The semi-arid regions experience long dry spells and erratic rainfall less than 500mm per annum. This is often poorly distributed over three months. In addition the areas experience high temperatures of about 38º Celsius resulting in high evaporation rates. Where soils are poor there is also deep percolation. Water received therefore quickly disappears within a few hours of a rainstorm. Farmers in Manama Communal Area in Gwanda district of Zimbabwe have modified the standard contour ridges and the infiltration pits to suit these conditions and named the technique - Manama Infield Rainwater Harvesting Storage Facility. This was after the realisation that farmers were losing water after harvesting it, resulting in total crop failures especially during the dry spells.

Dead levelmeaning

Watts 1/2″ 009-QT RPZ reduced pressure zone assembly is designed to prevent the flow of polluted water from entering into the potable water supply.

Dead Levelgame

Farmers have observed that dead level contours harness rainwater but quickly lose that water due to evaporation and deep percolation. This brought the innovation of constructing the underground tanks described below. See picture below (Figure 2) of completed dead level contour. The minimum depth and width should be 30cm and 1500cm respectively. The length should be from end to end of the field.

Dead LevelP

This consists of a dead level contour with storage underground tanks made from local materials. The capacity range from 5m3 to 20m3 depending on farmer preference. A dead level contour is a channel dug in the field with a zero gradient or slopes, so that water does not flow but is harnessed and stored in the channel. The underground storage tanks are constructed in such a way that they are covered to reduce evaporation and rammed to reduce deep percolation.

Watts 1/2″ 009-QT RPZ reduced pressure zone assembly is designed to prevent the flow of polluted water from entering into the potable water supply due to back siphonage and or back pressure in accordance with national plumbing codes and water authority requirements. Its compact modular design facilitates easy maintenance with a single access cover for in-line repairs. It is ideal for protection in continuous pressure piping applications and at cross-connections identified as health hazards and for contaminants at the service line entrance. This assembly consists of a bronze body, NPT end connections, quarter turn ball valve shutoffs with tee handles, top mounted test cocks, two in-line independent check valves, captured springs, and replaceable check seats with an internal relief valve for reduced space requirements.

To achieve maximum benefits from the facility, maintenance should be given utmost priority. During the dry season (usually soon after harvesting) when all water has been used from the tank remove the temporary top plaster.

The Manama In-field Rainwater Harvesting Storage Facility has enabled farmers in semi-arid areas to plan for and cope with disasters such as drought and diversify strategies for sustainable livelihoods. Formerly 'waste lands' have become productive fields giving farmers a worthwhile investment of their time in dryland farming.

All the tanks in the last dead level contour may need a non-permeable layer therefore a thicker layer may be required. However all other tanks must be semi-permeable. Mix termitaria with water to make mortar and plaster up to the marked root zone level of your deep-rooted crops.