Sedimentation of small and medium sized dams: discussion issues
Authors: Tumbare Michael James 
Published: August 2013

Purpose

There has been a general promotion of small and medium sized dams as the solution to supply water for domestic, sanitation and other livelihood purposes in the less industrialised countries of the world. This paper aims to communicate and share ideas and experiences with policy makers and other engineering practitioners in issues related to the sedimentation of, and the development of small and medium sized dams so that relevant issues are taken into account in the planning, design and implementation of such small and medium sized dams.

Design/methodology/approach

This paper, which is a viewpoint, utilises the findings of various research work carried out in Zimbabwe and findings from other regional and international literature as a basis for discussion and arriving at some engineering and other developmental policy recommendations. The research work utilised and analysed in this paper is based on actual field work carried out by others as cited.

Findings

The paper concludes that the following policy and technical issues should always be borne in mind in the promotion of small and medium sized dams: the predicted increase in rainfall intensities due to climate change/variability requires the review of existing small and medium sized dam spillway capacity designs; an increase in the minimum storage ratios of small and medium sized dams should be made from the current recommended 0.1‐0.3; further research work is required to validate the postulation that rainfall intensities are increasing due to the effects of climate change/variability resulting in increased sedimentation of reservoirs; whilst sediments are required for ecosystem sustenance, they can also be viewed as a pollutant in respect of certain other human water supply needs; do not build small dams on large catchments as such small dams will silt‐up quickly and thereafter pose challenges in the management and disposal of the accumulated sediments and nutrients when decommissioning/rehabilitating them; every dam site, irrespective of the resultant dam size, should be developed to its maximum potential in respect of the dam site's water yield and/or prevailing topography; WHO predicts that road traffic injuries will rise to become the fifth leading cause of death by 2030. The “vulnerable road users” and/or their estates should also receive like attention and timely compensation benefits as advocated for the large dam's “disadvantaged and vulnerable” people.

Originality/value

Every year, about 1 per cent of the world's reservoir capacities are lost to sedimentation. Most researchers postulate that an increase in the intensity of rainfall due to climate change/variability is imminent and will result in increased sediment loads with resultant negative impacts on dam reservoir life‐spans and usefulness. This paper discusses the advantages, disadvantages and efficiency of small and medium sized dams in satisfying the various beneficiary needs in the less industrialised countries of the world. The technical issues that have to be considered in the design and construction of such small and medium sized dams in order to minimise the negative impacts of sedimentation in their development are also presented and discussed. The opinions and conclusions drawn in the viewpoint are those of the author.