Abstract:
Sri Lanka is vulnerable to the changing climate because of the departures from
the usual rainfall. This paper analyses the consistency in trends of rainfall in the dry zone
of Sri Lanka with particular emphasis on the infl uence of four monsoon seasons on the
regional agriculture. The data analyzed consists of the daily rainfall records (1996-2015)
at 10 stations distributed throughout the dry zone of Sri Lanka. The non-parametric
Mann-Kendall and Sen-Theil statistical methods were used for the investigation which
is appropriate for the non-normal data with missing or censored records. To analyse the
data with seasons, modifi ed seasonal Mann-Kendall trend test was used. The pre-whitening
method was applied to remove autocorrelation from the time series. Though the
results show an increasing annual rainfall, a consistent reduction has been revealed in
monthly rainfall during June and July. Nearly 30% of the stations demonstrated a statistically
signifi cant (p<0.05) increase in rainfall during the northeast monsoon season. However,
statistically signifi cant decline in monthly rainfall during June and July led the dry zone
drier, which may have reduced the availability of the irrigable surface water during Yala
(minor rainy) season. Findings of rainfall variation in dry zone help speculate water
availability for crop requirement in the dry zone in Sri Lanka.
