ABSTRACT

Implications of dam development on soil, water, vegetation and socio-economic characteristics were investigated in the study. Soil studies involved collection of samples at 0-15cm and 15-30cm depths prior to excavation (control sample), from epicenter of location where overburden were heaped (point A) and 2m away from overburden (point B). Samples were analyzed for pH, OC, OM, N, P, K, Ca, Mg, Na, ECEC, Fe, Mn, Zn and Cu). Water samples were collected upstream, inside dam and downstream and analyzed for pH, Cl, K, Na, Ca, conductivity, turbidity, total solids, total dissolved solids, dissolved oxygen, biological oxygen demand, NO3, Fe, Mn, Zn and Cu. Vegetation study involved dividing the 200m X 200m dam area into 4 transects within which sampling was done using improvised quadrat of 3 different sizes. Questionnaire and interviews were used to elicit responses from inhabitants of the area on the socio-economic implications of the dam project. Soil analysis results showed changes due to heaping of overburden on top soil. pH, N, P, K, Ca, Mg, Na, OC, OM, Fe, Zn, Mn and Cu at 0-15cm depth before dam construction were 5.05, 0.2mg/kg, 49.1mg/kg, 0.17mg/kg, 4.2cmol/kg, 2.3cmol/kg, 0.16cmol/kg, 2.62%, 4.51%, 3.52mg/kg, 4.41mg/kg, 1.36mg/kg and 0.54mg/kg respectively before construction, while after construction values (from point A) increased to 6.0, 0.18mg/kg, 42.5mg/kg, 0.21mg/kg, 4.75cmol/kg, 2.8cmol/kg, 0.39cmol/kg, 2.02%, 3.5%, 7.79mg/kg, 6.43mg/kg, 2.55mg/kg and 2.48mg/kg respectively because of dam construction. This translates to about 50% significant change in soil characteristics. Water analysis results also showed some changes attributable to dam development as pH, K, Na, Ca and Mg, concentrations changed from 6.55, 3.42mg/l, 133.3mg/l, 27mg/l, 14mg/l respectively before dam development to 6.73, 5.94mg/l, 3.0mg/l, 102.17mg/l, 28.06mg/l (inside dam) after dam development. Fe, Mn, Zn and Cu concentrations also increased even above permissible limit for these metals in drinking water. Prior to dam construction, phanerophytes dominated the landscape, but after dam construction, many of these trees and shrubs were removed giving way to abundant species of chamaephytes. Total species, number of individual species, density and species’ richness index before dam construction were 25, 2712, 0.0678 and 24.873 respectively which changed to 38, 2041, 0.0511 and 37.868 after dam construction resulting in a 25% loss in vegetation cover. Socio-economic analysis showed that dam construction affected the number of lands available for farming and other purposes. Its construction caused noise and increased concentration of dust particles. Majority of Ishiagu residents use Ivo river as the major source of water while Oviaovia and Ngele-Okwe streams are utilized by about 40% of residents especially those residing in Obinagu and Amagu villages. ARCC dam construction affected soil, water, vegetation and livelihoods of residents of the study area. Recommendations were made for sustainability of the project and protection of both environment and livelihoods from permanent or irreversible degradation.