Introduction

Hafirs, or water harvesting reservoirs, have a long history in East Africa, particularly in arid and semi-arid regions where water scarcity is a major challenge to agriculture and livelihoods. This traditional technology originated in Sudan and spread to other parts of the region. Hafirs are shallow, excavated basins that collect and store rainwater for various uses, such as irrigation, livestock watering, and domestic needs (Figure 1; Awad, 2024).

In Sudan, hafirs have been used for decades as a critical adaptation to recurring droughts, desertification, and water shortages. Hafir systems are instrumental in supporting agriculture and reducing the impact of seasonal water scarcity. International projects in Sudan, such as those funded by the European Union, have further refined and promoted hafir construction, emphasizing integrated catchment management to improve water availability, reduce resource-based conflicts, and enhance agricultural productivity.

In Kenya and Tanzania, the adoption of hafirs gained momentum through development initiatives aimed at improving water access for smallholder farmers and pastoralists. Their success lies in their simplicity and scalability, making them suitable for both small communities and larger agricultural settings. 

Installation of hafirs

The following steps for hafir construction are based on our experience, but can be adapted to fit local assets and constraints.

1. Site selection and preparation

Choose the right location for a hafir for maximum effectiveness and sustainability. Evaluate various factors to ensure the reservoir can efficiently collect and store water while meeting the community’s needs. Visually inspect the landscape and discuss placement with the local community. Factors to consider include:

• Slope: A gently sloping area is ideal for directing runoff into the hafir. Avoid steep slopes to minimize soil erosion. 
• Catchment area: Evaluate the size and characteristics of the catchment area to ensure sufficient water supply. Hafirs can be built at the household level for dry-season use and should be at least 10m³. For larger, agricultural or production use, hafirs must be much larger to meet crop water requirements in the off-season.
• Proximity to users: The site should be close to the intended beneficiaries, such as farms, schools, or livestock watering points.
• Ownership: Confirm that the land is free from disputes and that legal permissions are in place. Ask the community/landowner about future land plans to minimize the likelihood of having to transfer the hafir. 
• Community involvement: Engage the community to ensure the location meets their needs and they are willing to provide long-term maintenance. Discuss options with the community to align site selection with their priorities.
• Rainfall patterns: Analyze historical rainfall data to ensure the site can reliably collect water during the rainy season.
• Evaporation rates: In areas with high evaporation, the site should be strategically shaded or wind-protected if possible. Think of materials that can easily be accessed in your area (e.g. trees vs. physical covering material). In Arusha, Tanzania, we have been using the agriculture shed net.
• Ground preparations: Ground preparation includes clearing vegetation, rocks, and debris from the selected site. Consider what will be required to clear the site during the selection process.

2. Determine storage capacity and system design 

The storage capacity of a hafir is calculated based on its dimensions and shape. Most hafirs are trapezoidal or rectangular in shape, and their volume is determined using geometry. Trapezoidal hafirs have sloping sides (Figure 2), meaning their top dimensions are larger than the base dimensions (at the bottom of the excavated containment).

Calculate the volume using the trapezoidal formula:

For trapezoidal hafirs, the formula for volume is:
V=1/6·D·[(Lt·Wt)+(Lt·Wb)+(Lb·Wt)+(Lb·Wb)]
Where:

• D is the depth
• Lt is the top length
• Wt is the top width
• Lb is the bottom length
• Wb is the bottom width

Simplified rectangular approximation (if applicable):

For a hafir with vertical walls or minimal side slopes, use the rectangular formula:
V=L·W·D
Where:

• L is the length
• W is the width
• D is the depth

The volume of a hafir depends on the financial capacity preferences 1of the user because this will determine the quantity of materials needed. 

Measurement

To achieve accurate measurements for trapezoidal hafirs, it is best to begin by measuring and marking the bottom dimensions of the structure. Start digging the pit based on these bottom dimensions, ensuring the depth reaches the specified level. Once the pit is excavated to the required depth, the sides can be carefully cut and shaped to match the top dimensions while achieving the desired slopes. This approach ensures precision and efficiency in attaining the intended shape (Figure 3).

3. Prepare the reservoir structure (Figure 4)

Based on experience from Karatu, Tanzania, a team of 10 skilled workers using hand tools (e.g., pickaxes, shovels, and wheelbarrows) can collectively excavate an 85-cubic-meter reservoir in approximately 6 to 9 days, depending on soil conditions. Hard or rocky soils tend to slow down progress, while loose, sandy soils facilitate faster digging.

4. Install the geomembrane liner (Figure 5)

Install a geomembrane liner (impermeable polymer materials used for earth stabilization) to prevent water seepage, enhance the reservoir’s durability, and maintain the water quality in the hafir. Proper installation ensures long-term efficiency and minimizes water loss. For optimal installation, do the following. 

• Choose a high-quality geomembrane material suitable for the specific site conditions. Common options include high-density polyethylene (HDPE), low-density polyethylene (LDPE), or polyvinyl chloride (PVC) liners, each offering excellent impermeability, flexibility, and resistance to environmental stressors.
• Thoroughly clear and level the reservoir bed to remove sharp objects, debris, or irregularities that might puncture or damage the liner. As a protective underlayment, add a layer of fine sand or geotextile fabric (optional).
• Lay out the geomembrane with precision, ensuring proper alignment and overlap of panels. This prevents gaps or wrinkles that could compromise the liner’s integrity.
• Secure the liner edges in trenches around the hafir’s perimeter. This prevents displacement caused by water pressure, wind, or other external forces.

5. Design and connect the inlet system

Establish a reliable and efficient inlet system to ensure the hafir receives an adequate and consistent supply of water while minimizing sediment inflow and preventing damage to the reservoir structure (Figure 6). For maximum efficiency of the inlet system:

• Position the inlet to maximize water capture from natural sources such as rainfall, runoff, or diversion of water from streams. Ensure it is oriented to reduce the velocity of incoming water, which helps prevent erosion and sediment accumulation.

• 

  Include silt traps, upstream of the inlet to capture debris and reduce sediment inflow (Figure 7). This prevents clogging and maintains the reservoir’s water quality and storage capacity. 
• Install riprap,2 vegetation, or geotextiles around the inlet area to stabilize the soil and protect against erosion caused by water movement.
• Design the inlet for easy access, allowing for routine cleaning, inspection, and removal of debris to ensure uninterrupted water flow.

6. Establish and optimize the outlet system (Figure 8)

Ensure the outlet system is properly designed, installed, and connected to regulate the release of water from the hafir efficiently and safely. The outlet system should be robust, easy to operate, and suited to the specific requirements of the reservoir’s use, whether for irrigation, livestock, or human use. It needs to be accessible for regular inspection and maintenance. Include mechanisms to clear debris or blockages without requiring complex equipment or significant disruption to the reservoir. Integrate an emergency overflow or spillway near the outlet to manage excess water during heavy rainfall or flooding, reducing the risk of damage to the reservoir or surrounding infrastructure. Customize the outlet system based on the primary use of the hafir. For example, a multi-tiered outlet structure can accommodate various needs, such as water for irrigation at one level and livestock at another.

7. Cover and protect the reservoir (Figure 9)

Covering and protecting a hafir is essential for maintaining water quality, minimizing evaporation, and safeguarding the stored water from contamination and external damage. Create physical barriers or protective measures to shield the reservoir from environmental and human-related threats. Basic principles are as follows.

• Minimize evaporation: A significant amount of water can be lost to evaporation, especially in hot and arid climates. Cover the reservoir with floating covers, shade nets, or reflective materials to reduce this loss. In some cases, planting tall trees or installing shade structures around the perimeter can also help.
• Prevent contamination: Protect the reservoir to reduce the risk of contamination from debris, agricultural runoff, animal intrusion, and human activity. Install barriers like fences, silt traps, or even biodegradable nets to ensure the water remains clean and usable for its intended purposes.
• Improve structural integrity: Covers or protection mechanisms help guard the reservoir against soil erosion, strong winds, or flooding that could undermine its banks or walls. For earthen reservoirs, reinforce the sides with vegetation or protective materials to prevent erosion and structural damage.
• Security measures: Fencing the area and adding signage can restrict unauthorized access, thereby reducing the risk of accidental contamination, theft of stored water, or damage to the reservoir infrastructure.

8. Levelling and drainage system for the ground surrounding the hafir

Ensure proper levelling of the ground around the hafir to facilitate efficient water flow and prevent erosion. Design and implement a drainage system that directs excess runoff away from the hafir while minimizing sediment deposition within the water body. Use graded slopes to guide water into designated inlets and consider incorporating erosion control measures, such as planting vegetation to stabilize the soil. Additionally, monitor regularly and conduct maintenance as required to ensure the drainage system remains functional and effective in sustaining the hafir’s longevity and water quality.

9. Maintenance and monitoring

Regular maintenance and monitoring are crucial for ensuring the long-term efficiency, safety, and sustainability of a hafir. These activities help detect and address potential issues early, reducing water loss and maintaining the reservoir’s functionality. Common issues and their management include:

• 

  Sediment/Silt Accumulation: Regular inspections, particularly after rainy seasons, are necessary to monitor silt buildup 3 at the bottom of the hafir. If significant silt accumulation is detected, it can be removed using tools such as spades to restore the reservoir’s capacity.
• Damage to Liners: Liners can develop damage or leaks over time, compromising the hafir’s integrity. Regular checks should be conducted to identify tears, punctures, or wear. Prompt repairs (Figure 10) can prevent water leakage and ensure the reservoir remains operational.

Economic considerations

Costs for constructing a hafir will vary based on local availability of materials, labor, and hafir size. In East Africa, cost per cubic meter for the three major construction materials is vastly different, with geomembrane plastic the most affordable option (Table 1). Table 2 includes some cost considerations for a 60 m³ hafir with optional features included (netted cover, protective underlayment, fencing etc.). Community costs can be lowered by excluding some of these features, but exclusion adds potential risks. One option for fencing and coverings is to use living fences and thorny brush as barriers to deter animal or human entrance. This is appropriate for most smaller hafirs. 

Conclusion

Hafirs effectively capture runoff during the rainy season for use in the dry season, offering a sustainable solution to water needs. Hafirs are particularly useful in drylands, where rainfall is erratic and traditional water sources like rivers and wells are often insufficient. Involve all stakeholders in decision making, construction, and maintenance to ensure that the technology is appropriate, monitored, and successful. If you need help determining if a hafir is right for your community needs or planning your hafir project, please contact us at tru@echocommunity.org with the subject line “hafir.”

References