Evaluation of the expedition is finished

During the expedition in April of this year, we analysed among other things three possible locations for the construction of a year-round water supply for a village in Begu Valley in the high plateaus of Eritrea. In the meantime, we have evaluated the expedition and processed all data. The expedition report and the implementation proposal will be published shortly.

We reached the following conclusions:

 

Of all three locations, only the third exhibited an impermeable earth layer. In the other two locations, this layer might be below the depth accessible to us. An impermeable layer is essential for the storage of water, which is why we chose the third location.

The geological situation of the third location, upstream in the mountains, presents a clear limitation of the water reservoir because of its impermeable rock strata. But as the river shows here a low volume of water-storing sediments, we chose to build a sand-storage dam with a height of up to seven meters in order to increase the storage volume artificially.

 

But how does a sand-storage dam work? In a nutshell, you build the dam in stages so that during each rainfall the space behind the wall fills up with washed up large sediments while the fine sediments float along with the water. After the rainfall, you build the next section of the dam wall and retain once more the large sediments. This way, you obtain a homogeneous reservoir composed of large sediments without intermediate layers of fine sediments that would hinder it in filling completely with water.

As the construction speed depends on the frequency and distribution of rainfalls, 3.5 meters per rainy season are realistic in Eritrea. Construction will be divided into two stages and the duration of the project will be extended by one year. There is the advantage of the possibility to evaluate the first construction stage before beginning the second one and therefore incorporate this gained experience directly into the second stage of construction. The ongoing project can be optimized effectively.

A sand-storage dam during the rainy season

As pointed out earlier, the third location is situated in the mountains and therefore only accessible through an arduous path. Fetching water would involve a great physical effort, a major obstacle especially for women and children without donkeys. But the location in the mountains also offers the opportunity to use the altitude difference for the water transport. As only a water pipeline to the valley can ensure that the locals are able to use the new water source without limitations, we decided to provide the water transport to the valley. Through the altitude difference, no pumps or other high-maintenance technology are needed, an added plus for sustainability.

The last technical aspect of our project will be the repair of an already existing borehole at the second location, where we want to perform long-term measurements of its water level. These measurements will help to detect an impermeable layer that may be in a depth accessible to us, which would make it possible to determine the suitability of the location for the construction of a groundwater dam.

 

In brief, we will build a sand-storage-dam at the third location together with the water pipes leading to the valley and additionally repair an existing borehole at the second location where we will perform long-term measurements. The project will be scheduled to last two years, whereby the laying of the water pipes and the repair of the borehole will happen during the first one.

Alongside the technical aspect, the financing of the project must also be ensured.  We count on your support in order to achieve this! We will also look for further financing options like the BMZ and the NUE in order to impose the financial burden onto as many shoulders as possible.

Thank you for your interest in our project! We would appreciate if you could share our project with your friends and family!