Category: Goal: Reduce runoff

Posted on

Riparian Buffer Zones

Similar names: Conservation buffers, Stream corridor bank enhancement, Riparian buffer strips and hedges, Terrestrial buffers, Riparian buffer systems

Riparian buffer zones are the interface between land and a river, stream or creek often characterised by riparian woodlands, forests and riparian strips. The plant habitats and natural communities along the river banks are better known as riparian vegetation and they are characterised by hydrophilic plants, bushy vegetation and forest systems. The presence of riparian buffer zones is crucial due to their role as natural biofilters and their protection of aquatic environments from excessive sedimentation, polluted surface runoff and erosion. Furthermore, they provide shelter, shade and food for many aquatic species.

Often the riparian zones are damaged by various anthropogenic activities such as agriculture, construction and silviculture. In this case, biological restoration can take place, with the most common practices being erosion control and revegetation. Furthermore, in some places riparian zones are fully lacking and reintroducing them could bring plenty of benefits to the local ecosystems. Because of the great biological function these systems have in supporting a diversity of species and landscapes, they are in some places subject to national protection mechanisms.

Initiating and restoring riparian buffers is crucial for the healthy functioning of riparian ecosystems. The vegetation around the banks of the river slows the flow of water which controls the power of the river and the destruction that could occur downstream. When near agricultural land, the riparian buffers filter various pollutants from agricultural runoffs, enhancing water quality via biofiltration. 

Disclaimer: Check whether Riparian Buffer Zones are subject to national protection in your area, as this could help with their protection and restoration.

Posted on

Stone Lines

Similar names: Cordons pierreux, stone bunds.

Stone lines are stones grouped in the shape of a line and placed along contours. The stones can be of different sizes. The goal of these lines is to conserve the soil and reduce runoff, as they are used to slow down water runoff and break its velocity. Hence, they increase infiltration and retain sediment and seeds to make water and nutrients available for crops. Stone lines are most suitable for water harvesting on slightly sloping plains (up to 5%) in semi-arid regions. For slopes starting from 5%, stone bunds can be used (see eyebrow terraces).

Stone lines are an easy and cheap intervention if stones are available in the immediate surroundings. This intervention is widely used in Africa, both in dry and humid areas. Moreover, stone lines are often used in combination with Zai Pits intervention for the rehabilitation of degraded and crusted lands. It is applied in semi-arid areas, on sandy and loamy soils where the slope is lower than 5%. A great example can be seen in Niger, where the combination of the two techniques is applied to capture runoff, making infiltration more efficient and improving nutrient availability. The pits have a diameter of 20-30 cm, and a depth of 20-25 cm and are spaced about 1 m apart in each direction. Stone lines are spaced 20-25 m apart on slopes of 2-5%. With this layout stone lines are quite small, usually, three stones wide and only one stone high and they are placed, along the contour lines, by hand. Very often grass grows between the stones leading to a greater infiltration and helping the accumulation of fertile sediments. Maintenance-wise, stone lines need to be repaired annually, in particular after heavy precipitation events.

Posted on

Terracing

Terracing is a method of farming and soil conservation on hills and sloped lands. It was traditionally used by the Incas and is widely practised around the world today. It involves the building of platforms, and forming step-like structures along a slope. The main goal of bench terraces is to periodically interrupt the slope of the terrain with flat sections; this helps to decrease the speed of water runoff,  significantly reducing soil erosion and surface runoff. By slowing down water speed, this intervention stops the washing away of topsoil containing important nutrients and promotes better water infiltration and soil moisture. The flat benches of the terraces create more effective and productive areas to farm on steep terrain.

There are two main types of terracing techniques: graded terracing and level terracing. With graded terracing, the slope can vary along the length of the terrace to direct water in the desired direction; this is especially useful for less permeable land. With level terracing, the terraces follow a contour line and do not vary in slope along this line, this ensures that water is more evenly distributed along the terrace. Stone or wooden walls are often used to hold terraces in place, although a simple earth wall without supporting material can be used with slopes and terraces on the smaller side. This intervention is similar to Fanya Juu and Fanya Chini which are specific types of terraces.

Terracing offers several ecological and socioeconomic benefits. Ecologically, it prevents soil erosion by slowing water flow, allowing it to infiltrate the soil and retain valuable topsoil, which is essential for agriculture. Terracing also manages water more effectively by evenly distributing it across levels, conserving water, reducing irrigation needs, and promoting nutrient cycling. It creates diverse habitats for various plant and animal species, enhancing biodiversity. Additionally, terracing stabilizes slopes, reducing the risk of landslides by minimizing soil pressure and movement, especially in regions with wet seasons. Socioeconomically, terracing increases land productivity on slopes, allowing for larger crop beds and easier use of machinery, thus boosting agricultural efficiency.

Posted on

Vegetative Lines

Vegetative lines involve the planting of lines of vetiver grass following the contour lines, along stream banks and roadsides, to create a hedge. These hedges act like semi-permeable barriers, aimed to hinder surface erosion as they slow down run-off and retain sediments picked up by excess rainwater. This setup improves water infiltration and helps to increase the ground moisture level. Their root systems also help stabilise the soil and prevent further soil erosion. Thus this provides increased stabilisation of embankments, gully erosion, roads and slopes. Furthermore, water runoff and soil runoff reductions are observed, at around 57% and 80% respectively.

Vetiver grass can grow on slopes of > 50% and can be planted on a high variety of soils (red latosols, black cracking vertisols, roadside rubble, C-horizon gravels, laterites, sodic, and saline soils). Furthermore, vetiver grass is resistant to different types of climatic conditions: rainfall from 600mm to 6000 mm /year and extreme temperatures of -14°C to 55°C, and could survive several months submerged in water. Vetiver grass can support high levels of toxicity by manganese, aluminium and other metals and high levels of soil acidity, salinity, alkalinity, and acid sulphate conditions. All in all, they provide great solutions as they are non-invasive, fire resistant, and regrow quickly and be used as mulch, fuel (vetiver energy value is 55% the energy value of coal), and as fodder. Finally, vetiver grass is very efficient in stabilising Semi-Circular Bunds, Eyebrow Terraces or Negarim.

Very similar to the intervention described above is the so-called “Vegetative lines with cactus”. This intervention is based on the same principle as the Vegetative lines with vetiver grass, but it is suitable for drier environmental conditions (0 – 600mm). Like some other interventions, over time, this type of intervention can lead to the formation of terraces due to tillage and water erosion between the hedges.

Posted on

Fanya Chini

Similar names: Retention trenches, infiltration trenches

The name Fanya chini means “throw it downwards” in Kiswahili. It consists of trenches and earthen ridges facing downslope. This intervention aims to reduce soil erosion by breaking down long slopes into smaller sections. Thus, the speed of runoff will decrease, and water can infiltrate into the soil between the bunds. This will result in a reduction of nutrient leaching and increased water availability for crops. Fanya chini is common in areas with 300-600 mm of annual rainfall on 1-25% slopes. It is suitable for all types of relatively permeable soils (e.g. alluvial, red, laterite, brown, and shallow and medium black soil). Still, it doesn’t work very well with clayey soils or vertisols as these are not permeable.

One of the main benefits of Fanya chini is that it limits soil erosion from water runoff, and simultaneously improves water retention in the soil and increases water availability for crops. Furthermore, an increase in yield is observed, as well as improved soil fertility.

Posted on

Fanya Juu

Similar names: Terracing, Retention Trenches, Infiltration Trenches

The Fanya Juu technique is an agricultural practice that involves creating ridges along the contour lines of sloping land. The name Fanya Juu means “throw it upwards” in Kiswahili and is very similar to Fanya Chini as it consists of terrace bunds and ditches along the contour. This technique rapidly spread during the 1970s and 1980s and it is well known throughout Eastern Africa, the goal of Fanja Juu contour bunds is different depending on the environmental conditions of the areas within which they are applied. Their aim in semi-arid areas is to harvest and conserve rainfall, whereas, in sub-humid zones, contour bunds are constructed to discharge excess runoff. However, their main purpose is to prevent water and soil loss and to make conditions more suitable for plants to grow. 

Fanya Juu is suitable for slopes of 5-20%, similar to the ones that characterize Fanya Chini interventions. The species most often used in drier zones are Pennisetum Purpureum (Napier grass or Uganda grass) and Panicum Coloratum (also known in southern Africa as “white buffalograss”) and the harvest can be used as fodder for livestock. Fruit trees (e.g. citrus or bananas) can be planted either immediately above the embankment or below the ditch, where runoff tends to concentrate.

Posted on

Zai Pits

Similar names: Chololo pits (Tanzania), Zaï pits (Burkina Faso), tassa (Niger), agun pits (Sudan), kofyarpits (Nigeria), yamka (Kyrgyzstan), planting pits.

Zai Pits are small basins in which the seeds of annual or perennial crops are planted. The pits are then filled with Mulch, manure, compost or good soils to increase soil fertility and the capacity of the soils to retain water. Zai Pits can be beneficial for soil conditions and they are a very successful method which can allow for the growth of vegetation in dry areas. They are also very efficient in protecting seeds and soil organic matter from being washed away from water runoff. One of the major advantages of Zai Pits is that it increases water filtration, through the collection and concentration of water for the plants due to increasing termite activity. What is more, Zai Pits can collect more than 25% or more of run-off water. This as a result decreases water run-offs and evaporation. When looking at the bigger picture, Zai Pits can improve soil fertility and agricultural productivity of several crops and can increase production by up to 500% if well executed.

Zai Pits are an efficient method to increase yield productivity due to more water and nutrients available. This intervention is most suitable for flat or gently sloped terrains (0-5%) with a precipitation range of 350-600 mm/y.  Zai Pits can also work with other techniques such as stone contours and hand-dug trenches.

Posted on

Semi-Circular Bunds

Similar names: Demi-Lunes, Banquettes, Boomerangs, Water Bunds, Earth Bunds, Earthworks, Micro Basins, Half-Moons, Earth Smiles

The technique of creating Semi-Circular Bunds belongs to the overall category of water harvesting interventions and consists of half-moon-shaped basins dug in earth. The main goal of water harvesting, as the name suggests, is to collect water, and to make moisture available for vegetation for a longer time. This type of micro-catchment water harvesting technique is suitable for slopes up to 15%, however Bunds made of earth are seldom used in areas with slopes greater than 5% with a precipitation rate higher than 300 mm/y. At lesser slopes, Semi-Circular Bunds are also used in areas with higher rain falls.

Semi-Circular Bunds are a low cost intervention, where the time requirements of bund construction are very low as they can be implemented very fast, especially when the raw materials (plant residues) are available. The intervention also allows for the cultivation of plants and species that would not grow in previously dry conditions. Overall, the direct benefits of Semi-Circular Bunds can be realised in the short term and often after one year of implementation.

Posted on

Eyebrow Terraces

Similar names: Banquettes, Boomerangs, Terraces, Stone Bunds, Eyebrow Systems, Eyebrow Basins.

Eyebrow Terraces are a form of microcatchment water harvesting system. They are handmade micro basins, in the shape of an eyebrow, and are often made from soil and stones. Their main goal is to facilitate vegetation growth on steep slopes by collecting runoff water from a small catchment area and having it infiltrate the soil. This way, it is stored in the root zone and will be available for crops. They are usually situated on hillsides and can be used on up to 50% of slopes. The steeper the slope, the more the bunds have to be reinforced with stones. Eyebrow Terraces work well in areas characterised by 200-600 mm of annual rainfall. Reinforcing Eyebrow Terraces with stones on steep slopes makes them more resistant to the increased water speed caused by the slope. Instead, they can be some metres apart. After completion, the pit uphill from the eyebrow may fill with sediments and soil, thereby giving rise to terraces.

Some of the main advantages of Eyebrow Terraces are that they reduce the risk of flooding, while simultaneously increasing the on-site conversion of water through the facilitation of filtration. Furthermore, the intervention improves the yields in the area, by increasing the soil organic content, as sediments are trapped in the terraces.

Posted on

Grazing Management

Sustainable Grazing Management is about managing pasture and livestock in a way that prioritizes the long-term capability of a landscape. Its goal is to maintain healthy and productive pasturelands and provide economic benefits, and can be applied to range, pasture, and grasslands in all types of topographies and climates. The way grasslands are managed both directly and indirectly impacts the ecological health of the surrounding ecosystem, including the local water and mineral cycles as well as biological succession, in turn also creating socioeconomic effects for farmers and herders.

As opposed to more traditional and unsustainable practices such as extensive or continuous grazing where livestock graze on one large, open pastureland, there are several methods of more sustainable Grazing Management. Two examples of this are Rotational Grazing Management and Integrated crop-livestock grazing.