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Water Portal / Rainwater Harvesting / Groundwater recharge / Wells, shafts, and boreholes

2 bytes added, 23:24, 17 April 2012

→‎Water source considerations

Water to be recharged should be high quality since blockage due to suspended sediment, microbial growth or chemical precipitation is more likely over the smaller infiltration area of a well or borehole. In Namibia, water from the water treatment works is further treated with granular activated carbon and chlorination before being injected to avoid such problems. In certain cases in India, open large diameter wells that ran dry due to falling water tables (resulting from over-exploitation) are being used to recharge shallow aquifers directly from runoff water that enters the wells – the problem with such structures is that there is no process of water infiltrating through the soil to the aquifer, which would not only reduce sediment and microbiological load, but also have potential chemical contaminants like nitrates and pesticides. Direct recharge of untreated water via open wells is therefore discouraged in preference to infiltration through a soil or sand layer. However, since silt and contaminants can more easily enter through a well, course gravel is sometimes filled into it to act as a filter, which can be replaced if clogging becomes severe.

One source of higher quality water , that is a realistic source of recharge water , is rainwater from roof catchments. This has been used to recharge shallow aquifers in Mozambique where groundwater was saline, with the result that the water was diluted. Ground runoff is also being used where potentially contaminated runoff water is used to recharge aquifers but where it still must infiltrate a certain amount of soil later – however the risk of aquifer contamination and screen blockage is increased. Hand dug wells that previously dried up now have water all year round – an evaluation after 3 years showed that out of 120 hand-dug wells that had recharge boreholes created close by to aid recharge, very few were drying up like they were before. In addition, families in the area were starting to replicate the system on their own.

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