有助于对技术进行记录/评估的机构名称（如相关）HELVETAS (Swiss Intercooperation)
Trenches with soil bunds constructed in a tied manner along contour lines to trap surface runoff and sediments from degraded uplands
Contour Tied Trenches (CTT) were constructed to trap and retain surface runoff and sediments with the main objective of reducing flash flood risks from the Sou-rakhak watershed which was badly degraded due to overgrazing, excessive cutting of shrubs for fuel wood, rainfed cropping and recurring droughts. The technology was combined with other structural measures like soil bunds, check dams, water ponds, and plantation of fruit, non-fruit trees, fodder crops like alfalfa, Asafoetida and Cumin as cash crops. The watershed is also protected from grazing and shrub cutting by the participating communities. Community bakeries were constructed in the valleys and bio-briquette technology promoted for reducing shrub consump-tion/cutting.
Purpose of the Technology: Continuous Contour Trench (CCT) technology was applied to trap and retain surface runoff and sediments with the main objective of reducing flash flood risks from Sourakhak watershed and preventing damages due to flash floods in the valleys.
Establishment / maintenance activities and inputs: Feasibility studies were conducted and workers from three Community Develop-ment Councils (CDCs) of Roy-e Sang (Kahmard) implemented the construction works based on the technical proposals. The workers were organised by the Sourakhak watershed management committee and they got a daily wage of USD 5 for their labour inputs. About 670 families (276 person days/ha) participated in the construction of CTTs and other technologies.
One supervisor appointed by the communities and a watershed worker from HEL-VETAS Swiss Intercooperation side, both paid by the project, monitored the water-shed works with technical advice from the project staff. The work was carried out in phases and in 4 years (starting 2009) about 65,000 trenches were constructed. About 216 trenches were constructed per hectare and the construction cost was about 1450 USD/ha, which included 1380 USD for labour and 70 USD for tools. The International Swiss Re Award (2009), the Swiss Agency for Development and Cooperation (SDC), HELVETAS Swiss Intercooperation and the participating families financially contributed to the watershed management works.
Natural / human environment: Sourakhak watershed has a semi-arid and temperate climate. The area receives up to 400 mm rainfall (annually) and snow during winter time. The watershed elevation ranges from 2000-3000 m amsl and soil type is sandy-loam to clay type. The land users who applied thsi technology are mostly smallholders. The uplnad areas where the technology was applied is owned by the state, but local communities have long term land use rights.
Sourakhak watershed has a semi-arid and temperate climate. The area receives up to maximum 400 mm rainfall annually in a normal year and snow during winter. About 80% of the rain falls from March to June, with most rain falling in the months of April and May. The watershed is located at an elevation ranging from 2000-3000 m (amsl) and the soil is sandy-loam to clay type. The land users who applied the CTTs are mostly smallholders (with less than 1 ha irrigated land) and they reside in the valley bottoms. The upland areas, where the CTT have been constructed, belong to the state but the local communities have land and water use rights. From a climate change perspective, CTTs will not be much affected by temperature changes or drought. Some trenches could break if there is an extreme rainfall event.
- 1-10 平方千米
Total area covered by the SLM Technology is 3 km2.
About 65,000 trenches each measuring 5 m in length x 0.7 m in depth and 0.7 m in width (in middle) were constructed manually.
The project started in 2008.
Major land use problems (compiler’s opinion): Depleted soils, poor vegetative cover, deep gullies leading which trigger severe flash floods.
Major land use problems (land users’ perception): Severe flash floods from the degraded watershed.
Future (final) land use (after implementation of SLM Technology): Mixed: Mo: Other
Number of growing seasons per year: 1
Longest growing period in days: 180; Longest growing period from month to month: March to July
- Extensive grazing
Secondary types of degradation addressed: Bc: reduction of vegetation cover
Main causes of degradation: over-exploitation of vegetation for domestic use (Shrubs used for fuel), overgrazing (Mainly by sheep and goats), governance / institutional (No management system either by the government or local communities)
Secondary causes of degradation: droughts (Slow recovery of natural vegetation), population pressure, war and conflicts (Cutting of Juniper trees)
Technical specifications of Contour Tied Trench with soil bunds constructed at Sourakhak wa-tershed. Fruit and non-fruit trees have been planted at a few selected sites in the watershed as vegetative measures. The plant survival per cent was about 10% due to drought, rodent problem and poor adaptation of the tree saplings brought from a different natural environment. The sites are protected from grazing and shrub cutting leading to better land cover.
The trenches have the capacity to store about 159,250 cu.m of water. Kahmard receives up to 350 mm rainfall per year. Considering catchment area of 3 km2 the trenches can hold all the water if there was 50 mm rain at a time, which is rare.Trench size: 5 m (L), 1m at top and 0.4 m at bottom (W), 0.7 m (D)
Distance between trench in a row = 0.3-0.7 m and spacing between contours = 4-8 m depending on the slope (steeper slopes have less distance)
Soil bund size: 5.5 m (L), 0.7 m/0.4 m (W), 0.5 m (H)
The trenches have the capacity to store about 159,250 cu.m of water. Kahmard receives up to 350 mm rainfall per year. Considering catchment area of 3 km2 the trenches can hold all the water if there was 50 mm rainfall at a time, which is rare.
Location: Afghanistan. Kahmard/Bamyan
Technical knowledge required for field staff / advisors: high (Initial stages. It is a new technology for most field staff.)
Technical knowledge required for land users: high (Initial stages. Land users have to learn first where to apply, how to apply and maintain this technology and also the method for preparing contour lines.)
Main technical functions: control of dispersed runoff: retain / trap
Secondary technical functions: reduction of slope length, increase of infiltration
Retention/infiltration ditch/pit, sediment/sand trap
Spacing between structures (m): 4-8
Depth of ditches/pits/dams (m): 0.7
Width of ditches/pits/dams (m): 0.7
Length of ditches/pits/dams (m): 5
Height of bunds/banks/others (m): 0.5
Width of bunds/banks/others (m): 0.7
Length of bunds/banks/others (m): 5.5
Ahmad Ali Sediqi, HELVETAS Swiss Intercooperation
|1.||construction of trenches||summer and autumn|
|劳动力||Construction of trenches||persons/day/ha||276.0||5.0||1380.0||10.0|
Duration of establishment phase: 36 month(s)
|1.||Repair trenches||Spring/once per year|
Machinery/ tools: Shovel
- < 250毫米
- > 4,000毫米
Thermal climate class: temperate
- 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.
- 非常深（> 120厘米）
Soil fertility is low - medium
Soil drainage / infiltration is medium - good
Soil water storage capacity is medium
Availability of surface water: During rainy seasons
Water quality (untreated): Not good but used for animal drinking water using traditional water harvesting structures
Land users applying the Technology are mainly common / average land users
Difference in the involvement of women and men: Women are not allowed to work in these areas due to local customs.
Population density: 10-50 persons/km2
Annual population growth: 2% - 3%
Relative level of wealth: rich, average, poor
10% of the land users are rich.
40% of the land users are average wealthy.
50% of the land users are poor.
Market orientation of production system: Income from selling sheep and goats and items from livestotck products like carpets.
- < 0.5 公顷
- 0.5-1 公顷
- 1-2 公顷
- > 10,000公顷
Land is used by families of three community development councils in Kahmard district as common land
Increase in natural production due to increased moisture and area protection
As the area is closed for grazing and shrub cutting
Work is facilitated by watershed management committee
livelihood and human well-being
It has reduced flash flood risks. As a result, more area in the valleys is productive and damages to houses, roads, gardens, agriculture land have significantly reduced
Due to less flash floods
Stabilize CTTs with vegetative and management measures. Trench size should be based on hydro-meteorological parameters considering possibility of an extreme event occurring.
100% of land user families have adopted the Technology with external material support
|Reduce flash floods risks|
Helps in spring recharge
How can they be sustained / enhanced? CTTs should be maintained and combined with vegetation measures for better infiltration.
Reduce flash floods risks
How can they be sustained / enhanced? Maintenance and application of vegetative measures along with the trenches. For Instance planting of perennial forage species on the bunds like Alfalfa, Agropyron and Sainfoin..
CTTs considered better than staggered contour trench if the purpose is to control flash floods as it can trap more runoff and have less chances of damages
How can they be sustained / enhanced? Maintenance and correct implementation is necessary
Helps in the establishment of vegetation due to more soil moisture
How can they be sustained / enhanced? Combine with conservation practices like mulching
Potential technology for reducing flash flood risks
How can they be sustained / enhanced? More training and awareness about the limitations of this technology - where to apply and where not to apply
|Soil disturbed during digging and fine clay deposits in the trenches which reduces infiltration||Apply conservation trenches. Planting on the either ends of the trench and soil working to break the clay layering.|
|Establishment costs are high||Initial external support necessary. Linking relief to sustainable land management could be an option.|
|Loss of land for production due to trenching||ntegrate planting of trees and grasses.|
|Trenches break||CTTs must be of right size along the contour lines. Workers must be trained before implementation work and there must be proper supervision. The size of a trench and spacing between trenches should be based on hydro-met parameters. Also, avoid steep sandy (blue) and shallow rocky soil beds|