An investigative study on the volume of sediment accumulation in Tagwai dam reservoir using bathymetric and geostatistical analysis techniques

Abstract

Sustainable provision of potable water for domestic, industrial and development purposes in Minna has been elusive over the years due to several factors, including lack of spatial database (locations, depth, area, volume, etc.) and the threat by siltation and land use activities within the corridors of the reservoir area. This paper utilizes the data collected from fieldwork to investigate the volume of sediment accumulated in Tagwai reservoir basin over a period of 31 years since the dam was constructed in 1978. Sediment accumulation study in a dam is one of the useful methods of gathering information needed for its monitoring, maintenance, and sustainability. Leica TC1201 (total station) was used for perimeter survey, while Raytheon DE-119 (echo sounder) was adopted for depth measurement. A comparison was made between the designed reservoir volume (28.3 × 106 m3) and the computed volume (20.4 × 106 m3). A loss of about (7.9 × 106 m3) was recorded. Sediment accumulation gave 0.25 Mm3, a spread of about (0.80%) annually. Prediction and error analysis was done using geostatistical methods of Kriging/Co-kriging and Empirical Bayesian Kriging in ArcGIS software. The predicted root mean square errors are 0.0963 and 0.1189 for both methods which presented a good representation while testing with other available methods. It can be concluded that the storage capacity of the reservoir is depleting which has further exacerbated the shortage of water experienced in Minna metropolis therefore, urgent attention for de-silting is highly recommended.