Changes

Water Portal / Rainwater Harvesting / Groundwater recharge / Sand dam

160 bytes added, 23:06, 30 March 2012

→‎Building the sand dam (and wing wall)

* Avoid downstream erosion problems by making a protective slab (stilling basin) at the base of large stones set in concrete. Dimensions to be designed, but is not necessary where there is exposed rock bar downstream.

* In upstream parts of a catchment it is recommended that sand dams are always built in stages, since the availability of coarse material is generally limited and base flow is small or absent (base flow = sub-surface flow which aids surface flow so that silt/clay can still be flushed away once rainfall stops, rather than sinking directly into the sand bed). It has also been suggested that to build in stages over several years is also more beneficial for functioning of dam committees. Build them within a spillway, which was part of the first stage & wing wall construction.

* A piezometer or auger hole may be installed to allow a caretaker or watchman to estimate how much water is left and decide if rationing has to be introduced.

After the dam is built, an outlet for water extraction must be constructed for drinking, agriculture, etc.. Hand dug scoop holes are the simplest possibility, however the water can easily be contaminated. Covered wells, with hand or rope pumps protect the water much better. It is also possible to construct an outlet pipe with a tap. In certain designs for sand dams, a pipe is shown that takes water by gravity through the dam wall. These are said to not work well due to either a blocked intake, a broken tap on outlet side and the possibility of weakening the dam wall. <br>

Winona

Akvopedia-spade, akvouser, bureaucrat, emailconfirmed, staff, susana-working-group-1, susana-working-group-10, susana-working-group-11, susana-working-group-12, susana-working-group-2, susana-working-group-3, susana-working-group-4, susana-working-group-5, susana-working-group-6, susana-working-group-7, susana-working-group-8, susana-working-group-9, susana-working-group-susana-member, administrator, widget editor

30,949

edits