Abstract:
Socioeconomic aspects of life have changed due to alterations in the
climatic patterns. Sri Lanka needs to pay more attention to the climate
extremes as the available water resources are directly affected by these
changes. Hence planning and management of water resources based on
climatic patterns play a key role in sustainable development. Sustainable
planning and management of water resources of Aththanagalu Oya that
feeds many large and small scale multi-purpose water extraction schemes
in Sri Lanka is vital in the event of climate change. Thus, an analysis of
the shifts and trends of climatic patterns with respect to wet and dry
events within the Aththanagalu Oya basin was carried out to evaluate the
state and the extent of climate change using Standardized Precipitation
Index(SPI). Daily rainfall data covering the period from January 1991 to
February 2011 of Henarathgoda, Vincit, Chesterford, Kirindiwela,
Nittambuwa and Pasyala rainfall gauging stations which are located
within the Aththanagalu Oya catchment area were obtained from the
Department of Meteorology, Sri Lanka. Two periodic intervals of years
(1991-2000 and 2001-2011) were formulated and monthly accumulated
rainfall for each month of the considered periods were used as the input to
the SPI Model in Mat Lab R2007b (version 7.5). The events were ranked
into five classes (normal, mild moderate, severe and extreme) based on
the severity of each event and the variations in climate (with respect to
SPI) were evaluated using Paired Chi-Square method. A decrease in dry
events and an increase of the wet events in the climatic pattern of recent
years (2001-2011) compared to the past (from 1991 to 2000) in Vincit,
Kirindiwela, Nittambuwa and Pasyala could be observed in accordance
with the SPI analysis while an opposite trend was observed in
Henarathgoda and Chesterford. Unlike the predictions of many studies
which expect significant alterations in climate patterns in the recent years
than the past years, according to the SPI approach, only the wet events of Pasyala (a significant increasing trend of wetness) and the dry events of
Vincit (a significant decreasing trend of dryness) indicate significant
alterations in climatic patterns while the climatic variations indicated by
the rest of the areas are statistically insignificant. Hence, a significant
increase in wetness in Vincit and Pasyalain terms of both severity and
frequency of occurrence with variations of rainfall seasonality could be
predicted in accordance with the SPI.
