Abstract

The harnessing of runoff water from rainfall over land rather than allowing these waters to run into streams and rivers and eventually lost into the sea is attaining some popularity due to the increasing demand for scarce water resources. Sandy soils, especially in arid and semi-arid regions and along some coastal areas of Ghana (from Aflao to Tema New Town) do not generate sufficient rainwater runoff for storage because of their high permeability. This is important, as groundwater in these areas is mostly saline. To make such lands productive in terms of their ability to harvest rainwater, an experiment under laboratory conditions was conducted to apply top dressing on these land surfaces using less permeable soils on slopes of 20 and 30°. These adverse soil conditions were ameliorated with good results even though the conditions as pertains in the real world could not be completely simulated. Rather than have low or non-existent runoff from such lands from rainfall events, the application of a top dressing using a less permeable soil presented possibilities for harvesting and storing rainwater for agriculture and other uses. Harvested runoff water from rainfall of between 6 and 80 m³/ha was obtained on the treated soils under laboratory conditions from a previous situation of zero runoff from the untreated soil. The time taken to generate runoff was drastically reduced from 4,783 min (when no runoff was generated) to less than 70 min with the treatment. This presents a hopeful mechanism for developing water resources in areas of water scarcity to improve upon poverty and livelihoods of the communities affected.

Key words: Ghana, rainwater harvest, Overland flow, Deep percolation losses, Soil amelioration, Tottori dune sand, Koyama mash clay, Isahaya polder clay.