Sub-Surface Dams (SSD) [Kenya]
- Creation:
- Update:
- Compiler: Guyo Roba
- Editor: –
- Reviewers: Brigitte Zimmermann, Rima Mekdaschi Studer, Donia Mühlematter, Hanspeter Liniger, Joana Eichenberger
technologies_3340 - Kenya
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- Sub-Sarface Dams (SSD): June 22, 2018 (inactive)
- Sub-Sarface Dams (SSD): May 7, 2018 (inactive)
- Sub-Sarface Dams (SSD): July 17, 2018 (inactive)
- Sub-Sarface Dams (SSD): Aug. 15, 2018 (inactive)
- Sub-Surface Dams (SSD): Dec. 5, 2018 (inactive)
- Sub-Sarface Dams (SSD): Sept. 3, 2018 (inactive)
- Sub-Surface Dams (SSD): Nov. 2, 2021 (public)
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Expand all Collapse all1. General information
1.2 Contact details of resource persons and institutions involved in the assessment and documentation of the Technology
{'additional_translations': {}, 'value': 50, 'label': 'Name of project which facilitated the documentation/ evaluation of the Technology (if relevant)', 'text': 'Book project: Guidelines to Rangeland Management in Sub-Saharan Africa (Rangeland Management)', 'template': 'raw'}1.3 Conditions regarding the use of data documented through WOCAT
The compiler and key resource person(s) accept the conditions regarding the use of data documented through WOCAT:
Yes
1.4 Declaration on sustainability of the described Technology
Is the Technology described here problematic with regard to land degradation, so that it cannot be declared a sustainable land management technology?
No
2. Description of the SLM Technology
2.1 Short description of the Technology
Definition of the Technology:
These are constructions stretching across the sand filled dry riverbed, down towards the impermeable floor of the riverbed. They are totally submerged into the ground. For example by fully covering after construction by sand. This are done along dry rivers with huge sand deposits, which has high yield potential and where water can be easily extracted. The aim is to raise groundwater tables and increase the storage capacity for water withdrawals.
2.2 Detailed description of the Technology
Description:
The technology is applied in northern rangeland of Isiolo County which is managed under communal management systems. The aim of technology to reduce pasture and water availability imbalances. The dimensions of sub-surface dam include: a length of water spread (103m),width of the dam (15m), width of water spread (18m), effective dam height (2m), volume of retained sand (103 x 0.5(15 +18) x0.5 x2.0 = 5098.50m3) and the volume of water that can be abstracted from the sand bed (25/100x 5098.50m3 = 1274.6.36m3).
The technology functions as underground water storage infrastructure and the typical activities include, excavation of top porous soil, excavation of sample pits within the excavated area, checking filtration rates of soil, compaction of soil on which dam liners are laid, smoothing the sharp liners along which the dam liners are laid, making grooves to anchor the dam liner, laying the dam liner, anchoring the dam liner with a mixture of cement, water proof and sand with water (motor) and finally drying of the motor and filling back of sand.
The development of Sub-Surface Dams (SSDs) was done through Cash for Work program where local labours comprising of 40-50 persons are engaged in excavation, compactions and developing the liners. Farm tools like jembe, panga, spades and human labour are required to develop the SSD. The technology improves water supply/availability, thereby extending the period of livestock grazing in areas where typically water is depleted before the pasture hence improves water access for livestock in ways that support wider management and utilization of the rangeland and as such strength the resilience of pastoralists to droughts. This effectively gives pastoral groups, an extra grazing time (typically 2 extra months), a period usually not too long to encourage land degradation through over-grazing but long enough to enable pastoralist utilize the remaining pasture in wet season grazing areas. In so doing, the technology enable balanced use of vast communal lands without livestock retreating to dry season grazing areas.
In the process of the landscape level participatory planning with the communities: i) they identified different challenges, including need for decommissioning certain water points that they consider are contributing to over grazing and also attracting other communities, hence drive frequent conflicts, secondly, ii) they mapped areas in the rangeland where there is mismatch between water and pasture availability, most of these areas are in wet season grazing areas. So the next discussion was on what strategic water infrastructures that will enable herders to graze for 2 -3 extra months to enable them utilize the grass before they migrate to the traditional dry season grazing areas. So by design, the technology should only yield water that can allow settling for those extra months, not longer to the detriment of the rangeland
The technology was instrumental in fostering both balanced utilization of land and strengthening sustainable use of the vast rangeland by ensuring that herders utilize available pastures in the wet seasons grazing areas before moving to dry seasons grazing areas. The water stored through the technology stays longer, in this case study, the water lasted for 5 months after the end of the rainy season .
The area receives bimodal rainfall, long rain in March-May and short rain in November-December. With changing seasons/climate, the dry seasons can last up to 1 year in case of rainfall failure. Typically, dry seasons are 6-7 months (May- November).
Normally, the water is depleted within 2 months after the rainy period. The technology is also cheap and easy to understand and construct (especially in areas with clay as the underlying impermeable material) with a possibility of the communities to be taught how to identify suitable site and the entire process of construction. However, in areas without clay soil, the excavation of clay and transportation can be labour intensive and expensive.
2.3 Photos of the Technology
2.5 Country/ region/ locations where the Technology has been applied and which are covered by this assessment
Country:
Kenya
Region/ State/ Province:
Northern Kenya
Further specification of location:
Garba Tula, Isiolo County
Specify the spread of the Technology:
- applied at specific points/ concentrated on a small area
Map
×2.7 Introduction of the Technology
Specify how the Technology was introduced:
- through projects/ external interventions
3. Classification of the SLM Technology
3.1 Main purpose(s) of the Technology
- improve production
- reduce, prevent, restore land degradation
- adapt to climate change/ extremes and its impacts
- mitigate climate change and its impacts
- create beneficial economic impact
- create beneficial social impact
3.2 Current land use type(s) where the Technology is applied
Grazing land
Extensive grazing:
- Semi-nomadic pastoralism
Comments:
Communal grazing area that is shared by 2 and more pastoral groups
3.4 Water supply
Water supply for the land on which the Technology is applied:
- rainfed
3.5 SLM group to which the Technology belongs
- pastoralism and grazing land management
3.6 SLM measures comprising the Technology
structural measures
- S5: Dams, pans, ponds
3.7 Main types of land degradation addressed by the Technology
other
Comments:
Mismatch of pasture and water resources - there are areas where pastures are plenty but surface rain water is depleted earlier than pasture.
3.8 Prevention, reduction, or restoration of land degradation
Specify the goal of the Technology with regard to land degradation:
- prevent land degradation
- reduce land degradation
Comments:
The SSD technology increase water availability is period immediately after the rain, hence ensuring better pasture utilization and more sustainable use of land.
4. Technical specifications, implementation activities, inputs, and costs
4.1 Technical drawing of the Technology
Author:
Guyo Roba
Date:
16/04/2014
4.2 General information regarding the calculation of inputs and costs
Specify how costs and inputs were calculated:
- per Technology unit
Specify unit:
chamber
Specify currency used for cost calculations:
- USD
Indicate average wage cost of hired labour per day:
3.5 USD per day
4.3 Establishment activities
Activity | Timing (season) | |
---|---|---|
1. | Removing sand over dyke and man-days for excavating and transporting soil to dam site | 21 days for 45 casual labourers |
2. | Building and compaction soil in dam wall | 3 days for 45 casual labourers |
3. | Supplying water for compaction | 0.5 day for 45 casual labourers |
4. | Back-filling sand on dam | 1 day for 45 casual labourers |
5. | Supplying water for compacting clay in dam wall | 2 days for 45 casual labourers |
6. | Compacting soil and placing liners | 12 days for 45 casual labourers |
Comments:
The construction of SSD was done through “Cash for work” which is participatory process that involves community mobilization, identification of beneficiaries and formation of “Cash for work” committees, registrations and verification of beneficiaries and implementation/supervision of the work.
4.4 Costs and inputs needed for establishment
Specify input | Unit | Quantity | Costs per Unit | Total costs per input | % of costs borne by land users | |
---|---|---|---|---|---|---|
Labour | tools - jembe, spade etc. | pieces | 80.0 | 5.33 | 426.4 | |
Labour | Removing sand over dyke and Man-days for excavating and transporting soil to dam site | per day | 945.0 | 4.0 | 3780.0 | |
Labour | Building and compaction soil in dam wall | per day | 135.0 | 4.0 | 540.0 | |
Equipment | Supplying water for compaction | per day | 22.5 | 4.0 | 90.0 | |
Equipment | Back-filling sand on dam | per day | 45.0 | 4.0 | 180.0 | |
Equipment | Supplying water for compacting soil in dam wall | per day | 90.0 | 4.0 | 360.0 | |
Equipment | Compacting soil and placing liners | per day | 540.0 | 4.0 | 2160.0 | |
Total costs for establishment of the Technology | 7536.4 |
Comments:
As stated, the cash for work approach means that people get paid 4 USD per day for working on SSD until completion. There are phases where people participated in preliminary phases in meetings and consultation without payments but the actual work was done on cash for work basis.
4.5 Maintenance/ recurrent activities
Activity | Timing/ frequency | |
---|---|---|
1. | Training of communities to manage and maintain the structures | yearly |
4.6 Costs and inputs needed for maintenance/ recurrent activities (per year)
Specify input | Unit | Quantity | Costs per Unit | Total costs per input | % of costs borne by land users | |
---|---|---|---|---|---|---|
Labour | Labour for site protection and maintenance of hygiene | per site | 10.0 | 100.0 | 1000.0 | |
Total costs for maintenance of the Technology | 1000.0 |
Comments:
Water User Associations on the sites are trained on the management of the structures on behalf of the community e.g. on the protection of structure and hygiene maintenance.
4.7 Most important factors affecting the costs
Describe the most determinate factors affecting the costs:
Distance of the sub-surface dam from villages, extent of destruction by floods and human activities
5. Natural and human environment
5.1 Climate
Annual rainfall
- < 250 mm
- 251-500 mm
- 501-750 mm
- 751-1,000 mm
- 1,001-1,500 mm
- 1,501-2,000 mm
- 2,001-3,000 mm
- 3,001-4,000 mm
- > 4,000 mm
Specifications/ comments on rainfall:
because of the climate change, the rainfall is becoming more erratic.
Indicate the name of the reference meteorological station considered:
Isiolo
Agro-climatic zone
- semi-arid
5.2 Topography
Slopes on average:
- flat (0-2%)
- gentle (3-5%)
- moderate (6-10%)
- rolling (11-15%)
- hilly (16-30%)
- steep (31-60%)
- very steep (>60%)
Landforms:
- plateau/plains
- ridges
- mountain slopes
- hill slopes
- footslopes
- valley floors
Altitudinal zone:
- 0-100 m a.s.l.
- 101-500 m a.s.l.
- 501-1,000 m a.s.l.
- 1,001-1,500 m a.s.l.
- 1,501-2,000 m a.s.l.
- 2,001-2,500 m a.s.l.
- 2,501-3,000 m a.s.l.
- 3,001-4,000 m a.s.l.
- > 4,000 m a.s.l.
Indicate if the Technology is specifically applied in:
- concave situations
5.3 Soils
Soil depth on average:
- very shallow (0-20 cm)
- shallow (21-50 cm)
- moderately deep (51-80 cm)
- deep (81-120 cm)
- very deep (> 120 cm)
Soil texture (topsoil):
- coarse/ light (sandy)
Soil texture (> 20 cm below surface):
- coarse/ light (sandy)
Topsoil organic matter:
- medium (1-3%)
5.4 Water availability and quality
Ground water table:
5-50 m
Availability of surface water:
poor/ none
Water quality (untreated):
good drinking water
Is water salinity a problem?
No
Is flooding of the area occurring?
No
5.5 Biodiversity
Species diversity:
- high
Habitat diversity:
- high
5.6 Characteristics of land users applying the Technology
Sedentary or nomadic:
- Semi-nomadic
Market orientation of production system:
- mixed (subsistence/ commercial)
Off-farm income:
- less than 10% of all income
Relative level of wealth:
- average
Individuals or groups:
- groups/ community
Level of mechanization:
- manual work
Gender:
- men
Age of land users:
- middle-aged
5.7 Average area of land used by land users applying the Technology
- < 0.5 ha
- 0.5-1 ha
- 1-2 ha
- 2-5 ha
- 5-15 ha
- 15-50 ha
- 50-100 ha
- 100-500 ha
- 500-1,000 ha
- 1,000-10,000 ha
- > 10,000 ha
Is this considered small-, medium- or large-scale (referring to local context)?
- large-scale
5.8 Land ownership, land use rights, and water use rights
Land ownership:
- communal/ village
Land use rights:
- communal (organized)
Water use rights:
- communal (organized)
5.9 Access to services and infrastructure
health:
- poor
- moderate
- good
education:
- poor
- moderate
- good
technical assistance:
- poor
- moderate
- good
employment (e.g. off-farm):
- poor
- moderate
- good
markets:
- poor
- moderate
- good
energy:
- poor
- moderate
- good
roads and transport:
- poor
- moderate
- good
drinking water and sanitation:
- poor
- moderate
- good
financial services:
- poor
- moderate
- good
6. Impacts and concluding statements
6.1 On-site impacts the Technology has shown
Socio-economic impacts
Production
animal production
land management
Water availability and quality
water availability for livestock
Ecological impacts
Climate and disaster risk reduction
drought impacts
6.2 Off-site impacts the Technology has shown
water availability
6.3 Exposure and sensitivity of the Technology to gradual climate change and climate-related extremes/ disasters (as perceived by land users)
Climate-related extremes (disasters)
Climatological disasters
How does the Technology cope with it? | |
---|---|
drought | well |
Hydrological disasters
How does the Technology cope with it? | |
---|---|
general (river) flood | well |
Comments:
The technology copes very well with floods as the construction is embedded in the sand and thus very well protected.
6.4 Cost-benefit analysis
How do the benefits compare with the establishment costs (from land users’ perspective)?
Short-term returns:
positive
Long-term returns:
positive
How do the benefits compare with the maintenance/ recurrent costs (from land users' perspective)?
Short-term returns:
positive
Long-term returns:
very positive
Comments:
The technology has limited running and maintenance costs once its done fairly well.
6.5 Adoption of the Technology
- 1-10%
Of all those who have adopted the Technology, how many did so spontaneously, i.e. without receiving any material incentives/ payments?
- 0-10%
6.6 Adaptation
Has the Technology been modified recently to adapt to changing conditions?
No
6.7 Strengths/ advantages/ opportunities of the Technology
Strengths/ advantages/ opportunities in the land user’s view |
---|
The technology created opportunity to graze in wet season grazing areas for an averge extra 2 months period after rainy seasons. The technology has provided additional water that gave herders extra days to graze in wet season areas and utilize the pasture that would have been unutilized due to water constrains. In so doing, the land users utilized the pasture without retreating to traditional dry season grazing areas. |
The extra grazing months has reduced overall livestock mortality during droughts and also improved resilience of pastoral community. |
The distance travelled and effort required to access water was reduced. Community members reported reduced distances covered and time spent in search of water for livestock. In some instances the distance reduced from 12-15 Km to 3 Km. Community members also mentioned reduction in conflict incidences over water resources in some areas due to adequate supply of water as a result of construction of water infrastructure. |
The balanced utilization of the grazing area through SSD water provision, enables herd to graze in wet season grazing for slightly longer period and utilize pasture optimally, this however, does not mean that during that garzing period, there will be overgrazing. The volume of water available restricts the number of animals sustained by the grazing area. |
Strengths/ advantages/ opportunities in the compiler’s or other key resource person’s view |
---|
The technology has created an opportunity to optimally use the grazing area and overall reduced land degradation. The technology Improves access to water for livestock in ways which promote more sustainable management of rangeland resources and as such strengthening the resilience of local communities. |
The validation process prior to construction of the SSD is draws critical lessons of identifying and agreeing on where to construct the SSD in a way that fit within broader sustainable rangeland management in a manner that ensured sustainable and efficient utilization of pasture and browse resources in targeted areas. The increase in water supply allowed livestock to graze additional 2-3 months in target areas before shifting to dry grazing areas where previously they migrated before exhausting the pasture and browse resources due to water scarcity. The dry season grazing area is towards Merti, in Kom and Sabarwawa where there are deep boreholes, under, lock and key and only opened during dry seasons. In typical year, the dry season period is about 7 months. But when one rain season fail it goes to about 11 months. |
6.8 Weaknesses/ disadvantages/ risks of the Technology and ways of overcoming them
Weaknesses/ disadvantages/ risks in the land user’s view | How can they be overcome? |
---|---|
When the construction season for SSD is not well planned, there is likelihood/risks of the dams being washed away by flash floods. | Better planning and timing of the development of SDD, just slightly before the onset of rainfall. |
7. References and links
7.1 Methods/ sources of information
- compilation from reports and other existing documentation
When were the data compiled (in the field)?
11/01/2018
7.3 Links to relevant online information
Title/ description:
Promoting resilience by influencing water infrastructure development in community managed rangelands of Kenya
URL:
https://portals.iucn.org/library/sites/library/files/documents/2014-088.pdf
Title/ description:
Balancing water infrastructure in community-managed rangelands in the arid and semi-arid lands of Kenya
URL:
https://portals.iucn.org/library/sites/library/files/documents/2014-089.pdf
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