**2.2 Contamination of available water**

*Resources of Water*

**106**

**Figure 6.**

**Figure 5.**

*(source: World Bank database).*

In addition, pollution from agricultural production (urban farmers irrigating their crops with untreated wastewater) and industrial production has become one of the biggest challenges for Senegal's water resources [17]. In addition, because of the growing population and its corollary the increase in water needs, the lack of protection of water sources, the scarcity of the resource and the pollution it faces are a

*Urban population of three cities in Senegal: semi-annual estimates of the resident population from 1960 to 2035* 

source of hindrance improved and protected water.

*Evolution of water production by the SDE (SONES perimeter) from 1997 to 2015.*

The water sources available in Senegal are frequently affected by pollution of chemical, microbiological or thermal origin. Chemical contamination of this water, often used for drinking, can result from the presence of excess nutrients, acidification, salinity, heavy metals and organic pollutants [18]. Reports indicate that industries at 32.5% and agriculture at 14% are the sectors that contribute most to the economic development of any population [19]. On the other hand, 80% of the water contamination comes from these two important sectors. Agricultural practices, industrialization, mining, and open sewer lines parallel to the water system are responsible for most of the problems affecting water quality (**Figure 7**).

The lack of adequate management of liquid and solid waste results in the deposit of this waste directly into water bodies (**Figure 7**), which contributes to the vicious circle of water destruction. In fact, the growth and development of agriculture in Senegal has led to an increase in the use of fertilizers. Agrochemicals end up in bodies of water causing considerable pollution. In addition, most industrial water treatment plants discharge partially treated or totally untreated effluents into surface water sources, which often contain high levels of toxic substances. These pollutants and other pollutants of domestic origin continue to cause environmental problems [11]. Many Senegalese living in informal urban areas lack access to safe drinking water, often resulting in multiple epidemics that affect their health and livelihoods. In addition, large leaks in water pipes (**Figure 7**), dilapidated infrastructure and illegal connections still hinder the availability of drinking water supply. Due to the large leaks in the water channels, the treated water is sometimes contaminated before reaching the users.

#### **Figure 7.**

*Water quality degradation factors in Senegal: (1) CSS effluent discharges into Lake Guiers; (2) water line between the lake and Dakar damaged; (3) domestic uses on Falémé; (4) equipment for washing gold on the banks of the Falémé.*

### **2.3 Degradation of water sources**

The main sources of water in Senegal, beyond the groundwater, are surface water (rivers and lakes that are very attractive for agriculture and populations). The watersheds that cross the national territory have experienced two major pressures in recent years on their water resources: (a) pressures from natural sources (climate variability and change); (b) anthropogenic pressures (dams, rapid population growth and various productive activities) [3]. These pressures have had repercussions on the natural environment of the basin and its ecological diversity [20]. They have resulted in watershed degradation that has diverse and unpleasant consequences, often resulting in increased runoff, flash floods, reduced infiltration, erosion and siltation, to name just a few examples. The impacts of human activities (development, rapid population growth and various productive activities) related to the exploitation of resources for the satisfaction of the daily needs of the populations sometimes manifest themselves negatively on all the natural resources of the basin. Environmental protection of the watershed is important for the safety and sustainability of urban water supply. A healthy ecosystem ensures quality water for cities, reducing treatment costs and the danger to human health.

Activities such as gold mining are causing degradation of natural resources in the basin through reduced vegetation cover and deterioration of water quality. With the use of chemicals in the practice of this activity (leaching technique with cyanide or mercury and tailings ponds), pollution of water resources in the basin is multiplying. With the major developments (Diama and Manantali dams), flow control and water permanence in the basin have led to the partitioning of mining activities (extraction and washing with mercury release) and agricultural activities (large consumer fertilizers and pesticides) with far-reaching consequences [21]. This results in severe degradation and deterioration of animal and plant resources [22]. With this destruction of freshwater ecosystems, the Senegal River finds itself in a situation of loss of some of its functions, how important, and may alter its hydrological functioning [23].

#### **2.4 Invasive species**

Biotic factors affect water resources. For example, the presence of invasive species such as hyacinth, Salvinia, Pistia and Typha causes ecological imbalance. The proliferation of plants and invasive species in major bodies of water, including aquatic plants, is of increasing concern. Typha and algae are plants that contribute to the deterioration of the water quality of the lake because of the very toxic substances secreted that can reduce the good water quality (**Figure 8**). They degrade surface water resources and may even have contributed to the eutrophication of freshwater lake ecosystems. These invasive species block rivers and greatly influence water quality. In Senegal, built dams (such as Diama and Manantali on the Senegal River) play an important role in the reliable and sustainable supply of water. However, these developments, by permitting the permanence and softening of the water, have led to the proliferation of certain species such as Typha australis and *Pistia stratiotes* and the appearance of new species such as Potamogaton Schweinfurthis and *Ceratophyllum demersum* [24]. Overall, the country faces serious problems of resource protection.

Several environmental impacts, at the origin of the deterioration of water quality, result from the invasion of water bodies by vegetation [25]: siltation of hydraulic axes; the formation of caps with loss of hydraulicity; increased evapotranspiration; the threat to adjacent wetlands; the decrease of the dissolved oxygen level. The proliferation of macrophytes can therefore make it difficult to access water, slow down the flow of water in the canals, block the pumps.

**109**

**Figure 8.**

*lake.*

*Water Resources and Their Management in an Increasing Urban Demography: The Case…*

*DOI: http://dx.doi.org/10.5772/intechopen.90218*

**3. Interventions on the water challenges**

**3.1 Implementation of relevant policies**

Despite the water problems facing urban populations, Senegal has sufficient water resources to meet demand if available resources are properly managed [6]. Senegal's internal renewable surface water resources are estimated at 23.8 km3

*Degradation of water quality in Senegal by invasive plants: (1) Typha australis on the lake of Guiers; (2) freshwater algae in the lake water; (3) invading lake water plan; (4) degradation of the water quality of the* 

of water resources offers opportunities for exploitation ranging from surface water abstraction to the use of boreholes in areas with limited surface water resources [10].

Like many other countries, Senegal has adopted several policies at the national

and renewable groundwater resources are in the order of 3.5 km3

internal renewable water resources estimated at 25.8 km3

(SW), operating company, private operator [6, 27].

mon part between surface water and groundwater is estimated at 1.5 km3

and regional levels to guide the conservation and management of its water resources. It has put in place crucial reforms in the water sector which have led to the promulgation of certain regulatory texts and conventions, such as Law 81-13 of 4 March 1981 on the Water Code creation of various associations of water resource users [3]. Thus, in 1995, the public authorities give a very marked inflection to the organization of the sector, as well in urban as rural. Indeed, a reform of the urban water subsector was initiated through the Water Sector Project, which led to the separation of drinking water from sanitation. This reform embodied by Law No. 95-10 of 7 April 1995 resulted in the creation of two different entities that are responsible for the management of the sub-sector of urban water: the National Water Company of Senegal (SONES), a heritage company, and Senegalese Waters

/year

/year and

/year. The com-

/year [26]. The diversity

*Water Resources and Their Management in an Increasing Urban Demography: The Case… DOI: http://dx.doi.org/10.5772/intechopen.90218*

**Figure 8.**

*Resources of Water*

**2.4 Invasive species**

problems of resource protection.

down the flow of water in the canals, block the pumps.

**2.3 Degradation of water sources**

The main sources of water in Senegal, beyond the groundwater, are surface water (rivers and lakes that are very attractive for agriculture and populations). The watersheds that cross the national territory have experienced two major pressures in recent years on their water resources: (a) pressures from natural sources (climate variability and change); (b) anthropogenic pressures (dams, rapid population growth and various productive activities) [3]. These pressures have had repercussions on the natural environment of the basin and its ecological diversity [20]. They have resulted in watershed degradation that has diverse and unpleasant consequences, often resulting in increased runoff, flash floods, reduced infiltration, erosion and siltation, to name just a few examples. The impacts of human activities (development, rapid population growth and various productive activities) related to the exploitation of resources for the satisfaction of the daily needs of the populations sometimes manifest themselves negatively on all the natural resources of the basin. Environmental protection of the watershed is important for the safety and sustainability of urban water supply. A healthy ecosystem ensures quality water for

Activities such as gold mining are causing degradation of natural resources in the basin through reduced vegetation cover and deterioration of water quality. With the use of chemicals in the practice of this activity (leaching technique with cyanide or mercury and tailings ponds), pollution of water resources in the basin is multiplying. With the major developments (Diama and Manantali dams), flow control and water permanence in the basin have led to the partitioning of mining activities (extraction and washing with mercury release) and agricultural activities (large consumer fertilizers and pesticides) with far-reaching consequences [21]. This results in severe degradation and deterioration of animal and plant resources [22]. With this destruction of freshwater ecosystems, the Senegal River finds itself in a situation of loss of some of its functions, how important, and may alter its hydrological functioning [23].

Biotic factors affect water resources. For example, the presence of invasive species such as hyacinth, Salvinia, Pistia and Typha causes ecological imbalance. The proliferation of plants and invasive species in major bodies of water, including aquatic plants, is of increasing concern. Typha and algae are plants that contribute to the deterioration of the water quality of the lake because of the very toxic substances secreted that can reduce the good water quality (**Figure 8**). They degrade surface water resources and may even have contributed to the eutrophication of freshwater lake ecosystems. These invasive species block rivers and greatly influence water quality. In Senegal, built dams (such as Diama and Manantali on the Senegal River) play an important role in the reliable and sustainable supply of water. However, these developments, by permitting the permanence and softening of the water, have led to the proliferation of certain species such as Typha australis and *Pistia stratiotes* and the appearance of new species such as Potamogaton Schweinfurthis and *Ceratophyllum demersum* [24]. Overall, the country faces serious

Several environmental impacts, at the origin of the deterioration of water quality, result from the invasion of water bodies by vegetation [25]: siltation of hydraulic axes; the formation of caps with loss of hydraulicity; increased evapotranspiration; the threat to adjacent wetlands; the decrease of the dissolved oxygen level. The proliferation of macrophytes can therefore make it difficult to access water, slow

cities, reducing treatment costs and the danger to human health.

**108**

*Degradation of water quality in Senegal by invasive plants: (1) Typha australis on the lake of Guiers; (2) freshwater algae in the lake water; (3) invading lake water plan; (4) degradation of the water quality of the lake.*
