Trends in Agriculturally-Relevant Rainfall Characteristics for Small-Scale Agriculture in Northern Ghana

This study set out to investigate the trends of agriculturally-relevant rainfall characteristics among small-scalefarmers in the rainfall-sensitive dry savanna agro-ecological zone of northern Ghana. Interviews are used toidentify characteristics of rainfall which are deemed by the farmers as important in their food production. Timeseries daily rainfall data from 1960-2007 is then used to identify trends in these variables which include theamount and temporal distribution of rainfall, occurrence of extreme daily rainfall events, the onset of rains, riskof dry spells and coefficient of variability of rains. The risk of dry spells for varying number of days followingthe planting period is computed using first-order Markov chain modeling. We find that there is a significantincrease in mean rainfall per rain day and the coefficient of variation or summer rainfall amounts. No significantchange in the onset of rains, the annual rainfall amount or maximum rainfall days are established. However, asignificant decrease in the number of rain days and the probability of dry spells of up to seven and eleven days inthe first four weeks of the planting season is revealed. There is need for development of an agricultural policyscalefarmers, and to improve management practices to accommodate and adapt to the new challenges of varyingrainfall.