Challenges to Clean Water in Africa

25 min

Let's begin

In its plan for the Sebeya catchment, the Rwanda Water Resources Board records a problem that shows after every heavy storm: the river runs brown with mud. Mines and erosion from hillside farms give the Sebeya "high to extremely high river sediment loads", and drinking-water and hydropower intakes "often need to shut down during periods of extreme sediment loading" (RWB, 2019). Plenty of water, but not clean water. This lesson studies the three great challenges to clean water in Africa: scarcity, pollution and silting.

Definition

Water scarcity: not having enough safe water to meet people's needs. Physical scarcity: too little water exists, e.g. in the Sahara and much of the Sahel. Economic scarcity: water exists, but money, pipes, pumps or treatment to deliver it are lacking, the more common case in tropical Africa.

1. Scarcity

Causes. Low and unreliable rainfall and droughts (the Sahel, the Horn of Africa); high evaporation; shrinking lakes and rivers (Lake Chad, Lesson 2); fast-growing towns that need more water each year; and too little investment in dams, pipes and treatment.
Effects. Long walks to fetch water, often by women and children, which takes time from school and work; water-borne diseases where people must use unsafe sources; crop failure and loss of livestock; conflict between herders and farmers over water points.

2. Pollution

Figure 6 shows where the main pollutants enter a river.

Figure 6: sources of threats to clean water in a catchment. Drawn by Ganzaa.

Sewage and solid waste from towns spread diseases such as cholera and typhoid; plastic waste blocks channels.
Industrial waste water may carry chemicals and heat.
Mining releases silt, and sometimes harmful metals or processing chemicals. RWB investigated mining concessions in Kamonyi District from 7 to 11 September 2026, checking waste water, drainage, sediment control and mine waste, and sampling water upstream and downstream (RWB, 2026). In Ghana, illegal gold mining has turned rivers brown (see the video).
Fertiliser runoff adds nutrients to lakes, causing eutrophication: algae and weeds such as water hyacinth spread, use up oxygen when they rot, and kill fish. Lake Victoria has suffered from water hyacinth.

Al Jazeera English: Ghana river pollution. Watch for how mining upstream affects people who drink the water downstream, and why treatment becomes harder and costlier.

3. Silting (siltation)

When forest and grass are removed from steep slopes, rain washes soil into streams. The silt makes water muddy and costly to treat, fills reservoirs and lakes so they hold less water, smothers fish breeding grounds, wears out turbines, and raises river beds so floods spread more easily. RWB (2019) links all of these in the Sebeya catchment: erosion from hillside agriculture and mines, sediment that shuts water and hydropower intakes, recurrent floods in Nyundo and Kanama sectors, and deforestation that "increases siltation of rivers".

Solutions

Problem	Solutions
Scarcity	Rainwater harvesting from roofs; boreholes and protected springs; small dams and reservoirs; repairing leaks; drip irrigation; sharing water fairly through catchment plans
Pollution	Sewage treatment and latrines away from water; collecting solid waste; treating factory waste water; enforcing rules for mines (RWB inspections); using fertiliser carefully; boiling or chlorinating drinking water
Silting	Terraces and contour bunds on hillsides; replanting trees on steep slopes; grass strips and protected buffer zones along rivers and lakes; sediment traps at mines; catchment management plans such as RWB's

Definition

Siltation: the build-up of fine soil (silt) carried by water in rivers, lakes and reservoirs. Eutrophication: the over-enrichment of water with nutrients, which causes algae and weeds to grow fast and oxygen to fall. Catchment management plan: a plan for using and protecting all the land and water of one catchment, e.g. RWB's Sebeya plan.

Worked example

Worked example 1: a chain of cause and effect. Using the Sebeya catchment, explain how farming on steep hillsides can cut a town's water supply.

Steep hillsides are farmed with little ground cover, and the soils erode easily.
Heavy rain washes soil into the Sebeya, giving very high sediment loads (RWB, 2019).
Water intakes cannot treat such muddy water and must shut down, and settling basins must be cleared.
So people downstream lose their water supply, and hydropower stops, even though the river is full.

Worked example

Worked example 2: eutrophication in steps. Put the stages in order and explain the last one.

Fertiliser and sewage wash into a lake.
Extra nitrates and phosphates feed algae and water weeds, which spread over the surface.
Light is cut off; plants below die.
Bacteria that decompose the dead plants use up the dissolved oxygen.
Fish suffocate: the lake loses its fishing and becomes costly to treat for drinking.

Warning

Clear water is not always safe water. Germs and dissolved chemicals are invisible. In an exam, separate water quantity (scarcity) from water quality (pollution and silt), and give a solution for each.

Tip

Three S's. Scarcity (too little), Sewage and other pollutants (too dirty), Silt (too muddy). For each, give a cause, an effect, a named example and a solution.

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Practice

Distinguish between physical and economic water scarcity, with an example of each.
Give three sources of water pollution shown in Figure 6.
Describe the stages of eutrophication.
State two effects of siltation on a reservoir used for HEP.
Using the Sebeya case, explain why a full river can still leave people without water.
Suggest three measures that would reduce silt entering the Sebeya.
Evaluate rainwater harvesting as a solution to water scarcity in rural Rwanda.

Show answersHide answers

Physical: not enough water exists, e.g. the Sahara or northern Niger. Economic: water exists but the means to supply safe water (money, pipes, treatment) are lacking, e.g. many rural areas in the tropics.
Any three: hillside erosion (silt); mining (silt, metals); town sewage and plastic; factory waste water; fertiliser runoff; runoff from cleared slopes.
Nutrients enter the water → algae and weeds grow fast → light is blocked, plants die → decomposing bacteria use up oxygen → fish die.
Any two: it fills the reservoir, so less water is stored; it wears turbines and blocks intakes; operations stop for cleaning.
The water carries so much sediment from mines and eroding hillsides that intakes for drinking water and hydropower must shut down (RWB, 2019).
Any three: terraces on hillside farms; replanting trees on steep slopes; grass strips and protected buffer zones along the river; sediment-control basins at mines; enforcing RWB rules.
Strengths: cheap, close to home, uses Rwanda's two rainy seasons, reduces runoff and erosion. Weaknesses: tanks cost money; storage runs out in the long dry season; water must be kept covered and clean. A good answer judges it a valuable supplement to springs and piped water, not a full solution.

11. Scarcity

22. Pollution

33. Silting (siltation)

4Solutions

1. Scarcity

2. Pollution

3. Silting (siltation)

Solutions