1.2 Detalles de contacto de las personas de referencia e instituciones involucradas en la evaluación y la documentación de la Tecnología

Nombre del proyecto que financió la documentación/ evaluación de la Tecnología (si fuera relevante)

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

Nombre de la(s) institución(es) que facilitaron la documentación/ evaluación de la Tecnología (si fuera relevante)

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

1.3 Condiciones referidas al uso de datos documentados mediante WOCAT

¿Cuándo se compilaron los datos (en el campo)?

01/07/2012

El compilador y la/s persona(s) de referencia claves aceptan las condiciones acerca del uso de los datos documentados mediante WOCAT:

Sí

1.4 Declaración de la sostenibilidad de la Tecnología descrita

¿La Tecnología aquí descrita resulta problemática en relación a la degradación de la tierra, de tal forma que no puede considerársela una tecnología sostenible para el manejo de la tierra?

No

2.1 Breve descripción de la Tecnología

Definición de la Tecnología:

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

2.2 Descripción detallada de la Tecnología

Descripción:

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 Fotografías de la Tecnología

2.5 País/ región/ lugares donde la Tecnología fue aplicada y que se hallan comprendidos por esta evaluación

2.6 Fecha de la implementación

Si no se conoce el año preciso, indique la fecha aproximada:

• 10-50 años atrás

2.7 Introducción de la Tecnología

Especifique cómo se introdujo la Tecnología:

• mediante proyectos/ intervenciones externas

Comentarios (tipo de proyecto, 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 Propósito(s) principal(es) de la Tecnología MST

• reducir, prevenir, restaurar la degradación del suelo

3.2 Tipo(s) actuales de uso de la tierra donde se aplica la Tecnología

Comentarios:

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 Información adicional sobre el uso de tierras

Provisión de agua para la tierra donde se aplica la Tecnología:

• mixta de secano – irrigada

Número de temporadas de cultivo por año:

• 1

Especifique:

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

3.4 Grupo MST al que pertenece la Tecnología

• Manejo de irrigación: (incl. provisión de agua, invernaderos)
• diversión y drenaje de agua
• manejo de agua superficial (manantial, río, lagos, mar):

3.5 Difusión de la Tecnología

Comentarios:

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

3.6 Medidas MST que componen la Tecnología

Comentarios:

Specification of other structural measures: water-spreading weirs

3.7 Principales tipos de degradación del suelo encarados con la Tecnología

Comentarios:

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 Prevención, reducción o restauración de la degradación del suelo

Especifique la meta de la Tecnología con relación a la degradación de la tierra:

• restaurar/ rehabilitar tierra severamente degradada

4.1 Dibujo técnico de la Tecnología

4.2 Especificaciones técnicas/ explicaciones del dibujo 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 Información general sobre el cálculo de insumos y costos

otra / moneda nacional (especifique):

CFA Franc

Indique la tasa de cambio de USD a la moneda local (si fuese relevante): 1 USD =:

517,0

4.4 Actividades de establecimiento

	Actividad	Tipo de medida	Momento
1.	accurate preliminary studies to design the system	Estructurales
2.	transport of stones	Estructurales
3.	construction of water-spreading weir	Estructurales

4.5 Costos e insumos necesarios para el establecimiento

	Especifique insumo	Unidad	Cantidad	Costos por unidad	Costos totales por insumo	% de los costos cubiertos por los usuarios de las tierras
Otros	total construction	ha	1,0	2901,0	2901,0	100,0
Costos totales para establecer la Tecnología					2901,0

4.6 Actividades de establecimiento/ recurrentes

	Actividad	Tipo de medida	Momento/ frequencia
1.	upstream watershed development to prevent sand filling of the bottomlands	Estructurales
2.	any necessary technical adjustments must be made when flaws are detected	Estructurales

4.8 Factores más determinantes que afectan los costos:

Describa los factores más determinantes que afectan los costos:

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 Topografía

5.3 Suelos

5.4 Disponibilidad y calidad de agua

5.5 Biodiversidad

5.6 Las características de los usuarios de la tierra que aplican la Tecnología

Indique otras características relevantes de los usuarios de las tierras:

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 Área promedio de la tierra que pertenece a o es arrendada por usuarios de tierra que aplican la Tecnología

5.8 Tenencia de tierra, uso de tierra y derechos de uso de agua

Tenencia de tierra:

• estado

Derechos de uso de tierra:

• comunitarios (organizado)

Derechos de uso de agua:

• comunitarios (organizado)

Comentarios:

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

5.9 Acceso a servicios e infraestructura

6.1 Impactos in situ demostrados por la Tecnología

Impactos socioeconómicos

Producción

Disponibilidad y calidad de agua

Impactos socioculturales

Impactos ecológicos

Ciclo de agua/ escurrimiento de sedimento

Suelo

Otros impactos ecológicos

6.2 Impactos fuera del sitio demostrados por la Tecnología

6.3 Exposición y sensibilidad de la Tecnología al cambio climático gradual y a extremos relacionados al clima/ desastres (desde la percepción de los usuarios de tierras)

Cambio climático gradual

Cambio climático gradual

	Estación	tipo de cambios climáticos/ climas extremos	¿Cómo es que la tecnología soporta esto?
temperatura anual		incrementó	bien

Extremos (desastres) relacionados al clima

Desastres climatológicos:

	¿Cómo es que la tecnología soporta esto?
tormenta de lluvia local	bien
tormenta de viento	bien

Desastres climatológicos

	¿Cómo es que la tecnología soporta esto?
sequía	bien

Desastres hidrológicos

	¿Cómo es que la tecnología soporta esto?
inundación general (río)	bien

Otras consecuencias relacionadas al clima

Otras consecuencias relacionadas al clima

	¿Cómo es que la tecnología soporta esto?
periodo reducido de crecimiento	bien

6.4 Análisis costo-beneficio

¿Cómo se comparan los beneficios con los costos de establecimiento (desde la perspectiva de los usuarios de tierra)?

¿Cómo se comparan los beneficios con los costos de mantenimiento/ recurrentes (desde la perspectiva de los usuarios de tierra)?

6.5 Adopción de la Tecnología

Comentarios:

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 Fuerzas/ ventajas/ oportunidades de la Tecnología

Fuerzas/ ventajas/ oportunidades desde la perspectiva del usuario de la tierra
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

Fuerzas/ ventajas/ oportunidades desde la perspectiva del compilador o de otra persona de referencia clave
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 Debilidades/ desventajas/ riesgos de la Tecnología y formas de sobreponerse a ellos

Debilidades/ desventajas/ riesgos desde la perspectiva del compilador o de otra persona de referencia clave	¿Cómo sobreponerse a ellas?
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/ fuentes de información

7.2 Vínculos a las publicaciones disponibles

Título, autor, año, 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.

¿Dónde se halla disponible? ¿Costo?

http://agriwaterpedia.info/wiki/Main_Page