A visit to all the localities affected by the project shows that access to drinking water is made difficult by the lack of hydraulic structures. The purpose of this visit was to:

For the 2020-2021 school year, the municipality has:

Health infrastructure is increasing and modernizing, thus reducing the mortality rate at the commune level [9] .

Most of the health infrastructures are located on the Cabrousse-Diembéring axis; the islands are less provided with them. Details are given in Table 1 .

Tourism is the largest source of revenue for the town, the town officially has seventeen (17) hotels (including Club Med based in Cap Skirring since 1973), nineteen (19) inns and camps, twelve (12) bars-restaurants, the majority of which are located in Cap Skirring, guest houses, four (04) travel agencies, an eco-park, etc. [10]

Although it is surrounded by water, the municipality of Diembering lacks drinking water, especially on the islands. Many households use rainwater retention cisterns or get their supplies (buy) from 20-litre cans, despite the presence of SODECA (Casamançaise bottling company) with its brand of mineral water “La Casamançaise”, sold everywhere in Senegal [11] .

The current state of drinking water distribution equipment is illustrated by Figures 1-4 .

These figures show how the supply of drinking water poses many difficulties in the municipality. In addition, the situation is more critical in the islands which are faced with a dilemma [12] :

A subdivision of the project area into sectors has been made. This subdivision meets a double criterion: geographical and hydraulic [13] .

Consequently, the type of network adapting to this situation is therefore a Multi-Village Water Supply (AEMV). [14]

The estimation method used is geometric growth due to the young and growing population. The growth rate is proportional to the population.

$Pn=P_0\left(1+\tau \right)n$(1)

with:

P: Future population by 2040 (Hbt)

P₀: Current population (Hbt)

n: Number of years separating the reference year at the considered horizon

τ: Average annual population growth rate in (%)

The growth rate of the municipality is 2.66% ( Table 2 ).

It was done on the basis of the population at the project horizon, taking into account domestic and social needs.

The specific consumption per inhabitant is estimated at 27 litres/day

$\text{Q\_domestique}=\text{C\_s}*\text{Pop}$(2)

Table 3 illustrates the estimate of domestic needs over the project horizon.

The distribution network is sized on the basis of the hourly peak flow given by Equation (3).

$\text{Qph}=\left(\text{Djm}*\text{Cps}*\text{Cpj}\right)/\left(\eta r*24\right)*\text{Cph}$(3)

Thus, the design flow values at the project horizon are given in Table 4 [15] .

The design flows in each section are assessed on the basis of the hourly peak flows at the service points.

Thus, the specific throughput, en-route services and nodes are given by Equations (4)-(6).

$Q_s=\frac{Q_p}{{{\displaystyle \sum }}^{\text{}}Li}$(4)

Q_p: Hourly peak flow Qph (l/s)

Li: Line length (m)

Q_s: 0,003321617 l/s.m

$Q_r=Q_s*Lij$(5)

$Q_i={{\displaystyle \sum }}^{\text{}}\left(\frac{Q_{ri}}{2}\right)$(6)

The calculation of the diameters of the pipes will be done by setting an acceptable speed of 1 m/s (in the water distribution pipes, 0.6 < V < 2.5 m/s), the diameters are obtained by the formula next:

$Dth=\sqrt{\frac{4*Q}{\pi *V}}$(7)

Dth: theoretical diameter (en m)

Q: section flow rate (en m³/s)

V: speed fixed at 1 m/s

Knowing the normalized diameters of each section, the real flow velocities are obtained by Equation (8):

$V=\frac{4*Q}{\pi *D^2}$(8)

V: real speed (en m/s)

Q: section flow rate (en m³/s)

D: nominal diameter (en m)

The formula of Hazen-William which makes it possible to describe the turbulent flows of water with a relative precision is the formula adopted for the calculation of the losses of linear loads (Equation (9)).

$\Delta HL=\frac{10.675*Q^{1.852}}{C_{HW}{}^{1.852}*D^{4.87}}$(9)

Singular head losses are due to sudden changes in the flow at singularities and are illustrated by Equation (10).

$\Delta HL=K*\frac{V^2}{2g}=K\left(\frac{8*Q^2}{g*{\pi }^2*D^4}\right)$(10)

K: the head loss coefficient specific to each singularity

V: average speed

For water distribution pipes, the singular head losses represent 5 to 10% of the linear head losses.

$\Delta Hs=10\%\Delta HL$(11)

The tank volume can be determined using three (3) methods, namely the table method, the simplified method and the graphical method. The simplified method which estimates the storage capacity between 25% and 50% of the peak daily consumption with an average of 33% gives:

$\begin{array}{c}{V}_{reservoir}=Cpj\ast Djm\ast 33\%+firereserve\\ V_{reservoir}=182803{\text{m}}^3\end{array}$(12)

By referring to the usual volumes of water towers in Senegal, we obtain water towers of 200 m³.