Water loss, sediment deposition-pond age relationships in Lagos State, Nigeria

Abstract

The issue of sediment in aquatic environments has been a topic of concern for many decades because it harbouring pathogen and decrease water depth.  . The investigation was carried out to identify and proffer solutions to some environmental and management problems that have hitherto affected fish production sub-sector of the economy, using Lagos State, (Western) Nigeria  as a case study. Both surveying and experimental methods were used. The results indicated that of water loss from ponds resulting from evaporation and seepage ranged from 2.5 – 4.6 day^-1. Percentage reduction in pond water depth during dry season ranged from 70 – 81 % as compared to the observed percentage increase during rainy season with range of values as, 17 – 34%. The mean rise and fall in water depth were 24.7 ± 3.8 % and 47.6 ± 11.7% respectively. The fall in water depth during dry season was almost twice its rise during rainy season. The degree of variation among ponds was found to be significant (t =2.11 at p = 0.05). The mean rate of soft sediment depth was 10.5 ± 1.8 cm yr^-1, while the soft sediment depth in silty sand ponds doubled those from mixed sandy ponds. The predictive equation indicated that soft sediment accumulation was found to increase with year of pond operation. The results showed significant correlation (t = 1.988. p = 0.05) between soft sediment and year of pond operation.