The Thal desert (Punjabi: تَھل صحرا, romanized: Thal Sahrā'h; Urdu: صحرائے تھل, romanized: Sehrā-é-Thal) is situated at 31°10' N and 71°30' E in the province of Punjab, Pakistan. Located near the Pothohar Plateau, the area falls under the Indomalayan biogeographic realm and stretches for a length of approximately 190 miles (310 km) with a maximum breadth of 70 miles (119 km). It is bound by the piedmont of the northern Salt Range, the Indus River floodplains in the west and the Jhelum and Chenab rivers' floodplains in the east. It is a subtropical sandy desert that resembles the deserts of Cholistan and Thar geographically. The region is characterized by sand dunes, prone to massive shifting and rolling, as well as scant rainfall, high diurnal variation of temperature and high wind velocity. Aridity is a common feature and perennial grasses make up much of the vegetation. Agriculture and livestock rearing form the main sources of livelihood for the population, who live in small scattered settlements throughout the desert.
Geography The Thal desert of Pakistan lies at altitudes above sea levels of approximately 200m in the north which gradually decrease to around 120m in the south. It falls under the agro-ecological zone-III and is a sandy, arid to semi-arid region. The desert primarily consists of the districts of Bhakkar, Layyah, Muzzafargarh and Kot Addu, all of whom display very similar geographical features, much of Khushab and Mianwali, as well as a portion of district Jhang lying to the west of river Jhelum. The main towns of the region, which see the greatest human activity, include Roda Thal, Mankera, Hayderabad Thal, Bharary, Dullewala, Piplan, Kundiyan, Chowk Azam, Saraye Muhajir, Mehmood Shaheed Thal, Rang Pur, Jandan Wala, Mari Shah Sakhira, Noorpur Thal, Daduwala Thal, Katimar Thal, Shah Hussain Thal, and Muzaffargarh. The desert largely consists of ridges of sand dunes and rolling sand plains which alternate with narrow valleys of flatter, more cultivable land. These sand dunes are a prominent feature of the zone and consist of sediment reworked by wind and brought in by the Indus River, which lays upstream of the orogenic front. They commonly reach heights of around 175m and cover 50-60% of the Thal desert. The area is also underlain by Quaternary fluvial and eolian deposits over 350m thick in southern areas, and even thicker in the central region of the desert. This underlying alluvium consists largely of laterally continuous bodies of fine to coarse sand, with minor gravel and isolated mud lenses. Coarser deposits occur in the north closer to the Salt Range, but otherwise the distribution of grain sizes is irregular. The currently active Indus River floodplain stretches > 20 km in width at the southern edges of the desert and the abandoned floodplain reaches even wider, covering areas of higher ground. These uplands are actively eroded by the Jhelum River and form up to scarps which face the floodplain. As compared to the Upper Indus sand, the sand dunes of the Thal are poorer in quartz and sedimentary to low-rank metasedimentary rock fragments. However, they are higher in feldspars, volcanic, metavolcanic and metabasite rock fragments and heavy minerals. The dune sand is thought to be derived from the Transhimalayan arcs (40–45%, predominantly from the Kohistan arc), the Karakorum-Hindukush Ranges (40–50%, of which a third is via the Kabul River), the Nanga Parbat massif (< 10%), and the Himalayan belt (< 10%, inclusive of detritus recycled by the Soan River).
Climate The Thal desert is a subtropical sandy region with severe climatic conditions that are prone to temperature extremes. Approximately 50% of the region sees hyper-arid climatic conditions (annual rainfall less than 200mm) and the remaining half sees semi-arid climatic conditions (annual rainfall between 200mm and 500mm). The desert is also characterised by strong winds that blow year-round and can cause serious wind erosion that leads to local crop damage.
Temperature
Summers in the area see temperatures generally range from 32o C - 40o C and average around 35o C between June and July. However, southern borne hot winds blowing with high velocity can see these temperatures rise to over 45 °C. Dust storms, resulting from unsteady thermal conditions, are also common in the summer months. This has made crop cultivation challenging as the soil becomes difficult to bind, leading to extensive erosion and losses for the farming community. In the winter, temperatures vary between 3o C and 8o C and are accompanied by cold, dry winds from the north. In January, temperatures can reach near freezing point.
Precipitation The Thal Desert's rainfall patterns are low and erratic with mean annual values ranging between 150 and 350mm. The majority of precipitation occurs between the months of June and August; however, there is high variability across seasons and even years. Total annual rainfall has been seen to progressively decrease from the northern end of the desert to the south. It also displays cyclic fluctuations where two to three years of continued decreased rainfall is followed up by several years of higher precipitation levels. Hailstorms, generated by air turbulence owing to the high temperature difference between the warm surface and the cold upper atmosphere, are also common between March and April and can cause severe damage to crop and buildings.
Vegetation and Flora
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