Home Cointzio, Mexico Gully control: experimental results and conclusions

Gully control: experimental results and conclusions Print

In the Cointzio basin, land degradation is mainly due to free grazing of cows. To avoid this, a global solution must be searched and must be adapted to different environmental situations. Due to the critical economic situation of farmers, men and women can act only with subsidies (local projects), managed by political authorities.

The Cointzio basin has different kinds of soil erosion due to the type of climate (temperate semi-humid with a 6 months rainy season), soils and geomorphology as well as land uses (some mechanized farming, mainly rainfed agriculture with free grazing cattle, forest, recent avocado plantations). Apart from the land degradation, the downstream effect is the refilling of the Cointzio dam used for drinking water of the capital of Michoacán, as well as occasional severe flooding. One of the techniques tested is the gully control.

 

Experiment: gully control to limit sediment delivery
To control gullies, stone dams (gabions) were constructed involving local stakeholders.

The scheme has been funded by the Mexican Ministry of Environment and Natural Resources (SEMARNAT) for 4 years. Identification and location of the stone dams constructed in the last decade in the Cointzio watershed are available in a spatial database (GIS) of SEMARNAT. Semi-quantitative evaluation of the effectiveness of stone dams to control gully erosion was carried out by measuring the volume of sediment trapped and the status of the installation as a whole.

 

Results

The semi quantitative evaluation of the stone dams build to control gullies show the following resuslts.

  • 90% of this dams are in good condition 4 years after construction.
  • 80% of the check dams have very few or no sediments at all.
  • The remaining 20% check dams have 10 to 20% of their capacity filled by the sediments. Usually, the first check dam located at the upper stream in a series of check dams is filled by the sediment (10-20% filling) meaning that constructing one check dam can control gully formation. However the area tested is on volcanic tuffs material and not on very degraded soil.

 

How well does it work?

No evaluation results were given so this analysis cannot be made.

 

Stakeholders' opinions

Evaluation and effectiveness of control of gully erosion by small dams was discussed with some farmers. They are interested in soil conservation works but they consider that the dams are probably not so useful.

 

Conclusions
For the construction of check dams it needs good studies especially to identify the critical areas. Check dams should be constructed starting from the upper part of the watershed. 80% of the check dams have very few or no sediments at all. The remaining 20% check dams have 10 to 20% of their capacity filled by the sediments. The location of gully control and the influenc downstream has to be spatially analyzed in a watershed context.

 

More details ...
»Field experiment results and conclusions in all study sites

 

 

 
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Acknowledgement

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The DESIRE project was 
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Global Change and
Ecosystem.
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