Commentary: Society must learn from its mistakesBy Dr. Lulseged Ayalew, Germany; July 23, 2000It was not long ago when radio Ethiopia reported that the managers of the Koka and Melka Wakena hydroelectric power-generating stations disclosed that the silt accumulated in the reservoirs since the two dams went operational has now reached a "critical stage". This normally means there is a shortage of water, and then there was a need to go to the power rationing system. In the last few weeks, a series of critiques appeared in Ethiopian press and most citizens express their disappointment on Ethiopian Electric and Power Corporation. Where does the problem lie? Why the people is suffering a lot? And how many of us really know that the problem is the sign of poor system of engineering? Hey, by the way, is there any concrete solution? Let's see these questions one by one. First of all, silt is accumulated as a result of siltation. Siltation is the process whereby fine particles of sand, mud and other material picked up by moving water are deposited to form a sediment. In engineering, siltation is generally considered as the most common problem, or to put it in another way, as the "cancer" of dams because it largely determines the lifetime of a certain project. Its effect actually varies from area to area. Dams in tropical areas where rivers are rich in silt are more affected by siltation than those in temperate zones. The Nile River is among the most silt-laden rivers in the world. Our Blue Nile specially carries every year about 1.285 billion tons of soil to the Mediterranean Sea. Siltation is closely related with deforestation and soil erosion. It is known that deforestation dramatically increases the risk of flooding. Soil erosion not only deprives the area of nutrition and deteriorates the quality of the land, but also silts up dams and dykes, elevates the river bed and, therefore, the water level, and aggravate flood devastation. When the catchment area of a river is heavily forested, the elaborate root system of the trees acts as a vast sponge which soaks up rainfall, releasing it only very slowly to the river below and subject the area to minimum erosion. Once the forest cover has been removed, however, the run-off (as a proportion of rainfall) is vastly increased. Thus, a recent UNESCO study found that, when forested, the watershed of one selected river only releases between 1 and 3 % of the total rainfall. However, once the area was deforested, between 97 and 99% will be released to the river. During periods of heavy rainfall, therefore, the volume of water carried by rivers in deforested areas can be massive and the soil becomes vulnerable to erosion. A study shows that a natural rain forest looses only 1 ton of soil per hectare to erosion. Soil losses increase to between 20 and 30 tons once the trees have been removed and the land put to cultivation. The above statements have been proved by the situation in Ethiopia. Excessive siltation has interfered not only in the case of power generation in Koka, but also in the distribution of drinking water in Addis and in fish production in many places. We all remember how water was rationed throughout Addis before the set up of the Akaki groundwater distribution network and the construction of Dire dam. If one listens to the music "Asa abelashalehu Abay dar new bete" and observe the situation of fishes in the Blue Nile River today, it is easy to understand how the habitat has been changed in the last few decades. The biologists say that unchecked siltation alters aquatic habitat and suffocates fish eggs and bottom-dwelling organisms. Aquatic insects can live in the spaces between large grains, but their habitat is destroyed when silt and sand fills in these spaces. The loss of aquatic insects over the long term adversely impacts fish and other wildlife that eat these insects. In the short term, silt can kill fish directly, destroy spawning beds, and increase water turbidity resulting in depressed photosynthetic rates. During the beginning of the last century, we heard that the forest coverage in Ethiopia was about 40%. Today only less than 3% is remaining. The forest coverage of the southern part of the country alone has decreased from 60% to 9% within the last 30 years. As a result, in the recent years, the threat of flooding of all the main rivers and their tributaries has been more often than ever. In 1997, the Metehara area was hit by a record-breaking flood of Awash River. A long-range bus has been taken away by running water just a few days ago in the same locality killing more than 50 people on board. Moreover, every year flood related natural hazards claim the life of an unknown number of people throughout the country. This all means that the environmental condition of the country has reached a critical state and there is a call for an appropriate action. Where does the problem lie? Is that there in the Menelik palace or at the grass-root level? In educational centers or in every individual's house? The answer is all of the above are correct. True, the government is highly accountable for it. In the last eight years, we have been told that we will recover the forest and plantation in just few years as if the ruling party is the "green-maker". But, the situation is still deteriorating. Because of the ever-increasing population, forests have been set ablaze in every corner of the country and cleared of vegetation for cultivation purposes. Due to the shortage of fuel and electricity, fire-woods are still the only energy source of most urban residents and almost all peasants. These days, it is quite easy for anybody to produce charcoal from the little remained government owned "protected forests" and sell it in an open market. The land-policy system is actually accountable to such kind of destruction and to other problems related to deforestation. It is like you are giving your son a house and at the same time order him not to sell it even if he starves, except the properties inside the house. The farmers are allowed to sell every organism they find on the land but not the soil itself. Is a barren-land useful for the government and the people at the end? The government has also done little in mobilizing the people to plant trees and save the beauty of our forests. If the government wants, mobilization is quite easy as it did in the fight against Eritrean incursion. Even the last regime was successful in mobilizing the people against illiteracy. Mobilizing 30 million people (excluding the children and the elderly) may mean having 30 million trees every day. We heard that this system has worked well in Tigray region. Then why not in the center, south, west and east part of the country. I think it is there that the trees could grow fast as the soils are more fertile. The "Koreta" system to vegetate lands could work well, if it starts from more fertile soils. Kebeles and educational centers could also play a major role in curbing the problem of soil erosion if they are all ready to teach the people properly. In addition, the condition of our forests will be reestablished only when individuals are ready to do something good for the country. For example, if we all are planting trees as a gift for family members, or if we plant two or more trees for every tree we cut down, then the environmental condition of our surroundings will remain the same. We must respect our environment. It is the gift of our fathers. Otherwise, crying alone when the government imposes something unusual upon us will help us very little. The answer why we are suffering a lot in this modern world is, therefore, it is because we and our government do not respect nature. True, if we are de-electrifying our cities at this time when the world is more bright and colorful, then we are either behind our time or ahead of it (if we assume that there is some sort of blackout throughout the world in the near future). Despite the devastation of forests in the surrounding of rivers, sometimes a very good engineering itself can reduce the problem of siltation in reservoirs. Not all parts of the world is vegetated, yet small or large-scale dams exist almost everywhere in the world. There is siltation in China, Australia, New Zealand, Brazil etc. The world has also witnessed the presence of large dams in these countries. Why our dams are silted up so quickly while some others are still functional elsewhere? The answer is either our dams do not have the engineering means to minimize siltation or our maintenance system after construction is poor. The science says that a dam in an area of high amount of siltation needs a structure which controls sediments from entering the reservoir. I doubt if either of our dams have these structures or any other means. I do not have an idea how much money was needed in order to construct Koka and Melaka Wekena, but for sure it was comparable with any dam of their size in the modern world with every facility there in the site. Let's see the case of Gilgel Gibe for example. Millions of dollars has been secured recently in the form of a long-term loan for this project, although millions of birr was lost from local budget since 1986. All in all, the money could guarantee the construction of a big dam of world class. Yet, the problem of siltation is even not properly addressed in the current design. We are told that the dam will be finished in 2003, and we will hear that it is silted soon after few years of service. That is how management of engineering works is functioning in our country. If we remember, following the big drought in 1986, there was a plan to dam Borkena River in Kombolcha. I heard that an order was given from the President to the Construction Minster to finish it quickly so that it is useful for irrigation. Sadly enough, the design gave no attention to the geology and hydrology of the area. And then, the dam was taken away soon after the sediment-rich river was allowed to enter the reservoir. There are many similar cases if small dams, bridges and roads are taken into consideration. I have seen a design of bridge which is inclined upward in the new asphalt project of the Weldia-Alemata road. If there is flooding, the sediment load will for sure hit the town to the left unless they build something in the middle. I can witness how it was difficult to drive through the new road which connects Mekele and Adwa during the rainy season. The senior engineer of the Ministry of Water Resources, Dr. Mohammed Ahmed, has told us in early July through WIC that it will take about 50 years before half of the newly planned Tekezie dam is silted up. It is good if that will be the case, but I do not believe it if the same manner of design is employed again. Siltation in the north is even much worse than in the south. This all is simply to say that there is a problem of engineering in almost all of our dams and other structures such as roads and bridges. This, however, does not mean that our engineers are not qualified. There are renowned professionals, and I propose even not to depend on foreign specialists. The problem completely lies there in the management. It was once rumored that these problems are purposely done, in order to allocate money continuously for maintenance and rob it without the knowledge of the people. The last question refers to if there is any concrete solution to siltation. Of course, there is always a way out. I do not like to mention the engineering solution here. But I want to stress again that the money used to be allocated in most projects is enough to store the clear and drain off the muddy water as long as we use it properly. We should draw upon local and overseas experiences and from past failures. In many cases, reservoirs became fully-silted because the designers did not take into account correctly the soil erosion and sediment transport processes at places where no soil conservation practice was introduced. Today the society expects the useful life of a reservoir to be more over 40 to 50 years. One lesson from past experience is the need to consider the dam, the reservoir and the catchment as a complete system which cannot be dissociated. A total catchment management policy must be considered from the early stage of a reservoir design. Fully-silted reservoirs stand as a source of embarrassment for scientists and the public in general. Each reservoir failure must be a valuable teaching and pedagogic tool to heighten the awareness of students, professionals and government officials. Society must learn from its mistakes, not to repeat them again! |