RAINWATER HARVESTING PRACTICES AND DESIGN OF RAINWATER

HARVESTING SYSTEM FOR OTUKPA COMMUNITY, BENUE STATE, NIGERIA

1Onoja S.B; 2Ocheja I.E and 3Isikwue M.O 1,3 Department of Agricultural and Environmental Engineering,

University of Agriculture, Makurdi2Lower Benue River Basin Development Authority, Makurdi

samomyonoja@yahoo.com

Intoduction

• Sources of water for general human utilization include surface water, groundwater and lately rainwater harvesting

• Rainwater harvesting is the interception of precipitation for human use close to where it falls before it sinks into the ground (Thomas, 2000).

• Domestic Rainwater harvesting (DRWH), a sub-set of rainwater harvesting is usually manifest as roof run-off harvesting because ground run-off is too dirty for safe human consumption (Thomas, 2000)

• DRWH is motivated by exhaustion of surface supplies and the falling levels of aquifers

• In Otukpa community, both surface water supplies and groundwater are not available

• Every household in the community practices rainwater harvesting

Objectives

• To study the rainwater harvesting practices in Otukpa community• To design a rainwater harvesting system that utilizes similar material

resourcesMethodology• Number of villages in otukpa community were identified and total

population of the community was estimated for 2015, bearing in mind MDG for water supply

• Reconnaissance survey was carried out to identify the rainwater practices in the community

• Limited laboratory analysis were carried out to determine the quality of harvested rainwater in storage

• Standard procedures were followed to design a rainwater harvesting system using the same local materials

Results• Every building in the community had a roof-top rainwater harvesting system in one form or the other, using

corrugated iron sheets (Plates 1-3)• The harvesting was done using gutters and downpipes (made of local wood, bamboo, folded galvanized

iron sheets or PVC pipes), and led it to storage containers that range from simple pots to large ferrocement tanks that are either on the surface or underground or partly on the surface and partly underground.

• Efforts were made by the community to cover the storage reservoirs in different ways. These covers were however not good enough to protect against contamination from the environment

• The rainwater harvesting system of the community can be classified as partial as not all the rain that fell on the whole surface area of the rooftops were harvested by the available structures. The proportion of what was harvested to potential yield ranged from 5.06% to 23.05%.

• Results of the bacteriological study indicate that some of the storage points were contaminated while the samples collected directly from rainfall without passing through the rooftops and storage were consistently free from bacteriological presence.

• Based on the relationship W = 0.8 x A x R, an elevated rainwater harvesting system including harvesting surface and storage was designed for 450,000 litres to cater for about 250 people to last the critical months of March, April and May of the year

• The cost of the developing this system was found to be about N 3,000,000.00 (Three million naira only). This is very reasonable when compared with the sum of about N9,000,000.00 (Nine million naira only), the cost of drilling a motorized borehole in a basement formation and about N10,000,000.00 ( Ten million naira only), the cost of drilling a motorized borehole in a sedimentary formation

Rainwater harvesting practices

Plate 1Plate 2

Plate 3

Designed elevated rainwater harvesting system

Fig 1: Pictorial view of the designed elevated rainwater harvesting system

Plan

Fig 2: Plan of the rainwater harvesting system

Sections

Fig 3:Sections of the elevated rainwater harvesting system

Conclusions

• Rooftop rainwater harvesting is a practice of every household in Otukpa community

• This supply is however unable to sustain them through the dry period of the year

• An elevated rainwater harvesting system with capacity of 450,000 litres, for about 250 people with a unit cost of about N 3,000,000.00 was designed for Otukpa

• Governments, non-governmental Organisations (NGOs), International and Intergovernmental Organisations and Agencies are hereby called upon to fund these projects as a sustainable development for the community