Difference between revisions of "Mitigation and Intervention Techniques Related to Micro-hydro Power (MHP) Projects"
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*<u>Objectives</u>: A waterway is a natural or artificial drainage channel constructed along the steepest<br>slope or in a valley to receive/accommodate runoff from cut-off drains and graded terraces/bunds. The waterway carries the run-off to rivers, resevoirs or gullies safely without creating erosion. A vegetative waterway can be constructed in areas without stones. The main advantage is that waterways can be constructed for both very small and large size catchments, thus accomodating individual or communal needs for drainage and evacuation/use of excess run-off. Paved waterways are suitable in steeper terrains and areas with large amount of stones. | *<u>Objectives</u>: A waterway is a natural or artificial drainage channel constructed along the steepest<br>slope or in a valley to receive/accommodate runoff from cut-off drains and graded terraces/bunds. The waterway carries the run-off to rivers, resevoirs or gullies safely without creating erosion. A vegetative waterway can be constructed in areas without stones. The main advantage is that waterways can be constructed for both very small and large size catchments, thus accomodating individual or communal needs for drainage and evacuation/use of excess run-off. Paved waterways are suitable in steeper terrains and areas with large amount of stones. | ||
− | <br> | + | [[Image:Waterways.png|570x196px|Waterways.png]]<br> |
<br> | <br> | ||
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<br>'''Graded Soil Bund''' | <br>'''Graded Soil Bund''' | ||
− | *<u>Objectives</u>: Graded soil bund is similar in description with level soil bund. However, graded soil bund is upto a maximum of 1% inclined against the contour so that excess runoff is allowed to drain to the adjoining natural or artificial waterways. It is also possible and necessary to inculde tied ridges smaller in height within the channel of the terrace. The stored water within the ties can infiltrate into the soil while any above that height is drained out. Graded soil bunds can be made to gradually<br>develop in to benched type terraces through careful maintenace. Any integration of other measures such as stabilization and composting can be applied as it can be applied on level bunds. | + | *<u>Objectives</u>: Graded soil bund is similar in description with level soil bund. However, graded soil bund is upto a maximum of 1% inclined against the contour so that excess runoff is allowed to drain to the adjoining natural or artificial waterways. It is also possible and necessary to inculde tied ridges smaller in height within the channel of the terrace. The stored water within the ties can infiltrate into the soil while any above that height is drained out. Graded soil bunds can be made to gradually<br>develop in to benched type terraces through careful maintenace. Any integration of other measures such as stabilization and composting can be applied as it can be applied on level bunds.<br> |
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− | <br> | ||
<br>'''Graded Fanya Juu''' | <br>'''Graded Fanya Juu''' | ||
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#Increased crop and residue yields. | #Increased crop and residue yields. | ||
#Early harvest when there is shortage of food supply and also help farmers benefit from higher prices. | #Early harvest when there is shortage of food supply and also help farmers benefit from higher prices. | ||
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+ | [[Image:ImprovedSurfaceDrainage.png|315px|ImprovedSurfaceDrainage.png]] | ||
<br> | <br> | ||
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*<u>Objectives</u>: The stone bund reduces and stops the velocity of runoff and consequently reduces soil erosion and the steady decline in fertility and crop yields. They are semi-permeable structures unless sealed with soil in their upper side. They increase the moisture retention capacity of the soil profile and water availability to plants, and increase the efficiency of fertilizer applications if any. Through their water retention effect the stone bunds may allow some crop yield even in drought years. Stone bunds are entry points for application of organic residues or compost, especially in the first 2-3 meters behind the bund where soil is deeper. | *<u>Objectives</u>: The stone bund reduces and stops the velocity of runoff and consequently reduces soil erosion and the steady decline in fertility and crop yields. They are semi-permeable structures unless sealed with soil in their upper side. They increase the moisture retention capacity of the soil profile and water availability to plants, and increase the efficiency of fertilizer applications if any. Through their water retention effect the stone bunds may allow some crop yield even in drought years. Stone bunds are entry points for application of organic residues or compost, especially in the first 2-3 meters behind the bund where soil is deeper. | ||
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+ | [[Image:StoneBunds.png|315px|StoneBunds.png]]<br> | ||
'''<br>Stone Faced Soil Bunds''' | '''<br>Stone Faced Soil Bunds''' | ||
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*<u>Objectives</u>: The FJ reduces and stops the velocity of runoff and consequently reduces soil erosion and the steady decline of crop yields. They are impermeable structures intended to retain rainfall,<br>and hence, increase s.oil moisture, water availability to plants, and increase the efficiency of fertilizer application if any. Fanya juus bench quicker than soil bunds but are not as efficient in moisture conservation and more prone to breakages/overtopping. | *<u>Objectives</u>: The FJ reduces and stops the velocity of runoff and consequently reduces soil erosion and the steady decline of crop yields. They are impermeable structures intended to retain rainfall,<br>and hence, increase s.oil moisture, water availability to plants, and increase the efficiency of fertilizer application if any. Fanya juus bench quicker than soil bunds but are not as efficient in moisture conservation and more prone to breakages/overtopping. | ||
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+ | [[Image:FanyaJuuBund.png|400px|FanyaJuuBund.png]] | ||
'''<br>Bench Terracing''' | '''<br>Bench Terracing''' | ||
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*<u>Objectives</u>: Hillside terraces are physical structures constructed along the contours, generally suitable in steep degraded slopes and shallow soils (although common in other type of soils), suitable for tree planting and rather effective in controlling runoff and erosion. Common in most parts of Ethiopia, generally in dry areas to support area closure plantation and protect downstream fields. | *<u>Objectives</u>: Hillside terraces are physical structures constructed along the contours, generally suitable in steep degraded slopes and shallow soils (although common in other type of soils), suitable for tree planting and rather effective in controlling runoff and erosion. Common in most parts of Ethiopia, generally in dry areas to support area closure plantation and protect downstream fields. | ||
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+ | [[Image:HillsideTerraces.png|349x273px|HillsideTerraces.png]]<br> | ||
'''<br>Hillside Terrace with Trenches''' | '''<br>Hillside Terrace with Trenches''' | ||
*<u>Objectives</u>: HTTs is highly labour intensive - combine both effects of hillsides and trenches constructed immediately above the terrace stone riser, generally suitable for steep slopes (up to 50%) and shallowmedium depth soils (although common in other type of soils). Suitable for tree/shrubs planting and very effective in controlling runoff and erosion. HHTs ensure protection of downstream fields, and play a significant role in replenishing water tables. | *<u>Objectives</u>: HTTs is highly labour intensive - combine both effects of hillsides and trenches constructed immediately above the terrace stone riser, generally suitable for steep slopes (up to 50%) and shallowmedium depth soils (although common in other type of soils). Suitable for tree/shrubs planting and very effective in controlling runoff and erosion. HHTs ensure protection of downstream fields, and play a significant role in replenishing water tables. | ||
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+ | [[Image:HillsideTerraces and Trenches.png|347x324px|HillsideTerraces and Trenches.png]]<br> | ||
<br> | <br> | ||
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*<u>Objectives</u>: They are instrumental in increasing the size of plot and provide the right amount of water to crops at the the right time. The treadle pump, relative to the traditional rope and bucket system will increase irrigated surface areas and reduce irrigation labour time relative to the original irrigated surface area. Thus, resulting in increased production. | *<u>Objectives</u>: They are instrumental in increasing the size of plot and provide the right amount of water to crops at the the right time. The treadle pump, relative to the traditional rope and bucket system will increase irrigated surface areas and reduce irrigation labour time relative to the original irrigated surface area. Thus, resulting in increased production. | ||
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+ | [[Image:LowCostWaterLifting.png|650x287px|LowCostWaterLifting.png]]<br> | ||
'''<br>Low Cost Micro-ponds''' | '''<br>Low Cost Micro-ponds''' | ||
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#Reduce runoff and subsequently erosion and land degradation. | #Reduce runoff and subsequently erosion and land degradation. | ||
− | '''<br>Percolation | + | '''<br>Percolation Pond''' |
*<u>Objectives</u>: A percolation pond is a structure, constructed on any marginal land with pervious soil, with the following objectives:<br> | *<u>Objectives</u>: A percolation pond is a structure, constructed on any marginal land with pervious soil, with the following objectives:<br> | ||
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*Objectives: Increased frequency and uniformity of water application plus reduced competition from weeds results in improved plant growth and yield increases of 30 to 50 percent. The system is instrumental in increasing the size of plot and provide the right amount of water to crops at the the right time. Thus, resulting in increased production. | *Objectives: Increased frequency and uniformity of water application plus reduced competition from weeds results in improved plant growth and yield increases of 30 to 50 percent. The system is instrumental in increasing the size of plot and provide the right amount of water to crops at the the right time. Thus, resulting in increased production. | ||
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+ | [[Image:DripIrrigation.png|350px|DripIrrigation.png]]<br> | ||
'''<br>Roof Water Harvesting System''' | '''<br>Roof Water Harvesting System''' | ||
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*Objectives: River bed dams are a floodwater farming techniques where runoff waters are spread in valley bottoms of seasonal riverbeds, large gullies or natural water courses for improved crop and forage producdtion using a long, low structure, made from loose stone (occasionally some gabion baskets may be used). Developing gullies are healed at the same time. Occasionally it is required to raise the riverbed in order to guide spate floods into irrigation canals of spate irrigation schemes, or to accumulate river sediments for riverbed cultivation. In such a case, very strong dams are required that can resist powerful spate floods. It is a relatively low cost structure especially designed to resist heavy flooding. The structures are typically long, low dam walls across valleys. The large amount of work involved means that the technique is labor intensive and needs group approach. | *Objectives: River bed dams are a floodwater farming techniques where runoff waters are spread in valley bottoms of seasonal riverbeds, large gullies or natural water courses for improved crop and forage producdtion using a long, low structure, made from loose stone (occasionally some gabion baskets may be used). Developing gullies are healed at the same time. Occasionally it is required to raise the riverbed in order to guide spate floods into irrigation canals of spate irrigation schemes, or to accumulate river sediments for riverbed cultivation. In such a case, very strong dams are required that can resist powerful spate floods. It is a relatively low cost structure especially designed to resist heavy flooding. The structures are typically long, low dam walls across valleys. The large amount of work involved means that the technique is labor intensive and needs group approach. | ||
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+ | [[Image:Riverbed Dams.png|565x240px|Riverbed Dams.png]] | ||
'''<br>Small Stone Bunds with Run-on and Run-off Areas''' | '''<br>Small Stone Bunds with Run-on and Run-off Areas''' | ||
− | *<u>Objectives</u>: The main objective is to considerably increase the biomass production of forage grass and legumes pastures and fodder crops and/or allow the introduction of species having higher water requirements in abandoned, marginal and eroded dry areas. The principle of the system and its application is the same as for runoff/runon systems suggested for the cultivated areas. Rainfall multiplier systems for grazing land can also rehabilite fertility (decay of grass and increased moisture). In this respect, a few years pasture improvement and soil fertility restoration may allow the<br>area to be cropped again. The main difference between this measure and the one described for the cultivated land is that instead of food crops fodder plants are grown. The system is less demanding in terms of size of structures and management of the plots as fodder species require less water than food crops. | + | *<u>Objectives</u>: The main objective is to considerably increase the biomass production of forage grass and legumes pastures and fodder crops and/or allow the introduction of species having higher water requirements in abandoned, marginal and eroded dry areas. The principle of the system and its application is the same as for runoff/runon systems suggested for the cultivated areas. Rainfall multiplier systems for grazing land can also rehabilite fertility (decay of grass and increased moisture). In this respect, a few years pasture improvement and soil fertility restoration may allow the<br>area to be cropped again. The main difference between this measure and the one described for the cultivated land is that instead of food crops fodder plants are grown. The system is less demanding in terms of size of structures and management of the plots as fodder species require less water than food crops.<br> |
+ | |||
+ | [[Image:Bunds with run-off areas.png|456x309px|Bunds with run-off areas.png]]<br> | ||
<br>'''Narrow Stone Lines Along the Contour''' | <br>'''Narrow Stone Lines Along the Contour''' | ||
*<u>Objectives</u>: Stone lines are semi-permeable or permeable structures, intended to capture some moisture and thus allow the growth of spontaneous grass. By slowing down runoff they also decrease erosion, although not completely. This is a soil and moisture conservation measure suitable for rangelands and degraded grazing lands in dry areas. The measure is less labour intensive and material demanding than small stone faced soil bunds but less efficient. The principle is rainfall multiplier system but the measure is applicable only if stones are available. | *<u>Objectives</u>: Stone lines are semi-permeable or permeable structures, intended to capture some moisture and thus allow the growth of spontaneous grass. By slowing down runoff they also decrease erosion, although not completely. This is a soil and moisture conservation measure suitable for rangelands and degraded grazing lands in dry areas. The measure is less labour intensive and material demanding than small stone faced soil bunds but less efficient. The principle is rainfall multiplier system but the measure is applicable only if stones are available. | ||
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+ | [[Image:NarrowStoneLinesAlongContours.png|350px|NarrowStoneLinesAlongContours.png]]<br> | ||
'''<br>Stone Faced/Soil or Stone Bunds with Run-off/ Run-on Areas''' | '''<br>Stone Faced/Soil or Stone Bunds with Run-off/ Run-on Areas''' | ||
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*<u>Objectives</u>: CBTs are constructed on steep slopes to combinesoil and water conservation with water harvesting practices. They control erosion and retain moisture and are suitable for food/ tree crops and are effective in controlling runoff and erosion. They are also water harvesting structures, the riser acts as a catchment. Common in most parts of Ethiopia, (e.g Konso) generally in dry areas. Benching action eases cultivation operation by oxen, however, more appropriate to use. | *<u>Objectives</u>: CBTs are constructed on steep slopes to combinesoil and water conservation with water harvesting practices. They control erosion and retain moisture and are suitable for food/ tree crops and are effective in controlling runoff and erosion. They are also water harvesting structures, the riser acts as a catchment. Common in most parts of Ethiopia, (e.g Konso) generally in dry areas. Benching action eases cultivation operation by oxen, however, more appropriate to use. | ||
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+ | [[Image:ConservationBenchTerraces.png|300px|ConservationBenchTerraces.png]] | ||
'''<br>Tie Ridge (s)''' | '''<br>Tie Ridge (s)''' | ||
*<u>Objectives</u>: Tie ridges are small rectangular series of basins formed withing the furrow of cultivated fields mainly to increase surface storage and to allow more time for rainfall to infiltrate the soil. Making tied ridges manually is time and labor consuming. | *<u>Objectives</u>: Tie ridges are small rectangular series of basins formed withing the furrow of cultivated fields mainly to increase surface storage and to allow more time for rainfall to infiltrate the soil. Making tied ridges manually is time and labor consuming. | ||
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+ | [[Image:TieRidge.png|350px|TieRidge.png]] | ||
'''<br>The Zai and Planting Pit System''' | '''<br>The Zai and Planting Pit System''' | ||
*<u>Objectives</u>: Zai pits are systems of small pits dug along approximate contours allows the cultivation of crops on degraded lands. The zaï pits restore degraded lands (crusted, hard, compacted and poorly structured soils), thus increasing the land available for cultivation. It is a simple technique that, amongst others, landless or oxenless can practice because it requires only manual labour. | *<u>Objectives</u>: Zai pits are systems of small pits dug along approximate contours allows the cultivation of crops on degraded lands. The zaï pits restore degraded lands (crusted, hard, compacted and poorly structured soils), thus increasing the land available for cultivation. It is a simple technique that, amongst others, landless or oxenless can practice because it requires only manual labour. | ||
+ | |||
+ | [[Image:Zai and Planting Pits.png|500px|Zai and Planting Pits.png]] | ||
'''<br>Large Half Moons''' | '''<br>Large Half Moons''' | ||
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*<u>Objectives</u>: The measure is a rainfall multiplier system that allow cultivation of crops in low rainfall areas. It is applied in areas with sandy and sandy loamy soils affected by low fertility levels and thin<br>surface crusts that inhibit infiltration and increase runoff. Large half moons are suitable structures to enable cultivation of drought resistant crops in areas with very low rainfall. They intercept all runoff and stop erosion. It is also a measure suitable for rangelands and degraded grazing lands in dry areas (forage crops). | *<u>Objectives</u>: The measure is a rainfall multiplier system that allow cultivation of crops in low rainfall areas. It is applied in areas with sandy and sandy loamy soils affected by low fertility levels and thin<br>surface crusts that inhibit infiltration and increase runoff. Large half moons are suitable structures to enable cultivation of drought resistant crops in areas with very low rainfall. They intercept all runoff and stop erosion. It is also a measure suitable for rangelands and degraded grazing lands in dry areas (forage crops). | ||
− | <br>''' | + | [[Image:HalfMoons.png|531x331px|HalfMoons.png]] |
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+ | '''<br>''' | ||
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+ | '''Division Weir Design and Construction''' | ||
*<u>Objectives</u>: To divert stream flow for use during dry seasons for the purpose of small scale irrigation and for any other supplementary irrigation. | *<u>Objectives</u>: To divert stream flow for use during dry seasons for the purpose of small scale irrigation and for any other supplementary irrigation. |
Revision as of 07:08, 26 April 2011
The identification of appropriate mitigation and intervention techniques on the basis of the Environment Assessment is crucial for the implementation of a successful Watershed Action Plan in order to achieve a sustainable use of the catchment area and thus the MHP project. Biophysical as well as political mitigation and intervention techniques are listed in the table below:
BIOPHYSICAL MEASURES[1] |
|
Gully control |
Stone Checkdams
Brushwood Checkdams
Gully Reshaping, Filling and Revegetation
Sediment Storage and Overflow Earth Dams (SS Dams) for Productive Gully Control
|
Agro-forestry, Forage Development and Forestry |
Area Closure
Microbasins (MBs)
|
Soil Fertility Management and Biological Soil Conservation |
Compost Making
Fertilization and Manuring
Grass Strips along the Contours
|
Flood Control and Improved Drainage |
Waterways (Vegetative and Stone Paved)
Cut-off Drains
|
Physical Soil and Water Conservation |
Level Soil Bunds
|
Water harvesting |
Hand-dug Wells
Division Weir Design and Construction
|
POLITICAL MEASURES |
|
Education and training |
|
Income generating measures |
|
Participatory approach |
Box 1 shows three examples of how (rather simple) interventions can improve the environmental condition of the catchment. A more detailed list of mitigation and intervention techniques and the respective application can be found in DESTA, L. ET AL. (2005): Part 1: Community Based Participatory Watershed Development. Addis Ababa: Ministry of Agriculture and Rural Development, pages 69 – 165 and DESTA, L. ET AL. (2005): Part 2: Community Based Participatory Watershed Development: Annex. Addis Ababa: Ministry of Agriculture and Rural Development, pages 43 - 48.
Box 1:
|
References
- ↑ DESTA, L. ET AL. (2005): Part 1: Community Based Participatory Watershed Development: A Guideline. Addis Ababa: Ministry of Agriculture and Rural Development.
- ↑ HELVETAS (2005): Helvetas Wasser Fact Sheet: Quellen und Quellschutz.
- ↑ GALE, J.A. (unknown): Watershedss Wetland Management. http://www.water.ncsu.edu/watershedss/info/wetlands/manage.html#prot
- ↑ SUNGSUMARN, K. (1993): Why Eucalyptus is Not Adopted for Agroforestry. In: Kashio, M. et al. (Hrsg.)(1996): Reports Submitted to the Regional Expert Consultation on Eucalyptus - Volume II. Bangkok: FAO Regional Office for Asia and the Pacific.
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