1.2 ព័ត៌មានលម្អិតពីបុគ្គលសំខាន់ៗ និងស្ថាប័នដែលចូលរួមក្នុងការវាយតម្លៃ និងចងក្រងឯកសារនៃបច្ចេកទេស

ឈ្មោះគម្រោងដែលបានចងក្រងឯកសារ/ វាយតម្លៃលើបច្ចេកទេស (បើទាក់ទង)

Book project: Water Harvesting – Guidelines to Good Practice (Water Harvesting)

1.3 លក្ខខណ្ឌទាក់ទងទៅនឹងការប្រើប្រាស់ទិន្នន័យដែលបានចងក្រងតាមរយៈ វ៉ូខេត

អ្នកចងក្រង និង(បុគ្គលសំខាន់ៗ)យល់ព្រមទទួលយកនូវលក្ខខណ្ឌនានាទាក់ទងទៅនឹងការប្រើប្រាស់ទិន្នន័យដែលបានចងក្រងតាមរយៈវ៉ូខេត:

បាទ/ចា៎

2.1 ការពណ៌នាដោយសង្ខេបពីបច្ចេកទេស

និយមន័យបច្ចេកទេស:

Water-spreading weirs are structures that span the entire width of a valley to spread floodwater over the adjacent land area.

2.2 ការពណ៌នាលម្អិតពីបច្ចេកទេស

ការពណ៌នា:

Over the last 12 years water-spreading weirs have been introduced and improved as a new rehabilitation technique for degraded dry valleys in Burkina Faso, Niger and Chad. In Chad 104 water-spreading weirs were constructed in the scope of the two development projects, initiated by the German Technical Cooperation (GIZ) and the Swiss Development Cooperation (SDC) in the 1990s. Water-spreading weirs are made of natural stones and cement, and consist of a spillway in the actual riverbed and lateral abutments and wings. Floodwaters are spread over the adjacent land area above the structure, where they eventually overflow the lateral wings and then slowly flow back towards the riverbed below the structure. As a result the land area below the weir is flooded. The lateral spreading of the water causes the land area above and below the structure to be flooded and supplies it with sediment. Water infiltrates, gullies in the valley are filled and the riverbed is raised. Thanks to the infiltration, the groundwater table also rises in a few years.

Purpose of the Technology: In dry valleys in which water flows in the rivers for only a few days a year, the weirs serve to distribute the incoming runoff over the valley floor and allow as much water as possible to infiltrate the soil. The aquifer is thus replenished and is then available for agricultural use. In contrast to the various types of dams, the goal of water-spreading weirs is not to create reservoirs for later use. What water-spreading weirs do is cause a temporary flooding of the adjacent land area above and below the weir. Depending on user preferences, the primary goal may be 1) agricultural use, 2) sylvo-pastoral use or 3) the replenishment and rising of the water table.

Establishment / maintenance activities and inputs: Water-spreading weirs require detailed technical planning and experienced engineering and construction firms. The bulk of the work is performed using local materials and by village craftsmen and helpers.

Natural / human environment: Compared to small impoundment dams, retention basins and microweirs, water-spreading weirs are especially well-suited for shallow, wide valleys that, due to severe gully erosion, are no longer inundated by small and medium
volume floodwaters. The flooding no longer takes place because the actual riverbed has been deeply eroded and enlarged. However, water-spreading weirs are also suitable for improving agricultural productivity in more or less intact valley floors. Water-spreading weirs are successful in regions where precipitation during the growing season is erratic and where the weirs ensure a more evenly distributed water supply for crops, as well as in zones in which water enrichment makes one or two additional growing seasons possible. At the present time they are in use in a broad area where annual rainfall ranges from 50 to 1,200 mm/year.

2.3 ​រូបភាពនៃបច្ចេកទេស

2.5 ប្រទេស/តំបន់/ទីតាំងកន្លែង ដែលបច្ចេកទេសត្រូវបានអនុវត្ត និងបានគ្រប់ដណ្តប់ដោយការវាយតម្លៃនេះ

2.6 កាលបរិច្ឆេទនៃការអនុវត្ត

ប្រសិនបើមិនច្បាស់ឆ្នាំ សូមបញ្ជាក់កាលបរិច្ឆេទដែលប្រហាក់ប្រហែល:

• 10-50 ឆ្នាំ

2.7 ការណែនាំពីបច្ចេកទេស

សូមបញ្ជាក់តើបច្ចេកទេសត្រូវបានណែនាំឱ្យអនុវត្តដោយរបៀបណា:

• តាមរយៈគម្រោង / អន្តរាគមន៍ពីខាងក្រៅ

មតិយោបល់ (ប្រភេទនៃគម្រោង ។ល។):

The first water-spreading weirs were introduced during the 1990s in Chad through Swiss cooperation

3.1 គោលបំណងចម្បង (១​ ឬច្រើន)​ នៃបច្ចេកទេសនេះ

• ធ្វើឱ្យប្រសើរឡើងនូវផលិតកម្ម
• កាត់បន្ថយ, បង្ការ, ស្តារឡើងវិញនូវការធ្លាក់ចុះគុណភាពដី

3.2 ប្រភេទដីប្រើប្រាស់មួយប្រភេទ (ច្រើនប្រភេទ) ដែលបានអនុវត្តបច្ចេកទេស

មតិយោបល់:

Major land use problems (compiler’s opinion): Substantial degradation of drainage basins in the Sahel due to population growth and intense land-use pressure has been observed since the 1960s. Climate change has further amplified this trend. The expansion of agriculture and intensification of grazing and logging have caused the natural vegetation cover to decline. This process has been accelerated by severe droughts and has led to the degradation of the soils. Sparse vegetation cover and structurally damaged soils reduce rainfall infiltration into the soil, resulting in more runoff and soil erosion on plateaus and slopes. Runoff is concentrated in the valleys, in which heavy floodwaters
wash away fertile soils and lead to deep erosion of the riverbed. The annual, recurrent small and medium-size floods that normally cause temporary inundation of the valleys and deposition of fertile sediments no longer occur.

3.4 ការផ្គត់ផ្គង់ទឹក

ផ្សេងៗ (ឧ. ក្រោយពីទឹកជំនន់):

• Post-flooding

មតិយោបល់:

Water supply: Also mixed rainfed - irrigated and rainfed

3.5 ក្រុម SLM ដែលបច្ចេកទេសស្ថិតនៅក្នុង

• វិធានការអនុវត្តកាត់ទទឹងទីជម្រាល
• ការគ្រប់គ្រងប្រព័ន្ធស្រោចស្រព (រួមទាំងការផ្គត់ផ្គង់ទឹក ប្រព័ន្ធបង្ហូរ)
• ការបែងចែកទឹក និងប្រព័ន្ធបង្ហូរ

3.6 វិធានការ SLM ដែលបញ្ចូលនូវបច្ចេកទេស

3.7 កំណត់ប្រភេទនៃការធ្លាក់ចុះគុណភាពដីសំខាន់ៗដែលបច្ចេកទេសនេះបានដោះស្រាយ

មតិយោបល់:

Main type of degradation addressed: Wt: loss of topsoil / surface erosion, Wg: gully erosion / gullying, Hg: change in groundwater / aquifer level

Main causes of degradation: soil management (abandonment of fallow periods), deforestation / removal of natural vegetation (incl. forest fires) (for agricultural expansion), over-exploitation of vegetation for domestic use, droughts, population pressure

Secondary causes of degradation: overgrazing

3.8 ការពារ កាត់បន្ថយ ឬស្តារឡើងវិញនៃការធ្លាក់ចុះគុណភាពដី

បញ្ជាក់ពីគោលដៅរបស់បច្ចេកទេស ដែលផ្តោតទៅការធ្លាក់ចុះគុណភាពដី:

• ការកាត់បន្ថយការធ្លាក់ចុះគុណភាពដី
• ការជួសជុល/ ស្តារឡើងវិញនៃឱនភាពដីធ្ងន់ធ្ងរ

មតិយោបល់:

Main goals: rehabilitation / reclamation of denuded land

Secondary goals: mitigation / reduction of land degradation

4.1 គំនូសបច្ចេកទេសនៃបច្ចេកទេសនេះ

4.3 សកម្មភាពបង្កើត

	សកម្មភាព	រយៈពេល​ (រដូវកាល)
1.	Excavating the steps
2.	Excavating the wall foundations
3.	Pouring the foundations
4.	Building the walls
5.	Finishing the walls and filling the stilling basin

4.4 ថ្លៃដើម និងធាតុចូលដែលត្រូវការសម្រាប់ការបង្កើតបច្ចេកទេស

	បញ្ជាក់ពីធាតុចូល	ឯកតា	បរិមាណ	ថ្លៃដើមក្នុងមួយឯកតា	ថ្លៃធាតុចូលសរុប	% នៃថ្លៃដើមដែលចំណាយដោយអ្នកប្រើប្រាស់ដី
កម្លាំងពលកម្ម	Labour	ha	1,0	750,0	750,0	100,0
សម្ភារៈ	Total costs for equipment	ha	1,0	750,0	750,0
សម្ភារៈសាងសង់	Stone	ha	1,0	750,0	750,0
ថ្លៃដើមសរុបក្នុងការបង្កើតបច្ចេកទេស					2250,0

4.6 កំណត់ថ្លៃដើមសម្រាប់ការថែទាំ/ សកម្មភាពរបស់បច្ចេកទេស (ក្នុងរយៈពេលមួយឆ្នាំ)

	បញ្ជាក់ពីធាតុចូល	ឯកតា	បរិមាណ	ថ្លៃដើមក្នុងមួយឯកតា	ថ្លៃធាតុចូលសរុប	% នៃថ្លៃដើមដែលចំណាយដោយអ្នកប្រើប្រាស់ដី
កម្លាំងពលកម្ម	Labour	ha	1,0	50,0	50,0	100,0
សម្ភារៈ	Total costs for equipment	ha	1,0	50,0	50,0
សម្ភារៈសាងសង់	Stone	ha	1,0	50,0	50,0
ថ្លៃដើមសរុបសម្រាប់ការថែទាំដំណាំតាមបច្ចេកទេស					150,0

មតិយោបល់:

The costs were calculated per structure (one diversion weir). The length of the weir varies depending on the width of the valley it is constructed in. The weir has to span the whole valley which is usually between 100 and 1000 m wide.

5.1 អាកាសធាតុ

5.2 សណ្ឋានដី

5.3 ដី

បើអាចសូមភ្ជាប់ការពណ៌នាពីដីឱ្យបានច្បាស់ ឬព័ត៌មានដែលអាចទទួលបាន ឧ. ប្រភេទដី, pH ដី/ ជាតិអាស៊ីត, សមត្ថភាពផ្លាស់ប្តូរកាចុង, វត្តមាននីត្រូសែន, ភាពប្រៃ ។ល។:

Soil fertility: High
Soil drainage/infiltration: Medium (ranked 1) and good (ranked 2)
Soil water storage capacity: Medium

5.4 ទឹកដែលអាចទាញមកប្រើប្រាស់បាន និងគុណភាពទឹក

មតិយោបល់ និងលក្ខណៈពិសេសផ្សេងៗទៀតលើគុណភាព និងបរិមាណទឹក​ :

Availability of surface water: excess (during heavy rainfalls in the rainy season) or poor/ none (in the dry season)

5.5 ជីវៈចម្រុះ

5.6 លក្ខណៈនៃអ្នកប្រើប្រាស់ដីដែលអនុវត្តបច្ចេកទេស

សូមបញ្ជាក់ពីលក្ខណៈពាក់ព័ន្ធផ្សេងទៀតអំពីអ្នកប្រើប្រាស់ដី:

Population density: < 10 persons/km2
70% of the land users are poor.
Market orientation: Mixed (rainfed crops are for subsistence, post-rainy season crops and irrigated crops (vegetables) mainly for market)

5.7 ទំហំផ្ទៃដីជាមធ្យមនៃដីប្រើប្រាស់ដោយអ្នកប្រើប្រាស់ដី ក្នុងការអនុវត្ត​បច្ចេកទេស

5.8 ភាពជាម្ចាស់ដី កម្មសិទ្ធប្រើប្រាស់ដី និងកម្មសិទ្ធប្រើប្រាស់ទឹក

ភាពជាម្ចាស់ដី:

• ភូមិ

កម្មសិទ្ធិប្រើប្រាស់ដី:

• កិច្ចសន្យាជួល

មតិយោបល់:

In Chad, only the rainfed fields are in private family ownership and inheritable. Reclaimed irrigated fields and vegetable production fields go back to the community and can be redistributed.

6.1 ផលប៉ះពាល់ក្នុងបរិវេណអនុវត្តបច្ចេកទេសដែលកើតមាន

ផលប៉ះពាល់លើសេដ្ឋកិច្ចសង្គម

ផលិតផល

ចំណូល និងថ្លៃដើម

ផលប៉ះពាល់ទៅលើសេដ្ឋកិច្ចសង្គមផ្សេងៗ

ផលប៉ះពាល់ទៅលើវប្បធម៌សង្គម

ផលប៉ះពាល់ទៅលើអេកូឡូស៊ី

វដ្តទឹក/លំហូរ

ដី

ជីវចម្រុះ៖ ដំណាំ, សត្វ

6.2 ផលប៉ះពាល់ក្រៅបរិវេណអនុវត្តបច្ចេកទេសដែលកើតមាន

6.3 ភាពប្រឈម និងភាពរួសនៃបច្ចេកទេសទៅនឹងការប្រែប្រួលអាកាសធាតុ និងគ្រោះអាកាសធាតុ/ គ្រោះមហន្តរាយ (ដែលដឹងដោយអ្នកប្រើប្រាស់ដី)

ការប្រែប្រួលអាកាសធាតុ

ការប្រែប្រួលអាកាសធាតុ

	រដូវកាល	កើនឡើង ឬថយចុះ	លក្ខណៈឆ្លើយតបនៃបច្ចេកទេសទៅនឹងការប្រែប្រួលអាកាសធាតុ
សីតុណ្ហភាពប្រចាំឆ្នាំ		កើនឡើង	ល្អ

គ្រោះអាកាសធាតុ (មហន្តរាយ) ​

គ្រោះមហន្តរាយធម្មជាតិ

	លក្ខណៈឆ្លើយតបនៃបច្ចេកទេសទៅនឹងការប្រែប្រួលអាកាសធាតុ
ព្យុះភ្លៀងតាមតំបន់	ល្អ
ព្យុះកំបុតត្បូងតាមតំបន់	ល្អ

គ្រោះមហន្តរាយទឹក

	លក្ខណៈឆ្លើយតបនៃបច្ចេកទេសទៅនឹងការប្រែប្រួលអាកាសធាតុ
ទឹកជំនន់ទូទៅ (ទន្លេ)	ល្អ

6.4 ការវិភាគថ្លៃដើម និងអត្ថប្រយោជន៍

តើផលចំណេញ និងថ្លៃដើមត្រូវបានប្រៀបធៀបគ្នាយ៉ាងដូចម្តេច (ទស្សនៈរបស់អ្នកប្រើប្រាស់ដី)?

តើផលចំណេញ និងការថែទាំ/ ជួសជុលត្រូវបានប្រៀបធៀបគ្នាយ៉ាងដូចម្តេច (ទស្សនៈរបស់អ្នកប្រើប្រាស់ដី)?

មតិយោបល់:

Depending upon the users' experience and the availability of labour, it may take anywhere from 2 to 10 years before the rehabilitated land area reaches its optimum use potential.

6.5 ការទទួលយកបច្ចេកទេស

ក្នុងចំណោមគ្រួសារទាំងអស់ដែលបានអនុវត្តបច្ចេកទេស តើមានប៉ុន្មាន​គ្រួសារ​ដែល​ចង់​ធ្វើ​ដោយ​ខ្លួន​ឯង ដោយមិន​ទទួល​បាន​សម្ភារៈ​លើក​​ទឹកចិត្ត/​ប្រាក់ឧបត្ថម្ភ?​:

• 0-10%

មតិយោបល់:

100% of land user families have adopted the Technology with external material support

6000 land user families have adopted the Technology with external material support

Comments on acceptance with external material support: Between 4000 and 8000 households are direct beneficiaries of the construction of water-spreading weirs in Eastern Chad.

There is no trend towards spontaneous adoption of the Technology

Comments on adoption trend: It is unlikely that communities will be able to adopt this technology without external funding. Even for maintenance activities it remains to be seen if the communities will be capable of funding more extensive maintenance work with their low budgets.

6.7 ភាពខ្លាំង/ គុណសម្បត្តិ/ ឱកាសនៃបច្ចេកទេស

ភាពខ្លាំង/ គុណសម្បត្តិ/ ឱកាស​ ទស្សនៈរបស់បុគ្គលសំខាន់ៗ
Through the construction of water-spreading weirs, soils are regularly flooded and supplied with water and sediment. Thus, the arable land area and the yields of the rainy season crops serving as staple food increase. How can they be sustained / enhanced? Ensure proper maintenance of the system.
The more frequent flooding of the soils results in increased infiltration, and the groundwater level rises substantially.
Prior to rehabilitation, in most of the sites, it was only possible to grow a rainfed crop and perhaps an irrigated crop on some small areas of land. After, in addition to the rainfed crop grown on larger areas of land, it became possible to grow a post-rainy season crop (culture de contresaison) and, once the water table had risen, an irrigated crop (culture de décrue) as well. How can they be sustained / enhanced? Upscale water-spreading weirs to increase the number of people benefitting.
Post-rainy season crops and irrigated crops diversify agricultural production. They are used as a means of earning cash income. How can they be sustained / enhanced? Improve access to markets.
With their capacity to regulate annual floodwaters and harness them to stabilise production, water-spreading weirs are an effective measure for adapting to climate change in regions experiencing increasing variability in rainfall.

6.8 ភាពខ្សោយ/ គុណវិបត្តិ/ ហានិភ័យនៃបច្ចេកទេស និងវិធីសាស្ត្រដោះស្រាយ

ភាពខ្សោយ/ គុណវិបត្តិ/ ហានិភ័យ ទស្សនៈរបស់អ្នកចងក្រងឬបុគ្គលសំខាន់ៗ	តើបច្ចេកទេសទាំងនោះបានដោះស្រាយបញ្ហាដូចម្តេច?
It can be assumed that one third of the weirs will require complete renovation every 20 years	The renovation of these weirs can be done for approximately 10% of the initial construction costs
Maintenance of the weirs by the management committees is still a weak area. Funds expected from user fees for the plots are often inadequately collected and too low to cover costs. Some management committees lose their drive and neglect their duties.	New fundings sources have to be found and tapped.
In spite of the great potential for the use of water-spreading weirs and the very promising results, implementation will continue to depend in the medium term on outside funding, as it is unlikely that the communal budgets will be able to fund investments of this size.	The existing knowledge hast to be spread.
Know-how and experience for the construction of water-spreading weirs are still concentrated among a few countries.

7.1 វិធីសាស្ត្រ/ ប្រភពនៃព័ត៌មាន

7.2 ឯកសារយោងដែលបានចេញផ្សាយ

ចំណងជើង អ្នកនិពន្ធ ឆ្នាំ ISBN:

Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) (2011). Water-spreading weirs for the development of degraded dry river valleys. Experience from the Sahel. Frankfurt and Eschborn, GIZ and KFW.

មានប្រភពមកពីណា? ថ្លៃដើមប៉ុន្មាន?

http://www.gtz.de/de/dokumente/giz2012-en-water-spreading-weirs-sahel.pdf

ចំណងជើង អ្នកនិពន្ធ ឆ្នាំ ISBN:

Direction du développement et de la coopération DDC (2012). Gestion des eaux de ruissellement dans le Tchad sahélien. Bern, DDC.

មានប្រភពមកពីណា? ថ្លៃដើមប៉ុន្មាន?

http://www.gopa.de/uploads/tx_bdojobopps/PRODOC_Tchad.pdf