Valuing Water Recharge in the Face of Damming the Farin Ruwa Wetlands for Electricity Generation in the Benue Trough of Central Nigeria

Abstract

Nasarawa, a state authority in Nigeria has planned a hydro-electric dam upstream of Farin Ruwa wetlands which has the potential of directly disrupting the natural flow of the Farin Ruwa River and by extension the Dep river system in the Benue trough. It is therefore important not only to identify this potential but to quantify it in economic terms so as to serve as a basis for policy to protect the environment. Data on dry-season farming were sourced from irrigated floodplain farmers occupying an area of 2,500 ha. From the data collected, an economic valuation of per hectare agricultural production of irrigated land was conducted. The survey was conducted around the Farin Ruwa segment of the Dep river system in Nasarawa State of Nigeria between September and December 2009. Using two welfare change measures, it valued the recharge function based on estimated production functions and assumed changes in groundwater recharge and levels. The study found out that that irrigation agriculture using water from the shallow groundwater aquifer was 41,233 Naira (US$ 278.6) per hectare and the total potential welfare loss for the whole wetlands as a result a potential drop in groundwater levels by 1m in depth due to the damming of the Dep river system was 1,062,832,391.06 Naira (US $ 7,181,299.94). The study also found out that groundwater recharge is immense importance to wetland farming in the region. It also confirmed that reduced recharge resulting from lower levels of groundwater due to the damming of the Dep river system to generate electricity has the potential of generating high welfare losses for farmers who rely on the floodplains for dry season farming.