**2. Study area**

Hunza is a glaciated sub-catchment of the Upper Indus Basin (UIB) and is located in the western Karakoram Himalayan region of Pakistan (**Figure 1**). The basin lies within the extent of 74°02<sup>0</sup> –75°48<sup>0</sup> E and 35°54<sup>0</sup> –37°05<sup>0</sup> N and encompasses 13,671 km<sup>2</sup> of the catchment area.

The elevation of the basin ranged from 1391 to 7850 m. About 20% catchment area of the basin is covered by glaciers [41] and there are 110 glacial lakes in the basin [42]. It is the main tributary of the Indus Basin Irrigation System (IBIS) and it contributes about 12% of UIB streamflows upstream of Tarbela dam [43]. The climate of the Hunza basin is arid to semi-arid and is normally categorized by two seasons, October to March as winter and April to September as summer. The weather conditions vary within the basin. At low altitudes, weather is hot whereas at high altitudes winters are cold and there are extensive variations in temperature extremes [44]. The mean total annual precipitation varies with respect to altitude;

#### **Figure 1.**

*Location map of the study area.*

low altitude station such as Naltar (2858 m) receives more precipitation i.e. 660 mm as compared to high altitude station Khunjerab (4730 m) which receives 165 mm of precipitation. The meteorological station installed in between Naltar and Khunjerab (i.e. Ziarat, 3669 m) receives 292 mm of precipitation [45, 46].

The temporal variations in meteorological variables of Khunjerab station (using data of 1995–2009) are displayed in **Table 1**. **Table 1** shows that the maximum temperature varies between 11.1°C (January) to 11.6°C (July) whereas minimum temperature varies from 21.3°C (January) to 1.3°C (July). The maximum relative humidity in the basin varies from 59% (March) to 91% (August) while minimum relative humidity varies from 23% (March) to 52% (December). The daily solar radiation in the Hunza basin varies from 2563 (December) to 5148 (May) watt/m<sup>2</sup> .


#### **Table 1.**

*Monthly average variations in meteorological variables of Khunjerab (1995–2012).*

*Prediction of Relative Humidity in a High Elevated Basin of Western Karakoram by Using… DOI: http://dx.doi.org/10.5772/intechopen.98226*
