Is Dodoma on the Brink of an Ecological Sinkhole Crisis Waiting to Implode?

Picture taken on August 26, 2018 of a sinkhole which first appeared in July after the collapse of the surface layer and grew bigger as days went by, in the village of Pinzon de Morado, municipality of Coyuca de Catalan, Guerrero State, Mexico. - The State government reported that the hole was caused by works done in a mine that operated in the area ten years ago. (Photo by FRANCISCO ROBLES / AFP) (Photo credit should read FRANCISCO ROBLES/AFP/Getty Images)

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Dodoma is the Capital City of Tanzania and is bustling with activities catalyzed by a political decision to be the Capital City of Tanzania. One of the driving reasons for choosing Dodoma to be the capital city was that her location is strategically central to the Tanzanian nation, befitting access to public services. This article explores the ecological challenges of Dodoma, previously called DODOMEA, meaning “sinking”, could live up to her former buzzword.

With the City’s over-dependence upon extracted underground water to feed a growing population, are we not drilling a sinkhole or a combination of sinkholes, which, one day, this beautiful City would sink underneath with all of its hosts and supporting infrastructures? This discourse peeks at a postulation of a sinkhole swallowing Dodoma due to underground water extraction and whether mitigating factors can be advocated to alleviate a potential human calamity of untold consequences to humanity, other living and mobile and immobile infrastructure.

Could Dodoma Dodoma precipitously sink because excessive water extraction for human use creates an underground super sinkhole that one day will collapse because it cannot support the weight over it? It is a fascinating question that demands our collective consideration.

Florida Sinkholes May Offer Lasting Lessons

Cases of sinkholes emanating from human activities are growing, and developed countries such as the US have experienced a recurrence of sinkholes swallowing huge parts of the land, which sometimes include infrastructures such as houses, roads, and bridges, among others.

The concept of sinkholes reads like a scientific movie that extrapolates futuristic events, but in this circumstance, the narratives are real and cannot be wished away. In the US, Florida epitomizes the plight of the uncontrolled sinking of boreholes leading into huge spaces underground that sometimes are incapable of carrying the weight above them, resulting in a sinkhole. Cases of houses with people and cars inside being swallowed by the sinkholes are growing. Parts of roads being destroyed by sinkholes are also on the ascendant.

The question geologists have been mulling over is what causes sinkholes and whether remedial measures exist to contain them. While underground water drilling is attributed to the creation of sinkholes, it does not fully explain why the rocks underneath cede to the weight above the yielding sinkholes.

Read related: Dodoma: Infrastructure Developments Shaping Tanzania’s Capital.

Some geologists claim that the type of soils, rocks and geological formations contribute to the proliferation of sinkholes. Sinkholes are a naturally occurring geological feature that is common in Florida. Much of our Florida sits on a bedrock of carbonate rock, primarily made of highly porous limestone. Water dissolves the limestone, creating cracks and holes in the stone. The soil above then seeps down, causing a pit to form. Much of central Florida has so many sinkholes that it has earned the nickname “sinkhole alley.”

As a result of climate change and land development, sinkhole formation in Florida is increasing. Periods of severe drought followed by intense rainfall can destabilize the ground, leading to major outbreaks of new sinkholes opening. As the sea level rises, groundwater rises along with it, increasing the flooding of sinkholes further. Even in moderate weather, man-made development increases the likelihood of sinkholes.

The equipment used in development can divert rainwater to areas more susceptible to sinkhole formation, the weight of buildings can press upon weak spots in the ground, and pumping groundwater disrupts the water table – a boundary between the soil and the area where groundwater saturates the carbonate rock below.

Sinkhole formation is unpredictable and can form quickly, leading to property damage, injury or even loss of life. Unexpected Sinkhole formation can also have ramifications for the environment as the sinkhole collects runoff polluted by substances including pesticides, gasoline, and fertilizers.

In 2016, a sinkhole about 100 feet wide and 300 feet deep opened at a central Florida fertilizer plant, which resulted in water that contained low-level radiation and other pollutants into the Florida aquifer (Florida’s primary source of drinking water).

What Can We Say of Dodoma?

For Dodoma to harbour sinkholes, several factors need to be considered. One is the effect of human activities, whether they exacerbate the formation of sinkholes. A question we need to address is the determination of impacts imposed on the areas where major boreholes and physical human activities are located.

Second is the type of rocks and soils around the areas where major water domestic extraction is being carried out. The Dodoma system is composed of rocks of mainly sedimentary origin, along with mafic volcanic and ultramafic intrusives. High-grade metamorphic rocks such as granulites, garnet-amphibolite gneisses, greenschist-facies talc, chlorite, and sericite schists are prevalent. The more granite the soils are, the more vulnerable to sinkholes crating the topsoils.

Also, read Dodoma: Tanzania’s Ambitious Journey to Relocate Its Capital.

Third is the precipitation. The mean annual rainfall at Dodoma is 567 mm, and the dry season is 7–8 months long. Granitic rocks of Precambrian age underlie all catchments. Pediment slopes and rocky inselbergs are the predominant landforms. The land use is a combination of cattle grazing and cultivation. The perennial vicious cyclic distribution may stress out the soils and the underneath rocks, causing disruptions that may create the soil subsurface, ceding into gaping sinkholes.

Fourth is the rate of soil erosion and sedimentation to determine the effect of the movement of soils with changes in topsoil weight and whether they overall affect the development of rock fissures that create sinkholes. Reduction of stock numbers, overgrazing and excessive burning of grass and mulch are necessary in order to combat soil erosion.

Conclusion Remarks

Dodoma may live her original title of Dodomea, meaning sinking, if appropriate measures are not taken to study and address potential hazards caused by uncontrolled human activities, precipitation, and soil erosion. Human activities that pose immediate concerns are subsurface water extraction, infrastructural developments and lack of studies to investigate the types of rocks that support human activities on the top of soils.

I recommend that further investments in Dodoma be slowed pending comprehensive studies that will guide future human activities there. Government efforts to wean Dodoma residents from drilled water for domestic use should be hailed and encouraged. We cannot overlook potential ecological disasters confronting Dodoma without doing the right thing: solving pending ecological disasters that may not be very far on the horizon.

The author is a Development Administration specialist in Tanzania with over 30 years of practical experience, and has been penning down a number of articles in local printing and digital newspapers for some time now.

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