Water Bunds Transforming Tanzania’s Deserts into Thriving Grasslands

(The featured image is an artist interpretation of a water bund) In Arusha, Tanzania, local communities have successfully transformed barren, desert-like areas into thriving grasslands using strategic pit digging (water bunds), and other regreening techniques. This effort is part of a broader initiative led by the Dutch-Kenyan NGO Justdiggit, which collaborates with local farmers and pastoralists to combat desertification.

Arusha, located in northern Tanzania, is known for its diverse landscapes, which range from lush highlands to arid plains. The region is a key hub for both tourism and agriculture, but it has faced huge challenges due to climate change.

The local economy in Arusha is heavily dependent on agriculture, with many residents engaged in farming and pastoralism. The Maasai community, known for their semi-nomadic lifestyle, is particularly prominent in the region. They traditionally rely on livestock herding, which has become increasingly difficult. The region used to have a bimodal rainfall pattern, with two distinct rainy seasons: the “long rains” from March to May and the “short rains” from October to December. But unpredictable rainfall patterns, prolonged droughts due to the changing climate have caused land degradation and shrinking pasturelands.

We will focus on how water bunds are constructed and where the idea originated from.

What is a Water Bund?

Water bunds, also known as contour bunds or earthen bunds, are embankments constructed across slopes to control the flow of water and prevent soil erosion. They are typically built along the contour lines of a hill or slope, which allows them to slow down rainwater runoff and enable water to percolate into the soil rather than flowing rapidly downhill.

These structures help improve groundwater recharge, reduce soil erosion, and enhance the fertility of agricultural land by keeping moisture in the soil. Water bunds are widely used in dryland farming areas, particularly in regions prone to drought, as they help conserve both soil and water resources, leading to more sustainable agricultural practices.

In addition to agriculture, water bunds play a key role in managing watershed areas and improving the ecological health of degraded lands.

About Judstdiggit

Justdiggit began as a response to the growing environmental challenges of desertification and land degradation in Africa. The organization was founded in 2010 by Dutch environmentalists and entrepreneurs, including Dennis Karpes, one of the co-founders of the well-known environmental initiative Dance4Life, and Peter Westerveld, an artist and inventor with a deep interest in landscape restoration.

The inspiration behind Justdiggit’s creation was to find scalable, nature-based solutions to combat the rapid spread of desertification in Africa, which was severely affecting communities and ecosystems. The founders were motivated by the belief that if local communities could be empowered with simple, low-cost techniques, they could reverse the damage done to their land and restore it to its former productivity and biodiversity.

Peter Westerveld brought his extensive knowledge of landscape hydrology to the project, having already experimented with similar techniques in various parts of Africa. His innovative ideas on rainwater harvesting and land restoration laid the groundwork for what would become the core strategies of Justdiggit.

From its inception, Justdiggit aimed to work closely with local communities, governments, and other stakeholders to ensure that their interventions were culturally appropriate, sustainable, and scalable. Over the years, the organization has expanded its projects across several countries in East Africa, including Tanzania, Kenya, and Ethiopia, reaching thousands of farmers and pastoralists.

Origins of Water Bunds

The concept of water bunds, also known as earth bunds, originates from traditional rainwater harvesting practices that have been used for centuries in various arid and semi-arid regions around the world. These practices were initially developed by indigenous communities to manage and conserve scarce water resources, particularly in areas where rainfall is infrequent and erratic.

Water bunds are closely related to ancient agricultural methods used in Africa, the Middle East, and South Asia, where farmers adapted their techniques to the harsh environmental conditions. In these regions, communities learned to dig shallow pits or contour bunds on sloped land to capture and store rainwater. This not only provided a crucial water source during dry periods but also helped reduce soil erosion and improve land fertility.

The specific practice of creating semicircular water bunds was further developed and popularized in recent decades by organizations focusing on sustainable agriculture and land restoration. The NGO Justdiggit which we mentioned earlier has been instrumental in reviving and scaling up the use of water bunds in East Africa, particularly in Tanzania.

Overall, the idea of water bunds is rooted in traditional knowledge but has been adapted and modernized by environmental and development organizations to address contemporary challenges of climate change and land degradation.

How to Construct Water Bunds

Constructing a water bund is quite straightforward. First, a suitable location is selected, usually on a slope where rainwater naturally flows. The shape of the bund is then marked on the ground, typically forming a semicircle with the open side facing uphill to capture maximum runoff. The bund is dug to a depth of about 30-50 cm (12-20 inches), with the excavated soil piled on the downhill side to create a small embankment.

The inside of the bund is shaped and smoothed to ensure it efficiently traps water, and sometimes grass seeds or small trees are planted inside or around the bund to stabilize the soil and increase water absorption. Regular maintenance is required to remove silt and repair any damage caused by heavy rains, ensuring that the bunds continue to provide benefits over time​.

Before the construction of water bunds in regions like Arusha, Tanzania, rainwater was largely wasted due to surface runoff. The landscape in these arid and semi-arid areas often has hard, compacted soil that is unable to absorb water quickly. When it rained, instead of seeping into the ground, most of the water would flow rapidly across the surface, causing several problems:

  1. Soil Erosion: The fast-moving runoff would carry away topsoil, which is essential for plant growth. This erosion not only degraded the land further but also made it even more difficult for vegetation to take root in the future. Over time, this process contributed to desertification, where once-productive land turned barren​.
  2. Loss of Water: Much of the water that flowed across the surface would either evaporate or drain away to lower areas, leaving the land parched soon after the rains stopped. This meant that the water was not available to support crops, pasture, or even recharge local groundwater sources. The loss of this valuable resource exacerbated the challenges faced by local farmers and pastoralists​.
  3. Reduced Agricultural Productivity: With minimal water retention in the soil, crop yields were poor, and the available pasture for livestock was insufficient. This led to food insecurity and economic hardship for many communities, especially in areas heavily dependent on rain-fed agriculture.

In addition to water bunds, they also implement “Kisiki Hai” or Farmer Managed Natural Regeneration (FMNR). This technique focuses on reviving tree stumps and promoting the growth of new shoots, which improves the landscape’s ability to retain moisture and provide shade, further supporting the growth of grass and other plants.

200,000 Water Bunds

The impact of these traditional, low-cost technique efforts has been substantial. Over 200,000 bunds have been dug in the Arusha region, leading to the regeneration of thousands of trees and millions of liters of water retained in the soil. These actions have not only transformed the landscape but also improved local livelihoods by increasing the availability of pasture and arable land.

The success of these regreening projects demonstrates that with the right techniques and community involvement, even the most degraded lands can be restored and made productive again.

Sustainability is Key

The practice of using water bunds a highly sustainable technique for several reasons:

  1. Low-Cost and Low-Tech: Water bunds are a low-cost and low-tech solution that can be implemented with minimal resources. They do not require advanced technology or expensive materials, making them accessible to communities with limited financial means. This simplicity also ensures that local communities can easily construct, maintain, and repair the bunds without external assistance, which supports long-term sustainability.
  2. Enhancing Water Retention and Soil Health: Water bunds improve the soil’s ability to retain water, which is crucial in arid and semi-arid regions. By capturing rainwater that would otherwise run off, bunds allow the water to slowly seep into the soil, recharging groundwater and supporting plant growth. This increased water retention helps to stabilize the soil, reduce erosion, and promote the growth of vegetation, which further improves the land’s resilience to drought and desertification​.
  3. Supporting Local Agriculture: The enhanced soil moisture and fertility resulting from water bunds directly benefit local agriculture. With more consistent water availability, crops can grow more reliably, which increases food security and provides a stable income for farmers. The improved pastureland also supports livestock, which is vital for the livelihoods of pastoral communities, particularly in regions like Arusha​.
  4. Promoting Biodiversity: As water bunds encourage the growth of native vegetation, they also contribute to increased biodiversity. A more diverse plant life provides habitat and food sources for a variety of wildlife, helping to restore ecological balance in degraded areas. This increase in biodiversity further strengthens the resilience of the ecosystem to environmental stresses like climate change​.
  5. Mitigating Climate Change: By restoring degraded lands and promoting vegetation growth, water bunds contribute to carbon sequestration. Plants absorb carbon dioxide from the atmosphere as they grow, which helps to mitigate the effects of climate change. This carbon capture is particularly important in areas that have been heavily deforested or degraded.
  6. Empowering Local Communities: The process of constructing and maintaining water bunds empowers local communities by providing them with the knowledge and skills needed to manage their environment sustainably. This community-driven approach ensures that the benefits of the practice are long-lasting and that the local population has a vested interest in maintaining the restored landscapes​.

By constructing water bunds, communities were able to address these issues effectively. The bunds slowed down the water flow, allowing it to infiltrate the soil, thereby reducing erosion, retaining moisture, and gradually restoring the fertility of the land.