Changing rainfall patterns since the 1970s in Rift Valley, Kenya
The rainfall patterns during the peak growing season of March, April and May have been changing over the past few decades in the province of Rift Valley, Kenya. Since the 1970s, rainfall during this season has increased in quantity but decreased in the number of days rained. This has resulted in an increase of rain intensity. These changing rainfall patterns in this part of Kenya are a part of climate change resulting from increasing annual temperatures and warming sea surface temperatures in the southwest Indian Ocean. The increase in rain intensity has caused soil erosion and infertile land. The decrease in rain days resulted in a shorter growing season. These factors affect the socioeconomic lives of the people in Rift Valley as their income and food is largely dependent on agriculture and subsistence farming. Agricultural adaptations are being adopted by farmers living in Rift Valley to combat the decrease in crop yield due to changing rainfall patterns. Changing patterns of rainfall during peak season in Rift Valley The rainfall patterns in Rift Valley, Kenya, have changed over the past few decades in quantity, number of days rained, and intensity. The rainfall patterns in Rift Valley are bimodal with their primary season occurring in March, April and May and a secondary one occurring in October, November and December. There is also a small tertiary rain season occurring in June, July and August. A study was conducted to measure changing rainfall patterns during the peak growing seasons of March, April and May in Rift Valley between the years of 1976 and 2005. The study revealed that rainfall during the peak growing season had increased by 18mm. This increase was steady over the three decades as indicated in Table 1; however, the number of days rained decreased in this time period. The data illustrates this using the average number of days rained in March, April and May. Between 1976 and 1985, the average number of rain days was 29 days, decreasing to 26 days between 1996 and 2005. Increasing rainfall with fewer rain days indicates an increase in the intensity of rainfall. This was true for the months of April and May but March showed a decrease in rain intensity. In the years between 1976 and 1985, rainfall intensity was 7.7mm/h and increased to 10.2mm/h between the years of 1996 and 2005. In May, the rainfall intensity was 5.9mm/h in the years between 1976 and 1985 and increased to 8.4mm/h in the years between 1986 and 1995. March, however, did not follow the trend of increasing rainfall intensity showing little variation. There was a decrease in March’s rainfall intensity from 6.5mm/h in the years of 1976 and 1985 to 7.4mm/h in the years of 1986 to 1995. The high rainfall in the primary rain season of March, April and May have led to suppressed rainfall in the secondary and tertiary rain seasons and a decline in the annual rainfall performance. Cause of changes Changing rainfall patterns in Rift Valley, Kenya, is a part