Abstract

Yield is used to characterise the capacity of a water resource. It is a fundamental water-supply planning concept, and an understanding of its attributes is critical for those who participate in water-supply issues. This study tends to carry out firm yield analysis by employing both the accumulated difference method (ADM) and reverse chronology method (RCM) in order to ascertain the minimum storage capacity required to sustain the required yield of kainji reservoir system without interruption. In applying (ADM), the inflows were accumulated and the difference calculated. The minimum inflow within the year of record was determined to be the firm yield. The yield of 30x109m3 was hypothetically chosen to determine the minimum capacity to sustain it without interruption during the period under record. Similarly the firm yield analysis was also done by employing the method of reverse chronology (RCM) to confirm the result in the accumulated difference method. This method is based on the premise that what is the minimum volume that has to be in storage at the end of the previous year plus the inflow can meet the demand during the current year.  This was carried out by starting with the last year of the record and working back to the first year and the difference between the inflow and the required yield was determined. The shortages were then observed form the difference obtained; the maximum shortage was then selected as the required capacity.The firm yield was determined to be 22.7283×109m3. The minimum capacity required to sustain a yield of 30×109m3 per annum (the average annual demand) without interruption during the period under record was determined to be 7.3431×109m3. The interaction between the reservoir elements were significant considering the correlation matrix applied. 

Keywords

reservoir capacity, firm yield, inflow, accumulated, chronology, storage