1.2 تفاصيل الاتصال بالأشخاص الرئيسيين لمصدر المعلومات والمؤسسات المشاركة في تقييم وتوثيق التقنية

اسم المشروع الذي سهّل توثيق/تقييم التقنية (إذا كان ذلك على صلة)

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

اسم المؤسسة (المؤسسات) التي سهلت توثيق/تقييم التقنية (إذا كان ذلك على صلة)

Africa Sand Dam Foundation (ASDF) - كينيا

اسم المؤسسة (المؤسسات) التي سهلت توثيق/تقييم التقنية (إذا كان ذلك على صلة)

Excellent Development Ltd. (Excellent Development Ltd.) - المملكة المتحدة

1.3 الشروط المتعلقة باستخدام البيانات الموثقة من خلال WOCAT

متى تم تجميع البيانات (ميدانيا)؟:

27/03/2012

يوافق جامع المعلومات والشخص (لاشخاص) الرئيسي لمصدر المعلومات على الشروط المتعلقة باستخدام البيانات الموثقة من خلال WOCAT:

نعم

2.1 وصف مختصر للتقنية

تعريف التقنية:

A sand dam is a stone masonry barrier across a seasonal sandy riverbed that traps rainwater and sand flowing down the catchment.

2.2 وصف تفصيلي للتقنية

الوصف:

A sand dam is typically 1 - 5 metres high and 10-50 metres across. When it rains the dam captures soil laden water behind it – the sand in the water sinks to the bottom, whilst the silt remains suspended in the water. Eventually the dams fill with sand - sometimes after only one rainfall or over 1 – 3 seasons. 25 to 40% of the volume of the sand held is actually water. A mature sand dam can store millions of litres of water – refilling after each rainfall providing a year round supply to over 1,000 people.

Purpose of the Technology: Sand dams are a simple, low cost and low maintenance, replicable rainwater harvesting technology. They provide a clean, local water supply for domestic and farming use and are suited to arid and semi-arid areas of the world. It is a solution that is scaleable and has a broader application for use as a rural and game park road crossing to replace less effective culvert bridges.

Establishment / maintenance activities and inputs: Sand dams are the lowest cost form of rainwater harvesting and its robust nature and very low operational and maintenance costs make it particularly suited to remote and poorly served regions. A typical dam using 500 bags of cement would approx be 40 metres in length with a spillway 2 metres above the bedrock. The dam is constructed using stone masonry placed in timber formwork. Such a dam costs approximately USD 11,800 (in 2012 prices). This consists of materials (cement, steel reinforcement, timber, transport) and dam permit USD 8,800 (75%), project management including technical support from skilled local artisans and dam designers USD 2150 (18%) and finance and administration costs of implementing organisation USD 850 (7%). Local people freely contribute their labour to collect rock, sand and water, terrace and protect the immediate catchment and construct the dam. If this contribution was costed and included the cost of the dam would almost double. The maintenance and repair costs of the dam provided it has been well designed and constructed is negligible. Local users are responsible for the management and repair of the dam and its abstraction system. Where a hand pump is fitted, local users fund the repair and replacement of the pump as required. The purchase and repair of petrol powered water pumps which some groups use to irrigate adjacent land is the responsibility of the members of the local group.

Natural / human environment: Because the water is stored within the sand, evaporation losses are very low, the sand filters the water and water-vector diseases such as malaria are controlled. Sand dams provide significant environmental benefits such as aquifer recharge, increased downstream flows in the dry-season, rejuvenation of river ecologies and moderation of floods. As such, it contributes to ecosystem services and climate change adaption.

2.3 صور التقنية

2.5 البلد/المنطقة/المواقع التي تم تنفيذ التقنية فيها والتي يغطيها هذا التقييم

2.6 تاريخ التنفيذ

في حالة عدم معرفة السنة بالتحديد، يرجى الإشارة إلى التاريخ التقريبي:

• منذ 10-50 سنة

2.7 إدخال التقنية

حدد كيف تم إدخال التقنية:

• من خلال المشاريع/ التدخلات الخارجية

التعليقات (نوع المشروع، الخ):

Sand dams are an ancient technology. Examples are found across the world's drylands although the greatest concentration is found in Kenya. They were introduced to Kenya in the 1950s from India. Dams were pioneered in Machakos and Makueni counties of Kenya by Joshua Mukusya, a visionary farmer and development worker, in 1978. He worked with a range of agencies to develop and implement the technology. In 1990, staff trained by Joshua set up SASOL to pioneer sand dams in the neighbouring county of Kitui. In 2002, Joshua teamed up with Simon Maddrell, Excellent Development's director, to establish Excellent Development Kenya, now Utooni Development Organisation (UDO) to scale up the work. Sadly, in 2011, Joshua passed away. In 2010, Excellent Development formed a strategic partnership with the Kenyan NGO, Africa Sand Dam Foundation (ASDF), to support the wider uptake beyond Kenya. Today, ASDF, SASOL and UDO are the three NGOs with the most experience of building successful sand dams, approx. 130 dams / year, although many other NGOs have adopted the technology.

3.1 الغرض الرئيسي ( الأغراض الرئيسية) للتقنية

• access to water

3.2 نوع (أنواع) استخدام الأراضي الحالية حيث يتم تطبيق التقنية

التعليقات:

Major land use problems (compiler’s opinion): Drylands are characterised by intense and variable rainfall and a lack of vegetative cover. As a result, drylands are prone to droughts, flooding and soil erosion which result in endemic water and food scarcity.

Major land use problems (land users’ perception): “We used to fetch water from Londokwe; we could spend a night to collect water. One way was 3 to 10 km and up to 12 hours or more to go and come back [because of the time taken to queue]. If we could not make it to the river, we would send our children to fetch water. When they went fetching water that would mean they did not go to school. At times people would fight over fetching water from other people’s scoop holes. Scoop holes would be guarded in turns. The gourds [water containers] would be damaged and the water poured down. Children would not go to school [as they needed to] take care of the young ones as the parents went to fetch water. Children would fail to go to school because they were hungry – just because there was no water to cook."
Yikiuuku SHG

3.4 مجموعةالإدارة المستدامة للأراضي التي تنتمي إليها هذه التقنية

• حصاد المياه

3.5 انتشار التقنية

حدد انتشار التقنية:

• منتشرة بالتساوي على مساحة

إذا كانت التقنية منتشرة بالتساوي على منطقة ما، فحدد المنطقة التقريبية المغطاة:

• 10,000-1,000 كم2

التعليقات:

Over 1000 dams have been built to date in these counties, predominantly by 3 organisations: Utooni Development organisation, SASOL and Africa Sand Dam Foundation in an approx. triangular area bordered by Machakos, Kitui and Mitio Andei.

3.6 التدابير التقنية في مجال إلادارة المستدامة للأراضي

التعليقات:

Main measures: structural measures

3.7 الأنواع الرئيسية من تدهور الأراضي التي تناولتها التقنية

التعليقات:

Main type of degradation addressed: Hs: change in quantity of surface water

Secondary types of degradation addressed: Bq: quantity / biomass decline, Bs: quality and species composition /diversity decline, Ha: aridification, Hg: change in groundwater / aquifer level

Main causes of degradation: Heavy / extreme rainfall (intensity/amounts), droughts

3.8 منع أو حد أو عكس تدهور الأراضي

تحديد هدف التقنية فيما يتعلق بتدهور الأراضي:

• منع تدهور الأراضي
• الحد من تدهور الأراضي

4.1 الرسم الفني للتقنية

4.2 المواصفات الفنية/شروحات الرسم الفني

Cross-section of sand dam

Technical knowledge required for field staff / advisors: moderate (The technical skills required to site, design and supervise construction. These skills have and can be developed locally.)

Technical knowledge required for land users: low (Knowledge of local rivers and their flood levels essential. Basic knowledge of stone masonry useful)

Main technical functions: control of concentrated runoff: retain / trap, water harvesting / increase water supply, improvement of water quality, buffering / filtering water

Secondary technical functions: increase of groundwater level / recharge of groundwater, sediment retention / trapping, sediment harvesting, increase of biomass (quantity), promotion of vegetation species and varieties (quality, eg palatable fodder)

Dam/ pan/ pond
Depth of ditches/pits/dams (m): 1-5
Width of ditches/pits/dams (m): 1-2
Length of ditches/pits/dams (m): 5-50

Specification of dams/ pans/ ponds: Capacity 5,000m3

Catchment area: 300 km2m2

4.3 معلومات عامة بخصوص حساب المدخلات والتكاليف

عملة أخرى/ عملة وطنية (حدد):

Kenyan Shilling

أشر إلى سعر الصرف من الدولار الأمريكي إلى العملة المحلية (إذا كان ذا صلة): 1 دولار أمريكي =:

83,0

4.4 أنشطة التأسيس

	النشاط	نوع التدبير	التوقيت
1.	Collection of rock, sand and water	بنيوية أو هيكلية	1-3 months before construction
2.	Construct dam	بنيوية أو هيكلية	During dry season
3.	Cure dam	بنيوية أو هيكلية	For 4 weeks after construction
4.	Terracing and protection of immediate catchment	بنيوية أو هيكلية	1-3 months before construction

4.5 التكاليف والمدخلات اللازمة للتأسيس

	تحديد المدخلات	الوحدة	الكمية	التكاليف لكل وحدة	إجمالي التكاليف لكل مدخل	% من التكاليف التي يتحملها مستخدمو الأراضي
العمالة	Collection of rock, sand and water	Persons/day	220,0	2,5	550,0	100,0
العمالة	Terracing and protection of immediate catchment	Persons/day	100,0	2,5	250,0	100,0
العمالة	Construct dam	Persons/day	500,0	2,5	1250,0	90,0
العمالة	Cure dam	Persons/day	50,0	2,5	125,0	100,0
معدات	Tools	per dam	1,0	300,0	300,0
مواد البناء	Cement (bag = 50kg)	bags	500,0	9,15	4575,0
مواد البناء	Steel (12m x Y20 steel bar)	pieces	7,0	45,7	319,9
مواد البناء	Steel	per dam	1,0	1000,0	1000,0
غير ذلك	Skilled labour	per dam	1,0	3000,0	3000,0
إجمالي تكاليف إنشاء التقنية					11369,9

التعليقات:

Duration of establishment phase: 6 month(s)

4.6 الصيانة/الأنشطة المتكررة

	النشاط	نوع التدبير	التوقيت/الوتيرة
1.	Inspect and if necessary extend spillway or repair erosion around dam	بنيوية أو هيكلية	As required / annually
2.	Maintain hand pump if fitted	بنيوية أو هيكلية	As required / annually

4.7 التكاليف والمدخلات اللازمة للصيانة/للأنشطة المتكررة (سنويًا)

التعليقات:

In 2012, in Machakos County, Kenya, the cost of materials and technical support for a dam using 250 bags of cement is USD 7,000 and USD 11,700 for a 500 bag dam. The costs in 2.6.1 are based on a 500 bag dam. The volume of a 500 bag dam is approx 140m3 of stone masonry of which 40% is mortar (sand and cement) and 60% is rock. Such a dam will typically be appropriate on rivers 30m wide and with a spillway 3 metres above the bedrock in the river bed level. Costs rise by up to 50% in more remote regions or countries. Sand dams require a lot of hard work. Community members collect the required stones, sand and water, support construction and terrace the land around the dam. If this in-kind contribution is included the costs would rise by 100%. In Kenya, with a long tradition of building sand dams, it takes from 6 to 12 weeks to plan and prepare for construction and 2 days to 2 weeks to build the dam. In other areas, with less experience and/or less community commitment, building a dam may take 6 months or more.

4.8 أهم العوامل المؤثرة على التكاليف

قدم وصفا لأهم العوامل التي تؤثر على التكاليف:

Each dam is individually designed. The size, design and cost of a dam varies considerably with the size of the river and to a lesser extent, location and transport costs. Sand dams are the world’s lowest cost method of capturing rainwater in dry rural areas by a factor of 3 to 30 times compared to rain water harvesting tanks, earth dams, haffirs and rock catchments.

5.1 المناخ

5.2 طوبوغرافيا

التعليقات والمواصفات الإضافية بشأن التضاريس:

Land forms: Sand dams only suit seasonal rivers with sufficient sandy sediment and an accessible bedrock

Altitudinal zone: Also 1,001-1,500 m a.s.l.

Slopes on average: Also moderate

5.3 التربة

إذا كان متاحًا، قم بإرفاق وصف كامل للتربة أو تحديد المعلومات المتوفرة، على سبيل المثال نوع التربة، الرقم الهيدروجيني/ درجة حموضة التربة، قدرة التبادل الكاتيوني، النيتروجين، الملوحة وما إلى ذلك.

Soil water storage capacity: The aquifer behind the dam must consist of sandy sediments with a high porosity and drainable porosity

5.4 توافر المياه ونوعيتها

تعليقات ومواصفات أخرى بشأن نوعية المياه وكميتها:

Availability of surface water: Sand dams only suit seasonal rivers

Water quality (untreated): Good drinking water because the sand filters the water. Water abstracted through an infiltration gallery has a high bacterialogical quality but water is often used for small scale irrigation and livestock watering.

5.5 التنوع البيولوجي

التعليقات والمواصفات الإضافية بشأن التنوع البيولوجي:

Sand dams rejuvenate riverine ecologies and increase local biodiversity

5.6 خصائص مستخدمي الأراضي الذين يطبقون التقنية

اذكر الخصائص الأخرى ذات الصلة لمستخدمي الأراضي:

Land users applying the Technology are mainly common / average land users

Difference in the involvement of women and men: The dams are built by members of registered self-help groups, typically 50 members / group and two-thirds women. The primary concerns of these groups tend to be food and water. Sand dams provide for people, livestock and crops. Water collection and farming are primarily undertaken by women in Kikamba culture and hence women have the greatest vested interest to imrpove food and water availability. Many men migrate away from the area in search of work.

Population density: 50-100 persons/km2

Annual population growth: 2% - 3%

Off-farm income specification: This varies considerably, but most self-help group members are subsistence farmers

5.7 متوسط مساحة الأرض المملوكة أو المستأجرة من قبل مستخدمي الأراضي الذين يطبقون التقنية

5.8 ملكية الأراضي، وحقوق استخدام الأراضي، وحقوق استخدام المياه

ملكية الارض:

• دولة

حقوق استخدام الأراضي:

• مجتمعي (منظم)

حقوق استخدام المياه:

• مجتمعي (منظم)

التعليقات:

Legal agreements for construction and access between the self-help group and the owners of land adjacent to the dam and registering the dam and its associated water rights by the self-help group with the Kenyan Water Resources Management Authority (WRMA) is vital to safeguarding water rights, controlling water and sand abstraction, formalising the authority of the self-help group to levy water tarriffs if appropriate and ensuring there is open access to all to water from scoop holes.

5.9 الوصول إلى الخدمات والبنية التحتية

6.1 الآثار التي أظهرتها التقنية في الموقع

الآثار الاجتماعية والاقتصادية

الإنتاج

توافر المياه ونوعيتها

الدخل والتكاليف

آثار اجتماعية واقتصادية أخرى

الآثار الاجتماعية والثقافية

الآثار الايكولوجية

دورة المياه / الجريان السطحي

التربة

التنوع البيولوجي: الغطاء النباتي، الحيوانات

الحد من مخاطر المناخ والكوارث

6.2 الآثار التي أظهرتها التقنية خارج الموقع

6.3 تعرض التقنية وحساسيتها لتغير المناخ التدريجي والظواهر المتطرفة/الكوارث المرتبطة بالمناخ (كما يراها مستخدمو الأراضي)

تغير مناخ تدريجي

تغير مناخ تدريجي

	الموسم	نوع التغير المناخي/ المتطرف	كيف تتعامل التقنية مع ذلك؟
درجة الحرارة السنوية		زيادة	جيدا

الظواهر المتطرفة / الكوارث المرتبطة بالمناخ

الكوارث الجوية

	كيف تتعامل التقنية مع ذلك؟
عاصفة ممطرة محلية	جيدا
عاصفة هوائية محلية	جيدا

الكوارث المناخية

	كيف تتعامل التقنية مع ذلك؟
جفاف	جيدا

الكوارث الهيدرولوجية

	كيف تتعامل التقنية مع ذلك؟
فيضان عام (نهر)	جيدا

العواقب الأخرى المتعلقة بالمناخ

العواقب الأخرى المتعلقة بالمناخ

	كيف تتعامل التقنية مع ذلك؟
انخفاض فترة النمو	جيدا

التعليقات:

The capacity of the spillway would be increased to control peak flood events

6.4 تحليل التكلفة والعائد

كيف يمكن مقارنة العوائد نسبة لتكاليف الإنشاء (من وجهة نظر مستخدمي الأراضي)؟

كيف تتم مقارنة العوائدمع كلفة الصيانة/التكاليف المتكررة (من وجهة نظر مستخدمي الأراضي)؟

التعليقات:

The very low cost of operating and maintaining sand dams means they are well suited to remote, poorly served regions. Because it is a low cost technology that requires a major community contribution and the knowledge and skills of locally trained artisans, it’s a solution particularly suited to community ownership and self-supply. This contributes to effective implementation.

6.5 اعتماد التقنية

من بين جميع الذين تبنوا التقنية، كم عدد الذين فعلوا ذلك بشكل تلقائي، أي دون تلقي أي حوافز مادية/مدفوعات؟:

• 10-0‏%

التعليقات:

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

Comments on acceptance with external material support: Sand dams require external material support including technical advice to correctly site, design and construct

There is a little trend towards spontaneous adoption of the Technology

Comments on adoption trend: There is some evidence of spontaneous adoption amongst development agencies working in regions suited to sand dams.

6.7 نقاط القوة / المزايا / الفرص التي توفرها التقنية

نقاط القوة/ المزايا/ الفرص من وجهة نظر مستخدمي الأراضي
“I will be able to rent a plot of land near to the sand dam and grow vegetables (tomatoes, peppers, and French beans). My animals will also be healthy because they will always be able to drink here, even during the droughts.” Mauwa Maingi, self-help group member, aged 87, 2010
Mbatha Mbuli, 83. "My family collects water from a near-by well, about ½ Km away, but the water is very salty. It takes one hour to collect water, and needs 6 trips to fetch enough to last the day. There is a pipeline nearby but we must pay 2 shillings per 20 litres. I planted 9 different crops last year, but only 2 survived. I wanted to work with Excellent on this project because I had heard that the projects you support help communities like us to build sand dams, grow trees and create seed banks. I would like to grow trees like Neem in the future and a sand dam here will really help with that. Excellent shares in the interests of the community and they listen to the community and take direction from us"
Stephen Hussey, Dabane Trust, 2011 “Dabane has made its name by getting water out of sand rivers – Our next step is to ensure we don’t over abstract – the answer to that, especially upstream, is sand dams. Without a doubt.”
Milka Mutunga, Kilili Catchment SHG, Kenya 2009-10 "The distance that I used to travel in order to fetch water has been reduced..now I am able to plant more vegetables close to my home. I have learnt how to dig terraces which have helped in increasing the yields that I harvest from my farm..If this is not development then I do not know what development means"
Kimanthi Ngovi, Yikiuuku SHG “The sand dams have done an incredible work for us – water availability at a shorter distance has helped me in saving time for other activities. When water was a long way away I had to get time to collect water in one day and dig terraces on the other day. Today I can fetch water and dig terraces on the same day.”

نقاط القوة/ المزايا/ الفرص من وجهة نظر جامع المعلومات أو غيره من الاشخاص الرئيسيين لمصدر المعلومات
Sand dams provide a safe, reliable, year round, local supply of water for people, crops and livestock in water scarce environments How can they be sustained / enhanced? The very low cost of operating and maintaining sand dams means they are well suited to remote, poorly served regions. Community ownership is critical to their effective management.
Sand dams save farmers hours every day that they can invest in improving their farms to grow more food and create the potential for farmers to irrigate trees and crops, water livestock and generate an income How can they be sustained / enhanced? Don’t build a sand dam in isolation. An independent evaluation in 2010 of 2 sand dam programmes found the long term impacts on poverty, food security and incomes were greatest when sand dams were integrated within a wider community development programme aimed at improving food production, livestock management and land management practice.
Because it is a low cost technology that requires a major community contribution and the knowledge and skills of locally trained artisans, it’s a solution particularly suited to community ownership and self-supply. This contributes to effective implementation. How can they be sustained / enhanced? Don’t short cut community ownership. Communities better understand and are able to implement solutions to their problems if they are central to the planning of the solution. Genuine community commitment and ownership from initial planning to on-going management is vital to realise the intended benefits and full potential created by a dam. Legal registration and agreements to safeguard community access and water rights help this.
Sand dams provide significant environmental benefits such as aquifer recharge, increased downstream flows in the dry-season, rejuvenation of river ecologies and moderation of floods. As such, it contributes to eco-system services and climate change adaption. How can they be sustained / enhanced? Support terracing, tree planting and conservation farming in the wider catchment. This conserves soil and water on farms, increases aquifer recharge and base flows into the dam and reduces the amount of silt in the sand dam aquiver. Research and disseminate evidence of these benefits and the value of these eco-system services
The technology is scaleable and has a broader application for use as a rural and game park road crossing to replace less effective culvert bridges. How can they be sustained / enhanced? In order to upscale this solution, there is a need for greater awareness and advocacy of the technology and its benefits amongst these groups. Nothing generates interest in sand dams more than exposure to successful examples

6.8 نقاط ضعف / مساوىء / مخاطر التقنية وسبل التغلب عليها

نقاط الضعف/ المساوىء/ المخاطر من وجهة نظر جامع المعلومات أو غيره من الاشخاص الرئيسيين لمصدر المعلومات	كيف يمكن التغلب عليها؟
Although sand dams are technically replicable, their application in new contexts requires careful understanding and consideration.	Excellent Development has developed a framework tool to help agencies identify the political, economic, social, technical, legal and environmental factors that should be taken account of when introducing sand dams to a new context.
Sand dams require the technical knowledge and skills of local artisans in order to correctly site, design and construct them	The technical barriers to adoption are low: The technical skills required have and can be developed locally. Learning exchanges between implementing organisations and developing technical manuals and resources aids this learning
This is a drylands solution. Sand dams can only be built on seasonal rivers with sufficient sandy sediment and where the bedrock or impermeable layer is accessible in the river bed.	Increase awareness of the criteria that determine the technical suitability of a site. Use simple field tests, such as sediment seiving and probing, to assess potential sites and to map the potenial application of sand dams.

7.2 المراجع للمنشورات المتاحة

العنوان، المؤلف، السنة، النظام القياسي الدولي لترقيم الكتب ISBN:

Be buffered website including Managing the Water Buffer for Development and Climate Change Adaptation. Groundwater recharge, retention, reuse and rainwater storage. Steenbergen F. van and A. Tuinhof. (2009) which includes sand dams

متاح من أين؟كم التكلفة؟:

www.bebuffered.com/3rbook