Assessment of Climate Change at Spatiao-Temporal Scales and its Impact on Stream Flows in Mangla Watershed

The Mangla reservoir was built for irrigation as well as power generation. The variability in climatic variables (temperature and precipitation) at spatial and temporal scales affects the streamflows. To consider the hydro-climatic unpredictability, 50 years (1961-2010) record was scrutinized. The time series were divided in two periods of 25 years each (1961-1985, 1 and 19862010, 2). Results of the current investigation revealed that the mean temperature in annual as well as in spring, winter and autumn seasons has been increased however the summer temperature has decreased for the period 1961-2010. Declining trends were observed in annual temperature for the 1st period whereas 2nd period showed more warming. The results of annual and seasonal precipitation indicate that trends in the 1 period were not consistent while in the 2 period trends were decreasing in all basins. The annual streamflows in rivers Kanshi, Poonch, Kunhar, Neelum, and Jhelum (at Azad Pattan) have decreased upto 41, 5, 34, 24 and 45% respectively with increase of 1 C annual mean temperature for the period 1961-2010. On the other hand, trends in annual mean temperature showed cooling trends for the 1period and this yield increased streamflow for rivers Kanshi, Kunhar, Neelum and Jhelum upto 21, 11, 4 and 10% respectively. In 2 period, the annual mean temperature has increased in all the basins. The annual streamflows in rivers Kanshi, Poonch, Kunhar, Neelum, and Jhelum have decreased upto 46, 32, 43, 43 and 51% respectively. In 2nd period the streamflows in rivers Kanshi, Poonch, Kunhar, Neelum, and Jhelum have decreased upto 35, 37, 5, 11 and 11 % in spring season with increase of 1 C temperature. Divergent to this, there was a reverse situation in the 1period for the spring season. The summer mean temperature has been decreased upto 1C and the streamflows in rivers Poonch, Kunhar, Neelum and Jhelum have decreased upto 2, 11, 11 and 33% per decade respectively for the whole period. Similarly in the 2 period the streamflows have reduced upto 29, 32, 12, 46 and 36% in rivers Kanshi, Poonch, Kunhar, Neelum and Jhelum respectively. The trends, caused by climate change, have impacts on the streamflows that should be considered by the water managers for the better water management in a water scarce country like Pakistan.