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Natural ground catchment and Open water reservoir

1,523 bytes added, 16:48, 6 April 2012

→‎Other considerations

# Digging deeper to have a larger volume to surface area ratio. The Charco dam from Tanzania incorporates this through hemispherical design. The problem might be greater levels of investment needed with increased depth. Experience digging reservoirs in Sudan using food-for-work showed that the deeper the dam, the higher the food ratio.

# Planting trees around the pond will act as a windbreak, thereby reducing evaporation.

* Microbiological and chemical water quality is likely to not be acceptable for direct consumption.# Water is likely to have a high microbial content due to runoff from contaminated land, as well as communal access to the water by humans and animals. # Where runoff is from agricultural areas, there is a possibility of pesticides and fertilizers entering the pond water and sediments – some of which have harmful effects for the aquatic environment and human health. Tests in Côte d’Ivoire showed that in pond water originating from runoff via vegetable plots, levels of pyrethroid compounds were significant. Lack of information and awareness, combined with lax legislation means that many different chemicals might be being used in agriculture. # Water in ponds is also prone to cyanobacterial proliferation. Cyanobacteria can be harmful to human health and can cause minor disorders such as headaches, through to lethal deterioration of hepatic functions and promotion of liver cancer. However, the impact of cyanobacteria has largely been neglected in developing countries due to lack of expertise and inefficiency of monitoring programmes (if they exist). It seems that the start of the rainy season is the most likely time for cyanobacterial proliferation. There are several things that can be done to reduce risks by reducing nutrient loads entering the reservoir – such as rehabilitating vegetation in the runoff zone which can use some of the nutrient enriched water before it enters the reservoir* Construct pond during the dry season.

* Fish can be introduced to eat mosquito larvae, while at the same time providing a source of nutrition. Mudfish are a good option as they can survive dry periods in the silt at the base of pond.

* Experience from South Africa indicates that access to finance seems to be important in allowing farmers to implement ponds.

Winona

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