3.2.2. Precipitation

Monsoon and Western Disturbances were both sources of precipitation in Pakistan. Pakistan experienced widespread flooding from July through September due to the monsoon season. From October–May, precipitation spread over the whole of Pakistan due to western disturbances, with the heaviest rain falling in Northern Pakistan. However, in June, Western Disturbances sometimes affect the northern areas of Pakistan. On rare occasions, the pre-monsoon season might begin in this month as well. In the first week of

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the month, the country was battered by a Monsoonal downpour reminiscent of August's, when an extremely low air pressure system (29") developed over Kashmir and then swept eastward into Northern Pakistan. Devastating rains fell from 1–5 September, bringing death and destruction to many cities. The rivers Chenab, Jhelum, Ravi, Sutlej, and Indus in Pakistan all overflowed their banks during the latter two days of the period, which were particularly rainy. According to the Pakistan Meteorological Department, the region in northern Pakistan received around 200 mm of rain between 1 and 5 September 2014, as shown in Figure 3. A powerful low-pressure region formed in the Bay of Bengal in the latter days of August, after the extreme drought conditions in Sindh throughout the months of July and August. In the first two weeks of September 2012, a low-pressure region came into Sindh, bringing with it torrential rains in Upper Sindh. Jacobabad received 481 mm of rain in only 7 days, and 441 mm of rain in just 36 h, both world records. Larkana set a record with 239 mm, while Sukkur set a record with 206 mm. The worst of the flooding occurred in the Larkana district. In the last week of July 2010, Pakistan saw unprecedented severe monsoon rainfall, leading to flooding in the provinces of Balochistan and Sindh. Over 200 mm of rain occurred in a 24 h period in several locations in Khyber Pakhtunkhwa and Punjab. The previous 24 h rainfall record in Peshawar was 187 mm in April of 2009, but the recent total of 274 mm smashed that mark. The province of Khyber Pakhtunkhwa had rainfall in the cities of Risalpur, Cherat, Saidu Sharif, Mianwali, and Kohat.

**Figure 3.** Precipitation extreme events in Pakistan (**a**) Precipitation in 2010 < 200 mm; (**b**) precipitation ≥ 200 mm; (**c**) heavy precipitation in a single season; (**d**) precipitation >200 and < 400 mm; (**e**) all the regions in Pakistan in which extreme precipitation events occurred.

### 3.2.3. Vulnerability Due to Climate Change

Climate change's impact and the occurrence of extreme events on the Indus Basin's water supply are still impossible to predict. There is a lot of guesswork involved in predicting how melting glaciers, melting snow, glacial retreat, and changes in precipitation will affect specific areas. About 45% of the flow to the basin comes from glacier melt and snow in the Himalayas, making it very susceptible to climate change and glacial melt [6]. Spanning six different countries in Asia—Pakistan, Nepal, India, China, Bhutan, and Bangladesh—is the Hindu Kush Himalaya (HKH) range. There are many major rivers in this area, including the Indus, Brahmaputra, and Ganges. Nearly one billion people rely on these rivers as their primary supply of drinking water. The loss of local glaciers is consistent with global trends, providing more evidence that glacial retreat has increased over the last century. New projections sugges<sup>t</sup> that the pace of glacier melt caused by a rise in global temperature will accelerate in the coming years. This will increase river flow by 40% [3]. In the long term, however, the Indus River's typical flows will decrease by over 60% [2]. In addition, rising temperatures are expected to increase evapotranspiration rates across the irrigated Indus Basin, leading to higher demands for irrigation water and fiercer competition for surface and groundwater supplies among the provinces. Between May and

September, monsoon rainfall, glacier, and snowmelt account for over 85% of the yearly flow in the Indus Basin. The intensity, location, and timing of monsoon activity are all predicted to shift, causing widespread changes to the hydrological system during the next decade or two. One result of this shift in the hydrological system is the devastating flood that hit Pakistan in 2010. The thawing of glaciers had little effect on this.
