1.2 Detalhes do contato das pessoas capacitadas e instituições envolvidas na avaliação e documentação da tecnologia

Nome do projeto que facilitou a documentação/avaliação da Tecnologia (se relevante)

Good Practices in Soil and Water Conservation - A contribution to adaptation and farmers ́ resilience towards climate change in the Sahel (GIZ)

Nome da(s) instituição(ões) que facilitou(ram) a documentação/ avaliação da Tecnologia (se relevante)

Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) GmbH (GIZ) - Alemanha

1.3 Condições em relação ao uso da informação documentada através de WOCAT

Quando os dados foram compilados (no campo)?

01/07/2012

O/a compilador/a e a(s) pessoa(s) capacitada(s) aceitam as condições relativas ao uso de dados documentados através da WOCAT:

Sim

1.4 Declaração de sustentabilidade da tecnologia descrita

A tecnologia descrita aqui é problemática em relação a degradação da terra de forma que não pode ser declarada uma tecnologia de gestão sustentável de terra?

Não

2.1 Descrição curta da tecnologia

Definição da tecnologia:

Water-spreading weirs slow the flow of water, spread it over a wider area, increase infiltration and reduce erosion.

2.2 Descrição detalhada da tecnologia

Descrição:

The water-spreading weir technique was developed in Burkina Faso, Niger and Chad in the late 1990s and early 2000s. They are suitable as a land improvement measure for 90% of valleys in the Sahel area. These weirs regulate floodwater in medium-sized watercourses and in wider degraded valley bottoms with a pronounced low-water channel. They are constructed with local materials and have a spillway in the middle, abutments on either side and long wingwalls to spread the water over a large area.
In order to reverse the degradation process in a valley, it is necessary to ensure the comprehensive rehabilitation of the degraded parts of the valley. This is why the technique requires an overall assessment of the valley in order to identify the causes of degradation. In order to restore the water system in a degraded valley, a series of weirs is generally required.

Water-spreading weirs slow the flow of water in valleys and spread it over a wider area where it can infiltrate into the soil. In this way, they control river floodwater, and this reduces erosion and the loss of water. At the same time, sediments improve soil fertility and replenish the water table. When water flow is low in the valley, all the water passes over the spillway. When floodwater flow is stronger, the water is channelled towards the sides and flows over the outer lower wingwalls. When the floodwaters are at their heaviest, the water flows over even the higher walls. Downstream, the waters rejoin the low-water channel. Water-spreading weirs permit the reclamation and rehabilitation of degraded land and the restoration of vegetation cover. Thanks to the weirs, water flowing through the valleys can be used for crop growing, livestock raising and forestry.
Thanks to the infiltration of considerable amounts of water, water-spreading weirs contribute to raising the water table by several metres and improving ecological conditions in adjacent areas. As a result, vegetation cover is restored, which has a positive effect on biodiversity. By 2010, German cooperation had established water-spreading weirs in Niger to improve 10,000 hectares of land in valleys. Sorghum yields increased by between 50% and 100% per ha, from 400 kg to 800 kg per ha. The production of sorghum was 10 to 15 times higher in the improved areas than it had been before. As water-spreading weirs raise the water table, areas can be developed (or abandoned farmland restored) for market gardening and horticulture, with two or three crop harvests a year. The produce is used to supplement the food available and can also be sold (especially market garden produce).
The amount of time spent by women and girls fetching water is reduced by several hours a day. Horticulture generates extra income to cover family expenses, such as education and health care. Growing crops outside the rainy season generates work all year round, which reduces temporary migration.

This technique requires accurate preliminary studies to design the system. The more degraded the valley, the more complex the work is. Improving severely degraded valleys requires extensive experience, and any necessary technical adjustments must be made when flaws are detected.
If the weirs are built to a high standard, with a certain amount of upkeep, they will last. Major repairs are beyond the means of the communities, which is why commune authorities are often assigned the role of project owner. However, this is not yet a satisfactory solution, as in most countries in the Sahel, commune authorities are still weak.

This technique has great potential for climate change adaptation in two scenarios: 1) Water-spreading weirs distribute the watershed’s water over wide areas of land in the valley bottom. This enables water resources to be used more efficiently in low-rainfall periods, during dry spells and when the rainy season ends early. 2) In high-rainfall periods and/or in the event of heavy downpours, water-spreading weirs slow the flow of water, thereby preventing or reducing gully and river bank erosion and protecting areas downstream.

2.3 Fotos da tecnologia

2.5 País/região/locais onde a tecnologia foi aplicada e que estão cobertos nesta avaliação

2.6 Data da implementação

Caso o ano exato seja desconhecido, indique a data aproximada:

• 10-50 anos atrás

2.7 Introdução da tecnologia

Especifique como a tecnologia foi introduzida:

• através de projetos/intervenções externas

Comentários (tipos de projeto, etc.):

The water-spreading weir technique was developed in Burkina Faso, Niger and Chad in the late 1990s and early 2000s.
By 2010, German cooperation had established water-spreading weirs in Niger to improve 10,000 hectares of land in valleys.

3.1 Principal/principais finalidade(s) da tecnologia

• Reduz, previne, recupera a degradação do solo

3.2 Tipo(s) atualizado(s) de uso da terra onde a tecnologia foi aplicada

Comentários:

Major land use problems (compiler’s opinion): soil erosion by water and wind erosion, surface runoff, lack of infiltration, fertility decline
Constraints of common grazing land
Constraints of forested government-owned land or commons

3.3 Mais informações sobre o uso da terra

Abastecimento de água para a terra na qual a tecnologia é aplicada:

• Misto de precipitação natural-irrigado

Número de estações de cultivo por ano:

• 1

Especifique:

Longest growing period in days: 120, Longest growing period from month to month: August to October

3.4 Grupo de GST ao qual pertence a tecnologia

• Gestão de irrigação (inclusive abastecimento de água, drenagem)
• Desvio e drenagem de água
• Gestão de água de superfície (nascente, rio, lagos, mar)

3.5 Difusão da tecnologia

Comentários:

By 2010, German cooperation had established water-spreading weirs in Niger to improve 10,000 hectares of land in valleys

3.6 Medidas de GST contendo a tecnologia

Comentários:

Specification of other structural measures: water-spreading weirs

3.7 Principais tipos de degradação da terra abordados pela tecnologia

Comentários:

Main causes of degradation: crop management (annual, perennial, tree/shrub) (Unadapted landuse methods, reduced or abandoned fallow periods), floods, droughts, population pressure (rapidly growing population increasing pressure on land), land tenure (insecure access to land)

3.8 Redução, prevenção ou recuperação da degradação do solo

Especifique o objetivo da tecnologia em relação a degradação da terra:

• Recuperar/reabilitar solo severamente degradado

4.1 Desenho técnico da tecnologia

4.2 Especificações técnicas/ explicações do desenho técnico

Water-spreading weirs are constructed with local materials and have a spillway in the middle, abutments on either side and long wingwalls to spread the water over a large area.

Technical knowledge required for field staff / advisors: high
Technical knowledge required for land users: low
Main technical functions: control of dispersed runoff: impede / retard, control of concentrated runoff: impede / retard, control of concentrated runoff: drain / divert, increase of infiltration, increase / maintain water stored in soil, increase of groundwater level / recharge of groundwater, water harvesting / increase water supply, water spreading
Secondary technical functions: improvement of ground cover

Dam/ pan/ pond
Depth of ditches/pits/dams (m): 1
Length of ditches/pits/dams (m): 50-100

4.3 Informação geral em relação ao cálculo de entradas e custos

Outro/moeda nacional (especifique):

CFA Franc

Indique a taxa cambial do dólar norte americano para a moeda local (se relevante): 1 USD =:

517,0

4.4 Atividades de implantação

	Atividade	Tipo de medida	Periodicidade
1.	accurate preliminary studies to design the system	Estrutural
2.	transport of stones	Estrutural
3.	construction of water-spreading weir	Estrutural

4.5 Custos e entradas necessárias para a implantação

	Especifique a entrada	Unidade	Quantidade	Custos por unidade	Custos totais por entrada	% dos custos arcados pelos usuários da terra
Outros	total construction	ha	1,0	2901,0	2901,0	100,0
Custos totais para a implantação da tecnologia					2901,0

4.6 Atividades recorrentes/manutenção

	Atividade	Tipo de medida	Periodicidade/frequência
1.	upstream watershed development to prevent sand filling of the bottomlands	Estrutural
2.	any necessary technical adjustments must be made when flaws are detected	Estrutural

4.8 Fatores mais importantes que afetam os custos

Descreva os fatores mais determinantes que afetam os custos:

The cost of improving land with water-spreading weirs is 0.25 to 1.5 million CFA francs per hectare (2901 US Dollar per ha). Labour:
• team formed by 25 people for 2 to 3 months, depending on the size of the structure.
Lorries to transport stones:
• 150 to 200 lorryloads (skip loader – 4.5 m3 per load) at a rate of 10 to 15 lorryloads a day.
Cost of construction:
• 1 medium-sized weir 50 m long and 1 m high with 200 m long wingwalls plus basin: 15 million CFA francs
• 1 weir 100 m long and 1 m high with basin: 30 to 32 million CFA francs
• stonework: 25,000 CFA francs/m3
• basin: 15,000 CFA francs/m3.

5.1 Clima

5.2 Topografia

5.3 Solos

5.4 Disponibilidade e qualidade de água

5.5 Biodiversidade

5.6 Características dos usuários da terra que utilizam a tecnologia

Indique outras características relevantes dos usuários da terra:

Population density: 10-50 persons/km2
Annual population growth: 3% - 4% (mostly poor households below poverty line).
Off-farm income specification: men migrate temporarily or permanently to cities for off-farm income
Growing crops outside the rainy season generates work all year round, which reduces temporary migration.

5.7 Média da área de terra própria ou arrendada por usuários da terra que utilizam a tecnologia

5.8 Propriedade de terra, direitos de uso da terra e de uso da água

Propriedade da terra:

• Estado

Direitos do uso da terra:

• Comunitário (organizado)

Direitos do uso da água:

• Comunitário (organizado)

Comentários:

traditional land use rights on fields, communal land on pasture and forest land

5.9 Acesso a serviços e infraestrutura

6.1 Impactos no local mostrados pela tecnologia

Impactos socioeconômicos

Produção

Disponibilidade e qualidade de água

Impactos socioculturais

Impactos ecológicos

Ciclo hídrico/escoamento

Solo

Outros impactos ecológicos

6.2 Impactos externos mostrados pela tecnologia

6.3 Exposição e sensibilidade da tecnologia às mudanças climáticas graduais e extremos/desastres relacionados ao clima (conforme o ponto de vista dos usuários da terra)

Mudança climática gradual

Mudança climática gradual

	Estação do ano	Tipo de mudança climática/extremo	Como a tecnologia lida com isso?
Temperatura anual		aumento	bem

Extremos (desastres) relacionados ao clima

Desastres meteorológicos

	Como a tecnologia lida com isso?
Temporal local	bem
Tempestade de vento local	bem

Desastres climatológicos

	Como a tecnologia lida com isso?
Seca	bem

Desastres hidrológicos

	Como a tecnologia lida com isso?
Inundação geral (rio)	bem

Outras consequências relacionadas ao clima

Outras consequências relacionadas ao clima

	Como a tecnologia lida com isso?
Período de crescimento reduzido	bem

6.4 Análise do custo-benefício

Como os benefícios se comparam aos custos de implantação (do ponto de vista dos usuários da terra)?

Como os benefícios se comparam aos custos recorrentes/de manutenção(do ponto de vista dos usuários da terra)?

6.5 Adoção da tecnologia

Comentários:

There is a little trend towards spontaneous adoption of the Technology
In most countries in the Sahel, commune authorities are still weak. Without external support, the potential for replication is very low.

6.7 Pontos fortes/vantagens/oportunidades da tecnologia

Pontos fortes/vantagens/oportunidades na visão do usuário da terra
Growing crops outside the rainy season generates work all year round, which reduces temporary migration.
The amount of time spent by women and girls fetching water is reduced by several hours a day
If the weirs are built to a high standard, with a certain amount of upkeep, they will last

Pontos fortes/vantagens/oportunidades na visão do/a compilador/a ou de outra pessoa capacitada
Water-spreading weirs permit the reclamation and rehabilitation of degraded land and the restoration of vegetation cover. Suitable as a land improvement measure for 90% of valleys in the Sahel area.
Slow the flow of water in valleys and spread it over a wider area where it can infiltrate into the soil. The control of river floodwater reduces erosion and the loss of water.
sediments improve soil fertility and replenish the water table, vegetation cover is restored
As water-spreading weirs raise the water table, areas can be developed (or abandoned farmland restored) for market gardening and horticulture, with two or three crop harvests a year. The produce is used to supplement the food available and can also be sold (especially market garden produce).
Horticulture generates extra income to cover family expenses, such as education and health care.

6.8 Pontos fracos, desvantagens/riscos da tecnologia e formas de superá-los

Pontos fracos/vantagens/riscos na visão do/a compilador/a ou de outra pessoa capacitada	Como eles podem ser superados?
The evaluation carried out by the FICOD (investment fund for local authorities) in 2010 highlighted the serious problem of sand filling siltation in valleys when additional measures are not implemented in a watershed’s upstream areas to ensure the overall development of the whole watershed area.	To ensure that the effectiveness of water-spreading weirs is long-lasting, upstream watershed development is essential to prevent sand filling of the bottomlands.
Major repairs are beyond the means of the communities, which is why commune authorities are often assigned the role of project owner. However, this is not yet a satisfactory solution, as in most countries in the Sahel, commune authorities are still weak.

7.1 Métodos/fontes de informação

7.2 Referências às publicações disponíveis

Título, autor, ano, ISBN:

Good Practices in Soil and Water Conservation. A contribution to adaptation and farmers´ resilience towards climate change in the Sahel. Published by GIZ in 2012.

Disponível de onde? Custos?

http://agriwaterpedia.info/wiki/Main_Page