 million m3 in 2050 i.e. a doubling of the total volume in 50 years.

5.1.3 Scenario C

This scenario saw a doubling of the storage capacity of small reservoirs in Ghana to 240 million m3 in 2050 while keeping everything else similar to the conditions in scenario A.

5.1.4 Scenario D

In this scenario both the storage capacities of small reservoirs in Ghana and Burkina Faso were increased linearly to double their original value in 2050.

5.2 Climate change

This part describes the climate change scenario's that where made and the assumptions behind them.

Climate change can have several possibilities in the Volta region one investigation found by putting one of the IPCC scenario's in a meteorological model of the region that the yearly rainfall would increase by 5%, but that rainfall in April will decrease by 70%(Kunstmann and Jung, 2005) This means that the wet season will become shorter than.

Three types of scenario's were made.

1. Type A Decrease in rainfall in April but an increase in yearly rainfall

2. Type B : same climatologically changes different implementation in WEAP

3. Type c: Overall decrease in rain.

Type A and B describe the same climatologically conditions, however the implementation in WEAP differs. In Type A only the rainfall in the catchments was adjusted in type B also the head flow was changed.

In type C only the rainfall in the catchments was changed. The data used can be found on the accompanying cd.

Chapter 6 The Results

6.1 The results of the small reservoir scenario's

The overall results showed a similar trend in all the scenarios. Since the scope of this report was to focus on the impact of the development of small reservoirs on Hydropower production, we will begin by looking the results of the various scenarios on hydropower production at Akosombo Dam.

In general, the trend for all the scenarios is a decrease in the power generation from 6 TWh in 2000 to 5TWh by 2050. While the decrease is less for the reference scenario which only takes into account population growth, the decrease for Scenario D is the largest followed by increase in the reservoirs only in Burkina Faso.

While the downward trend was as expected, it was also expected that the difference in the rate of decrease between the reference scenario and the other would be larger since not only is the population growing but so is the storage of water in the reservoirs. After looking at the results in 1 we can see that this was not the case. Since the amount of precipitation and head flow into the rivers remained the same the total supply of water into both the cities and irrigation sites of our WEAP model did not change. With only the population i.e. demand for irrigation increasing this was first met with the supply from the small reservoirs then the rivers as would be expected in real life in places where going to rivers was a last resort. But since the overall flow into Lake Volta will decrease more from increasing losses from the irrigation demand sites and the increasing capacity of small reservoirs, the magnitude of the losses will be somewhat similar.

This can be explained by the fact that an increasing population will use more water from the rivers. The increasing population will also be using more water from the small reservoirs. But as the population increases its water consumption it also builds more small reservoirs to take more water. Since the two growths are hand in hand it implies that the trends of decrease of water stored in Lake Volta should also be close and similar. And that is what our results show.

If we now look more closely at the average monthly trends from 2000-2050 it shows us what we expect to see i.e. during the dry season between October and May the monthly average dwindle to almost zero power production. It picks up and achieves its maximum during the rainy season between June and September.

A similar trend can be seen with the monthly variation of unmet demand for the irrigation needs in the region ( 3). In general unmet demand from all demand sites is seen to increase over the next 50 years for all the scenarios ( 4). It is interesting to note that the unmet demand for the scenarios where small reservoirs are being increased show a higher ‘unmet' demand than the reference scenario. This brings out a very interesting point: although the new small reservoirs are being built to meet the challenges of a decrease in supply of water for irrigation it may in some cases have an opposite effect. The more the rainwater is stored in the Volta River Basin without adequate protection against losses from leakages and evaporation, the more of it will be wasted instead of being utilised for different purposes. This stored water which could otherwise have infiltrated the soil and joined the ground water is now being temporarily lost from the system altogether.

This brings about a very good point about whether or not small reservoirs are in themselves a solution to the problems of increasing ‘unmet' demand. If used properly and governed and controlled in a highly efficient manner then small reservoirs may be effective in their intended design. On the other hand increasing the numbers of leaking reservoirs serves only to take the highly precious and scarce water away from the users.

From this the point about leakages comes to mind. Where the unmet demand deviates from the path of the reference point we can assume that this has been caused by leakages in the small reservoirs. Once the leakages are constant over time they become a circulating part of the system again and hence the leakages go back to becoming water available for stream flow in the rivers. Hence unmet demand for reservoir scenarios joins the reference trends again.

Based on the results above we can say safely that while the increasing reservoirs do have an effect on the storage volumes in Lake Volta, the patterns that emerge are not extremely different from the general trends which arise simply from population growths. But having looked at the influence of the wet and the dry seasons on the availability of water it can be predicted that climate change scenarios especially those related to precipitation will have a much larger effect on the overall patterns of power generation and small reservoir production.

6.2 Results of the climate change scenario's

This section discusses the results of the climate change scenarios. It discusses the impact of the climate change on hydropower generation and unmet water demand.

6.2.1 Climate change and hydropower

As can be seen in 9 the hydropower generation is not affected by climate change type A (overall increase in precipitation, shorter wet season. Under that scenario only the monthly pattern of hydropower generation is influenced (see 10).

Climate type C an overall decrease in rainfall leads to a much faster decline of hydropower generation.

6.2.2 Climate change and unmet demand

Climate change type A doesn't influence the total unmet demand neither negative nor positive ( 11). It also doesn't influence the monthly pattern of unmet demand.

Climate change type C does increase the unmet demand, but not very significantly.

6.3 Climate change and small reservoirs combined
6.4 Climate change Type A

Climate change type A (an overall increase in rain, but shorter wet season) didn't influence the yearly power generation. For the small reservoirs only an increase in both Ghana and Burkina Fasso influenced yearly power generation. It led to a faster decline.

When the small reservoir scenario's are combined also the increase of small reservoirs in Burkina Fasso leads to a stronger decline in hydro power generation.

A combination of climate change type A and an increase in small reservoirs in Burkina Fasso and Ghana and Burkina Fasso also leads to a higher unmet demand.

6.4.1 Climate scenario C

Chapter 7 Conclusions and recommendations

7.1 Conclusions

In the future there will be more water shortage in the Volta region. The most important factor causing this is the rise in demand due to population growth. The construction of small reservoirs and diminishing rainfall due to climate change only play a minor role in this. The pattern of the rainfall may somewhat change over the year. It could be that the wet season becomes shorter.

The countries in the Volta basin should take overall measures to deal with this growing water shortage.

7.2 Recommendations

1. Regulate the building of small reservoirs by governing the type of structures, volumes and locations of the small reservoirs.

2. Stimulate water saving

3. Invest in efficient irrigation systems

4. Try to stimulate use of crops that need less water

5. Stimulate power saving

6. Invest in other types of electricity generation

7. Reduce leakages in the entire supply system of water in to the demand sites.

8. Build smaller dams which generate electricity.

9. Try to control population growth through family

10. More research about the possible consequences of climate change is necessary

Chapter 8 Discussion

8.1 Limitations of the modelling study

A modelling study like this always has its limitations. The time available was limited and therefore a relatively simple model was made. There were several scenario's made, but these took only two factors into account namely the development of small reservoirs and the change in rainfall patterns due to climate change. Other factors that are certainly of influence like the population growth rate weren't examine further.

Although some policy options are given in Chapter 7 none of these were actually tested in the model to see if and how effective they may be.

Even for the factors that were taken into account only a limited amount of futures can be generated and examined.

In particular climate change also cannot be examined fully. The possible changes in climate in the future are very much clouded in uncertainty. The two types of scenario's that were made were only two of the large range of possible changes to the climate in the future.

8.2 Integrated water management

According to Mitchell integrated water management can be defined in three ways, which correspond to different levels of aggregation.

The most low level consideration involves the “systematic consideration of various dimensions of water: Surface water, ground water, quantity and quality.” On this level water is considered as a system consisting of several components(Mitchell, 1990)

On the next level water can be considered as a system itself, it is also a subsystem of a larger system in which it interacts with other systems. Changes in one system have impact on the other systems. On this level the interactions between land, water and the environment are recognized(Mitchell, 1990)

On an even broader level interrelationships between the water system and socio-economic systems are taken into account. The approach on this level was recommended by the Brundtland commission(Mitchell, 1990).

The water scarcity problem in the Volta basin plays on all three levels. On the first level it is a problem of a lack of quantity or the distribution of the quantity over the year. On the second level the problem can be framed as related to land use. For agriculture the water is needed.

On the highest level the problem becomes a socio economic problem. The countries in the Volta region need water for development but amongst other social development. Although the problem is mainly a problem of water quantity it needs a broader perspective to be solved. Policy options need to be sought in the reduction of water use. These solutions lie on the higher levels.

[1] WEAP ("Water Evaluation and Planning" system) is a user-friendly software tool that takes an integrated approach to water resources planning.

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