In the Punjab province of Pakistan, monsoon rainfall can be divided into three distinct regions based on the amount of rainfall and its reliability.
The region of high reliability of heavy rains
This comprises the northern and north-eastern divisions of Punjab, namely Rawalpindi and Gujranwala divisions. Typical representative stations are Murree Hill Station and the Rawalpindi Plateau in Rawalpindi Division and the foothill plains around Sialkot in Gujranwala Division.
Murree receives the most rainfall; up to 35 inches in the three months of June, July and August with a frequency of a sharp drop every other day, followed by Rawalpindi receiving no less than 28 inches in the aforementioned months. The number of rainy days is 10-12 in the monsoon months.
Sialkot, in the Gujranwala division, ranks third in both amount and frequency of rainfall. Here, the rainfall in the monsoon months is about 25 inches with 8-9 rainy days in each of the monsoon months.
The common characteristic of the three stations mentioned above is not the quantity but, above all, the reliability of the precipitations. This is quite extraordinary in these places. The amount of rainfall varies only +/- 10 percent of the average in normal years and even in the worst years it does not vary much beyond 15 percent.
The Region of Moderate Precipitation and Low Reliability
This forms part of eastern central Punjab; Lahore is the main representative of this region. Here the rainfall amounts of the three months of July, August and September fall to about 17 inches and the number of rainy days falls to about 5-6 in the monsoon months. The amount of rainfall is not as important in Lahore as the low reliability or high variability of monsoonal rainfall. Every 3-4 years or so, rainfall can vary by as much as 25 percent of the long-term average. Some years are extraordinary. In August 1996, up to 18 inches fell in three days in August, while Lahore’s annual rainfall total is only 28 inches.
The Region of Low Precipitation and Very Low Reliability
This covers a huge area. Actually, it comprises all the districts of Punjab other than the central north, north east and east districts. The typical station is the southwestern city of Multan. In Multan, only about 5 to 6 inches of rain is recorded in the three monsoon months, the no. of the rainy days are around 2-3 in each month. Also, the amount of rainfall is highly unreliable and extremely variable; sometimes they can drop as much as 10 inches in 24 hours during a period of tremendously heavy rain. This is more than Multan’s total annual rainfall.
In short, less than a third of Pakistan’s Punjab province receives reliable, heavy rainfall from the monsoons. The remaining two-thirds of the province are not only deficient in rainfall, but also receive highly variable rainfall from year to year during the monsoons.
