SPATIO-Temporal Change Analysis of Climate Induced Hydrological Extreme Events in the Swat River Basin, Khyber Pakhtunkhwa, Pakistan

Abstract

The study deals with spatio-temporal change analysis of temperature, precipitation and streamflow extreme events in the Swat River Basin, Pakistan. The impacts of climate change particularly extreme events are not uniform: in fact, some regions are more affected than others, so it is important to know that when and which area is how much vulnerable to climate change? Hence, spatio-temporal analysis. Similarly, the study area is highly susceptible to flood due to ice/snow melting, rough terrain and heavy rainfall in monsoon. Three hydropower plants are there on the river with total operational capacity of around 123 MW and has a further potential of almost 1000 MW. Likewise, the area is important from tourism point of view and is known as “Eastern Switzerland” throughout the country. Data collection involve two datasets from two different sources. The daily temperature and precipitation data from the year 1989 to 2018 of Dir, Kalam, Malam Jabba and Saidu Sharif station was provided by Pakistan Meteorological Department, while the streamflow data of “Chakdara” gauge was taken from WAPDA. For trend analysis in observed data, the study employed Mankendall and a Spearman’s Rho tests while for projection of temperature/precipitation, SDSM (Statistical Downscaling Model) with CanESM2 GCM was used. Adaptation capacity of the people of the area was gauged by using stratified random sampling technique to assess the current adaptation capacity, gaps in the capacity and actions required to fill those gaps. R2 between monthly simulated and historical temperature ranged between 0.82 and 0.91 and 0.92 to 0.96 for calibration and validation periods, correspondingly. Areal precipitation experienced R2 of 0.49 for training and 0.35 for confirmation period. Historical temperature exhibited insignificant declining trend at every station excluding Saidu Sharif, while precipitation experienced rising trend at Kalam and Malam Jabba and diminishing trend at Saidu Sharif and Dir. A remarkable increasing trend was found in the discharge on annual maximum time-series and a notable rise was there on monthly scale in October, November, December, and January. From March till August, the runoff has shown a decreasing trend where a remarkable decreasing tendency was noticed for June/July. More than 2 ºC increase was observed in projected annual maximum (2041 to 2060) temperature (Areal and Dir), while for Malam Jabba, Kalam, and Saidu Sharif: about 1 ºC increase was noticed. Similarly, about 12% rise was noticed in seasonal precipitation (summer and autumn) and annual maximum (areal) under all scenarios except RCP 4.5 where 20% and 32% rise was observed in summer and autumn seasons, correspondingly. While simulating maximum precipitation/temperature, the performance of SDSM was satisfactory. Adaptation options for safeguarding lives/livelihood and environmental/ecological resources of the area include: formulation of appropriate risk management system for protecting crops, development of livestock surveillance/disease detecting system, institutional reforms, raising awareness and promoting innovative research, forest management, enhancing adaptation capacity and reducing poverty. Future research aims by including other sources of climate data (like remotely sensed climate data appropriate for hilly watersheds) to reduce the uncertainties in the results due to limited weather stations in the study area and adopting a multi-model approach. The study will help in evaluating impact of climate change on environment, agriculture, human health, tourism and water resources of the area for strengthening local decision-making, adaptive capacity and strategic planning